U.S. patent application number 15/002769 was filed with the patent office on 2016-08-04 for metal powder for powder metallurgy, compound, granulated powder, and sintered body.
The applicant listed for this patent is Seiko Epson Corporation. Invention is credited to Hidefumi Nakamura.
Application Number | 20160222496 15/002769 |
Document ID | / |
Family ID | 55273132 |
Filed Date | 2016-08-04 |
United States Patent
Application |
20160222496 |
Kind Code |
A1 |
Nakamura; Hidefumi |
August 4, 2016 |
METAL POWDER FOR POWDER METALLURGY, COMPOUND, GRANULATED POWDER,
AND SINTERED BODY
Abstract
A metal powder comprising particles, which contain Fe, Cr, C and
Si, and in which when one element selected from the group
consisting of Ti, V, Y, Zr, Nb, Hf, and Ta is defined as a first
element, and one element selected from the group consisting of Ti,
V, Y, Zr, Nb, Hf, and Ta, and having a higher group number in the
periodic table than that of the first element or having the same
group number in the periodic table as that of the first element and
a higher period number in the periodic table than that of the first
element is defined as a second element, the first element is
contained in a proportion of 0.01% by mass or more and 0.5% by mass
or less, and the second element is contained in a proportion of
0.01% by mass or more and 0.5% by mass or less.
Inventors: |
Nakamura; Hidefumi;
(Hachinohe, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seiko Epson Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
55273132 |
Appl. No.: |
15/002769 |
Filed: |
January 21, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 5/00 20130101; B22F
3/24 20130101; B22F 1/0059 20130101; B22F 3/15 20130101; C22C 38/04
20130101; C22C 38/46 20130101; B22F 2003/248 20130101; B22F 3/15
20130101; B22F 2998/10 20130101; B22F 3/15 20130101; B22F 2003/248
20130101; B22F 2003/248 20130101; B22F 3/1021 20130101; B22F 3/10
20130101; B22F 2202/03 20130101; B22F 1/0059 20130101; B22F 1/0059
20130101; B22F 2003/247 20130101; B22F 2003/248 20130101; B22F
3/1021 20130101; B22F 3/10 20130101; B22F 3/02 20130101; B22F 3/02
20130101; B22F 9/04 20130101; C22C 38/02 20130101; C22C 38/50
20130101; C22C 38/42 20130101; B22F 2999/00 20130101; C22C 33/0285
20130101; B22F 2999/00 20130101; C22C 38/002 20130101; C22C 38/005
20130101; B22F 2998/10 20130101; C22C 38/12 20130101; B22F 2301/35
20130101; C22C 38/48 20130101; B22F 2998/10 20130101 |
International
Class: |
C22C 38/50 20060101
C22C038/50; B22F 9/04 20060101 B22F009/04; B22F 5/00 20060101
B22F005/00; C22C 38/48 20060101 C22C038/48; C22C 38/00 20060101
C22C038/00; C22C 38/42 20060101 C22C038/42; C22C 38/12 20060101
C22C038/12; C22C 38/04 20060101 C22C038/04; C22C 38/02 20060101
C22C038/02; B22F 1/00 20060101 B22F001/00; C22C 38/46 20060101
C22C038/46 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 29, 2015 |
JP |
2015-016091 |
Claims
1. A metal powder for powder metallurgy, comprising particles,
which contain Fe as a principal component, Cr in a proportion of
10% by mass or more and 30% by mass or less, C in a proportion of
0.1% by mass or more and 2% by mass or less, and Si in a proportion
of 0.2% by mass or more and 1.5% by mass or less, and in which when
one element selected from the group consisting of Ti, V, Y, Zr, Nb,
Hf, and Ta is defined as a first element, and one element selected
from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta, and
having a higher group number in the periodic table than that of the
first element or having the same group number in the periodic table
as that of the first element and a higher period number in the
periodic table than that of the first element is defined as a
second element, the first element is contained in a proportion of
0.01% by mass or more and 0.5% by mass or less, and the second
element is contained in a proportion of 0.01% by mass or more and
0.5% by mass or less, wherein the number of crystals in the cross
section of the particle is 1 or more and 5 or less on average.
2. The metal powder for powder metallurgy according to claim 1,
wherein the crystal contains Fe as a principal component, and the
particle further includes a region, which has a smaller volume than
the crystal, and in which the ratio of the content of Si to the
content of Fe is higher than in the crystal.
3. The metal powder for powder metallurgy according to claim 1,
wherein in the cross section of the particle, the circle equivalent
diameter of the crystal is 1% or more and 100% or less the circle
equivalent diameter of the particle.
4. The metal powder for powder metallurgy according to claim 1,
wherein the crystal has a martensite crystal structure.
5. A compound, comprising the metal powder for powder metallurgy
according to claim 1 and a binder which binds the particles of the
metal powder for powder metallurgy to one another.
6. A compound, comprising the metal powder for powder metallurgy
according to claim 2 and a binder which binds the particles of the
metal powder for powder metallurgy to one another.
7. A compound, comprising the metal powder for powder metallurgy
according to claim 3 and a binder which binds the particles of the
metal powder for powder metallurgy to one another.
8. A compound, comprising the metal powder for powder metallurgy
according to claim 4 and a binder which binds the particles of the
metal powder for powder metallurgy to one another.
9. A granulated powder, wherein the granulated powder is obtained
by granulating the metal powder for powder metallurgy according to
claim 1.
10. A granulated powder, wherein the granulated powder is obtained
by granulating the metal powder for powder metallurgy according to
claim 2.
11. A granulated powder, wherein the granulated powder is obtained
by granulating the metal powder for powder metallurgy according to
claim 3.
12. A granulated powder, wherein the granulated powder is obtained
by granulating the metal powder for powder metallurgy according to
claim 4.
13. A sintered body, wherein the sintered body is produced by
sintering the metal powder for powder metallurgy according to claim
1.
14. A sintered body, wherein the sintered body is produced by
sintering the metal powder for powder metallurgy according to claim
2.
15. A sintered body, wherein the sintered body is produced by
sintering the metal powder for powder metallurgy according to claim
3.
16. A sintered body, wherein the sintered body is produced by
sintering the metal powder for powder metallurgy according to claim
4.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. 2015-016091 filed on Jan. 29, 2015. The entire
disclosure of Japanese Patent Application No. 2015-016091 is hereby
incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a metal powder for powder
metallurgy, a compound, a granulated powder, and a sintered
body.
[0004] 2. Related Art
[0005] In a powder metallurgy method, a composition containing a
metal powder and a binder is molded into a desired shape to obtain
a molded body, and the obtained molded body is degreased and
sintered, whereby a sintered body is produced. In such a process
for producing a sintered body, an atomic diffusion phenomenon
occurs among particles of the metal powder, whereby the molded body
is gradually densified, resulting in sintering.
[0006] For example, JP-A-2012-87416 proposes a metal powder for
powder metallurgy which contains Zr and Si, with the remainder
including at least one element selected from the group consisting
of Fe, Co, and Ni, and inevitable elements. According to such a
metal powder for powder metallurgy, the sinterability is enhanced
by the action of Zr, and a sintered body having a high density can
be easily produced.
[0007] The thus obtained sintered body has recently become widely
used for a variety of machine parts, structural parts, and the
like.
[0008] However, depending on the use of a sintered body, further
densification is needed in some cases. In such a case, a sintered
body is further subjected to an additional treatment such as a hot
isostatic pressing treatment (HIP treatment) to increase the
density, however, the workload is significantly increased, and also
an increase in the cost is inevitable.
[0009] Therefore, an expectation for realization of a metal powder
capable of producing a sintered body having a high density without
performing an additional treatment or the like has increased.
SUMMARY
[0010] An advantage of some aspects of the invention is to provide
a metal powder for powder metallurgy, a compound, and a granulated
powder, each of which is capable of producing a sintered body
having a high density, and a sintered body having a high
density.
[0011] The advantage can be achieved by aspects of the invention
described below.
[0012] A metal powder for powder metallurgy according to an aspect
of the invention includes particles, which contain Fe as a
principal component, Cr in a proportion of 10% by mass or more and
30% by mass or less, C in a proportion of 0.1% by mass or more and
2% by mass or less, and Si in a proportion of 0.2% by mass or more
and 1.5% by mass or less, and in which when one element selected
from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta is
defined as a first element, and one element selected from the group
consisting of Ti, V, Y, Zr, Nb, Hf, and Ta, and having a higher
group number in the periodic table than that of the first element
or having the same group number in the periodic table as that of
the first element and a higher period number in the periodic table
than that of the first element is defined as a second element, the
first element is contained in a proportion of 0.01% by mass or more
and 0.5% by mass or less and the second element is contained in a
proportion of 0.01% by mass or more and 0.5% by mass or less,
wherein the number of crystals in the cross section of the particle
is 1 or more and 5 or less on average.
[0013] According to this, a metal powder for powder metallurgy
capable of producing a sintered body having a high density is
obtained.
[0014] In the metal powder for powder metallurgy according to the
aspect of the invention, it is preferred that the crystal contains
Fe as a principal component, and the particle further includes a
region, which has a smaller volume than the crystal, and in which
the ratio of the content of Si to the content of Fe is higher than
in the crystal.
[0015] According to this, a metal powder for powder metallurgy
capable of producing a sintered body having a high relative density
and excellent mechanical properties is obtained.
[0016] In the metal powder for powder metallurgy according to the
aspect of the invention, it is preferred that in the cross section
of the particle, the circle equivalent diameter of the crystal is
1% or more and 100% or less the circle equivalent diameter of the
particle.
[0017] According to this, the crystal can dominantly behave with
respect to the sinterability of the particles when they are fired.
That is, the particles behave as if they were single crystal
grains, and therefore, the sintering rate is increased, and thus,
this configuration greatly contributes to an increase in the
sintered density.
[0018] In the metal powder for powder metallurgy according to the
aspect of the invention, it is preferred that the crystal has a
martensite crystal structure.
[0019] The martensite crystal structure includes a body-centered
cubic lattice in the form of a solid solution supersaturated with,
for example, C. This body-centered cubic lattice is formed by
transformation from a face-centered cubic lattice accompanying
firing or a heat treatment after firing, and the volume thereof is
expanded at that time. Therefore, a metal powder for powder
metallurgy having a martensite crystal structure is capable of
producing a sintered body having a high hardness.
[0020] A compound according to an aspect of the invention includes
the metal powder for powder metallurgy according to the aspect of
the invention and a binder which binds the particles of the metal
powder for powder metallurgy to one another.
[0021] According to this, a compound capable of producing a
sintered body having a high density is obtained.
[0022] A granulated powder according to an aspect of the invention
is obtained by granulating the metal powder for powder metallurgy
according to the aspect of the invention.
[0023] According to this, a granulated powder capable of producing
a sintered body having a high density is obtained.
[0024] A sintered body according to an aspect of the invention is
produced by sintering the metal powder for powder metallurgy
according to the aspect of the invention.
[0025] According to this, a sintered body having a high density is
obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0027] FIG. 1 is a view schematically showing the cross sections of
particles contained in an embodiment of a metal powder for powder
metallurgy according to the invention.
[0028] FIG. 2 is a view schematically showing the crystal structure
of the particle shown in FIG. 1.
[0029] FIG. 3 is an enlarged view of an area A surrounded by the
dashed line in FIG. 2.
[0030] FIG. 4A shows one example of a TEM image (bright field
image) of the cross section of a particle 1, and FIG. 4B shows one
example of a TEM image (dark field image) of the cross section of
the particle 1 shown in FIG. 4A.
[0031] FIG. 5 is a partial enlarged view of an area B surrounded by
the dashed line shown in FIG. 4A and is an observation image when
the area B was observed with a high-angle annular dark field
scanning transmission electron microscope.
[0032] FIG. 6 shows one example of the EDX spectrum of a high Si
concentration region shown in FIG. 5 and shows a spectrum obtained
by a point analysis at a position (Position 1 in FIG. 6)
corresponding to the high Si concentration region shown in FIG.
5.
[0033] FIG. 7 shows one example of the EDX spectrum of an Fe-based
alloy crystal shown in FIG. 5 and shows a spectrum obtained by a
point analysis at a position (Position 2 in FIG. 7) corresponding
to the Fe-based alloy crystal shown in FIG. 5.
[0034] FIG. 8A shows one example of a TEM image (bright field
image) of the cross section of a particle containing 6 or more
Fe-based alloy crystals, and FIG. 8B shows one example of a TEM
image (dark field image) of the cross section of the particle shown
in FIG. 8A.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0035] Hereinafter, a metal powder for powder metallurgy, a
compound, a granulated powder, and a sintered body according to the
invention will be described in detail with reference to preferred
embodiments shown in the accompanying drawings.
Metal Powder for Powder Metallurgy
[0036] First, a metal powder for powder metallurgy according to the
invention will be described.
[0037] In powder metallurgy, a sintered body having a desired shape
can be obtained by molding a composition containing a metal powder
for powder metallurgy and a binder into a desired shape, followed
by degreasing and firing. According to such a powder metallurgy
technique, a sintered body with a complicated and fine shape can be
produced in a near-net shape (a shape close to a final shape) as
compared with the other metallurgy techniques.
[0038] With respect to the metal powder for powder metallurgy to be
used in the powder metallurgy, an attempt to increase the density
of a sintered body to be produced by appropriately changing the
composition thereof has been made. However, in the sintered body,
pores are liable to be generated, and therefore, in order to obtain
mechanical properties comparable to those of ingot materials, it
was necessary to further increase the density of the sintered
body.
[0039] For example, in the past, the obtained sintered body was
further subjected to an additional treatment such as a hot
isostatic pressing treatment (HIP treatment) to increase the
density. However, such an additional treatment requires much time,
labor, and cost, and therefore becomes an obstacle to the expansion
of the application of the sintered body.
[0040] In consideration of the above-mentioned problems, the
present inventors have made intensive studies to find conditions
for obtaining a sintered body having a high density without
performing an additional treatment. As a result, they found that
the density of a sintered body can be increased by optimizing the
chemical composition and the crystal structure of each particle
contained in a metal powder, and thus completed the invention.
[0041] Specifically, the metal powder for powder metallurgy
according to this embodiment includes particles, which contain Fe
as a principal component, Cr in a proportion of 10% by mass or more
and 30% by mass or less, C in a proportion of 0.1% by mass or more
and 2% by mass or less, Si in a proportion of 0.2% by mass or more
and 1.5% by mass or less, the below-mentioned first element in a
proportion of 0.01% by mass or more and 0.5% by mass or less, and
the below-mentioned second element in a proportion of 0.01% by mass
or more and 0.5% by mass or less. Further, the number of crystals
in the cross section of the particle is 1 or more and 5 or less on
average. According to the metal powder for powder metallurgy
containing such particles, when the particles are sintered in a
firing step, the sintering is promoted and densification proceeds.
As a result, a sintered body having a sufficiently high density can
be produced without performing an additional treatment.
[0042] Such a sintered body has excellent mechanical properties.
Due to this, the sintered body can be widely applied also to, for
example, machine parts, structural parts, and the like, to which an
external force is applied.
[0043] The first element is one element selected from the group
consisting of the following seven elements: Ti, V, Y, Zr, Nb, Hf,
and Ta, and the second element is one element selected from the
group consisting of the above-mentioned seven elements and having a
higher group number in the periodic table than that of the first
element or one element selected from the group consisting of the
above-mentioned seven elements and having the same group number in
the periodic table as that of the element selected as the first
element and a higher period number in the periodic table than that
of the first element.
[0044] Hereinafter, the configuration of the metal powder for
powder metallurgy according to this embodiment will be described in
further detail. In the following description, the "metal powder for
powder metallurgy" is sometimes simply referred to as "metal
powder", and each of the multiple particles constituting the metal
powder for powder metallurgy is sometimes simply referred to as
"particle".
[0045] FIG. 1 is a view schematically showing the cross sections of
particles contained in an embodiment of the metal powder for powder
metallurgy according to the invention, and FIG. 2 is a view
schematically showing the crystal structure of the particle shown
in FIG. 1.
[0046] A particle 1 shown in FIG. 1 is constituted by an Fe-based
alloy. As shown in FIG. 2, the particle 1 includes one or more and
5 or less crystals on average in the cross section.
[0047] The crystal is preferably a crystal containing Fe as a
principal component. Then, these crystals occupy most (90% or more
in terms of area ratio) of the cross section of the particle 1.
Therefore, these crystals have an influence on the properties of
the particle 1 (metal powder for powder metallurgy) and the
properties of a sintered body to be produced from the particle
1.
[0048] That is, the particle 1 is a particle having a very small
number of Fe-based alloy crystals contained therein. Such a
particle 1 can be said to be single-crystalline or polycrystalline
close to single-crystalline, and behaves in the same manner as a
single crystal when it is fired. Therefore, when the metal powder
for powder metallurgy is fired, sintering proceeds at an excellent
sintering rate derived from the single crystal. As a result, a
sintered body having few internal gaps and a high relative density
can be produced.
[0049] The clause "Fe is contained as a principal component in the
crystal" refers to a state in which Fe is an element contained at
the highest concentration in a local chemical composition of the
crystal. The chemical composition of the crystal can be determined
by, for example, a qualitative and quantitative analysis by energy
dispersive X-ray spectrometry.
[0050] The cross-sectional view of the particle 1 shown in FIG. 2
is an example showing the presence of typical crystals among many
particles contained in the metal powder for powder metallurgy.
[0051] The particle 1 shown in FIG. 2 includes four Fe-based alloy
crystals 2. The adjacent Fe-based alloy crystals 2 are separated by
a linear grain boundary 3.
[0052] As described above, the particle 1 includes 1 or more and 5
or less Fe-based alloy crystals 2 on average in the cross section
of the particle.
[0053] The average number of the Fe-based alloy crystals 2 in the
cross section of the particle 1 is a value obtained by observing
the cross sections of 10 or more particles 1 contained in the metal
powder as observation targets with an electron microscope, counting
the number of the Fe-based alloy crystals 2 contained in each
particle 1 by visual observation of an observation image, and
averaging the counts in all the observation targets. As the
electron microscope, for example, a transmission electron
microscope (TEM) is used, and the observation can be performed in a
bright field image. When it is difficult to clearly specify the
grain boundary 3 in the bright field image, the grain boundary 3
may be easily specified by changing the bright field image into a
dark field image in some cases.
[0054] The circle equivalent diameter of the Fe-based alloy crystal
2 (the diameter of a circle having the same area as that of the
cross section of the Fe-based alloy crystal 2) is preferably 1% or
more and 100% or less, more preferably 3% or more and less than
100% of the circle equivalent diameter of the particle 1 (the
diameter of a circle having the same area as that of the cross
section of the particle 1). When the ratio of the crystal grain
diameter of the Fe-based alloy crystal 2 to the diameter of the
particle 1 falls within the above range, the Fe-based alloy crystal
2 can dominantly behave with respect to the sinterability of the
particles 1 when they are fired. That is, the particle 1 behaves as
if it was a single crystal grain, and therefore, the sintering rate
is increased, and thus, this configuration greatly contributes to
an increase in the sintered density.
[0055] FIG. 3 is an enlarged view of an area A surrounded by the
dashed line in FIG. 2.
[0056] In the area A shown in FIG. 3, a high Si concentration
region 4, which has a smaller volume than the Fe-based alloy
crystal 2, and in which the ratio of the content of Si to the
content of Fe is higher than in the Fe-based alloy crystal 2, is
present. By the presence of such a high Si concentration region 4,
a sintered body produced by using the metal powder containing the
particle 1 has a high relative density and excellent mechanical
properties.
[0057] The high Si concentration region 4 is a region, which is
present in the inside of the Fe-based alloy crystal 2 or at the
grain boundary 3, and in which the ratio of the content of Si to
the content of Fe is higher than in the Fe-based alloy crystal 2.
The contents of these elements can be determined by, for example,
the qualitative and quantitative analysis of each of the Fe-based
alloy crystal 2 and the high Si concentration region 4 by energy
dispersive X-ray spectrometry (EDX). Further, as a simple way, the
height of a peak of Fe located at near 6.4 keV and the height of a
peak of Si located at near 1.8 keV in the EDX spectrum are
determined, and the ratio of the height of the peak of Si to the
height of the peak of Fe is calculated, whereby the ratio of the
content of Si to the content of Fe can be obtained.
[0058] Therefore, when the content of Fe in the Fe-based alloy
crystal 2 is represented by Fe(2), the content of Si therein is
represented by Si(2), the content of Fe in the high Si
concentration region 4 is represented by Fe(4), and the content of
Si therein is represented by Si(4), the particle 1 satisfies the
following formula (1).
Si(2)/Fe(2)<Si(4)/Fe(4) (1)
[0059] The position of the high Si concentration region 4 in the
cross section of the particle 1 is not particularly limited, but is
preferably at the grain boundary 3. According to this, the
sintering rate of the Fe-based alloy crystal 2 is particularly
increased, and thus, a sintered body having a particularly high
relative density can be produced.
[0060] The shape of the high Si concentration region 4 in the cross
section of the particle 1 is not particularly limited and may be
any shape, but is preferably a circle, a polygon, or a shape
equivalent thereto. By including the high Si concentration region 4
in such a shape, the sinterability of the particle 1 is further
enhanced, and the relative density of a sintered body produced by
using the metal powder containing such particles 1 is further
increased.
[0061] In other words, the shape of the high Si concentration
region 4 is preferably a shape having a low aspect ratio.
Specifically, the average of the aspect ratio defined by the major
axis/minor axis of the high Si concentration region 4 is preferably
1 or more and 3 or less, more preferably 1 or more and 2 or less.
By including the high Si concentration region 4 in such a shape,
the sinterability of the particle 1 is further enhanced, and the
relative density of a sintered body produced by using the metal
powder containing such particles 1 is further increased in the same
manner as described above.
[0062] The "major axis" of the high Si concentration region 4 is
the maximum length of the high Si concentration region 4, and the
"minor axis" is the maximum length in the direction perpendicular
to the major axis.
[0063] Further, the particle 1 preferably satisfies the following
formula (2), more preferably satisfies the following formula
(3).
1.2.times.Si(2)/Fe(2)<Si(4)/Fe(4)<1 (2)
1.3.times.Si(2)/Fe(2)<Si(4)/Fe(4)<0.8 (3)
[0064] Here, FIG. 4A shows one example of a TEM image (bright field
image) of the cross section of the particle 1, and FIG. 4B shows
one example of a TEM image (dark field image) of the cross section
of the particle 1 shown in FIG. 4A.
[0065] In the TEM image (bright field image) shown in FIG. 4A, two
Fe-based alloy crystals 2 contained in the particle 1 are shown.
Further, a line based on a difference in shading indicated by the
arrows in FIG. 4A is the grain boundary 3 located on a boundary
between the two Fe-based alloy crystals 2.
[0066] Further, in the TEM image (dark field image) shown in FIG.
4B, among the two Fe-based alloy crystals 2, one Fe-based alloy
crystal 2 located on the upper right side appears in a light color
and the other Fe-based alloy crystal 2 located on the lower left
side appears in a dark color. By observing the Fe-based alloy
crystals 2 in the dark field image, the contrast between the two
Fe-based alloy crystals 2 can be enhanced based on the difference
in the type of crystal.
[0067] Further, FIG. 5 is a partial enlarged view of an area B
surrounded by the dashed line shown in FIG. 4A and is an
observation image when the area B was observed with a high-angle
annular dark field scanning transmission electron microscope. A
dark color portion indicated by the arrow in FIG. 5 is the high Si
concentration region 4. By comparison of FIGS. 4A and 4B with FIG.
5, it is found that the high Si concentration region 4 is located
at the grain boundary 3.
[0068] FIG. 6 shows one example of the EDX spectrum of the high Si
concentration region 4 shown in FIG. 5 and shows a spectrum
obtained by a point analysis at a position (Position 1 in FIG. 6)
corresponding to the high Si concentration region 4 shown in FIG.
5. Further, FIG. 7 shows one example of the EDX spectrum of the
Fe-based alloy crystal 2 shown in FIG. 5 and shows a spectrum
obtained by a point analysis at a position (Position 2 in FIG. 7)
corresponding to the Fe-based alloy crystal 2 shown in FIG. 5.
[0069] As shown in these examples of the EDX spectra, according to
the EDX spectrum at the position corresponding to the high Si
concentration region 4, it is shown that the amount of Si is
increased with respect to the amount of Fe as compared with that at
the position corresponding to the Fe-based alloy crystal 2.
[0070] On the other hand, FIG. 8A shows one example of a TEM image
(bright field image) of the cross section of a particle containing
6 or more Fe-based alloy crystals, and FIG. 8B shows one example of
a TEM image (dark field image) of the cross section of the particle
shown in FIG. 8A. The particle shown in FIGS. 8A and 8B has a
chemical composition containing no first element or second element
described above and corresponds to Comparative Example with respect
to the invention.
[0071] As shown in FIGS. 8A and 8B, in the particle having a
chemical composition containing no first element or second element,
many crystals are generated. Such a particle can be said to be
polycrystalline close to microcrystalline, and behaves in a
different manner from a single crystal when it is fired. Therefore,
when the metal powder containing such particles is fired, the
sintering rate is decreased, resulting in decreasing the relative
density of a sintered body.
[0072] The Fe-based alloy crystal 2 preferably has a martensite
crystal structure. The martensite crystal structure includes a
body-centered cubic lattice in the form of a solid solution
supersaturated with, for example, C. This body-centered cubic
lattice is formed by transformation from a face-centered cubic
lattice accompanying firing or a heat treatment after firing, and
the volume thereof is expanded at that time. Therefore, the
Fe-based alloy crystal 2 having a martensite crystal structure
enables the production of a sintered body having a high
hardness.
[0073] It can be determined whether or not the metal powder for
powder metallurgy has a martensite crystal structure by, for
example, X-ray diffractometry.
[0074] Hereinafter, one example of the chemical composition of the
particle 1 will be described in further detail.
[0075] In the chemical composition of the whole particle 1, Fe is
an element (principal component) whose content is the highest and
has an influence on the properties of the sintered body. The
content of Fe in the whole particle 1 is 50% by mass or more.
Cr
[0076] Cr (chromium) is an element which provides corrosion
resistance to a sintered body to be produced. By using the metal
powder containing Cr, a sintered body capable of maintaining high
mechanical properties over a long period of time is obtained.
[0077] The content of Cr in the particle 1 is set to 10% by mass or
more and 30% by mass or less, but is set to preferably 10.5% by
mass or more and 20% by mass or less, more preferably 11% by mass
or more and 18% by mass or less. If the content of Cr is less than
the above lower limit, the corrosion resistance of a sintered body
to be produced may be insufficient depending on the overall
composition. On the other hand, if the content of Cr exceeds the
above upper limit, the sinterability is deteriorated depending on
the overall composition so that it may become difficult to increase
the density of the sintered body.
C
[0078] C (carbon) can particularly enhance the sinterability when
it is used in combination with the below-mentioned first element
and second element.
[0079] Specifically, the first element and the second element each
form a carbide by binding to C. By dispersedly depositing this
carbide, an effect of preventing the significant growth of crystal
grains is exhibited. A clear reason for obtaining such an effect
has not been known, but one of the reasons therefor is considered
to be because the dispersed deposit serves as an obstacle to
inhibit the significant growth of crystal grains, and therefore, a
variation in the size of crystal grains is suppressed. Accordingly,
it becomes difficult to generate pores in a sintered body, and also
the increase in the size of crystal grains is prevented, and thus,
a sintered body having a high density and excellent mechanical
properties is obtained.
[0080] The content of C in the particle 1 is set to 0.1% by mass or
more and 2% by mass or less, but is set to preferably 0.35% by mass
or more and 1.15% by mass or less, more preferably 0.4% by mass or
more and 1.1% by mass or less. If the content of C is less than the
above lower limit, crystal grains are liable to grow depending on
the overall composition so that the mechanical properties of the
sintered body are insufficient. On the other hand, if the content
of C exceeds the above upper limit, the amount of C is too large
depending on the overall composition so that the sinterability is
deteriorated instead.
Si
[0081] Si (silicon) is an element which provides corrosion
resistance and high mechanical properties to a sintered body to be
produced, and by using the metal powder containing Si, a sintered
body capable of maintaining high mechanical properties over a long
period of time can be obtained.
[0082] The content of Si in the particle 1 is set to 0.2% by mass
or more and 1.5% by mass or less, but is set to preferably 0.3% by
mass or more and 1% by mass or less, more preferably 0.5% by mass
or more and 0.8% by mass or less. If the content of Si is less than
the above lower limit, the effect of the addition of Si is weakened
depending on the overall composition so that the corrosion
resistance and the mechanical properties of a sintered body to be
produced may be deteriorated. On the other hand, if the content of
Si exceeds the above upper limit, the amount of Si is too large
depending on the overall composition so that the corrosion
resistance and the mechanical properties may be deteriorated
instead.
Mn
[0083] Mn is an element which is added as needed and provides
corrosion resistance and high mechanical properties to a sintered
body to be produced in the same manner as Si.
[0084] The content of Mn in the particle 1 is not particularly
limited, but is preferably 0.01% by mass or more and 1.25% by mass
or less, more preferably 0.03% by mass or more and 0.3% by mass or
less, further more preferably 0.05% by mass or more and 0.2% by
mass or less. By setting the content of Mn within the above range,
a sintered body having a high density and excellent mechanical
properties is obtained. Further, Mn can increase the mechanical
strength while suppressing the decrease in elongation. Further, Mn
can suppress the increase in brittleness at a high temperature
(when glowing).
[0085] If the content of Mn is less than the above lower limit, the
corrosion resistance and the mechanical properties of a sintered
body to be produced may not be sufficiently enhanced depending on
the overall composition. On the other hand, if the content of Mn
exceeds the above upper limit, the corrosion resistance and the
mechanical properties may be deteriorated instead.
Ni
[0086] Ni is an element which is added as needed and provides
corrosion resistance and heat resistance to a sintered body to be
produced.
[0087] The content of Ni in the particle 1 is not particularly
limited, but is preferably 0.05% by mass or more and 0.6% by mass
or less, more preferably 0.06% by mass or more and 0.4% by mass or
less, further more preferably 0.07% by mass or more and 0.25% by
mass or less. By setting the content of Ni within the above range,
a sintered body which maintains excellent mechanical properties
over a long period of time can be obtained.
[0088] If the content of Ni is less than the above lower limit, the
corrosion resistance and the heat resistance of a sintered body to
be produced may not be sufficiently enhanced depending on the
overall composition. On the other hand, if the content of Ni
exceeds the above upper limit, the corrosion resistance and the
heat resistance may be deteriorated instead.
[0089] Further, Mn and Ni are contained in a total proportion of
preferably 0.05% by mass or more and 1.6% by mass or less, more
preferably 0.08% by mass or more and 1.3% by mass or less, further
more preferably 0.1% by mass or more and 1% by mass or less.
According to this, the mechanical properties of the sintered body
can be particularly enhanced.
First Element and Second Element
[0090] The first element and the second element each deposit a
carbide or an oxide (hereinafter also collectively referred to as
"carbide or the like"). It is considered that this deposited
carbide or the like inhibits the significant growth of crystal
grains when the metal powder is sintered. As a result, as described
above, it becomes difficult to generate pores in a sintered body,
and also the increase in the size of crystal grains is prevented,
and thus, a sintered body having a high density and excellent
mechanical properties is obtained.
[0091] In addition, although a detailed description will be given
later, the deposited carbide or the like promotes the accumulation
of silicon oxide at a crystal grain boundary, and as a result, the
sintering is promoted and the density is increased while preventing
the increase in the size of crystal grains.
[0092] The first element and the second element are two elements
selected from the group consisting of the following seven elements:
Ti, V, Y, Zr, Nb, Hf, and Ta, but preferably include an element
belonging to group III A or group IV A in the long periodic table
(Ti, Y, Zr, or Hf). By including an element belonging to group III
A or group IV A as at least one of the first element and the second
element, oxygen contained as an oxide in the metal powder is
removed and the sinterability of the metal powder can be
particularly enhanced.
[0093] The first element is only required to be one element
selected from the group consisting of the following seven elements:
Ti, V, Y, Zr, Nb, Hf, and Ta as described above, but is preferably
an element belonging to group III A or group IV A in the long
periodic table in the group consisting of the above-mentioned seven
elements. An element belonging to group 3A or group 4A removes
oxygen contained as an oxide in the metal powder and therefore can
particularly enhance the sinterability of the metal powder.
According to this, the concentration of oxygen remaining in the
crystal grains after sintering can be decreased. As a result, the
content of oxygen in the sintered body can be decreased, and the
density can be increased. Further, these elements are elements
having high activity, and therefore are considered to cause rapid
atomic diffusion. Accordingly, this atomic diffusion acts as a
driving force, and thereby a distance between particles of the
metal powder is efficiently decreased and a neck is formed between
the particles, so that the densification of a molded body is
promoted. As a result, the density of the sintered body can be
further increased.
[0094] On the other hand, the second element is only required to be
one element selected from the group consisting of the following
seven elements: Ti, V, Y, Zr, Nb, Hf, and Ta and different from the
first element as described above, but is preferably an element
belonging to group V A in the long periodic table in the group
consisting of the above-mentioned seven elements. An element
belonging to group V A particularly efficiently deposits the
above-mentioned carbide or the like, and therefore, can efficiently
inhibit the significant growth of crystal grains during sintering.
As a result, the formation of fine crystal grains is promoted, and
thus, the density of the sintered body can be increased and also
the mechanical properties of the sintered body can be enhanced.
[0095] Incidentally, by the combination of the first element with
the second element composed of the elements as described above, the
effects of the respective elements are exhibited without inhibiting
each other. Due to this, the metal powder containing such a first
element and a second element enables the production of a sintered
body having a particularly high density.
[0096] More preferably, a combination of an element belonging to
group 4A as the first element with Nb as the second element is
adopted.
[0097] Further, more preferably, a combination of Zr or Hf as the
first element with Nb as the second element is adopted.
[0098] By adopting such a combination, the above-mentioned effect
becomes more prominent.
[0099] In the case where the first element is particularly Zr, Zr
is a ferrite forming element, and therefore deposits a
body-centered cubic lattice phase. This body-centered cubic lattice
phase has more excellent sinterability than the other crystal
lattice phases, and therefore contributes to the densification of a
sintered body.
[0100] The atomic radius of Zr is slightly larger than that of Fe.
Specifically, the atomic radius of Fe is about 0.117 nm, and the
atomic radius of Zr is about 0.145 nm. Therefore, Zr is
solid-dissolved in Fe, but is not completely solid-dissolved
therein, and part of Zr is deposited as a carbide or the like.
According to this, an appropriate amount of a carbide or the like
is deposited, and therefore, the increase in the size of crystal
grains can be effectively prevented while promoting the sintering
and increasing the density.
[0101] In the case where the second element is particularly Nb, the
atomic radius of Nb is slightly larger than that of Fe, but
slightly smaller than that of Zr. Specifically, the atomic radius
of Fe is about 0.117 nm, and the atomic radius of Nb is about 0.134
nm. Therefore, Nb is solid-dissolved in Fe, but is not completely
solid-dissolved therein, and part of Nb is deposited as a carbide
or the like. According to this, an appropriate amount of a carbide
or the like is deposited, and therefore, the increase in the size
of crystal grains can be effectively prevented while promoting the
sintering and increasing the density.
[0102] The content of the first element in the particle 1 is set to
0.01% by mass or more and 0.5% by mass or less, but is set to
preferably 0.03% by mass or more and 0.3% by mass or less, more
preferably 0.05% by mass or more and 0.2% by mass or less. If the
content of the first element is less than the above lower limit,
the effect of the addition of the first element is weakened
depending on the overall composition so that the density of a
sintered body to be produced may not be sufficiently increased. On
the other hand, if the content of the first element exceeds the
above upper limit, the amount of the first element is too large
depending on the overall composition so that the ratio of the
above-mentioned carbide or the like is too high, and therefore, the
densification may be deteriorated instead.
[0103] The content of the second element in the particle 1 is set
to 0.01% by mass or more and 0.5% by mass or less, but is set to
preferably 0.03% by mass or more and 0.3% by mass or less, more
preferably 0.05% by mass or more and 0.2% by mass or less. If the
content of the second element is less than the above lower limit,
the effect of the addition of the second element is weakened
depending on the overall composition so that the density of a
sintered body to be produced may not be sufficiently increased. On
the other hand, if the content of the second element exceeds the
above upper limit, the amount of the second element is too large
depending on the overall composition so that the ratio of the
above-mentioned carbide or the like is too high, and therefore, the
densification may be deteriorated instead.
[0104] Further, as described above, each of the first element and
the second element deposits a carbide or the like, however, in the
case where an element belonging to group III A or group IV A is
selected as the first element as described above and an element
belonging to group V A is selected as the second element as
described above, it is presumed that when the metal powder is
sintered, the timing when a carbide or the like of the first
element is deposited and the timing when a carbide or the like of
the second element is deposited differ from each other. It is
considered that due to the difference in timing when a carbide or
the like is deposited in this manner, sintering gradually proceeds
so that the generation of pores is prevented, and thus, a dense
sintered body is obtained. That is, it is considered that by the
presence of both of the carbide or the like of the first element
and the carbide or the like of the second element, the increase in
the size of crystal grains can be suppressed while increasing the
density of the sintered body.
[0105] In addition, it is considered that in the particle 1, the
carbide or the like of the first element and the carbide or the
like of the second element act as "nuclei", and the accumulation of
silicon oxide occurs. By the accumulation of silicon oxide in a
crystal grain (in the Fe-based alloy crystal 2) or at a crystal
grain boundary (at the grain boundary 3), the concentration of
oxides inside the crystal is decreased, and therefore, sintering is
promoted. As a result, it is considered that the densification of
the sintered body is further promoted when the particles 1 are
sintered.
[0106] The particle 1 is only required to contain two elements
selected from the group consisting of the above-mentioned seven
elements, but may further contain an element which is selected from
this group and is different from these two elements. That is, the
particle 1 may contain three or more elements selected from the
group consisting of the above-mentioned seven elements. According
to this, the above-mentioned effect can be further enhanced, which
slightly varies depending on the combination of the elements to be
contained.
[0107] Further, it is preferred to set the ratio of the content of
the first element to the content of the second element in
consideration of the mass number of the first element and the mass
number of the second element.
[0108] Specifically, when a value obtained by dividing the content
E1 (mass %) of the first element by the mass number of the first
element is represented by X1 and a value obtained by dividing the
content E2 (mass %) of the second element by the mass number of the
second element is represented by X2, X1/X2 is preferably 0.3 or
more and 3 or less, more preferably 0.5 or more and 2 or less,
further more preferably 0.75 or more and 1.3 or less. By setting
the ratio X1/X2 within the above range, the balance between the
deposition amount of the carbide or the like of the first element
and the deposition amount of the carbide or the like of the second
element can be optimized. According to this, pores remaining in a
molded body can be eliminated as if they were swept out
sequentially from the inside, and therefore, pores generated in a
sintered body can be minimized. Accordingly, a metal powder capable
of producing a sintered body having a high density and excellent
mechanical properties can be obtained by setting the ratio X1/X2
within the above range.
[0109] Here, with respect to a specific example of the combination
of the first element with the second element, based on the
above-mentioned range of the ratio X1/X2, the ratio (E1/E2) of the
content E1 of the first element to the content E2 of the second
element is calculated.
[0110] For example, in the case where the first element is Zr and
the second element is Nb, since the mass number of Zr is 91.2 and
the mass number of Nb is 92.9, E1/E2 is preferably 0.29 or more and
2.95 or less, more preferably 0.49 or more and 1.96 or less.
[0111] In the case where the first element is Hf and the second
element is Nb, since the mass number of Hf is 178.5 and the mass
number of Nb is 92.9, E1/E2 is preferably 0.58 or more and 5.76 or
less, more preferably 0.96 or more and 3.84 or less.
[0112] In the case where the first element is Ti and the second
element is Nb, since the mass number of Ti is 47.9 and the mass
number of Nb is 92.9, E1/E2 is preferably 0.15 or more and 1.55 or
less, more preferably 0.26 or more and 1.03 or less.
[0113] In the case where the first element is Nb and the second
element is Ta, since the mass number of Nb is 92.9 and the mass
number of Ta is 180.9, E1/E2 is preferably 0.15 or more and 1.54 or
less, more preferably 0.26 or more and 1.03 or less.
[0114] In the case where the first element is Y and the second
element is Nb, since the mass number of Y is 88.9 and the mass
number of Nb is 92.9, E1/E2 is preferably 0.29 or more and 2.87 or
less, more preferably 0.48 or more and 1.91 or less.
[0115] In the case where the first element is V and the second
element is Nb, since the mass number of V is 50.9 and the mass
number of Nb is 92.9, E1/E2 is preferably 0.16 or more and 1.64 or
less, more preferably 0.27 or more and 1.10 or less.
[0116] In the case where the first element is Ti and the second
element is Zr, since the mass number of Ti is 47.9 and the mass
number of Zr is 91.2, E1/E2 is preferably 0.16 or more and 1.58 or
less, more preferably 0.26 or more and 1.05 or less.
[0117] In the case where the first element is Zr and the second
element is Ta, since the mass number of Zr is 91.2 and the mass
number of Ta is 180.9, E1/E2 is preferably 0.15 or more and 1.51 or
less, more preferably 0.25 or more and 1.01 or less.
[0118] In the case where the first element is Zr and the second
element is V, since the mass number of Zr is 91.2 and the mass
number of V is 50.9, E1/E2 is preferably 0.54 or more and 5.38 or
less, more preferably 0.90 or more and 3.58 or less.
[0119] Also in the case of a combination other than the
above-mentioned combinations, E1/E2 can be calculated in the same
manner as described above.
[0120] Further, the presence of the high Si concentration region 4
can also be determined by, for example, a mapping analysis by
energy dispersive X-ray spectrometry (EDX).
[0121] The content E1 of the first element and the content E2 of
the second element are as described above, respectively, however,
the sum of the contents of these elements is preferably 0.05% by
mass or more and 0.6% by mass or less, more preferably 0.10% by
mass or more and 0.48% by mass or less, further more preferably
0.12% by mass or more and 0.24% by mass or less. By setting the sum
of the content of the first element and the content of the second
element within the above range, the densification of a sintered
body to be produced becomes necessary and sufficient.
[0122] When the ratio of the sum of the content of the first
element and the content of the second element to the content of Si
is represented by (E1+E2)/Si, (E1+E2)/Si is preferably 0.1 or more
and 0.7 or less, more preferably 0.15 or more and 0.6 or less,
further more preferably 0.2 or more and 0.5 or less in terms of
mass ratio. By setting the ratio (E1+E2)/Si within the above range,
a decrease in the toughness or the like when Si is added is
sufficiently compensated by the addition of the first element and
the second element. As a result, a metal powder capable of
producing a sintered body which has excellent mechanical properties
such as toughness in spite of having a high density and also has
excellent corrosion resistance attributed to Si is obtained. In
addition, in the particle 1, necessary and sufficient accumulation
of silicon oxide occurs by using the carbide or the like of the
first element and the carbide or the like of the second element as
nuclei, and in the case where an element such as Cr or Ni is
contained in the particle 1 other than Fe, an oxidation reaction of
such an element is easily suppressed. Therefore, also from this
viewpoint, the sinterability of the particle 1 is enhanced, and
thus, a sintered body having a higher density, excellent mechanical
properties, and excellent corrosion resistance can be obtained.
[0123] With respect to the positional relationship between the
carbide or the like of the first element or the carbide or the like
of the second element and silicon oxide, it is not always necessary
for the carbide or the like to be located at the center of silicon
oxide, and for example, these components may have a positional
relationship such that silicon oxide is accumulated inside the
carbide or the like.
[0124] Further, when the ratio of the sum of the content of the
first element and the content of the second element to the content
of C is represented by (E1+E2)/C, (E1+E2)/C is preferably 1 or more
and 16 or less, more preferably 2 or more and 13 or less, further
more preferably 3 or more and 10 or less. By setting the ratio
(E1+E2)/C within the above range, an increase in the hardness and
the suppression of a decrease in the toughness when C is added, and
an increase in the density brought about by the addition of the
first element and the second element can be achieved. As a result,
the particle 1 capable of producing a sintered body which has
excellent mechanical properties such as tensile strength and
toughness is obtained.
Another Element
[0125] The particle 1 may contain, other than the above-mentioned
elements, at least one element of Mo, Pb, S, and Al as needed.
These elements may be inevitably contained in some cases.
[0126] Mo is an element which enhances the corrosion resistance of
a sintered body to be produced.
[0127] The content of Mo in the particle 1 is not particularly
limited, but is preferably 0.2% by mass or more and 0.8% by mass or
less, more preferably 0.3% by mass or more and 0.6% by mass or
less. By setting the content of Mo within the above range, the
corrosion resistance of a sintered body to be produced can be
further enhanced without causing a large decrease in the density of
the sintered body.
[0128] Pb is an element which enhances the machinability of a
sintered body to be produced.
[0129] The content of Pb in the particle 1 is preferably 0.03% by
mass or more and 0.5% by mass or less, more preferably 0.05% by
mass or more and 0.3% by mass or less. By setting the content of Pb
within the above range, the machinability of a sintered body to be
produced can be further enhanced.
[0130] S is an element which enhances the machinability of a
sintered body to be produced.
[0131] The content of S in the particle 1 is not particularly
limited, but is preferably 0.5% by mass or less, more preferably
0.01% by mass or more and 0.3% by mass or less. By setting the
content of S within the above range, the machinability of a
sintered body to be produced can be further enhanced without
causing a large decrease in the density of the sintered body.
[0132] Al is an element which enhances the oxidation resistance of
a sintered body to be produced.
[0133] The content of Al in the particle 1 is not particularly
limited, but is preferably 0.5% by mass or less, more preferably
0.05% by mass or more and 0.3% by mass or less. By setting the
content of Al within the above range, the oxidation resistance of a
sintered body to be produced can be further enhanced without
causing a large decrease in the density of the sintered body.
[0134] To the particle 1, B, Se, Te, Pd, W, Co, N, Cu, or the like
may be added other than the above-mentioned elements. At this time,
the contents of these elements are not particularly limited, but
the content of each of these elements is preferably less than 0.1%
by mass, and also the total content of these elements is preferably
less than 0.2% by mass. These elements may be inevitably contained
in some cases.
[0135] The particle 1 may contain impurities. Examples of the
impurities include all elements other than the above-mentioned
elements, and specific examples thereof include Li, Be, Na, Mg, P,
K, Ca, Sc, Zn, Ga, Ge, Ag, In, Sn, Sb, Os, Ir, Pt, Au, and Bi. The
incorporation amounts of these impurity elements are preferably set
such that the content of each of the impurity elements is less than
the content of each of Fe, Cr, Si, the first element, and the
second element. Further, the incorporation amounts of these
impurity elements are preferably set such that the content of each
of the impurity elements is less than 0.03% by mass, more
preferably less than 0.02% by mass. Further, the total content of
these impurity elements is set to preferably less than 0.3% by
mass, more preferably less than 0.2% by mass. These elements do not
inhibit the effect as described above as long as the contents
thereof are within the above range, and therefore may be
intentionally added to the metal powder.
[0136] Meanwhile, O (oxygen) may also be intentionally added to or
inevitably mixed in the metal powder, however, the amount thereof
is preferably about 0.8% by mass or less, more preferably about
0.5% by mass or less. By controlling the amount of oxygen in the
particle 1 within the above range, the sinterability is enhanced,
and thus, a sintered body having a high density and excellent
mechanical properties is obtained. Incidentally, the lower limit
thereof is not particularly set, but is preferably 0.03% by mass or
more from the viewpoint of ease of mass production or the like.
[0137] Fe is a component (principal component) whose content is the
highest in the alloy constituting the metal powder for powder
metallurgy according to the invention and has a great influence on
the properties of the sintered body. The content of Fe is not
particularly limited, but is preferably 50% by mass or more.
[0138] The compositional ratio of the particle 1 can be determined
by, for example, Iron and steel--Atomic absorption spectrometric
method specified in JIS G 1257 (2000), Iron and steel--ICP atomic
emission spectrometric method specified in JIS G 1258 (2007), Iron
and steel--Method for spark discharge atomic emission spectrometric
analysis specified in JIS G 1253 (2002), Iron and steel--Method for
X-ray fluorescence spectrometric analysis specified in JIS G 1256
(1997), gravimetric, titrimetric, and absorption spectrometric
methods specified in JIS G 1211 to G 1237, or the like.
Specifically, for example, an optical emission spectrometer for
solids (spark optical emission spectrometer, model: SPECTROLAB,
type: LAVMB08A) manufactured by SPECTRO Analytical Instruments GmbH
or an ICP device (model: CIROS-120) manufactured by Rigaku
Corporation can be used.
[0139] Incidentally, the methods specified in JIS G 1211 to G 1237
are as follows.
[0140] JIS G 1211 (2011): Iron and steel--Methods for determination
of carbon content
[0141] JIS G 1212 (1997): Iron and steel--Methods for determination
of silicon content
[0142] JIS G 1213 (2001): Iron and steel--Methods for determination
of manganese content
[0143] JIS G 1214 (1998): Iron and steel--Methods for determination
of phosphorus content
[0144] JIS G 1215 (2010): Iron and steel--Methods for determination
of sulfur content
[0145] JIS G 1216 (1997): Iron and steel--Methods for determination
of nickel content
[0146] JIS G 1217 (2005): Iron and steel--Methods for determination
of chromium content
[0147] JIS G 1218 (1999): Iron and steel--Methods for determination
of molybdenum content
[0148] JIS G 1219 (1997): Iron and steel--Methods for determination
of copper content
[0149] JIS G 1220 (1994): Iron and steel--Methods for determination
of tungsten content
[0150] JIS G 1221 (1998): Iron and steel--Methods for determination
of vanadium content
[0151] JIS G 1222 (1999): Iron and steel--Methods for determination
of cobalt content
[0152] JIS G 1223 (1997): Iron and steel--Methods for determination
of titanium content
[0153] JIS G 1224 (2001): Iron and steel--Methods for determination
of aluminum content
[0154] JIS G 1225 (2006): Iron and steel--Methods for determination
of arsenic content
[0155] JIS G 1226 (1994): Iron and steel--Methods for determination
of tin content
[0156] JIS G 1227 (1999): Iron and steel--Methods for determination
of boron content
[0157] JIS G 1228 (2006): Iron and steel--Methods for determination
of nitrogen content
[0158] JIS G 1229 (1994): Steel--Methods for determination of lead
content
[0159] JIS G 1232 (1980): Methods for determination of zirconium in
steel
[0160] JIS G 1233 (1994): Steel--Method for determination of
selenium content
[0161] JIS G 1234 (1981): Methods for determination of tellurium in
steel
[0162] JIS G 1235 (1981): Methods for determination of antimony in
iron and steel
[0163] JIS G 1236 (1992): Method for determination of tantalum in
steel
[0164] JIS G 1237 (1997): Iron and steel--Methods for determination
of niobium content
[0165] Further, when C (carbon) and S (sulfur) are determined,
particularly, an infrared absorption method after combustion in a
current of oxygen (after combustion in a high-frequency induction
heating furnace) specified in JIS G 1211 (2011) is also used.
Specifically, a carbon-sulfur analyzer, CS-200 manufactured by LECO
Corporation can be used.
[0166] Further, when N (nitrogen) and O (oxygen) are determined,
particularly, a method for determination of nitrogen content in
iron and steel specified in JIS G 1228 (2006) and a method for
determination of oxygen content in metallic materials specified in
JIS Z 2613 (2006) are also used. Specifically, an oxygen-nitrogen
analyzer, TC-300/EF-300 manufactured by LECO Corporation can be
used.
[0167] The particle 1 as described above is preferably contained in
the metal powder for powder metallurgy as much as possible, and
specifically, the particle 1 is contained in the metal powder for
powder metallurgy in an amount of preferably 50% by number or more,
more preferably 60% by number or more. According to such a metal
powder for powder metallurgy, the effect as described above is more
reliably exhibited, and a sintered body having a high density and
excellent mechanical properties can be more reliably produced.
[0168] The average particle diameter of the metal powder for powder
metallurgy according to the invention is preferably 0.5 .mu.m or
more and 30 .mu.m or less, more preferably 1 .mu.m or more and 20
.mu.m or less, further more preferably 2 .mu.m or more and 10 .mu.m
or less. By using the metal powder for powder metallurgy having
such a particle diameter, pores remaining in a sintered body are
extremely reduced, and therefore, a sintered body having a
particularly high density and particularly excellent mechanical
properties can be produced.
[0169] The average particle diameter can be obtained as a particle
diameter when the cumulative amount obtained by cumulating the
percentages of the particles from the smaller diameter side reaches
50% in a cumulative particle size distribution on a mass basis
obtained by laser diffractometry.
[0170] If the average particle diameter of the metal powder for
powder metallurgy is less than the above lower limit, the
moldability is deteriorated in the case where the shape is
difficult to mold, and therefore, the sintered density may be
decreased. On the other hand, if the average particle diameter of
the metal powder exceeds the above upper limit, spaces between the
particles become larger during molding, and therefore, the sintered
density may be decreased also in this case.
[0171] The particle size distribution of the metal powder for
powder metallurgy is preferably as narrow as possible.
Specifically, when the average particle diameter of the metal
powder for powder metallurgy is within the above range, the maximum
particle diameter of the metal powder is preferably 200 .mu.m or
less, more preferably 150 .mu.m or less. By controlling the maximum
particle diameter of the metal powder for powder metallurgy within
the above range, the particle size distribution of the metal powder
for powder metallurgy can be made narrower, and thus, the density
of the sintered body can be further increased.
[0172] Here, the "maximum particle diameter" refers to a particle
diameter when the cumulative amount obtained by cumulating the
percentages of the particles from the smaller diameter side reaches
99.9% in a cumulative particle size distribution on amass basis
obtained by laser diffractometry.
[0173] When the minor axis of each particle of the metal powder for
powder metallurgy is represented by S (.mu.m) and the major axis
thereof is represented by L (.mu.m), the average of the aspect
ratio defined by S/L is preferably about 0.4 or more and 1 or less,
more preferably about 0.7 or more and 1 or less. The metal powder
for powder metallurgy having an aspect ratio within this range has
a shape relatively close to a spherical shape, and therefore, the
packing factor when the metal powder is molded is increased. As a
result, the density of the sintered body can be further
increased.
[0174] Here, the "major axis" is the maximum length in the
projected image of the particle, and the "minor axis" is the
maximum length in the direction perpendicular to the major axis.
Incidentally, the average of the aspect ratio can be obtained as
the average of the measured aspect ratios of 100 or more
particles.
[0175] The tap density of the metal powder for powder metallurgy
according to the invention is preferably 3.5 g/cm.sup.3 or more,
more preferably 4 g/cm.sup.3 or more. According to the metal powder
for powder metallurgy having such a high tap density, when a molded
body is obtained, the interparticle packing efficiency is
particularly increased. Therefore, a particularly dense sintered
body can be obtained in the end.
[0176] The specific surface area of the metal powder for powder
metallurgy according to the invention is not particularly limited,
but is preferably 0.1 m.sup.2/g or more, more preferably 0.2
m.sup.2/g or more. According to the metal powder for powder
metallurgy having such a large specific surface area, a surface
activity (surface energy) is increased so that it is possible to
easily sinter the metal powder even if less energy is applied.
Therefore, when a molded body is sintered, a difference in
sintering rate hardly occurs between the inner side and the outer
side of the molded body, and thus, the decrease in the sintered
density due to the pores remaining inside the molded body can be
suppressed.
Method for Producing Sintered Body
[0177] Next, a method for producing a sintered body using such a
metal powder for powder metallurgy according to the invention will
be described.
[0178] The method for producing a sintered body includes (A) a
composition preparation step in which a composition for producing a
sintered body is prepared, (B) a molding step in which a molded
body is produced, (C) a degreasing step in which a degreasing
treatment is performed, and (D) a firing step in which firing is
performed. Hereinafter, the respective steps will be described
sequentially.
(A) Composition Preparation Step
[0179] First, the metal powder for powder metallurgy according to
the invention and a binder are prepared, and these materials are
kneaded using a kneader, whereby a kneaded material (composition)
is obtained.
[0180] In this kneaded material (an embodiment of the compound
according to the invention), the metal powder for powder metallurgy
is uniformly dispersed.
[0181] The metal powder for powder metallurgy according to the
invention is produced by, for example, any of a variety of
powdering methods such as an atomization method (such as a water
atomization method, a gas atomization method, or a spinning water
atomization method), a reducing method, a carbonyl method, and a
pulverization method.
[0182] Among these, the metal powder for powder metallurgy
according to the invention is preferably a metal powder produced by
an atomization method, more preferably a metal powder produced by a
water atomization method or a spinning water atomization method.
The atomization method is a method in which a molten metal (metal
melt) is caused to collide with a fluid (liquid or gas) sprayed at
a high speed to atomize the metal melt into a fine powder and also
to cool the fine powder, whereby a metal powder is produced. By
producing the metal powder for powder metallurgy through such an
atomization method, an extremely fine powder can be efficiently
produced. Further, the shape of the particle of the obtained powder
is closer to a spherical shape by the action of surface tension.
Due to this, when the metal powder is molded, a molded body having
a high packing factor is obtained. That is, a powder capable of
producing a sintered body having a high density can be obtained. In
addition, the cooling rate of the metal melt is very high, and
therefore, the particle 1 in which the sizes of the Fe-based alloy
crystals 2 are uniform can be obtained.
[0183] In the case where a water atomization method is used as the
atomization method, the pressure of water (hereinafter referred to
as "atomization water") to be sprayed to the molten metal is not
particularly limited, but is set to preferably about 75 MPa or more
and 120 MPa or less (750 kgf/cm.sup.2 or more and 1200 kgf/cm.sup.2
or less), more preferably about 90 MPa or more and 120 MPa or less
(900 kgf/cm.sup.2 or more and 1200 kgf/cm.sup.2 or less).
[0184] The temperature of the atomization water is also not
particularly limited, but is preferably set to about 1.degree. C.
or higher and 20.degree. C. or lower.
[0185] The atomization water is often sprayed in a cone shape such
that it has a vertex on the falling path of the metal melt and the
outer diameter gradually decreases downward. In this case, the
vertex angle .theta. of the cone formed by the atomization water is
preferably about 10.degree. or more and 40.degree. or less, more
preferably about 15.degree. or more and 35.degree. or less.
According to this, a metal powder for powder metallurgy having a
composition as described above can be reliably produced.
[0186] Further, by using a water atomization method (particularly,
a spinning water atomization method), the metal melt can be cooled
particularly quickly. Due to this, a powder having high quality can
be obtained in a wide alloy composition range.
[0187] The cooling rate when cooling the metal melt in the
atomization method is preferably 1.times.10.sup.4.degree. C./s or
more, more preferably 1.times.10.sup.5.degree. C./s or more. By the
quick cooling in this manner, a homogeneous metal powder for powder
metallurgy can be obtained. As a result, a sintered body having
high quality can be obtained.
[0188] The thus obtained metal powder for powder metallurgy may be
classified as needed. Examples of the classification method include
dry classification such as sieving classification, inertial
classification, and centrifugal classification, and wet
classification such as sedimentation classification.
[0189] Examples of the binder include polyolefins such as
polyethylene, polypropylene, and ethylene-vinyl acetate copolymers,
acrylic resins such as polymethyl methacrylate and polybutyl
methacrylate, styrenic resins such as polystyrene, polyesters such
as polyvinyl chloride, polyvinylidene chloride, polyamide,
polyethylene terephthalate, and polybutylene terephthalate, various
resins such as polyether, polyvinyl alcohol, polyvinylpyrrolidone,
and copolymers thereof, and various organic binders such as various
waxes, paraffins, higher fatty acids (such as stearic acid), higher
alcohols, higher fatty acid esters, and higher fatty acid amides.
These can be used alone or by mixing two or more types thereof.
[0190] The content of the binder is preferably about 2% by mass or
more and 20% by mass or less, more preferably about 5% by mass or
more and 10% by mass or less with respect to the total amount of
the kneaded material. By setting the content of the binder within
the above range, a molded body can be formed with good moldability,
and also the density is increased, whereby the stability of the
shape of the molded body and the like can be particularly enhanced.
Further, according to this, a difference in size between the molded
body and the degreased body, that is, so-called a shrinkage ratio
is optimized, whereby a decrease in the dimensional accuracy of the
finally obtained sintered body can be prevented. That is, a
sintered body having a high density and high dimensional accuracy
can be obtained.
[0191] In the kneaded material, a plasticizer may be added as
needed. Examples of the plasticizer include phthalate esters (such
as DOP, DEP, and DBP), adipate esters, trimellitate esters, and
sebacate esters. These can be used alone or by mixing two or more
types thereof.
[0192] Further, in the kneaded material, other than the metal
powder for powder metallurgy, the binder, and the plasticizer, for
example, any of a variety of additives such as a lubricant, an
antioxidant, a degreasing accelerator, and a surfactant can be
added as needed.
[0193] The kneading conditions vary depending on the respective
conditions such as the metal composition or the particle diameter
of the metal powder for powder metallurgy to be used, the
composition of the binder, and the blending amount thereof.
However, for example, the kneading temperature can be set to about
50.degree. C. or higher and 200.degree. C. or lower, and the
kneading time can be set to about 15 minutes or more and 210
minutes or less.
[0194] Further, the kneaded material is formed into a pellet (small
particle) as needed. The particle diameter of the pellet is set to,
for example, about 1 mm or more and 15 mm or less.
[0195] Incidentally, depending on the molding method described
below, in place of the kneaded material, a granulated powder may be
produced. The kneaded material, the granulated powder, and the like
are examples of the composition to be subjected to the molding step
described below.
[0196] The embodiment of the granulated powder according to the
invention is directed to a granulated powder obtained by binding a
plurality of metal particles to one another with a binder by
subjecting the metal powder for powder metallurgy according to the
invention to a granulation treatment.
[0197] Examples of the binder to be used for producing the
granulated powder include polyolefins such as polyethylene,
polypropylene, and ethylene-vinyl acetate copolymers, acrylic
resins such as polymethyl methacrylate and polybutyl methacrylate,
styrenic resins such as polystyrene, polyesters such as polyvinyl
chloride, polyvinylidene chloride, polyamide, polyethylene
terephthalate, and polybutylene terephthalate, various resins such
as polyether, polyvinyl alcohol, polyvinylpyrrolidone, and
copolymers thereof, and various organic binders such as various
waxes, paraffins, higher fatty acids (such as stearic acid), higher
alcohols, higher fatty acid esters, and higher fatty acid amides.
These can be used alone or by mixing two or more types thereof.
[0198] Among these, as the binder, a binder containing a polyvinyl
alcohol or polyvinylpyrrolidone is preferred. These binder
components have a high binding ability, and therefore can
efficiently form the granulated powder even in a relatively small
amount. Further, the thermal decomposability thereof is also high,
and therefore, the binder can be reliably decomposed and removed in
a short time during degreasing and firing.
[0199] The content of the binder is preferably about 0.2% by mass
or more and 10% by mass or less, more preferably about 0.3% by mass
or more and 5% by mass or less, further more preferably about 0.3%
by mass or more and 2% by mass or less with respect to the total
amount of the granulated powder. By setting the content of the
binder within the above range, the granulated powder can be
efficiently formed while preventing significantly large particles
from being formed or the metal particles which are not granulated
from remaining in a large amount. Further, since the moldability is
improved, the stability of the shape of the molded body and the
like can be particularly enhanced. Further, by setting the content
of the binder within the above range, a difference in size between
the molded body and the degreased body, that is, so-called a
shrinkage ratio is optimized, whereby a decrease in the dimensional
accuracy of the finally obtained sintered body can be
prevented.
[0200] Further, in the granulated powder, any of a variety of
additives such as a plasticizer, a lubricant, an antioxidant, a
degreasing accelerator, and a surfactant may be added as
needed.
[0201] Examples of the granulation treatment include a spray drying
method, a tumbling granulation method, a fluidized bed granulation
method, and a tumbling fluidized bed granulation method.
[0202] In the granulation treatment, a solvent which dissolves the
binder is used as needed. Examples of the solvent include inorganic
solvents such as water and carbon tetrachloride, and organic
solvents such as ketone-based solvents, alcohol-based solvents,
ether-based solvents, cellosolve-based solvents, aliphatic
hydrocarbon-based solvents, aromatic hydrocarbon-based solvents,
aromatic heterocyclic compound-based solvents, amide-based
solvents, halogen compound-based solvents, ester-based solvents,
amine-based solvents, nitrile-based solvents, nitro-based solvents,
and aldehyde-based solvents, and one type or a mixture of two or
more types selected from these solvents is used.
[0203] The average particle diameter of the granulated powder is
not particularly limited, but is preferably about 10 .mu.m or more
and 200 .mu.m or less, more preferably about 20 .mu.m or more and
100 .mu.m or less, further more preferably about 25 .mu.m or more
and 60 .mu.m or less. The granulated powder having such a particle
diameter has favorable fluidity, and can more faithfully reflect
the shape of a molding die.
[0204] The average particle diameter can be obtained as a particle
diameter when the cumulative amount obtained by cumulating the
percentages of the particles from the smaller diameter side reaches
50% in a cumulative particle size distribution on amass basis
obtained by laser diffractometry.
(B) Molding Step
[0205] Subsequently, the kneaded material or the granulated powder
is molded, whereby a molded body having the same shape as that of a
target sintered body is produced.
[0206] The method for producing a molded body (molding method) is
not particularly limited, and for example, any of a variety of
molding methods such as a powder compacting (compression molding)
method, a metal injection molding (MIM) method, and an extrusion
molding method can be used.
[0207] The molding conditions in the case of a powder compacting
method among these methods are preferably such that the molding
pressure is about 200 MPa or more and 1000 MPa or less (2
t/cm.sup.2 or more and 10 t/cm.sup.2 or less), which vary depending
on the respective conditions such as the composition and the
particle diameter of the metal powder for powder metallurgy to be
used, the composition of the binder, and the blending amount
thereof.
[0208] The molding conditions in the case of a metal injection
molding method are preferably such that the material temperature is
about 80.degree. C. or higher and 210.degree. C. or lower, and the
injection pressure is about 50 MPa or more and 500 MPa or less (0.5
t/cm.sup.2 or more and 5 t/cm.sup.2 or less), which vary depending
on the respective conditions.
[0209] The molding conditions in the case of an extrusion molding
method are preferably such that the material temperature is about
80.degree. C. or higher and 210.degree. C. or lower, and the
extrusion pressure is about 50 MPa or more and 500 MPa or less (0.5
t/cm.sup.2 or more and 5 t/cm.sup.2 or less), which vary depending
on the respective conditions.
[0210] The thus obtained molded body is in a state where the binder
is uniformly distributed in spaces between the particles of the
metal powder.
[0211] The shape and size of the molded body to be produced are
determined in anticipation of shrinkage of the molded body in the
subsequent degreasing step and firing step.
(C) Degreasing Step
[0212] Subsequently, the thus obtained molded body is subjected to
a degreasing treatment (binder removal treatment), whereby a
degreased body is obtained.
[0213] Specifically, the binder is decomposed by heating the molded
body, whereby the binder is removed from the molded body. In this
manner, the degreasing treatment is performed.
[0214] Examples of the degreasing treatment include a method of
heating the molded body and a method of exposing the molded body to
a gas capable of decomposing the binder.
[0215] In the case of using a method of heating the molded body,
the conditions for heating the molded body are preferably such that
the temperature is about 100.degree. C. or higher and 750.degree.
C. or lower and the time is about 0.1 hours or more and 20 hours or
less, and more preferably such that the temperature is about
150.degree. C. or higher and 600.degree. C. or lower and the time
is about 0.5 hours or more and 15 hours or less, which slightly
vary depending on the composition and the blending amount of the
binder. According to this, the degreasing of the molded body can be
necessarily and sufficiently performed without sintering the molded
body. As a result, it is possible to reliably prevent the binder
component from remaining inside the degreased body in a large
amount.
[0216] The atmosphere when the molded body is heated is not
particularly limited, and an atmosphere of a reducing gas such as
hydrogen, an atmosphere of an inert gas such as nitrogen or argon,
an atmosphere of an oxidative gas such as air, a reduced pressure
atmosphere obtained by reducing the pressure of such an atmosphere,
or the like can be used.
[0217] Examples of the gas capable of decomposing the binder
include ozone gas.
[0218] Incidentally, by dividing this degreasing step into a
plurality of steps in which the degreasing conditions are
different, and performing the plurality of steps, the binder in the
molded body can be more rapidly decomposed and removed so that the
binder does not remain in the molded body.
[0219] Further, according to need, the degreased body may be
subjected to a machining process such as grinding, polishing, or
cutting. The degreased body has a relatively low hardness and
relatively high plasticity, and therefore, the machining process
can be easily performed while preventing the degreased body from
losing its shape. According to such a machining process, a sintered
body having high dimensional accuracy can be easily obtained in the
end.
(D) Firing Step
[0220] The degreased body obtained in the above step (C) is fired
in a firing furnace, whereby a sintered body is obtained.
[0221] By this firing, in the metal powder for powder metallurgy,
diffusion occurs at the boundary surface between the particles,
resulting in sintering. At this time, by the mechanism as described
above, the degreased body is rapidly sintered. As a result, a
sintered body which is dense and has a high density on the whole is
obtained.
[0222] The firing temperature varies depending on the composition,
the particle diameter, and the like of the metal powder for powder
metallurgy used in the production of the molded body and the
degreased body, but is set to, for example, about 980.degree. C. or
higher and 1330.degree. C. or lower, and preferably set to about
1050.degree. C. or higher and 1260.degree. C. or lower.
[0223] Further, the firing time is set to 0.2 hours or more and 7
hours or less, but is preferably set to about 1 hour or more and 6
hours or less.
[0224] In the firing step, the firing temperature or the
below-described firing atmosphere may be changed in the middle of
the step.
[0225] By setting the firing conditions within such a range, it is
possible to sufficiently sinter the entire degreased body while
preventing the sintering from proceeding excessively to cause
oversintering and increase the size of the crystal structure. As a
result, a sintered body having a high density and particularly
excellent mechanical properties can be obtained.
[0226] Further, since the firing temperature is a relatively low
temperature, it is easy to control the heating temperature in the
firing furnace to be a fixed temperature, and therefore, it is also
easy to maintain the temperature of the degreased body at a fixed
temperature. As a result, a more homogeneous sintered body can be
produced.
[0227] Further, since the firing temperature as described above is
a temperature which can be sufficiently realized using a common
firing furnace, and therefore, an inexpensive firing furnace can be
used, and also the running cost can be kept low. In other words, in
the case where the temperature exceeds the above-mentioned firing
temperature, it is necessary to employ an expensive firing furnace
using a special heat resistant material, and also the running cost
may be increased.
[0228] The atmosphere when performing firing is not particularly
limited, however, in consideration of prevention of significant
oxidation of the metal powder, an atmosphere of a reducing gas such
as hydrogen, an atmosphere of an inert gas such as argon, a reduced
pressure atmosphere obtained by reducing the pressure of such an
atmosphere, or the like is preferably used.
[0229] The thus obtained sintered body has a high density and
excellent mechanical properties. That is, a sintered body produced
by molding a composition containing the metal powder for powder
metallurgy according to the invention and a binder, followed by
degreasing and sintering has a higher relative density than a
sintered body obtained by sintering a metal powder in the related
art. Therefore, according to the invention, a sintered body having
a high density which could not be obtained unless an additional
treatment such as an HIP treatment is performed can be realized
without performing an additional treatment.
[0230] Specifically, according to the invention, for example, the
relative density can be expected to be increased by 2% or more as
compared with the related art, which slightly varies depending on
the composition of the metal powder for powder metallurgy.
[0231] As a result, the relative density of the obtained sintered
body can be expected to be, for example, 97% or more (preferably
98% or more, more preferably 98.5% or more). The sintered body
having a relative density within such a range has excellent
mechanical properties comparable to those of ingot materials
although it has a shape as close as possible to a desired shape by
using a powder metallurgy technique, and therefore, the sintered
body can be applied to a variety of machine parts, structural
parts, and the like with virtually no post-processing.
[0232] Further, the tensile strength and the 0.2% proof stress of a
sintered body produced by molding a composition containing the
metal powder for powder metallurgy according to the invention and a
binder, followed by degreasing and sintering are higher than those
of a sintered body obtained by performing sintering in the same
manner using a metal powder in the related art. This is considered
to be because by optimizing the alloy composition and the crystal
structure of the particle, the sinterability of the metal powder is
enhanced, and thus, the mechanical properties of a sintered body to
be produced using the metal powder are enhanced.
[0233] Further, the sintered body produced as described above has a
high surface hardness. Specifically, as one example, the Vickers
hardness of the surface of the sintered body is expected to be 570
or more and 1200 or less, which slightly varies depending on the
composition of the metal powder for powder metallurgy, and further
is expected to be preferably 600 or more and 1000 or less. The
sintered body having such a hardness has particularly high
durability.
[0234] The sintered body has a sufficiently high density and
excellent mechanical properties even without performing an
additional treatment, however, in order to further increase the
density and enhance the mechanical properties, a variety of
additional treatments may be performed.
[0235] As the additional treatment, for example, an additional
treatment of increasing the density such as the HIP treatment
described above may be performed, and also a variety of quenching
treatments, a variety of sub-zero treatments, a variety of
tempering treatments, and the like may be performed. These
additional treatments may be performed alone or two or more
treatments thereof may be performed in combination.
[0236] Among these treatments, in the quenching treatment, after
the sintered body is heated to about 980.degree. C. or higher and
1200.degree. C. or lower for about 0.2 hours or more and 3 hours or
less, a rapid cooling treatment is performed. By doing this, an
austenite crystal structure can be transformed into a martensite
crystal structure, which varies also depending on the composition
of the metal powder for powder metallurgy. Accordingly, this
treatment is preferably used, for example, when a sintered body
containing a martensite crystal structure is produced.
[0237] For the rapid cooling in the quenching treatment, water
cooling, oil cooling, or the like is used.
[0238] Further, the sub-zero treatment is a treatment in which an
austenite crystal structure which is not transformed into a
martensite crystal structure by the quenching treatment and is
retained is transformed into martensite by cooling. The retained
austenite crystal structure is often transformed into martensite
over time, however, at this time, the volume of the sintered body
changes. Therefore, a problem occurs that the size of the sintered
body changes over time. Therefore, by performing the sub-zero
treatment after the quenching treatment, the retained austenite
crystal structure can be transformed into martensite partly
forcibly, and thus, the occurrence of the problem that the size
changes over time can be prevented.
[0239] In the cooling of the sintered body, for example, dry ice,
carbon dioxide gas, liquid nitrogen, or the like is used.
[0240] In the sub-zero treatment, it is preferred that the
temperature is about 0.degree. C. or lower and the time is about
0.2 hours or more and 3 hours or less.
[0241] Further, the tempering treatment is a treatment in which the
sintered body having undergone the quenching treatment is heated
again at a lower temperature than in the quenching treatment. By
doing this, toughness can be provided while decreasing the hardness
of the sintered body.
[0242] In the tempering treatment, it is preferred that the
temperature is about 100.degree. C. or higher and 200.degree. C. or
lower and the time is about 0.3 hours or more and 5 hours or
less.
[0243] In the firing step and a variety of additional treatments
described above, a light element in the metal powder (in the
sintered body) is volatilized, and the composition of the finally
obtained sintered body slightly changes from the composition of the
metal powder in some cases.
[0244] For example, the content of C in the final sintered body may
change within the range of 5% or more and 100% or less (preferably
within the range of 30% or more and 100% or less) of the content of
C in the metal powder for powder metallurgy, which varies depending
on the conditions for the step or the conditions for the
treatment.
[0245] Also the content of O in the final sintered body may change
within the range of 1% or more and 50% or less (preferably within
the range of 3% or more and 50% or less) of the content of O in the
metal powder for powder metallurgy, which varies depending on the
conditions for the step or the conditions for the treatment.
[0246] On the other hand, as described above, the produced sintered
body may be subjected to an HIP treatment as part of the additional
treatments to be performed as needed, however, even if the HIP
treatment is performed, a sufficient effect is not exhibited in
many cases. In the HIP treatment, the density of the sintered body
can be further increased, however, in the first place, the density
of the sintered body obtained according to the invention has
already been sufficiently increased at the end of the firing step.
Therefore, even if the HIP treatment is further performed,
densification hardly proceeds any further.
[0247] In addition, in the HIP treatment, it is necessary to apply
pressure to a material to be treated through a pressure medium, and
therefore, the material to be treated may be contaminated, the
composition or the physical properties of the material to be
treated may unintentionally change accompanying the contamination,
or the color of the material to be treated may change accompanying
the contamination. Further, by the application of pressure,
residual stress is generated or increased in the material to be
treated, and a problem such as a change in the shape or a decrease
in the dimensional accuracy may occur as the residual stress is
released over time.
[0248] On the other hand, according to the invention, a sintered
body having a sufficiently high density can be produced without
performing such an HIP treatment, and therefore, a sintered body
having an increased density and also an increased strength can be
obtained in the same manner as in the case of performing an HIP
treatment. Such a sintered body is less contaminated and
discolored, and also an unintended change in the composition or
physical properties, or the like occurs less, and also a problem
such as a change in the shape or a decrease in the dimensional
accuracy occurs less. Therefore, according to the invention, a
sintered body having high mechanical strength and dimensional
accuracy, and excellent durability can be efficiently produced.
[0249] Further, the sintered body produced according to the
invention requires almost no additional treatments for enhancing
the mechanical properties, and therefore, the composition and the
crystal structure tend to become uniform in the entire sintered
body. Due to this, the sintered body has high structural anisotropy
and therefore has excellent durability against a load from every
direction regardless of its shape.
[0250] Incidentally, it is confirmed that in the thus produced
sintered body, the porosity near the surface thereof is often
relatively lower than inside the sintered body. The reason therefor
is not clear, however, one of the reasons is that by the addition
of the first element and the second element, the sintering reaction
more easily proceeds near the surface of the molded body than
inside the molded body.
[0251] Specifically, when the porosity near the surface of the
sintered body is represented by A1 and the porosity inside the
sintered body is represented by A2, A2-A1 is preferably 0.1% or
more and 3% or less, more preferably 0.2% or more and 2% or less.
The sintered body showing the value of A2-A1 within the above range
not only has necessary and sufficient mechanical strength, but also
can easily flatten the surface. That is, by polishing the surface
of such a sintered body, a surface having high specularity can be
obtained.
[0252] Such a sintered body having high specularity not only has
high mechanical strength, but also has excellent aesthetic
properties. Therefore, such a sintered body is favorably used also
for application requiring excellent aesthetic appearance.
[0253] Incidentally, the porosity A1 near the surface of the
sintered body refers to a porosity in a 25-.mu.m radius region
centered on the position at a depth of 50 .mu.m from the surface of
the cross section of the sintered body. Further, the porosity A2
inside the sintered body refers to a porosity in a 25-pt radius
region centered on the position at a depth of 300 .mu.m from the
surface of the cross section of the sintered body. These porosities
are values obtained by observing the cross section of the sintered
body with a scanning electron microscope and dividing the area of
pores present in the region by the area of the region.
[0254] Hereinabove, the metal powder for powder metallurgy, the
compound, the granulated powder, and the sintered body according to
the invention have been described with reference to preferred
embodiments, however, the invention is not limited thereto.
[0255] Further, the sintered body according to the invention is
used for, for example, parts for transport machinery such as parts
for automobiles, parts for bicycles, parts for railroad cars, parts
for ships, parts for airplanes, and parts for space transport
machinery (such as rockets); parts for electronic devices such as
parts for personal computers and parts for mobile phone terminals;
parts for electrical devices such as refrigerators, washing
machines, and cooling and heating machines; parts for machines such
as machine tools and semiconductor production devices; parts for
plants such as atomic power plants, thermal power plants,
hydroelectric power plants, oil refinery plants, and chemical
complexes; parts for timepieces, metallic tableware, jewels,
ornaments such as frames for glasses, and all other sorts of
structural parts.
EXAMPLES
[0256] Next, Examples of the invention will be described.
1. Production of Sintered Body (Zr--Nb Based)
Sample No. 1
[0257] (1) First, a metal powder having a composition shown in
Table 1 produced by a water atomization method was prepared.
[0258] The composition of the powder shown in Table 1 was
identified and quantitatively determined by an inductively coupled
high-frequency plasma optical emission spectrometry (ICP analysis
method). In the ICP analysis, an ICP device (model: CIROS-120)
manufactured by Rigaku Corporation was used. Further, in the
identification and determination of C, a carbon-sulfur analyzer
(CS-200) manufactured by LECO Corporation was used. Further, in the
identification and determination of O, an oxygen-nitrogen analyzer
(TC-300/EF-300) manufactured by LECO Corporation was used.
[0259] (2) Subsequently, the metal powder and a mixture (organic
binder) of polypropylene and a wax were weighed at a mass ratio of
9:1 and mixed with each other, whereby a mixed starting material
was obtained.
[0260] (3) Subsequently, this mixed starting material was kneaded
using a kneader, whereby a compound was obtained.
[0261] (4) Subsequently, this compound was molded using an
injection molding device under the following molding conditions,
whereby a molded body was produced.
[0262] Molding Conditions
[0263] Material temperature: 150.degree. C.
[0264] Injection pressure: 11 MPa (110 kgf/cm.sup.2)
[0265] (5) Subsequently, the obtained molded body was subjected to
a heat treatment (degreasing treatment) under the following
degreasing conditions, whereby a degreased body was obtained.
[0266] Degreasing Conditions
[0267] Degreasing temperature: 500.degree. C.
[0268] Degreasing time: 1 hour (retention time at the degreasing
temperature)
[0269] Degreasing atmosphere: nitrogen atmosphere
[0270] (6) Subsequently, the obtained degreased body was fired
under the following firing conditions, whereby a sintered body was
obtained. The shape of the sintered body was determined to be a
cylinder with a diameter of 10 mm and a thickness of 5 mm.
[0271] Firing Conditions
[0272] Firing temperature: 1200.degree. C.
[0273] Firing time: 3 hours (retention time at the firing
temperature)
[0274] Firing atmosphere: argon atmosphere
[0275] (7) Subsequently, the obtained sintered body was subjected
to a quenching treatment under the following conditions.
[0276] Quenching Treatment Conditions
[0277] Quenching temperature: 980.degree. C.
[0278] Quenching time: 4 hours
[0279] Quenching atmosphere: argon atmosphere
[0280] Cooling method: water cooling
[0281] (8) Subsequently, the sintered body having undergone the
quenching treatment was subjected to a sub-zero treatment under the
following conditions.
[0282] Sub-Zero Treatment Conditions
[0283] Sub-zero treatment temperature: -196.degree. C.
[0284] Sub-zero treatment time: 2 hours
[0285] (9) Subsequently, the sintered body having undergone the
sub-zero treatment was subjected to a tempering treatment under the
following conditions.
[0286] Tempering Treatment Conditions
[0287] Tempering treatment temperature: 210.degree. C.
[0288] Tempering treatment time: 4 hours
Sample Nos. 2 to 67
[0289] Sintered bodies were obtained in the same manner as the
method for producing the sintered body of sample No. 1 except that
the composition and the like of the metal powder for powder
metallurgy were changed as shown in Table 1 or 2, respectively. The
sintered bodies of sample Nos. 36 and 67 were obtained by
performing an HIP treatment under the following conditions after
firing. Further, the sintered bodies of sample Nos. 28 to 30 and 57
to 59 were obtained by using the metal powder produced by a gas
atomization method, respectively, and indicated by "gas" in the
column of Remarks in Tables 1 and 2.
[0290] HIP Treatment Conditions
[0291] Heating temperature: 1100.degree. C.
[0292] Heating time: 2 hours
[0293] Applied pressure: 100 MPa
TABLE-US-00001 TABLE 1 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (Zr) (Nb) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 1 Example 12.88 0.90 0.73 0.07 0.07 0.10
0.07 <0.01 0.27 remainder 1.00 0.14 0.19 0.16 0.17 No. 2 Example
14.24 0.28 0.58 0.09 0.05 0.12 0.05 <0.01 0.24 remainder 1.80
0.14 0.24 0.50 0.17 No. 3 Example 11.63 1.13 0.78 0.05 0.06 0.07
0.05 <0.01 0.31 remainder 0.83 0.11 0.14 0.10 0.12 No. 4 Example
13.37 0.85 0.64 0.10 0.05 0.08 0.10 <0.01 0.25 remainder 2.00
0.15 0.23 0.18 0.18 No. 5 Example 12.54 0.98 0.75 0.05 0.10 0.11
0.06 <0.01 0.29 remainder 0.50 0.15 0.20 0.15 0.17 No. 6 Example
11.23 0.47 0.52 0.12 0.04 0.12 0.12 <0.01 0.22 remainder 3.00
0.16 0.31 0.34 0.24 No. 7 Example 14.87 0.98 0.69 0.04 0.12 0.09
0.05 <0.01 0.41 remainder 0.33 0.16 0.23 0.16 0.14 No. 8 Example
12.64 0.74 0.77 0.11 0.09 0.08 0.08 <0.01 0.30 remainder 1.22
0.20 0.26 0.27 0.16 No. 9 Example 13.89 0.65 0.51 0.05 0.05 0.11
0.05 <0.01 0.28 remainder 1.00 0.10 0.20 0.15 0.16 No. 10
Example 10.56 0.78 0.32 0.08 0.09 0.18 0.15 <0.01 0.25 remainder
0.89 0.17 0.53 0.22 0.33 No. 11 Example 16.26 1.05 0.62 0.08 0.06
0.05 0.07 <0.01 0.29 remainder 1.33 0.14 0.23 0.13 0.12 No. 12
Example 19.74 0.92 0.88 0.10 0.10 0.04 0.08 <0.01 0.48 remainder
1.00 0.20 0.23 0.22 0.12 No. 13 Example 23.69 0.41 0.44 0.08 0.08
0.07 0.06 <0.01 0.68 remainder 1.00 0.16 0.36 0.39 0.13 No. 14
Example 10.20 0.55 0.65 0.14 0.04 0.09 0.06 <0.01 0.19 remainder
3.50 0.18 0.28 0.33 0.15 No. 15 Example 12.91 0.81 0.68 0.03 0.14
0.07 0.07 <0.01 0.27 remainder 0.21 0.17 0.25 0.21 0.14 No. 16
Example 11.89 0.88 0.75 0.05 0.03 0.09 0.07 <0.01 0.23 remainder
1.67 0.08 0.11 0.09 0.16 No. 17 Example 12.78 0.74 0.61 0.12 0.12
0.11 0.06 <0.01 0.25 remainder 1.00 0.24 0.39 0.32 0.17 No. 18
Example 12.80 0.87 0.75 0.07 0.08 0.01 0.06 <0.01 0.24 remainder
0.88 0.15 0.20 0.17 0.07 gas No. 19 Example 12.80 0.87 0.75 0.07
0.08 0.30 0.05 <0.01 0.24 remainder 0.88 0.15 0.20 0.17 0.35 gas
No. 20 Example 12.80 0.87 0.75 0.07 0.08 1.00 0.60 <0.01 0.24
remainder 0.88 0.15 0.20 0.17 1.60 gas No. 21 Example 12.88 0.90
0.73 0.07 0.07 0.10 0.20 <0.01 0.27 remainder 1.00 0.14 0.19
0.16 0.30 No. 22 Example 12.75 0.93 0.71 0.01 0.07 0.11 0.07
<0.01 0.29 remainder 0.14 0.08 0.11 0.09 0.18 No. 23 Example
12.94 1.02 0.79 0.05 0.01 0.09 0.06 <0.01 0.31 remainder 5.00
0.06 0.08 0.06 0.15 No. 24 Example 11.56 0.63 0.54 0.21 0.07 0.11
0.08 <0.01 0.38 remainder 3.00 0.28 0.52 0.44 0.19 No. 25
Example 14.35 0.47 0.77 0.06 0.19 0.05 0.04 <0.01 0.41 remainder
0.32 0.25 0.32 0.53 0.09 No. 26 Example 12.11 0.51 0.53 0.20 0.17
0.11 0.08 <0.01 0.27 remainder 1.18 0.37 0.70 0.73 0.19 No. 27
Example 12.78 0.78 0.72 0.32 0.41 0.12 0.08 <0.01 0.31 remainder
0.78 0.73 1.01 0.94 0.20 No. 28 Example 13.37 0.85 0.64 0.10 0.05
0.08 0.10 <0.01 0.25 remainder 2.00 0.15 0.23 0.18 0.18 gas No.
29 Example 12.54 0.98 0.75 0.05 0.10 0.11 0.06 <0.01 0.29
remainder 0.50 0.15 0.10 0.15 0.17 gas No. 30 Example 11.23 0.47
0.52 0.12 0.04 0.12 0.12 <0.01 0.22 remainder 3.00 0.16 0.31
0.34 0.24 gas No. 31 Compar- 12.54 0.95 0.82 0.00 0.05 0.12 0.08
<0.01 0.25 remainder 0.00 0.05 0.06 0.05 0.20 ative Example No.
32 Compar- 12.95 0.76 0.78 0.04 0.00 0.08 0.10 <0.01 0.31
remainder -- 0.04 0.05 0.05 0.18 ative Example No. 33 Compar- 13.25
0.45 0.42 0.68 0.05 0.08 0.06 <0.01 0.27 remainder 13.60 0.73
1.74 1.62 0.14 ative Example No. 34 Compar- 13.58 0.58 0.36 0.03
0.62 0.07 0.05 <0.01 0.32 remainder 0.05 0.65 1.81 1.12 0.12
ative Example No. 35 Compar- 13.50 1.00 0.75 0.00 0.00 0.12 0.11
<0.01 0.33 remainder -- 0.00 0.00 0.00 0.23 ative Example No. 36
Compar- 13.50 1.00 0.75 0.00 0.00 0.12 0.11 <0.01 0.33 remainder
-- 0.00 0.00 0.00 0.23 HIP ative Example
TABLE-US-00002 TABLE 2 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (Zr) (Nb) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 37 Example 17.00 1.00 0.80 0.07 0.07
0.10 0.20 <0.01 0.27 remainder 1.00 0.14 0.18 0.14 0.30 No. 38
Example 16.78 0.98 0.58 0.09 0.05 0.12 0.25 <0.01 0.24 remainder
1.80 0.14 0.24 0.14 0.37 No. 39 Example 17.69 1.05 0.78 0.05 0.06
0.07 0.05 <0.01 0.31 remainder 0.83 0.11 0.14 0.10 0.12 No. 40
Example 16.23 1.04 0.52 0.12 0.04 0.09 0.15 <0.01 0.22 remainder
3.00 0.16 0.31 0.15 0.24 No. 41 Example 16.87 1.09 0.69 0.04 0.12
0.09 0.05 <0.01 0.41 remainder 0.33 0.16 0.23 0.15 0.14 No. 42
Example 17.64 0.68 0.77 0.11 0.09 0.08 0.08 <0.01 0.30 remainder
1.22 0.20 0.26 0.29 0.16 No. 43 Example 17.89 0.72 0.51 0.05 0.05
0.11 0.05 <0.01 0.28 remainder 1.00 0.10 0.20 0.14 0.16 No. 44
Example 16.50 1.12 0.32 0.08 0.09 0.18 0.15 <0.01 0.25 remainder
0.89 0.17 0.53 0.15 0.33 No. 45 Example 16.26 1.05 0.62 0.08 0.06
0.05 0.07 <0.01 0.29 remainder 1.33 0.14 0.23 0.13 0.12 No. 46
Example 17.74 0.96 0.88 0.10 0.10 0.04 0.08 <0.01 0.48 remainder
1.00 0.20 0.23 0.21 0.12 No. 47 Example 16.69 0.98 0.44 0.08 0.08
0.07 0.09 <0.01 0.57 remainder 1.00 0.16 0.36 0.16 0.16 No. 48
Example 17.81 0.96 0.75 0.07 0.08 0.01 0.06 <0.01 0.24 remainder
0.88 0.15 0.20 0.16 0.07 No. 49 Example 16.56 0.78 0.84 0.07 0.08
1.00 0.60 <0.01 0.24 remainder 0.88 0.15 0.18 0.19 1.60 No. 50
Example 17.56 0.95 0.81 0.01 0.07 0.12 0.08 <0.01 0.31 remainder
0.14 0.08 0.10 0.08 0.20 No. 51 Example 16.94 1.06 0.89 0.05 0.01
0.10 0.07 <0.01 0.29 remainder 5.00 0.06 0.07 0.06 0.17 No. 52
Example 17.56 0.78 0.54 0.21 0.07 0.11 0.08 <0.01 0.38 remainder
3.00 0.28 0.52 0.36 0.19 No. 53 Example 16.35 0.76 0.77 0.06 0.19
0.05 0.04 <0.01 0.41 remainder 0.32 0.25 0.32 0.33 0.09 No. 54
Example 17.78 0.99 0.72 0.41 0.35 0.13 0.09 <0.01 0.31 remainder
1.17 0.76 1.06 0.77 0.22 No. 55 Example 13.25 0.18 0.79 0.07 0.07
0.15 0.21 <0.01 0.25 remainder 1.00 0.14 0.18 0.78 0.36 No. 56
Example 13.02 0.36 0.81 0.08 0.06 0.08 0.19 <0.01 0.19 remainder
1.33 0.14 0.17 0.39 0.27 No. 57 Example 17.00 1.00 0.80 0.07 0.07
0.10 0.20 <0.01 0.27 remainder 1.00 0.14 1.18 0.14 0.30 gas No.
58 Example 16.78 0.98 0.58 0.09 0.05 0.12 0.25 <0.01 0.24
remainder 1.80 0.14 0.24 0.14 0.37 gas No. 59 Example 17.69 1.05
0.78 0.05 0.06 0.07 0.05 <0.01 0.31 remainder 0.83 0.11 0.14
0.10 0.12 gas No. 60 Compar- 17.54 0.99 0.82 0.00 0.06 0.11 0.09
<0.01 0.29 remainder 0.00 0.06 0.07 0.06 0.20 ative Example No.
61 Compar- 16.95 1.05 0.78 0.07 0.00 0.07 0.12 <0.01 0.32
remainder -- 0.07 0.09 0.07 0.19 ative Example No. 62 Compar- 17.00
1.12 0.42 0.59 0.04 0.06 0.07 <0.01 0.28 remainder 14.75 0.63
1.50 0.56 0.13 ative Example No. 63 Compar- 17.45 1.14 0.36 0.06
0.74 0.07 0.06 <0.01 0.35 remainder 0.08 0.80 2.22 0.70 0.13
ative Example No. 64 Compar- 13.25 0.18 0.79 0.04 0.00 0.15 0.21
<0.01 0.25 remainder -- 0.04 0.05 0.22 0.36 ative Example No. 65
Compar- 13.02 0.36 0.81 0.05 0.00 0.08 0.19 <0.01 0.19 remainder
-- 0.05 0.06 0.14 0.27 ative Example No. 66 Compar- 16.28 1.04 0.25
0.00 0.00 0.31 0.00 <0.01 0.42 remainder -- 0.00 0.00 0.00 0.31
ative Example No. 67 Compar- 16.28 1.04 0.25 0.00 0.00 0.31 0.00
<0.01 0.42 remainder -- 0.00 0.00 0.00 0.31 HIP ative
Example
[0294] In Tables 1 and 2, among the sintered bodies of the
respective sample Nos., those corresponding to the invention are
indicated by "Example", and those not corresponding to the
invention are indicated by "Comparative Example".
[0295] Each sintered body contained very small amounts of
impurities, but the description thereof in Tables 1 and 2 is
omitted.
Sample No. 68
[0296] (1) First, a metal powder having a composition shown in
Table 3 was produced by a water atomization method in the same
manner as in the case of sample No. 1.
[0297] (2) Subsequently, the metal powder was granulated by a spray
drying method. The binder used at this time was polyvinyl alcohol,
which was used in an amount of 1 part by mass with respect to 100
parts by mass of the metal powder. Further, a solvent (ion
exchanged water) was used in an amount of 50 parts by mass with
respect to 1 part by mass of polyvinyl alcohol. In this manner, a
granulated powder having an average particle diameter of 50 .mu.m
was obtained.
[0298] (3) Subsequently, this granulated powder was subjected to
powder compacting under the following molding conditions. In this
molding, a press molding machine was used. The shape of the molded
body to be produced was determined to be a cube with a side length
of 20 mm.
[0299] Molding Conditions
[0300] Material temperature: 90.degree. C.
[0301] Molding pressure: 600 MPa (6 t/cm.sup.2)
[0302] (4) Subsequently, the obtained molded body was subjected to
a heat treatment (degreasing treatment) under the following
degreasing conditions, whereby a degreased body was obtained.
[0303] Degreasing Conditions
[0304] Degreasing temperature: 450.degree. C.
[0305] Degreasing time: 2 hours (retention time at the degreasing
temperature)
[0306] Degreasing atmosphere: nitrogen atmosphere
[0307] (5) Subsequently, the obtained degreased body was fired
under the following firing conditions, whereby a sintered body was
obtained.
[0308] Firing Conditions
[0309] Firing temperature: 1200.degree. C.
[0310] Firing time: 3 hours (retention time at the firing
temperature)
[0311] Firing atmosphere: argon atmosphere
[0312] (6) Subsequently, the obtained sintered body was subjected
to a quenching treatment under the following conditions.
[0313] Quenching Treatment Conditions
[0314] Quenching temperature: 980.degree. C.
[0315] Quenching time: 4 hours
[0316] Quenching atmosphere: argon atmosphere
[0317] Cooling method: water cooling
[0318] (7) Subsequently, the sintered body having undergone the
quenching treatment was subjected to a sub-zero treatment under the
following conditions.
[0319] Sub-Zero Treatment Conditions
[0320] Sub-zero treatment temperature: -196.degree. C.
[0321] Sub-zero treatment time: 2 hours
[0322] (8) Subsequently, the sintered body having undergone the
sub-zero treatment was subjected to a tempering treatment under the
following conditions.
[0323] Tempering Treatment Conditions
[0324] Tempering treatment temperature: 210.degree. C.
[0325] Tempering treatment time: 4 hours
Sample Nos. 69 to 84
[0326] Sintered bodies were obtained in the same manner as in the
case of sample No. 68 except that the composition and the like of
the metal powder for powder metallurgy were changed as shown in
Table 3, respectively. The sintered body of sample No. 84 was
obtained by performing an HIP treatment under the following
conditions after firing.
[0327] HIP Treatment Conditions
[0328] Heating temperature: 1100.degree. C.
[0329] Heating time: 2 hours
[0330] Applied pressure: 100 MPa
TABLE-US-00003 TABLE 3 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (Zr) (Nb) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 68 Example 12.88 0.90 0.73 0.07 0.07
0.10 0.07 <0.01 0.27 remainder 1.00 0.14 0.19 0.16 0.17 Powder
com- pacting No. 69 Example 14.24 0.28 0.58 0.09 0.05 0.12 0.05
<0.01 0.24 remainder 1.80 0.14 0.24 0.50 0.17 Powder com-
pacting No. 70 Example 11.63 1.13 0.78 0.05 0.06 0.07 0.05 <0.01
0.31 remainder 0.83 0.11 0.14 0.10 0.12 Powder com- pacting No. 71
Example 13.37 0.85 0.64 0.10 0.05 0.08 0.10 <0.01 0.25 remainder
2.00 0.15 0.23 0.18 0.18 Powder com- pacting No. 72 Example 12.54
0.98 0.75 0.05 0.10 0.11 0.06 <0.01 0.29 remainder 0.50 0.15
0.20 0.15 0.17 Powder com- pacting No. 73 Example 11.23 0.47 0.52
0.12 0.04 0.12 0.12 <0.01 0.22 remainder 3.00 0.16 0.31 0.34
0.24 Powder com- pacting No. 74 Example 14.87 0.98 0.69 0.04 0.12
0.09 0.05 <0.01 0.41 remainder 0.33 0.16 0.23 0.16 0.14 Powder
com- pacting No. 75 Example 12.64 0.74 0.77 0.11 0.09 0.08 0.08
<0.01 0.30 remainder 1.22 0.20 0.26 0.27 0.16 Powder com-
pacting No. 76 Example 13.89 0.65 0.51 0.05 0.05 0.11 0.05 <0.01
0.28 remainder 1.00 0.10 0.20 0.15 0.16 Powder com- pacting No. 77
Example 10.56 0.78 0.32 0.08 0.09 0.18 0.15 <0.01 0.25 remainder
0.89 0.17 0.53 0.22 0.33 Powder com- pacting No. 78 Example 16.26
1.05 0.62 0.08 0.06 0.05 0.07 <0.01 0.29 remainder 1.33 0.14
0.23 0.13 0.12 Powder com- pacting No. 79 Compar- 12.54 0.95 0.82
0.00 0.05 0.12 0.08 <0.01 0.25 remainder 0.00 0.05 0.06 0.05
0.20 Powder ative com- Example pacting No. 80 Compar- 12.95 0.76
0.78 0.04 0.00 0.08 0.10 <0.01 0.31 remainder -- 0.04 0.05 0.05
0.18 Powder ative com- Example pacting No. 81 Compar- 13.25 0.45
0.42 0.68 0.05 0.08 0.06 <0.01 0.27 remainder 13.60 0.73 1.74
1.62 0.14 Powder ative com- Example pacting No. 82 Compar- 13.58
0.58 0.36 0.03 0.62 0.07 0.05 <0.01 0.32 remainder 0.05 0.65
1.81 1.12 0.12 Powder ative com- Example pacting No. 83 Compar-
13.50 1.00 0.75 0.00 0.00 0.12 0.11 <0.01 0.33 remainder -- 0.00
0.00 0.00 0.23 Powder ative com- Example pacting No. 84 Compar-
13.50 1.00 0.75 0.00 0.00 0.12 0.11 <0.01 0.33 remainder -- 0.00
0.00 0.00 0.23 HIP ative Example
[0331] In Table 3, among the metal powders for powder metallurgy
and the sintered bodies of the respective sample Nos., those
corresponding to the invention are indicated by "Example", and
those not corresponding to the invention are indicated by
"Comparative Example".
[0332] Each sintered body contained very small amounts of
impurities, but the description thereof in Table 3 is omitted.
2. Evaluation of Metal Powder (Zr--Nb Based)
[0333] With respect to the cross sections of the particles of the
metal powders for powder metallurgy of the respective sample Nos.
shown in Tables 1 to 3, the crystal structure was evaluated by
TEM.
[0334] As a result, in all the metal powders for powder metallurgy
corresponding to Example, the average number of the Fe-based alloy
crystals was 1 or more and 5 or less. Specifically, the lowest
average number was 1.2 and the highest average number was 4.6.
[0335] Further, in all the metal powders for powder metallurgy
corresponding to Example, the circle equivalent diameter of the
Fe-based alloy crystal was 1% or more and 100% or less the circle
equivalent diameter of the particle. Specifically, the lowest ratio
of the circle equivalent diameter of the Fe-based alloy crystal to
the circle equivalent diameter of the particle was 2%, and the
highest ratio thereof was 84%.
[0336] On the other hand, in all the metal powders for powder
metallurgy corresponding to Comparative Example, the average number
of the Fe-based alloy crystals was 6 or more. Specifically, the
lowest average number was 8.4 and the highest average number was
256.
[0337] Although not shown in the respective tables, when the same
evaluation as described above was performed also with respect to
metal powders having the same compositions shown in Tables 1 to 3
except that both Mn and Ni were not contained, the average number
of the Fe-based alloy crystals contained in the particle of each of
the metal powders for powder metallurgy corresponding to Example
was 1 or more and 5 or less as having been expected.
3. Evaluation of Sintered Body (Zr--Nb Based)
3.1 Evaluation of Relative Density
[0338] With respect to the sintered bodies of the respective sample
Nos. shown in Tables 1 to 3, the sintered density was measured in
accordance with the method for measuring the density of sintered
metal materials specified in JIS Z 2501 (2000), and also the
relative density of each sintered body was calculated with
reference to the true density of the metal powder for powder
metallurgy used for producing each sintered body.
[0339] The calculation results are shown in Tables 4 to 6.
3.2 Evaluation of Hardness
[0340] With respect to the sintered bodies of the respective sample
Nos. shown in Tables 1 to 3, the Vickers hardness was measured in
accordance with the Vickers hardness test method specified in JIS Z
2244 (2009).
[0341] Then, the measured hardness was evaluated according to the
following evaluation criteria.
Evaluation Criteria for Vickers Hardness
[0342] A: The Vickers hardness is 495 or more.
[0343] F. The Vickers hardness is less than 495.
[0344] The evaluation results are shown in Tables 4 to 6.
3.3 Evaluation of Tensile Strength, 0.2% Proof Stress, and
Elongation
[0345] With respect to the sintered bodies of the respective sample
Nos. shown in Tables 1 to 3, the tensile strength, 0.2% proof
stress, and elongation were measured in accordance with the metal
material tensile test method specified in JIS Z 2241 (2011).
[0346] Then, the measured values of these physical properties were
evaluated according to the following evaluation criteria.
Evaluation Criteria for Tensile Strength
[0347] A: The tensile strength of the sintered body is very high
(1800 MPa or more).
[0348] B: The tensile strength of the sintered body is high (1600
MPa or more and less than 1800 MPa).
[0349] C: The tensile strength of the sintered body is slightly
high (1400 MPa or more and less than 1600 MPa).
[0350] D: The tensile strength of the sintered body is slightly low
(1200 MPa or more and less than 1400 MPa).
[0351] E: The tensile strength of the sintered body is low (1000
MPa or more and less than 1200 MPa).
[0352] F: The tensile strength of the sintered body is very low
(800 MPa or more and less than 1000 MPa).
[0353] G: The tensile strength of the sintered body is particularly
low (less than 800 MPa).
Evaluation Criteria for 0.2% Proof Stress
[0354] A: The 0.2% proof stress of the sintered body is very high
(1200 MPa or more).
[0355] B: The 0.2% proof stress of the sintered body is high (1100
MPa or more and less than 1200 MPa).
[0356] C: The 0.2% proof stress of the sintered body is slightly
high (1000 MPa or more and less than 1100 MPa).
[0357] D: The 0.2% proof stress of the sintered body is slightly
low (900 MPa or more and less than 1000 MPa).
[0358] E: The 0.2% proof stress of the sintered body is low (800
MPa or more and less than 900 MPa).
[0359] F: The 0.2% proof stress of the sintered body is very low
(700 MPa or more and less than 800 MPa).
[0360] G: The 0.2% proof stress of the sintered body is
particularly low (less than 700 MPa).
Evaluation Criteria for Elongation
[0361] A: The elongation of the sintered body is very large (7% or
more).
[0362] B: The elongation of the sintered body is large (6% or more
and less than 7%).
[0363] C: The elongation of the sintered body is slightly large (5%
or more and less than 6%).
[0364] D: The elongation of the sintered body is slightly small (4%
or more and less than 5%).
[0365] E: The elongation of the sintered body is small (3% or more
and less than 4%).
[0366] F: The elongation of the sintered body is very small (2% or
more and less than 3%).
[0367] G: The elongation of the sintered body is particularly small
(less than 2%).
[0368] The above evaluation results are shown in Tables 4 to 6.
3.4 Evaluation of Fatigue Strength
[0369] With respect to the sintered bodies of the respective sample
Nos. shown in Tables 1 to 3, the fatigue strength was measured.
[0370] The fatigue strength was measured in accordance with the
test method specified in JIS Z 2273 (1978). The waveform of an
applied load corresponding to a repeated stress was set to an
alternating sine wave, and the minimum/maximum stress ratio
(minimum stress/maximum stress) was set to 0.1. Further, the
repeated frequency was set to 30 Hz, and the repeat count was set
to 1.times.10.sup.7.
[0371] Then, the measured fatigue strength was evaluated according
to the following evaluation criteria.
Evaluation Criteria for Fatigue Strength
[0372] A: The fatigue strength of the sintered body is 575 MPa or
more.
[0373] B: The fatigue strength of the sintered body is 555 MPa or
more and less than 575 MPa.
[0374] C: The fatigue strength of the sintered body is 535 MPa or
more and less than 555 MPa.
[0375] D: The fatigue strength of the sintered body is 515 MPa or
more and less than 535 MPa.
[0376] E: The fatigue strength of the sintered body is 495 MPa or
more and less than 515 MPa.
[0377] F: The fatigue strength of the sintered body is less than
495 MPa.
[0378] The above evaluation results are shown in Tables 4 to 6.
TABLE-US-00004 TABLE 4 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 1 Example 3.86 99.5 A A
A A A No. 2 Example 3.79 98.2 A B B B B No. 3 Example 3.84 98.4 A B
B B B No. 4 Example 3.92 99.3 A A A A A No. 5 Example 4.02 99.4 A A
A A A No. 6 Example 3.68 97.8 A B B B B No. 7 Example 3.77 98.2 A B
B B B No. 8 Example 3.81 98.8 A A A B B No. 9 Example 3.85 98.9 A A
A B B No. 10 Example 4.05 98.5 A B B B B No. 11 Example 3.97 98.9 A
A A B B No. 12 Example 3.92 98.6 A B B B B No. 13 Example 3.74 97.5
A B B C C No. 14 Example 3.81 97.2 A B B B B No. 15 Example 3.86
97.4 A B B B B No. 16 Example 3.88 97.1 A B B B B No. 17 Example
3.76 97.2 A B B B B No. 18 Example 3.84 97.0 A C C B B No. 19
Example 3.84 97.2 A B B C C No. 20 Example 3.86 96.8 A C C C C No.
21 Example 3.76 97.3 A B B B B No. 22 Example 3.77 95.8 A D D B B
No. 23 Example 3.94 96.2 A D C B B No. 24 Example 3.05 95.7 A D D D
D No. 25 Example 3.12 95.6 A D D D D No. 26 Example 3.09 95.5 A D D
D D No. 27 Example 2.85 95.1 A D D D D No. 28 Example 7.84 99.1 A A
A A A No. 29 Example 8.04 99.2 A A A A A No. 30 Example 7.23 98.3 A
B B B B No. 31 Compar- 3.67 93.8 F F F C C ative Example No. 32
Compar- 3.48 94.5 F E C C C ative Example No. 33 Compar- 2.97 94.8
F E E D D ative Example No. 34 Compar- 3.05 93.2 F F F D D ative
Example No. 35 Compar- 2.16 93.1 F F F F F ative Example No. 36
Compar- 3.04 99.2 A A A B B ative Example
TABLE-US-00005 TABLE 5 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 37 Example 4.15 99.5 A A
A A A No. 38 Example 4.03 99.6 A A A A A No. 39 Example 4.25 98.3 A
B B B B No. 40 Example 4.05 97.6 A B B B B No. 41 Example 3.98 97.5
A B B B B No. 42 Example 4.23 99.1 A B B B B No. 43 Example 5.36
99.2 A B B B B No. 44 Example 4.05 97.6 A B B B B No. 45 Example
4.14 99.3 A A A B B No. 46 Example 4.58 98.4 A B B B B No. 47
Example 6.35 98.9 A B B C C No. 48 Example 4.45 99.1 A C C B B No.
49 Example 10.8 98.9 A C C C C No. 50 Example 4.78 95.9 A D D B B
No. 51 Example 4.69 96.4 A D C B B No. 52 Example 4.36 95.7 A D D D
D No. 53 Example 4.12 95.6 A D D D D No. 54 Example 15.4 95.4 A D D
D D No. 55 Example 4.23 99.1 A B B B B No. 56 Example 3.87 99.3 A A
A A A No. 57 Example 8.31 99.3 A A A A A No. 58 Example 8.06 99.4 A
A A A A No. 59 Example 8.52 98.1 A B B B B No. 60 Compar- 4.58 93.7
A F F C C ative Example No. 61 Compar- 4.49 94.4 A E C C C ative
Example No. 62 Compar- 4.79 94.7 A E E D D ative Example No. 63
Compar- 4.56 93.6 A F F D D ative Example No. 64 Compar- 4.35 94.9
A F F F F ative Example No. 65 Compar- 3.78 94.6 A E E E E ative
Example No. 66 Compar- 2.28 93.3 F B B F F ative Example No. 67
Compar- 2.28 98.8 A A A B B ative Example
TABLE-US-00006 TABLE 6 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 68 Example 3.86 99.6 A A
A A A No. 69 Example 3.79 98.5 A B B B B No. 70 Example 3.84 98.6 A
B B B B No. 71 Example 3.92 99.5 A A A A A No. 72 Example 4.02 99.6
A A A A A No. 73 Example 3.68 98.1 A B B B B No. 74 Example 3.77
98.4 A B B B B No. 75 Example 3.81 98.9 A A A B B No. 76 Example
3.85 99.1 A A A B B No. 77 Example 4.05 98.7 A B B B B No. 78
Example 3.97 99.1 A A A B B No. 79 Compar- 3.67 94.0 F E D C C
ative Example No. 80 Compar- 3.48 94.6 F E C C C ative Example No.
81 Compar- 2.97 94.9 A E D D D ative Example No. 82 Compar- 3.05
93.5 F F E D D ative Example No. 83 Compar- 2.16 93.3 F F F F F
ative Example No. 84 Compar- 3.04 99.3 A A A B B ative Example
[0379] As apparent from Tables 4 to 6, it was confirmed that the
sintered bodies corresponding to Example each have a higher
relative density than the sintered bodies corresponding to
Comparative Example (excluding the sintered bodies having undergone
the HIP treatment). Further, it was also confirmed that there is a
significant difference in properties such as tensile strength, 0.2%
proof stress, elongation, and fatigue strength between the sintered
bodies corresponding to Example and the sintered bodies
corresponding to Comparative Example (excluding the sintered bodies
having undergone the HIP treatment).
[0380] On the other hand, by comparison of the values of the
respective physical properties between the sintered bodies
corresponding to Example and the sintered bodies having undergone
the HIP treatment, it was confirmed that the values of the physical
properties are all comparable to each other.
[0381] Although not shown in the respective tables, when the same
evaluation as described above was performed also with respect to
sintered bodies produced by using the metal powders having the same
compositions shown in Tables 1 to 3 except that both Mn and Ni were
not contained, the relative density and the mechanical properties
of the sintered bodies produced by using the metal powders for
powder metallurgy corresponding to Example were all favorable as
having been expected.
4. Production of Sintered Body (Hf--Nb Based)
Sample Nos. 85 to 105
[0382] Sintered bodies were obtained in the same manner as the
method for producing the sintered body of sample No. 1 except that
the composition and the like of the metal powder for powder
metallurgy were changed as shown in Table 7, respectively. The
sintered body of sample No. 105 was obtained by performing an HIP
treatment under the following conditions after firing.
[0383] HIP Treatment Conditions
[0384] Heating temperature: 1100.degree. C.
[0385] Heating time: 2 hours
[0386] Applied pressure: 100 MPa
TABLE-US-00007 TABLE 7 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (Zr) (Nb) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 85 Example 12.85 0.91 0.72 0.09 0.05
0.11 0.08 <0.01 0.29 remainder 1.80 0.14 0.19 0.15 0.19 No. 86
Example 14.22 0.29 0.59 0.07 0.07 0.13 0.06 <0.01 0.25 remainder
1.00 0.14 0.24 0.48 0.19 No. 87 Example 11.58 1.12 0.79 0.15 0.05
0.07 0.12 <0.01 0.32 remainder 3.00 0.20 0.25 0.18 0.19 No. 88
Example 13.42 0.84 0.65 0.11 0.06 0.08 0.11 <0.01 0.24 remainder
1.83 0.17 0.26 0.20 0.19 No. 89 Example 12.55 0.96 0.75 0.06 0.08
0.11 0.07 <0.01 0.31 remainder 0.75 0.14 0.19 0.15 0.18 No. 90
Example 10.53 0.77 0.34 0.13 0.07 0.18 0.15 <0.01 0.25 remainder
1.86 0.20 0.59 0.26 0.33 No. 91 Example 16.28 1.04 0.63 0.08 0.06
0.07 0.08 <0.01 0.28 remainder 1.33 0.14 0.22 0.13 0.15 No. 92
Example 19.76 0.92 0.86 0.12 0.08 0.04 0.08 <0.01 0.45 remainder
1.50 0.20 0.23 0.22 0.12 No. 93 Example 23.51 0.43 0.46 0.08 0.04
0.07 0.06 <0.01 0.65 remainder 2.00 0.12 0.26 0.28 0.13 No. 94
Example 12.75 0.86 0.76 0.11 0.05 0.01 0.06 <0.01 0.25 remainder
2.20 0.16 0.21 0.19 0.07 No. 95 Example 12.82 0.88 0.74 0.09 0.03
0.99 0.58 <0.01 0.23 remainder 3.00 0.12 0.16 0.14 1.57 No. 96
Example 12.73 0.92 0.71 0.03 0.07 0.10 0.08 <0.01 0.29 remainder
0.43 0.10 0.14 0.11 0.18 No. 97 Example 13.01 1.01 0.80 0.05 0.03
0.08 0.07 <0.01 0.31 remainder 1.67 0.08 0.10 0.08 0.15 No. 98
Example 14.38 0.45 0.76 0.08 0.11 0.05 0.04 <0.01 0.41 remainder
0.73 0.19 0.25 0.42 0.09 No. 99 Example 12.78 0.78 0.72 0.39 0.28
0.11 0.07 <0.01 0.29 remainder 1.39 0.67 0.93 0.86 0.18 No. 100
Compar- 12.56 093 0.81 0.00 0.06 0.12 0.07 <0.01 0.26 remainder
0.00 0.06 0.07 0.06 0.19 ative Example No. 101 Compar- 12.97 0.75
0.76 0.06 0.00 0.09 0.11 <0.01 0.32 remainder -- 0.06 0.08 0.08
0.20 ative Example No. 102 Compar- 13.27 0.46 0.43 0.71 0.07 0.09
0.05 <0.01 0.28 remainder 10.14 0.78 1.81 1.70 0.14 ative
Example No. 103 Compar- 13.55 0.59 0.35 0.03 0.68 0.07 0.06
<0.01 0.33 remainder 0.04 0.71 2.03 1.20 0.13 ative Example No.
104 Compar- 13.52 0.98 0.74 0.00 0.00 0.11 0.08 <0.01 0.32
remainder -- 0.00 0.00 0.00 0.19 ative Example No. 105 Compar-
13.52 0.98 0.74 0.00 0.00 0.11 0.08 <0.01 0.32 remainder -- 0.00
0.00 0.00 0.19 HIP ative Example
[0387] In Table 7, among the sintered bodies of the respective
sample Nos., those corresponding to the invention are indicated by
"Example", and those not corresponding to the invention are
indicated by "Comparative Example".
[0388] Each sintered body contained very small amounts of
impurities, but the description thereof in Table 7 is omitted.
5. Evaluation of Metal Powder (Hf--Nb Based)
[0389] With respect to the cross sections of the particles of the
metal powders for powder metallurgy of the respective sample Nos.
shown in Table 7, the crystal structure was evaluated by TEM.
[0390] As a result, in all the metal powders for powder metallurgy
corresponding to Example, the average number of the Fe-based alloy
crystals was 1 or more and 5 or less. Further, in all the metal
powders for powder metallurgy corresponding to Example, the circle
equivalent diameter of the Fe-based alloy crystal was 1% or more
and 100% or less the circle equivalent diameter of the
particle.
[0391] On the other hand, in all the metal powders for powder
metallurgy corresponding to Comparative Example, the average number
of the Fe-based alloy crystals was 6 or more.
6. Evaluation of Sintered Body (Hf--Nb Based)
6.1 Evaluation of Relative Density
[0392] With respect to the sintered bodies of the respective sample
Nos. shown in Table 7, the sintered density was measured in
accordance with the method for measuring the density of sintered
metal materials specified in JIS Z 2501 (2000), and also the
relative density of each sintered body was calculated with
reference to the true density of the metal powder for powder
metallurgy used for producing each sintered body.
[0393] The calculation results are shown in Table 8.
6.2 Evaluation of Hardness
[0394] With respect to the sintered bodies of the respective sample
Nos. shown in Table 7, the Vickers hardness was measured in
accordance with the Vickers hardness test method specified in JIS Z
2244 (2009).
[0395] Then, the measured hardness was evaluated according to the
evaluation criteria described in 3.2.
[0396] The evaluation results are shown in Table 8.
6.3 Evaluation of Tensile Strength, 0.2% Proof Stress, and
Elongation
[0397] With respect to the sintered bodies of the respective sample
Nos. shown in Table 7, the tensile strength, 0.2% proof stress, and
elongation were measured in accordance with the metal material
tensile test method specified in JIS Z 2241 (2011).
[0398] Then, the measured values of the physical properties were
evaluated according to the evaluation criteria described in
3.3.
[0399] The evaluation results are shown in Table 8.
6.4 Evaluation of Fatigue Strength
[0400] With respect to the sintered bodies of the respective sample
Nos. shown in Table 7, the fatigue strength was measured in the
same manner as in 3.4.
[0401] Then, the measured fatigue strength was evaluated according
to the evaluation criteria described in 3.4.
[0402] The evaluation results are shown in Table 8.
TABLE-US-00008 TABLE 8 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 85 Example 4.12 99.4 A A
A A A No. 86 Example 4.79 98.3 A B B B B No. 87 Example 3.84 98.7 A
A A B B No. 88 Example 5.92 99.4 A A A A A No. 89 Example 7.02 99.2
A A A A A No. 90 Example 2.08 98.6 A B B B B No. 91 Example 2.89
99.0 A A A A B No. 92 Example 3.92 98.7 A B B B B No. 93 Example
3.74 98.2 A B B B B No. 94 Example 9.87 98.9 A A A B C No. 95
Example 15.46 98.6 A A A B C No. 96 Example 23.48 98.8 A A A B C
No. 97 Example 11.59 98.5 A B B B B No. 98 Example 4.25 98.8 A B B
B B No. 99 Example 2.51 98.1 A B B B C No. 100 Compar- 4.23 94.6 F
E E C C ative Example No. 101 Compar- 4.56 94.8 F E E D D ative
Example No. 102 Compar- 4.79 95.1 F E E D D ative Example No. 103
Compar- 4.69 94.1 F F F D D ative Example No. 104 Compar- 6.21 93.4
F F F F F ative Example No. 105 Compar- 6.21 99.0 A A A B B ative
Example
[0403] As apparent from Table 8, it was confirmed that the sintered
bodies corresponding to Example each have a higher relative density
than the sintered bodies corresponding to Comparative Example
(excluding the sintered body having undergone the HIP treatment).
Further, it was also confirmed that there is a significant
difference in properties such as tensile strength, 0.2% proof
stress, elongation, and fatigue strength between the sintered
bodies corresponding to Example and the sintered bodies
corresponding to Comparative Example (excluding the sintered body
having undergone the HIP treatment).
[0404] On the other hand, by comparison of the values of the
respective physical properties between the sintered bodies
corresponding to Example and the sintered body having undergone the
HIP treatment, it was confirmed that the values of the physical
properties are all comparable to each other.
7. Production of Sintered Body (Ti--Nb Based)
Sample Nos. 106 to 118
[0405] Sintered bodies were obtained in the same manner as the
method for producing the sintered body of sample No. 1 except that
the composition and the like of the metal powder for powder
metallurgy were changed as shown in Table 9, respectively.
Sample No. 119
[0406] A metal powder, a Ti powder having an average particle
diameter of 40 .mu.m, and a Nb powder having an average particle
diameter of 25 .mu.m were mixed, whereby a mixed powder was
prepared. In the preparation of the mixed powder, each of the
mixing amounts of the metal powder, the Ti powder, and the Nb
powder was adjusted so that the composition of the mixed powder was
as shown in Table 9.
[0407] Then, a sintered body was obtained in the same manner as the
method for producing the sintered body of sample No. 1 using this
mixed powder.
TABLE-US-00009 TABLE 9 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (Ti) (Nb) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 106 Example 12.91 0.87 0.74 0.05 0.09
0.10 0.09 <0.01 0.28 remainder 0.56 0.14 0.19 0.16 0.19 No. 107
Example 14.25 0.31 0.55 0.07 0.07 0.16 0.06 <0.01 0.24 remainder
1.00 0.14 0.25 0.45 0.22 No. 108 Example 11.43 1.20 0.83 0.06 0.15
0.07 0.13 <0.01 0.29 remainder 0.40 0.21 0.25 0.18 0.20 No. 109
Example 12.84 0.86 0.75 0.06 0.05 1.05 0.51 <0.01 0.25 remainder
1.20 0.11 0.15 0.13 1.56 No. 110 Example 12.71 0.94 0.45 0.02 0.06
0.28 0.22 <0.01 0.29 remainder 0.33 0.08 0.18 0.09 0.50 No. 111
Example 13.11 1.02 0.81 0.04 0.03 0.54 0.15 <0.01 0.31 remainder
1.33 0.07 0.09 0.07 0.69 No. 112 Example 14.42 0.43 0.78 0.08 0.11
0.15 0.06 <0.01 0.38 remainder 0.73 0.19 0.24 0.44 0.21 No. 113
Example 12.77 0.76 0.71 0.41 0.32 0.09 0.08 <0.01 0.29 remainder
1.28 0.73 1.03 0.96 0.17 No. 114 Compar- 12.56 0.92 0.83 0.00 0.07
0.14 0.08 <0.01 0.25 remainder 0.00 0.07 0.08 0.08 0.22 ative
Example No. 115 Compar- 12.95 0.74 0.78 0.07 0.00 0.11 0.15
<0.01 0.34 remainder -- 0.07 0.09 0.09 0.26 ative Example No.
116 Compar- 13.26 0.45 0.42 0.73 0.07 0.12 0.06 <0.01 0.28
remainder 10.43 0.80 1.90 1.78 0.18 ative Example No. 117 Compar-
13.53 0.57 0.36 0.04 0.69 0.08 0.14 <0.01 0.34 remainder 0.06
0.73 2.03 1.28 0.22 ative Example No. 118 Compar- 13.58 0.96 0.75
0.00 0.00 0.13 0.06 <0.01 0.35 remainder -- 0.00 0.00 0.00 0.19
ative Example No. 119 Compar- 13.50 0.89 0.71 0.25 0.42 0.11 0.08
<0.01 0.48 remainder 0.60 0.67 0.94 0.75 0.19 Mixed ative powder
Example
[0408] In Table 9, among the sintered bodies of the respective
sample Nos., those corresponding to the invention are indicated by
"Example", and those not corresponding to the invention are
indicated by "Comparative Example".
[0409] Each sintered body contained very small amounts of
impurities, but the description thereof in Table 9 is omitted.
8. Evaluation of Metal Powder (Ti--Nb Based)
[0410] With respect to the cross sections of the particles of the
metal powders for powder metallurgy of the respective sample Nos.
shown in Table 9, the crystal structure was evaluated by TEM.
[0411] As a result, in all the metal powders for powder metallurgy
corresponding to Example, the average number of the Fe-based alloy
crystals was 1 or more and 5 or less. Further, in all the metal
powders for powder metallurgy corresponding to Example, the circle
equivalent diameter of the Fe-based alloy crystal was 1% or more
and 100% or less the circle equivalent diameter of the
particle.
[0412] On the other hand, in all the metal powders for powder
metallurgy corresponding to Comparative Example, the average number
of the Fe-based alloy crystals was 6 or more.
9. Evaluation of Sintered Body (Ti--Nb Based)
9.1 Evaluation of Relative Density
[0413] With respect to the sintered bodies of the respective sample
Nos. shown in Table 9, the sintered density was measured in
accordance with the method for measuring the density of sintered
metal materials specified in JIS Z 2501 (2000), and also the
relative density of each sintered body was calculated with
reference to the true density of the metal powder for powder
metallurgy used for producing each sintered body.
[0414] The calculation results are shown in Table 10.
9.2 Evaluation of Hardness
[0415] With respect to the sintered bodies of the respective sample
Nos. shown in Table 9, the Vickers hardness was measured in
accordance with the Vickers hardness test method specified in JIS Z
2244 (2009).
[0416] Then, the measured hardness was evaluated according to the
evaluation criteria described in 3.2.
[0417] The evaluation results are shown in Table 10.
9.3 Evaluation of Tensile Strength, 0.2% Proof Stress, and
Elongation
[0418] With respect to the sintered bodies of the respective sample
Nos. shown in Table 9, the tensile strength, 0.2% proof stress, and
elongation were measured in accordance with the metal material
tensile test method specified in JIS Z 2241 (2011).
[0419] Then, the measured values of the physical properties were
evaluated according to the above-mentioned evaluation criteria
described in 3.3.
[0420] The evaluation results are shown in Table 10.
9.4 Evaluation of Fatigue Strength
[0421] With respect to the sintered bodies of the respective sample
Nos. shown in Table 9, the fatigue strength was measured in the
same manner as in 3.4.
[0422] Then, the measured fatigue strength was evaluated according
to the evaluation criteria described in 3.4.
[0423] The evaluation results are shown in Table 10.
TABLE-US-00010 TABLE 10 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 106 Example 4.15 99.2 A
A A A A No. 107 Example 5.74 98.5 A B B B B No. 108 Example 3.46
98.6 A B B B B No. 109 Example 9.57 98.3 A B B B C No. 110 Example
4.75 98.8 A A A B B No. 111 Example 14.68 98.2 A B B B C No. 112
Example 3.78 99.0 A A A A B No. 113 Example 2.08 98.0 A B B C C No.
114 Compar- 4.55 94.5 F E E D D ative Example No. 115 Compar- 3.97
95.1 F E E D D ative Example No. 116 Compar- 2.78 95.3 F E E D D
ative Example No. 117 Compar- 3.08 93.8 F F F D D ative Example No.
118 Compar- 2.04 93.4 F F F F F ative Example No. 119 Compar- 4.29
95.6 A C C D D ative Example
[0424] As apparent from Table 10, it was confirmed that the
sintered bodies corresponding to Example each have a higher
relative density than the sintered bodies corresponding to
Comparative Example. It was also confirmed that there is a
significant difference in properties such as tensile strength, 0.2%
proof stress, elongation, and fatigue strength between the sintered
bodies corresponding to Example and the sintered bodies
corresponding to Comparative Example.
10. Production of Sintered Body (Nb--Ta Based)
Sample Nos. 120 to 132
[0425] Sintered bodies were obtained in the same manner as the
method for producing the sintered body of sample No. 1 except that
the composition and the like of the metal powder for powder
metallurgy were changed as shown in Table 11, respectively.
TABLE-US-00011 TABLE 11 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (Nb) (Ta) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 120 Example 12.88 0.86 0.72 0.05 0.09
0.10 0.12 <0.01 0.26 remainder 0.56 0.14 0.19 0.16 0.22 No. 121
Example 14.36 0.24 0.54 0.06 0.06 0.18 0.08 <0.01 0.24 remainder
1.00 0.12 0.22 0.50 0.26 No. 122 Example 11.39 1.18 0.86 0.05 0.15
0.08 0.13 <0.01 0.31 remainder 0.33 0.20 0.23 0.17 0.21 No. 123
Example 12.82 0.77 0.78 0.06 0.04 1.12 0.53 <0.01 0.45 remainder
1.50 0.10 0.13 0.13 1.65 No. 124 Example 12.68 0.82 0.46 0.02 0.07
0.32 0.31 <0.01 0.39 remainder 0.29 0.09 0.20 0.11 0.63 No. 125
Example 13.08 1.05 0.83 0.03 0.04 0.61 0.16 <0.01 0.32 remainder
0.75 0.07 0.08 0.07 0.77 No. 126 Example 14.45 0.44 0.79 0.09 0.11
0.16 0.07 <0.01 0.39 remainder 0.82 0.20 0.25 0.45 0.23 No. 127
Example 12.75 0.74 0.72 0.43 0.28 0.10 0.05 <0.01 0.25 remainder
1.54 0.71 0.99 0.96 0.15 No. 128 Compar- 12.64 0.93 0.87 0.00 0.09
0.16 0.12 <0.01 0.36 remainder 0.00 0.09 0.10 0.10 0.28 ative
Example No. 129 Compar- 12.97 0.72 0.76 0.11 0.00 0.15 0.09
<0.01 0.36 remainder -- 0.11 0.14 0.15 0.24 ative Example No.
130 Compar- 13.31 0.42 0.41 0.78 0.07 0.15 0.05 <0.01 0.19
remainder 11.14 0.85 2.07 2.02 0.20 ative Example No. 131 Compar-
13.56 0.59 0.35 0.05 0.75 0.06 0.15 <0.01 0.34 remainder 0.07
0.80 2.29 1.36 0.21 ative Example No. 132 Compar- 13.54 0.97 0.73
0.00 0.00 0.12 0.08 <0.01 0.35 remainder -- 0.00 0.00 0.00 0.20
ative Example
[0426] In Table 11, among the sintered bodies of the respective
sample Nos., those corresponding to the invention are indicated by
"Example", and those not corresponding to the invention are
indicated by "Comparative Example".
[0427] Each sintered body contained very small amounts of
impurities, but the description thereof in Table 11 is omitted.
11. Evaluation of Metal Powder (Nb--Ta Based)
[0428] With respect to the cross sections of the particles of the
metal powders for powder metallurgy of the respective sample Nos.
shown in Table 11, the crystal structure was evaluated by TEM.
[0429] As a result, in all the metal powders for powder metallurgy
corresponding to Example, the average number of the Fe-based alloy
crystals was 1 or more and 5 or less. Further, in all the metal
powders for powder metallurgy corresponding to Example, the circle
equivalent diameter of the Fe-based alloy crystal was 1% or more
and 100% or less the circle equivalent diameter of the
particle.
[0430] On the other hand, in all the metal powders for powder
metallurgy corresponding to Comparative Example, the average number
of the Fe-based alloy crystals was 6 or more.
12. Evaluation of Sintered Body (Nb--Ta Based)
12.1 Evaluation of Relative Density
[0431] With respect to the sintered bodies of the respective sample
Nos. shown in Table 11, the sintered density was measured in
accordance with the method for measuring the density of sintered
metal materials specified in JIS Z 2501 (2000), and also the
relative density of each sintered body was calculated with
reference to the true density of the metal powder for powder
metallurgy used for producing each sintered body.
[0432] The calculation results are shown in Table 12.
12.2 Evaluation of Hardness
[0433] With respect to the sintered bodies of the respective sample
Nos. shown in Table 11, the Vickers hardness was measured in
accordance with the Vickers hardness test method specified in JIS Z
2244 (2009).
[0434] Then, the measured hardness was evaluated according to the
evaluation criteria described in 3.2.
[0435] The evaluation results are shown in Table 12.
12.3 Evaluation of Tensile Strength, 0.2% Proof Stress, and
Elongation
[0436] With respect to the sintered bodies of the respective sample
Nos. shown in Table 11, the tensile strength, 0.2% proof stress,
and elongation were measured in accordance with the metal material
tensile test method specified in JIS Z 2241 (2011).
[0437] Then, the measured values of the physical properties were
evaluated according to the above-mentioned evaluation criteria
described in 3.3.
[0438] The evaluation results are shown in Table 12.
12.4 Evaluation of Fatigue Strength
[0439] With respect to the sintered bodies of the respective sample
Nos. shown in Table 11, the fatigue strength was measured in the
same manner as in 3.4.
[0440] Then, the measured fatigue strength was evaluated according
to the evaluation criteria described in 3.4.
[0441] The evaluation results are shown in Table 12.
TABLE-US-00012 TABLE 12 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 120 Example 4.22 98.9 A
A A A A No. 121 Example 5.78 98.2 A B B B B No. 122 Example 3.35
98.1 A B B B B No. 123 Example 9.05 97.8 A B B B C No. 124 Example
4.89 98.5 A B B B B No. 125 Example 13.26 98.0 A B B B C No. 126
Example 3.97 98.8 A A A A B No. 127 Example 2.12 97.8 A B B C C No.
128 Compar- 4.63 94.8 F F F D D ative Example No. 129 Compar- 3.87
95.3 F E E D D ative Example No. 130 Compar- 2.54 95.5 F E E D D
ative Example No. 131 Compar- 3.15 94.2 F F F D D ative Example No.
132 Compar- 2.13 94.1 F F F F F ative Example
[0442] As apparent from Table 12, it was confirmed that the
sintered bodies corresponding to Example each have a higher
relative density than the sintered bodies corresponding to
Comparative Example. It was also confirmed that there is a
significant difference in properties such as tensile strength, 0.2%
proof stress, elongation, and fatigue strength between the sintered
bodies corresponding to Example and the sintered bodies
corresponding to Comparative Example.
13. Production of Sintered Body (Y--Nb Based)
Sample Nos. 133 to 145
[0443] Sintered bodies were obtained in the same manner as the
method for producing the sintered body of sample No. 1 except that
the composition and the like of the metal powder for powder
metallurgy were changed as shown in Table 13, respectively.
TABLE-US-00013 TABLE 13 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (Y) (Nb) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 133 Example 12.84 0.84 0.73 0.08 0.09
0.09 0.16 <0.01 0.25 remainder 0.89 0.17 0.23 0.20 0.25 No. 134
Example 14.33 0.33 0.55 0.12 0.06 0.18 0.12 <0.01 0.24 remainder
2.00 0.18 0.33 0.55 0.30 No. 135 Example 11.36 1.15 0.87 0.07 0.15
0.09 0.12 <0.01 0.31 remainder 0.47 0.22 0.25 0.19 0.21 No. 136
Example 12.84 0.76 0.79 0.07 0.04 1.14 0.52 <0.01 0.46 remainder
1.75 0.11 0.14 0.14 1.66 No. 137 Example 12.65 0.80 0.45 0.02 0.06
0.33 0.32 <0.01 0.40 remainder 0.33 0.08 0.18 0.10 0.65 No. 138
Example 13.11 1.04 0.82 0.03 0.04 0.62 0.18 <0.01 0.29 remainder
0.75 0.07 0.09 0.07 0.80 No. 139 Example 14.48 0.45 0.78 0.12 0.11
0.16 0.08 <0.01 0.41 remainder 1.09 0.23 0.29 0.51 0.24 No. 140
Example 12.76 0.75 0.73 0.41 0.31 0.11 0.06 <0.01 0.28 remainder
1.32 0.72 0.99 0.96 0.17 No. 141 Compar- 12.66 0.94 0.88 0.00 0.10
0.17 0.13 <0.01 0.37 remainder 0.00 0.10 0.11 0.11 0.30 ative
Example No. 142 Compar- 13.01 0.74 0.78 0.09 0.00 0.16 0.10
<0.01 0.35 remainder -- 0.09 0.12 0.12 0.26 ative Example No.
143 Compar- 13.33 0.41 0.45 0.79 0.08 0.14 0.06 <0.01 0.22
remainder 9.88 0.87 1.93 2.12 0.20 ative Example No. 144 Compar-
13.58 0.61 0.36 0.06 0.77 0.07 0.17 <0.01 0.36 remainder 0.08
0.83 2.31 1.36 0.24 ative Example No. 145 Compar- 13.53 0.95 0.75
0.00 0.00 0.13 0.07 <0.01 0.34 remainder -- 0.00 0.00 0.00 0.20
ative Example
[0444] In Table 13, among the sintered bodies of the respective
sample Nos., those corresponding to the invention are indicated by
"Example", and those not corresponding to the invention are
indicated by "Comparative Example".
[0445] Each sintered body contained very small amounts of
impurities, but the description thereof in Table 13 is omitted.
14. Evaluation of Metal Powder (Y--Nb Based)
[0446] With respect to the cross sections of the particles of the
metal powders for powder metallurgy of the respective sample Nos.
shown in Table 13, the crystal structure was evaluated by TEM.
[0447] As a result, in all the metal powders for powder metallurgy
corresponding to Example, the average number of the Fe-based alloy
crystals was 1 or more and 5 or less. Further, in all the metal
powders for powder metallurgy corresponding to Example, the circle
equivalent diameter of the Fe-based alloy crystal was 1% or more
and 100% or less the circle equivalent diameter of the
particle.
[0448] On the other hand, in all the metal powders for powder
metallurgy corresponding to Comparative Example, the average number
of the Fe-based alloy crystals was 6 or more.
15. Evaluation of Sintered Body (Y--Nb Based)
15.1 Evaluation of Relative Density
[0449] With respect to the sintered bodies of the respective sample
Nos. shown in Table 13, the sintered density was measured in
accordance with the method for measuring the density of sintered
metal materials specified in JIS Z 2501 (2000), and also the
relative density of each sintered body was calculated with
reference to the true density of the metal powder for powder
metallurgy used for producing each sintered body.
[0450] The calculation results are shown in Table 14.
15.2 Evaluation of Hardness
[0451] With respect to the sintered bodies of the respective sample
Nos. shown in Table 13, the Vickers hardness was measured in
accordance with the Vickers hardness test method specified in JIS Z
2244 (2009).
[0452] Then, the measured hardness was evaluated according to the
evaluation criteria described in 3.2.
[0453] The evaluation results are shown in Table 14.
15.3 Evaluation of Tensile Strength, 0.2% Proof Stress, and
Elongation
[0454] With respect to the sintered bodies of the respective sample
Nos. shown in Table 13, the tensile strength, 0.2% proof stress,
and elongation were measured in accordance with the metal material
tensile test method specified in JIS Z 2241 (2011).
[0455] Then, the measured values of the physical properties were
evaluated according to the above-mentioned evaluation criteria
described in 3.3.
[0456] The evaluation results are shown in Table 14.
15.4 Evaluation of Fatigue Strength
[0457] With respect to the sintered bodies of the respective sample
Nos. shown in Table 13, the fatigue strength was measured in the
same manner as in 3.4.
[0458] Then, the measured fatigue strength was evaluated according
to the evaluation criteria described in 3.4.
[0459] The evaluation results are shown in Table 14.
TABLE-US-00014 TABLE 14 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 133 Example 4.37 99.0 A
A A A A No. 134 Example 5.81 98.3 A B B B B No. 135 Example 3.31
98.4 A B B B B No. 136 Example 9.68 98.1 A B B B C No. 137 Example
4.65 98.6 A B B B B No. 138 Example 13.78 97.8 A B B B B No. 139
Example 3.64 98.9 A A A A B No. 140 Example 2.05 97.9 A B B C C No.
141 Compar- 4.58 94.6 F E E D D ative Example No. 142 Compar- 4.02
95.2 F E E D D ative Example No. 143 Compar- 2.72 95.0 F E E E E
ative Example No. 144 Compar- 3.12 94.4 F D D E E ative Example No.
145 Compar- 2.09 94.1 F F F F F ative Example
[0460] As apparent from Table 14, it was confirmed that the
sintered bodies corresponding to Example each have a higher
relative density than the sintered bodies corresponding to
Comparative Example. It was also confirmed that there is a
significant difference in properties such as tensile strength, 0.2%
proof stress, elongation, and fatigue strength between the sintered
bodies corresponding to Example and the sintered bodies
corresponding to Comparative Example.
16. Production of Sintered Body (V--Nb Based)
Sample Nos. 146 to 158
[0461] Sintered bodies were obtained in the same manner as the
method for producing the sintered body of sample No. 1 except that
the composition and the like of the metal powder for powder
metallurgy were changed as shown in Table 15, respectively.
TABLE-US-00015 TABLE 15 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (V) (Nb) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 146 Example 12.88 0.92 0.74 0.06 0.09
0.10 0.17 <0.01 0.26 remainder 0.67 0.15 0.20 0.16 0.27 No. 147
Example 14.35 0.34 0.56 0.09 0.06 0.18 0.12 <0.01 0.24 remainder
1.50 0.15 0.27 0.44 0.30 No. 148 Example 11.38 1.09 0.85 0.07 0.15
0.11 0.08 <0.01 0.26 remainder 0.47 0.22 0.26 0.20 0.19 No. 149
Example 12.91 0.74 0.78 0.03 0.06 1.11 0.48 <0.01 0.45 remainder
0.50 0.09 0.12 0.12 1.59 No. 150 Example 12.63 0.81 0.44 0.02 0.05
0.35 0.34 <0.01 0.39 remainder 0.40 0.07 0.16 0.09 0.69 No. 151
Example 13.09 1.03 0.81 0.03 0.03 0.58 0.17 <0.01 0.28 remainder
1.00 0.06 0.07 0.06 0.75 No. 152 Example 14.51 0.44 0.76 0.11 0.12
0.15 0.09 <0.01 0.39 remainder 0.92 0.23 0.30 0.52 0.24 No. 153
Example 12.74 0.74 0.75 0.39 0.29 0.11 0.07 <0.01 0.29 remainder
1.34 0.68 0.91 0.92 0.18 No. 154 Compar- 12.65 0.97 0.91 0.00 0.11
0.18 0.14 <0.01 0.39 remainder 0.00 0.11 0.12 0.11 0.32 ative
Example No. 155 Compar- 12.89 0.73 0.76 0.10 0.00 0.17 0.12
<0.01 0.41 remainder -- 0.10 0.13 0.14 0.29 ative Example No.
156 Compar- 13.35 0.39 0.46 0.77 0.11 0.15 0.07 <0.01 0.25
remainder 7.00 0.88 1.91 2.26 0.22 ative Example No. 157 Compar-
13.62 0.63 0.38 0.07 0.81 0.08 0.21 <0.01 0.41 remainder 0.09
0.88 2.32 1.40 0.29 ative Example No. 158 Compar- 13.56 0.96 0.78
0.00 0.00 0.15 0.08 <0.01 0.36 remainder -- 0.00 0.00 0.00 0.23
ative Example
[0462] In Table 15, among the sintered bodies of the respective
sample Nos., those corresponding to the invention are indicated by
"Example", and those not corresponding to the invention are
indicated by "Comparative Example".
[0463] Each sintered body contained very small amounts of
impurities, but the description thereof in Table 15 is omitted.
17. Evaluation of Metal Powder (V--Nb Based)
[0464] With respect to the cross sections of the particles of the
metal powders for powder metallurgy of the respective sample Nos.
shown in Table 15, the crystal structure was evaluated by TEM.
[0465] As a result, in all the metal powders for powder metallurgy
corresponding to Example, the average number of the Fe-based alloy
crystals was 1 or more and 5 or less. Further, in all the metal
powders for powder metallurgy corresponding to Example, the circle
equivalent diameter of the Fe-based alloy crystal was 1% or more
and 100% or less the circle equivalent diameter of the
particle.
[0466] On the other hand, in all the metal powders for powder
metallurgy corresponding to Comparative Example, the average number
of the Fe-based alloy crystals was 6 or more.
18. Evaluation of Sintered Body (V--Nb Based)
18.1 Evaluation of Relative Density
[0467] With respect to the sintered bodies of the respective sample
Nos. shown in Table 15, the sintered density was measured in
accordance with the method for measuring the density of sintered
metal materials specified in JIS Z 2501 (2000), and also the
relative density of each sintered body was calculated with
reference to the true density of the metal powder for powder
metallurgy used for producing each sintered body.
[0468] The calculation results are shown in Table 16.
18.2 Evaluation of Hardness
[0469] With respect to the sintered bodies of the respective sample
Nos. shown in Table 15, the Vickers hardness was measured in
accordance with the Vickers hardness test method specified in JIS Z
2244 (2009).
[0470] Then, the measured hardness was evaluated according to the
evaluation criteria described in 3.2.
[0471] The evaluation results are shown in Table 16.
18.3 Evaluation of Tensile Strength, 0.2% Proof Stress, and
Elongation
[0472] With respect to the sintered bodies of the respective sample
Nos. shown in Table 15, the tensile strength, 0.2% proof stress,
and elongation were measured in accordance with the metal material
tensile test method specified in JIS Z 2241 (2011).
[0473] Then, the measured values of the physical properties were
evaluated according to the above-mentioned evaluation criteria
described in 3.3.
[0474] The evaluation results are shown in Table 16.
18.4 Evaluation of Fatigue Strength
[0475] With respect to the sintered bodies of the respective sample
Nos. shown in Table 15, the fatigue strength was measured in the
same manner as in 3.4.
[0476] Then, the measured fatigue strength was evaluated according
to the evaluation criteria described in 3.4.
[0477] The evaluation results are shown in Table 16.
TABLE-US-00016 TABLE 16 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 146 Example 4.42 98.8 A
A A A A No. 147 Example 5.96 98.1 A B B B B No. 148 Example 3.21
98.2 A B B B B No. 149 Example 10.25 97.9 A B B C C No. 150 Example
4.78 98.4 A B B B B No. 151 Example 14.26 97.7 A B B B C No. 152
Example 3.55 98.7 A A A B B No. 153 Example 2.18 97.7 A B B B C No.
154 Compar- 4.87 94.5 F E E D D ative Example No. 155 Compar- 3.89
95.1 F F F E E ative Example No. 156 Compar- 2.63 94.8 F F F E E
ative Example No. 157 Compar- 3.08 95.2 F E E D D ative Example No.
158 Compar- 2.15 94.1 F F F E E ative Example
[0478] As apparent from Table 16, it was confirmed that the
sintered bodies corresponding to Example each have a higher
relative density than the sintered bodies corresponding to
Comparative Example. It was also confirmed that there is a
significant difference in properties such as tensile strength, 0.2%
proof stress, elongation, and fatigue strength between the sintered
bodies corresponding to Example and the sintered bodies
corresponding to Comparative Example.
19. Production of Sintered Body (Ti--Zr Based)
Sample Nos. 159 to 171
[0479] Sintered bodies were obtained in the same manner as the
method for producing the sintered body of sample No. 1 except that
the composition and the like of the metal powder for powder
metallurgy were changed as shown in Table 17, respectively.
TABLE-US-00017 TABLE 17 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (Ti) (Zr) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 159 Example 12.86 0.89 0.72 0.07 0.08
0.09 0.16 <0.01 0.27 remainder 0.88 0.15 0.21 0.17 0.25 No. 160
Example 14.41 0.27 0.52 0.08 0.06 0.19 0.11 <0.01 0.19 remainder
1.33 0.14 0.27 0.52 0.30 No. 161 Example 11.35 1.11 0.86 0.06 0.16
0.12 0.08 <0.01 0.25 remainder 0.38 0.22 0.26 0.20 0.20 No. 162
Example 12.89 0.73 0.77 0.03 0.05 1.13 0.43 <0.01 0.46 remainder
0.60 0.08 0.10 0.11 1.56 No. 163 Example 12.61 0.79 0.43 0.02 0.04
0.33 0.29 <0.01 0.38 remainder 0.50 0.06 0.14 0.08 0.62 No. 164
Example 13.11 1.01 0.80 0.04 0.04 0.56 0.17 <0.01 0.28 remainder
1.00 0.08 0.10 0.08 0.73 No. 165 Example 14.53 0.45 0.77 0.11 0.20
0.15 0.09 <0.01 0.41 remainder 0.55 0.31 0.40 0.69 0.24 No. 166
Example 12.76 0.73 0.76 0.41 0.28 0.13 0.09 <0.01 0.31 remainder
1.46 0.69 0.91 0.95 0.22 No. 167 Compar- 12.68 0.98 0.93 0.00 0.12
0.19 0.15 <0.01 0.37 remainder 0.00 0.12 0.13 0.12 0.34 ative
Example No. 168 Compar- 12.86 0.72 0.77 0.11 0.00 0.18 0.13
<0.01 0.42 remainder -- 0.11 0.14 0.15 0.31 ative Example No.
169 Compar- 13.42 0.38 0.47 0.79 0.10 0.16 0.08 <0.01 0.26
remainder 7.90 0.88 1.89 2.34 0.24 ative Example No. 170 Compar-
13.65 0.64 0.37 0.08 0.81 0.09 0.23 <0.01 0.43 remainder 0.10
0.89 2.41 1.39 0.32 ative Example No. 171 Compar- 13.57 0.97 0.79
0.00 0.00 0.16 0.09 <0.01 0.41 remainder -- 0.00 0.00 0.00 0.25
ative Example
[0480] In Table 17, among the sintered bodies of the respective
sample Nos., those corresponding to the invention are indicated by
"Example", and those not corresponding to the invention are
indicated by "Comparative Example".
[0481] Each sintered body contained very small amounts of
impurities, but the description thereof in Table 17 is omitted.
20. Evaluation of Metal Powder (Ti--Zr Based)
[0482] With respect to the cross sections of the particles of the
metal powders for powder metallurgy of the respective sample Nos.
shown in Table 17, the crystal structure was evaluated by TEM.
[0483] As a result, in all the metal powders for powder metallurgy
corresponding to Example, the average number of the Fe-based alloy
crystals was 1 or more and 5 or less. Further, in all the metal
powders for powder metallurgy corresponding to Example, the circle
equivalent diameter of the Fe-based alloy crystal was 1% or more
and 100% or less the circle equivalent diameter of the
particle.
[0484] On the other hand, in all the metal powders for powder
metallurgy corresponding to Comparative Example, the average number
of the Fe-based alloy crystals was 6 or more.
21. Evaluation of Sintered Body (Ti--Zr Based)
21.1 Evaluation of Relative Density
[0485] With respect to the sintered bodies of the respective sample
Nos. shown in Table 17, the sintered density was measured in
accordance with the method for measuring the density of sintered
metal materials specified in JIS Z 2501 (2000), and also the
relative density of each sintered body was calculated with
reference to the true density of the metal powder for powder
metallurgy used for producing each sintered body.
[0486] The calculation results are shown in Table 18.
21.2 Evaluation of Hardness
[0487] With respect to the sintered bodies of the respective sample
Nos. shown in Table 17, the Vickers hardness was measured in
accordance with the Vickers hardness test method specified in JIS Z
2244 (2009).
[0488] Then, the measured hardness was evaluated according to the
evaluation criteria described in 3.2.
[0489] The evaluation results are shown in Table 18.
21.3 Evaluation of Tensile Strength, 0.2% Proof Stress, and
Elongation
[0490] With respect to the sintered bodies of the respective sample
Nos. shown in Table 17, the tensile strength, 0.2% proof stress,
and elongation were measured in accordance with the metal material
tensile test method specified in JIS Z 2241 (2011).
[0491] Then, the measured values of the physical properties were
evaluated according to the above-mentioned evaluation criteria
described in 3.3.
[0492] The evaluation results are shown in Table 18.
21.4 Evaluation of Fatigue Strength
[0493] With respect to the sintered bodies of the respective sample
Nos. shown in Table 17, the fatigue strength was measured in the
same manner as in 3.4.
[0494] Then, the measured fatigue strength was evaluated according
to the evaluation criteria described in 3.4.
[0495] The evaluation results are shown in Table 18.
TABLE-US-00018 TABLE 18 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 159 Example 4.51 98.8 A
A A A A No. 160 Example 6.05 98.4 A A A B B No. 161 Example 3.16
98.3 A A A A B No. 162 Example 10.37 98.1 A B B B C No. 163 Example
4.82 98.5 A B B B B No. 164 Example 14.15 98.2 A B B B B No. 165
Example 3.64 98.9 A A A B A No. 166 Example 2.11 98.2 A B B C C No.
167 Compar- 4.92 94.7 F C C C D ative Example No. 168 Compar- 3.96
95.3 F D D D E ative Example No. 169 Compar- 2.54 95.0 F F F D D
ative Example No. 170 Compar- 3.11 95.3 F E E E E ative Example No.
171 Compar- 2.24 94.3 F F F F F ative Example
[0496] As apparent from Table 18, it was confirmed that the
sintered bodies corresponding to Example each have a higher
relative density than the sintered bodies corresponding to
Comparative Example. It was also confirmed that there is a
significant difference in properties such as tensile strength, 0.2%
proof stress, elongation, and fatigue strength between the sintered
bodies corresponding to Example and the sintered bodies
corresponding to Comparative Example.
22. Production of Sintered Body (Zr--Ta Based)
Sample Nos. 172 to 184
[0497] Sintered bodies were obtained in the same manner as the
method for producing the sintered body of sample No. 1 except that
the composition and the like of the metal powder for powder
metallurgy were changed as shown in Table 19, respectively.
TABLE-US-00019 TABLE 19 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (Zr) (Ta) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 172 Example 12.83 0.87 0.73 0.07 0.12
0.11 0.17 <0.01 0.29 remainder 0.58 0.19 0.26 0.22 0.28 No. 173
Example 14.43 0.28 0.54 0.06 0.06 0.22 0.12 <0.01 0.25 remainder
1.00 0.12 0.22 0.43 0.34 No. 174 Example 11.33 1.09 0.84 0.06 0.16
0.08 0.12 <0.01 0.37 remainder 0.38 0.22 0.26 0.20 0.20 No. 175
Example 12.86 0.71 0.78 0.03 0.06 1.15 0.39 <0.01 0.45 remainder
0.50 0.09 0.12 0.13 1.54 No. 176 Example 12.59 0.81 0.45 0.02 0.10
0.34 0.28 <0.01 0.37 remainder 0.20 0.12 0.27 0.15 0.62 No. 177
Example 13.09 1.05 0.81 0.05 0.04 0.57 0.21 <0.01 0.34 remainder
1.25 0.09 0.11 0.09 0.78 No. 178 Example 14.55 0.43 0.78 0.12 0.22
0.16 0.10 <0.01 0.39 remainder 0.55 0.34 0.44 0.79 0.26 No. 179
Example 12.74 0.72 0.77 0.28 0.47 0.15 0.10 <0.01 0.29 remainder
0.66 0.75 0.97 1.04 0.25 No. 180 Compar- 12.66 0.97 0.92 0.00 0.11
0.21 0.16 <0.01 0.36 remainder 0.00 0.11 0.12 0.11 0.37 ative
Example No. 181 Compar- 12.85 0.71 0.76 0.10 0.00 0.19 0.12
<0.01 0.39 remainder -- 0.10 0.13 0.14 0.31 ative Example No.
182 Compar- 13.45 0.36 0.45 0.81 0.09 0.15 0.10 <0.01 0.27
remainder 9.00 0.90 2.00 2.50 0.25 ative Example No. 183 Compar-
13.66 0.63 0.38 0.09 0.82 0.10 0.21 <0.01 0.44 remainder 0.11
0.91 2.39 1.44 0.31 ative Example No. 184 Compar- 13.55 0.96 0.76
0.00 0.00 0.15 0.10 <0.01 0.39 remainder -- 0.00 0.00 0.00 0.25
ative Example
[0498] In Table 19, among the sintered bodies of the respective
sample Nos., those corresponding to the invention are indicated by
"Example", and those not corresponding to the invention are
indicated by "Comparative Example".
[0499] Each sintered body contained very small amounts of
impurities, but the description thereof in Table 19 is omitted.
23. Evaluation of Metal Powder (Zr--Ta Based)
[0500] With respect to the cross sections of the particles of the
metal powders for powder metallurgy of the respective sample Nos.
shown in Table 19, the crystal structure was evaluated by TEM.
[0501] As a result, in all the metal powders for powder metallurgy
corresponding to Example, the average number of the Fe-based alloy
crystals was 1 or more and 5 or less. Further, in all the metal
powders for powder metallurgy corresponding to Example, the circle
equivalent diameter of the Fe-based alloy crystal was 1% or more
and 100% or less the circle equivalent diameter of the
particle.
[0502] On the other hand, in all the metal powders for powder
metallurgy corresponding to Comparative Example, the average number
of the Fe-based alloy crystals was 6 or more.
24. Evaluation of Sintered Body (Zr--Ta Based)
24.1 Evaluation of Relative Density
[0503] With respect to the sintered bodies of the respective sample
Nos. shown in Table 19, the sintered density was measured in
accordance with the method for measuring the density of sintered
metal materials specified in JIS Z 2501 (2000), and also the
relative density of each sintered body was calculated with
reference to the true density of the metal powder for powder
metallurgy used for producing each sintered body.
[0504] The calculation results are shown in Table 20.
24.2 Evaluation of Hardness
[0505] With respect to the sintered bodies of the respective sample
Nos. shown in Table 19, the Vickers hardness was measured in
accordance with the Vickers hardness test method specified in JIS Z
2244 (2009).
[0506] Then, the measured hardness was evaluated according to the
evaluation criteria described in 3.2.
[0507] The evaluation results are shown in Table 20.
24.3 Evaluation of Tensile Strength, 0.2% Proof Stress, and
Elongation
[0508] With respect to the sintered bodies of the respective sample
Nos. shown in Table 19, the tensile strength, 0.2% proof stress,
and elongation were measured in accordance with the metal material
tensile test method specified in JIS Z 2241 (2011).
[0509] Then, the measured values of the physical properties were
evaluated according to the above-mentioned evaluation criteria
described in 3.3.
[0510] The evaluation results are shown in Table 20.
24.4 Evaluation of Fatigue Strength
[0511] With respect to the sintered bodies of the respective sample
Nos. shown in Table 19, the fatigue strength was measured in the
same manner as in 3.4.
[0512] Then, the measured fatigue strength was evaluated according
to the evaluation criteria described in 3.4.
[0513] The evaluation results are shown in Table 20.
TABLE-US-00020 TABLE 20 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 172 Example 4.22 98.8 A
A A A A No. 173 Example 6.29 98.5 A A A B B No. 174 Example 3.25
98.6 A A A A B No. 175 Example 9.86 98.2 A B B B B No. 176 Example
5.23 98.6 A A A B A No. 177 Example 14.39 98.4 A B B A A No. 178
Example 3.75 98.7 A A A B A No. 179 Example 2.08 98.3 A B B C C No.
180 Compar- 4.89 94.6 F E E E E ative Example No. 181 Compar- 4.21
95.2 A C C D D ative Example No. 182 Compar- 2.63 95.1 F D D E E
ative Example No. 183 Compar- 3.08 94.8 F F F E E ative Example No.
184 Compar- 2.39 94.2 F F F F F ative Example
[0514] As apparent from Table 20, it was confirmed that the
sintered bodies corresponding to Example each have a higher
relative density than the sintered bodies corresponding to
Comparative Example. It was also confirmed that there is a
significant difference in properties such as tensile strength, 0.2%
proof stress, elongation, and fatigue strength between the sintered
bodies corresponding to Example and the sintered bodies
corresponding to Comparative Example.
25. Production of Sintered Body (Zr--V Based)
Sample Nos. 185 to 197
[0515] Sintered bodies were obtained in the same manner as the
method for producing the sintered body of sample No. 1 except that
the composition and the like of the metal powder for powder
metallurgy were changed as shown in Table 21, respectively.
TABLE-US-00021 TABLE 21 Metal powder for powder metallurgy Alloy
composition (E1 + (E1 + E1 E2 E1/ E1 + E2)/ E2)/ Mn + Re- Sample Cr
C Si (Zr) (V) Mn Ni Cu O Fe E2 E2 Si C Ni marks No. -- mass % --
mass % -- -- mass % -- No. 185 Example 12.81 0.86 0.72 0.12 0.07
0.10 0.18 <0.01 0.28 remainder 1.71 0.19 0.26 0.22 0.28 No. 186
Example 14.44 0.27 0.55 0.07 0.11 0.19 0.12 <0.01 0.27 remainder
0.64 0.18 0.33 0.67 0.31 No. 187 Example 11.28 1.11 0.83 0.18 0.07
0.08 0.11 <0.01 0.38 remainder 2.57 0.25 0.30 0.23 0.19 No. 188
Example 12.88 0.72 0.79 0.06 0.02 1.15 0.36 <0.01 0.43 remainder
3.00 0.08 0.10 0.11 1.51 No. 189 Example 12.57 0.79 0.43 0.04 0.02
0.34 0.05 <0.01 0.39 remainder 2.00 0.06 0.14 0.08 0.39 No. 190
Example 13.11 1.02 0.90 0.05 0.04 0.56 0.21 <0.01 0.32 remainder
1.25 0.09 0.10 0.09 0.77 No. 191 Example 14.56 0.42 0.76 0.12 0.16
0.16 0.12 <0.01 0.36 remainder 0.75 0.28 0.37 0.67 0.28 No. 192
Example 12.72 0.71 0.78 0.27 0.45 0.12 0.09 <0.01 0.27 remainder
0.60 0.72 0.92 1.01 0.21 No. 193 Compar- 12.64 0.95 0.91 0.00 0.12
0.19 0.15 <0.01 0.34 remainder 0.00 0.12 0.13 0.13 0.34 ative
Example No. 194 Compar- 12.87 0.72 0.77 0.10 0.00 0.21 0.11
<0.01 0.37 remainder -- 0.10 0.13 0.14 0.32 ative Example No.
195 Compar- 13.48 0.34 0.44 0.81 0.11 0.16 0.12 <0.01 0.29
remainder 7.36 0.92 2.09 2.71 0.28 ative Example No. 196 Compar-
13.68 0.64 0.35 0.09 0.82 0.15 0.25 <0.01 0.44 remainder 0.11
0.91 2.60 1.42 0.40 ative Example No. 197 Compar- 13.57 0.92 0.77
0.00 0.00 0.16 0.12 <0.01 0.38 remainder -- 0.00 0.00 0.00 0.28
ative Example
[0516] In Table 21, among the sintered bodies of the respective
sample Nos., those corresponding to the invention are indicated by
"Example", and those not corresponding to the invention are
indicated by "Comparative Example".
[0517] Each sintered body contained very small amounts of
impurities, but the description thereof in Table 21 is omitted.
26. Evaluation of Metal Powder (Zr--V Based)
[0518] With respect to the cross sections of the particles of the
metal powders for powder metallurgy of the respective sample Nos.
shown in Table 21, the crystal structure was evaluated by TEM.
[0519] As a result, in all the metal powders for powder metallurgy
corresponding to Example, the average number of the Fe-based alloy
crystals was 1 or more and 5 or less. Further, in all the metal
powders for powder metallurgy corresponding to Example, the circle
equivalent diameter of the Fe-based alloy crystal was 1% or more
and 100% or less the circle equivalent diameter of the
particle.
[0520] On the other hand, in all the metal powders for powder
metallurgy corresponding to Comparative Example, the average number
of the Fe-based alloy crystals was 6 or more.
27. Evaluation of Sintered Body (Zr--V Based)
27.1 Evaluation of Relative Density
[0521] With respect to the sintered bodies of the respective sample
Nos. shown in Table 21, the sintered density was measured in
accordance with the method for measuring the density of sintered
metal materials specified in JIS Z 2501 (2000), and also the
relative density of each sintered body was calculated with
reference to the true density of the metal powder for powder
metallurgy used for producing each sintered body.
[0522] The calculation results are shown in Table 22.
27.2 Evaluation of Hardness
[0523] With respect to the sintered bodies of the respective sample
Nos. shown in Table 21, the Vickers hardness was measured in
accordance with the Vickers hardness test method specified in JIS Z
2244 (2009).
[0524] Then, the measured hardness was evaluated according to the
evaluation criteria described in 3.2.
[0525] The evaluation results are shown in Table 22.
27.3 Evaluation of Tensile Strength, 0.2% Proof Stress, and
Elongation
[0526] With respect to the sintered bodies of the respective sample
Nos. shown in Table 21, the tensile strength, 0.2% proof stress,
and elongation were measured in accordance with the metal material
tensile test method specified in JIS Z 2241 (2011).
[0527] Then, the measured values of the physical properties were
evaluated according to the above-mentioned evaluation criteria
described in 3.3.
[0528] The evaluation results are shown in Table 22.
27.4 Evaluation of Fatigue Strength
[0529] With respect to the sintered bodies of the respective sample
Nos. shown in Table 21, the fatigue strength was measured in the
same manner as in 3.4.
[0530] Then, the measured fatigue strength was evaluated according
to the evaluation criteria described in 3.4.
[0531] The evaluation results are shown in Table 22.
TABLE-US-00022 TABLE 22 Metal powder Evaluation results of sintered
body Average 0.2% particle Relative Vickers Tensile proof Elonga-
Fatigue Sample diameter density hardness strength stress tion
strength No. -- .mu.m % -- -- -- -- -- No. 185 Example 4.51 99.2 A
A A A A No. 186 Example 6.78 98.9 A A A B B No. 187 Example 3.24
99.1 A A A B B No. 188 Example 9.87 98.6 A A B B B No. 189 Example
5.02 98.8 A A B B B No. 190 Example 14.39 98.7 A A B B B No. 191
Example 3.82 99.0 A A A A B No. 192 Example 2.09 98.5 A B B B C No.
193 Compar- 4.85 95.0 F D D D D ative Example No. 194 Compar- 4.16
95.8 A C C D D ative Example No. 195 Compar- 2.78 95.2 F F F E E
ative Example No. 196 Compar- 3.11 95.0 F F F F F ative Example No.
197 Compar- 2.28 94.5 F F F F F ative Example
[0532] As apparent from Table 22, it was confirmed that the
sintered bodies corresponding to Example each have a higher
relative density than the sintered bodies corresponding to
Comparative Example. It was also confirmed that there is a
significant difference in properties such as tensile strength, 0.2%
proof stress, elongation, and fatigue strength between the sintered
bodies corresponding to Example and the sintered bodies
corresponding to Comparative Example.
28. Evaluation of Specularity of Sintered Body
28.1 Evaluation of Porosity Near Surface and Inside
[0533] First, each of the sintered bodies of the respective sample
Nos. shown in Table 23 was cut and the cross section was
polished.
[0534] Then, a porosity A1 near the surface of the sintered body
and a porosity A2 inside the sintered body were calculated and also
A2-A1 was calculated.
[0535] The above calculation results are shown in Table 23.
28.2 Evaluation of Specular Gloss
[0536] First, each of the sintered bodies of the respective sample
Nos. shown in Table 23 was subjected to a barrel polishing
treatment.
[0537] Then, the specular gloss of the sintered body was measured
in accordance with the method for measuring the specular gloss
specified in JIS Z 8741 (1997). The incident angle of light with
respect to the surface of the sintered body was set to 60.degree.,
and as a reference plane for calculating the specular gloss, a
glass having a specular gloss of 90 and a refractive index of 1.500
was used. Then, the measured specular gloss was evaluated according
to the following evaluation criteria.
Evaluation Criteria for Specular Gloss
[0538] A: The specularity of the surface is very high (the specular
gloss is 200 or more).
[0539] B: The specularity of the surface is high (the specular
gloss is 150 or more and less than 200).
[0540] C: The specularity of the surface is slightly high (the
specular gloss is 100 or more and less than 150).
[0541] D: The specularity of the surface is slightly low (the
specular gloss is 60 or more and less than 100).
[0542] E: The specularity of the surface is low (the specular gloss
is 30 or more and less than 60).
[0543] F: The specularity of the surface is very low (the specular
gloss is less than 30).
[0544] The above evaluation results are shown in Table 23.
TABLE-US-00023 TABLE 23 Evaluation Example/ Alloy results Sample
Comparative composition A2-A1 Specular No. Example E1 E2 [%] gloss
1 Example Zr Nb 0.8 A 31 Comparative 0.1 E Example 85 Example Hf Nb
0.8 A 101 Comparative 0.1 E Example 106 Example Ti Nb 1.1 A 115
Comparative 0.2 E Example 120 Example Nb Ta 0.4 C 128 Comparative
0.1 E Example 133 Example Y Nb 1.2 A 142 Comparative 0.1 E Example
146 Example V Nb 0.7 C 155 Comparative 0.2 E Example 159 Example Ti
Zr 0.4 C 169 Comparative 0.1 E Example 172 Example Zr Ta 0.6 B 182
Comparative 0.1 E Example 185 Example Zr V 0.6 B 195 Comparative
0.1 E Example
[0545] As apparent from Table 23, it was confirmed that the
sintered bodies corresponding to Example each have a higher
specular gloss than the sintered bodies corresponding to
Comparative Example. This is considered to be because the porosity
near the surface of the sintered body is low, and therefore, light
scattering is suppressed, however, the ratio of regular reflection
is increased.
* * * * *