U.S. patent application number 12/279471 was filed with the patent office on 2009-02-12 for iron-based powder mixture, and method of manufacturing iron-based compacted body and iron-based sintered body.
This patent application is currently assigned to JFE Steel Corporation a corporation of Japan. Invention is credited to Masashi Fujinaga, Tomoshige Ono, Yukiko Ozaki, Shigeru Unami.
Application Number | 20090041608 12/279471 |
Document ID | / |
Family ID | 38509266 |
Filed Date | 2009-02-12 |
United States Patent
Application |
20090041608 |
Kind Code |
A1 |
Ozaki; Yukiko ; et
al. |
February 12, 2009 |
IRON-BASED POWDER MIXTURE, AND METHOD OF MANUFACTURING IRON-BASED
COMPACTED BODY AND IRON-BASED SINTERED BODY
Abstract
An iron-based powder mixture for powder metallurgy is provided,
in which iron-based powder is blended with at least one selected
from talc and steatite, and preferably further blended with
metallic soap, thereby when a compacted body is sintered, furnace
environment is not adversely affected, and excellent compaction
performance is achieved even in a low temperature range of less
than 100.degree. C., and more preferably, an obtained sintered body
has excellent machining performance.
Inventors: |
Ozaki; Yukiko; (Chiba,
JP) ; Ono; Tomoshige; (Chiba, JP) ; Unami;
Shigeru; (Chiba, JP) ; Fujinaga; Masashi;
(Chiba, JP) |
Correspondence
Address: |
IP GROUP OF DLA PIPER US LLP
ONE LIBERTY PLACE, 1650 MARKET ST, SUITE 4900
PHILADELPHIA
PA
19103
US
|
Assignee: |
JFE Steel Corporation a corporation
of Japan
Chiyoda-ku, Tokyo
JP
|
Family ID: |
38509266 |
Appl. No.: |
12/279471 |
Filed: |
February 14, 2007 |
PCT Filed: |
February 14, 2007 |
PCT NO: |
PCT/JP2007/053125 |
371 Date: |
August 14, 2008 |
Current U.S.
Class: |
419/10 ; 419/66;
75/252 |
Current CPC
Class: |
B22F 2998/10 20130101;
C22C 38/12 20130101; B22F 2999/00 20130101; C22C 33/0264 20130101;
C22C 38/08 20130101; B22F 1/0003 20130101; C22C 38/16 20130101;
B22F 2999/00 20130101; B22F 2998/10 20130101; B22F 3/02 20130101;
B22F 1/007 20130101; B22F 1/0059 20130101; B22F 1/0003 20130101;
B22F 1/0003 20130101; B22F 3/10 20130101 |
Class at
Publication: |
419/10 ; 75/252;
419/66 |
International
Class: |
B22F 3/12 20060101
B22F003/12; B22F 1/00 20060101 B22F001/00; B22F 3/02 20060101
B22F003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2006 |
JP |
2006-037916 |
Dec 15, 2006 |
JP |
2006-337876 |
Claims
1.-9. (canceled)
10. An iron-based powder mixture containing: an iron-based powder,
and containing as additives, at least one selected from talc and
steatite, and fatty acid amide.
11. The iron-based powder mixture according to claim 10: wherein
the additives further contain metallic soap.
12. The iron-based powder mixture according to claim 10.: wherein
the iron-based powder mixture is further blended with alloying
powder.
13. The iron-based powder mixture according to claim 11: wherein
the iron-based powder mixture is further blended with alloying
powder.
14. The iron-based powder mixture according to claim 12: wherein
the iron-based powder is water-atomized alloyed steel powder
containing Mo of 0.3 to 0.5 mass %, Mn of 0.1 to 0.25 mass %, and
the remainder being Fe and inevitable impurities, and wherein the
alloying powder is Cu powder of 1 to 3 mass % and graphite powder
of 0.5 to 1.0 mass %.
15. The iron-based powder mixture according to claim 13: wherein
the iron-based powder is water-atomized alloyed steel powder
containing Mo of 0.3 to 0.5 mass %, Mn of 0.1 to 0.25 mass %, and
the remainder being Fe and inevitable impurities, and wherein the
alloying powder is Cu powder of 1 to 3 mass % and graphite powder
of 0.5 to 1.0 mass %.
16. An iron-based powder mixture: water-atomized alloyed steel
powder containing Mo of 0.3 to 0.5 mass %, Mn of 0.1 to 0.25 mass
%, and the remainder being Fe and inevitable impurities mixed with,
Cu powder of 1 to 3 mass %, graphite powder of 0.5 to 1.0 mass %,
at least one selected from talc and steatite in a range of 0.05 to
0.5 mass % in total, and fatty acid amide.
17. The iron-based powder mixture according to claim 16: wherein
the iron-based powder mixture further contains metallic soap.
18. A method of manufacturing an iron-based compacted body
comprising: filling the iron-based powder mixture according to
claim 10 in a die, and compacting the mixture at a temperature of
less than 100.degree. C.
19. A method of manufacturing an iron-based compacted body
comprising: filling the iron-based powder mixture according to
claim 11 in a die, and compacting the mixture at a temperature of
less than 100.degree. C.
20. A method of manufacturing an iron-based compacted body
comprising: filling the iron-based powder mixture according to
claim 12 in a die, and compacting the mixture at a temperature of
less than 100.degree. C.
21. A method of manufacturing an iron-based compacted body
comprising: filling the iron-based powder mixture according to
claim 13 in a die, and compacting the mixture at a temperature of
less than 100.degree. C.
22. A method of manufacturing an iron-based sintered body
comprising: filling the iron-based powder mixture according to
claim 10 in a die, compacting the mixture at a temperature of less
than 100.degree. C., and sintering an obtained iron-based compacted
body.
23. A method of manufacturing an iron-based sintered body
comprising: filling the iron-based powder mixture according to
claim 11 in a die, compacting the mixture at a temperature of less
than 100.degree. C., and sintering an obtained iron-based compacted
body.
24. A method of manufacturing an iron-based sintered body
comprising: filling the iron-based powder mixture according to
claim 12 in a die, compacting the mixture at a temperature of less
than 100.degree. C., and sintering an obtained iron-based compacted
body.
25. A method of manufacturing an iron-based sintered body
comprising: filling the iron-based powder mixture according to
claim 13 in a die, compacting the mixture at a temperature of less
than 100.degree. C., and sintering an obtained iron-based compacted
body.
Description
RELATED APPLICATIONS
[0001] This is a .sctn.371 of International Application No.
PCT/JP2007/053125, with an international filing date of Feb. 14,
2007 (WO 2007/105429, published Sep. 20, 2007), which is based on
Japanese Patent Application Nos. 2006-037916, filed Feb. 15, 2006,
and 2006-337876, filed Dec. 15, 2006.
TECHNICAL FIELD
[0002] This disclosure relates to an iron-based powder mixture
including iron-based power mixed with a lubricant, and alloying
powder as needed. The iron-based powder mixture is suitable for
powder metallurgy, and particularly suitable for compaction in a
temperature range from normal temperature to less than 100.degree.
C.
[0003] The disclosure further relates to a powder mixture for
powder metallurgy, which is preferable for manufacturing of
high-strength sintered parts for automobiles.
[0004] Moreover, the disclosure relates to a method of
manufacturing an iron-based compacted body using the iron-based
powder mixture as a material, and a method of manufacturing an
iron-based power sintered-body using the iron-based compacted body
as a material.
BACKGROUND
[0005] The iron-based powder mixture for powder metallurgy is
typically manufactured in a way that iron-based powder is added
with a lubricant and alloying powder and mixed, and furthermore
added with powder of free machining additives and mixed as
needed.
[0006] Here, the iron-based powder is a main component of the
powder mixture, and iron powder (including pure iron powder), or
alloyed steel powder is mainly used as the iron-based powder. The
alloyed steel powder contains an alloyed element. While steel
powder containing no C may be used as the alloyed steel powder,
steel powder containing C and iron powder containing no C are
generally called alloyed steel powder herein. In addition to the
above, partly diffused alloyed steel powder may be used, in which
an alloy element is bonded to pure iron powder or the like by
partial diffusion. In the application, the partly diffused alloyed
steel powder is assumed to be a type of the alloyed iron
powder.
[0007] The lubricant is an additive that is added particularly for
facilitating compaction or ejection of a compacted body from a die
after compaction. While various substances can be used for the
lubricant, the lubricant is selected in consideration of a mixing
property with iron-based powder or a decomposition property during
sintering. As an example of the lubricant, zinc stearate, aluminum
stearate, lead stearate and the like are listed. Various lubricants
are exemplified in U.S. Pat. No. 5,256,185 and the like.
[0008] The alloying powder is added mainly for adjusting a
composition and/or a structure of an iron-based compacted body or
an iron-based sintered body, and includes graphite powder, copper
powder, iron phosphide powder, molybdenum powder, and nickel
powder.
[0009] The powder of free machining additives (or free machining
elements), such as S or MnS, is added particularly for improving
machining performance of the sintered body.
[0010] Recently, with increase in demand for increasing strength of
sintered parts, as disclosed in Japanese Unexamined Patent
Application Publication JP-A-2-156002 (1990), Japanese Examined
Patent Application Publication JP-B-7-103404 (1995), and U.S. Pat.
No. 5,368,630, a warm compaction technique has been developed, in
which an iron-based powder mixture is compacted while being heated,
thereby increase in density and increase in strength of a compacted
body can be achieved. According to the technique, density of a
compacted body can be increased at a relatively low load by using a
phenomenon that iron-based powder is gradually reduced in
resistance to plastic deformation as the powder is heated.
[0011] However, such an iron-based powder mixture has the following
problems. That is, the warm compaction is a technique that a die
and powder are heated to high temperature before-hand, then the
iron-based powder mixture is compacted. As the heating temperature,
while a range of 70 to 120.degree. C. is described in
JP-A-2-156002, heating is substantially preferably performed at
100.degree. C. or more as described in JP-B-7-103404 and U.S. Pat.
No. 5,368,630. However, since it is very difficult that the
iron-based powder mixture having low heat conductivity is uniformly
heated to 100.degree. C. or more, and kept at the temperature,
productivity of sintered parts have been likely reduced. Moreover,
the iron-based powder mixture is heated for a long time, resulting
in a problem that the iron-based powder mixture is oxidized.
[0012] JP-A-9-104901 (1997) or JP-A-10-317001 (1998) discloses a
technique that an inorganic compound having a layered crystal such
as MoS.sub.2, carbon fluoride, and graphite is used as the
lubricant. However, when MoS.sub.2 is used, the MoS.sub.2 may be
decomposed during sintering, causing generation of harmful sulfur
gas that possibly contaminates a furnace. When carbon fluoride is
used so that the iron-based powder mixture is sintered in a
hydrogen atmosphere, there is fear that corrosive hydrogen fluoride
may be generated.
[0013] Therefore, it is desired to develop an iron-based powder
mixture having high compressibility similar to that of a
warm-compacted, iron-based powder mixture, even if it is not
subjected to warm compaction.
[0014] On the other hand, for the iron-based powder mixture, the
problem of machining performance is also desired to be solved.
[0015] When parts of various machines such as automobiles are
manufactured by a powder metallurgy technique, a powder mixture for
powder metallurgy is filled in a die and compacted, and furthermore
sintered. Parts of various machines obtained in this way
(hereinafter, called sintered parts) typically have a density of
5.0 to 7.2 g/cm.sup.3 respectively. Moreover, since each of the
sintered parts is good in dimension accuracy, a part having a
complicated shape can be produced.
[0016] The sintered parts are used for parts of various machines.
In particular, parts for automobiles (for example, gears) are
required to have high strength and high fatigue characteristics.
Thus, a technique of using a powder mixture for powder metallurgy,
which is added with an alloyed element, is variously investigated
to manufacture a sintered part having high strength and high
fatigue characteristics. For example, JP-B-45-9649 (1970) discloses
a powder mixture for powder metallurgy, which includes pure Fe
powder diffusion-bonded with powder of Ni, Cu, Mo or the like, and
is preferable for manufacturing a sintered part having high
strength and high fatigue characteristics, and is excellent in
compressibility. Moreover, as a powder mixture for powder
metallurgy preferable for manufacturing a sintered part having high
strength, JP-A-61-163239 (1986) discloses a powder mixture for
powder metallurgy, which includes low alloyed-steel powder, in
which C and Mo are contained, and Mn and Cr are substantially not
contained; the steel powder being added with Cu powder and/or Ni
powder, and furthermore, added with graphite powder. Moreover,
JP-A-63-114903 (1988) discloses a powder mixture for powder
metallurgy, in which Cu powder is diffusion-bonded to alloyed steel
powder containing Mo, Mn and C.
[0017] However, even if powder metallurgy techniques are used, when
a sintered part, which is required to have extremely strict
dimension accuracy, is manufactured, the sintered part needs to be
subjected to machining (such as cutting or drilling) after
sintering. However, since a sintered part is bad in machining
performance, a cutting tool used in the machining is signifycantly
worn. As a result, machining cost is increased, leading to increase
in manufacturing cost of a sintered part. Such degradation in
machining performance of a sintered part is caused by a phenomenon
that a solid surface intermittently appears in the inside of a work
material due to pores within the sintered part, which
intermittently give a shock to a tool during cutting, in addition,
heat conductivity of the sintered part is thus decreased, and
consequently temperature of the sintered part is increased during
cutting. The machining performance is significantly degraded as
strength of a sintered part is increased.
[0018] As described before, it is previously known that the powder
mixture for powder metallurgy is added with free machining
additives, thereby machining performance of a sintered part is
improved. The free machining additives have an effect of easily
breaking chips, or an effect of forming a thin built-up edge on a
surface of a cutting tool to improve lubricity of the cutting tool
(particularly, on a rake face).
[0019] However, free machining additives containing S as a main
component, like MoS.sub.2 described above, contaminate a furnace.
Moreover, in the techniques disclosed in JP-B-45-9649,
JP-A-61-163239, and JP-A-63-114903, since hardness of the obtained
sintered part is particularly high, even if the free machining
additives are added to the powder mixture for powder metallurgy,
significant improvement of machining performance cannot be
expected.
[0020] As a technique of eliminating a bad effect on -the furnace
to improve machining performance of a sintered part, a technique of
using an MgO--SiO.sub.2 composite oxide is proposed. For example,
JP-A-1-255604 (1989) discloses a technique that an MgO-SiO.sub.2
composite oxide (for example, anhydrous talc), in which
MgO/SiO.sub.2 is 0.5 or more and less than 1.0 in mol ratio, and
crystallization water is not contained, is blended to iron-based
powder as means of improving machining performance without reducing
mechanical properties (for example, strength) of a sintered body.
Moreover, JP-A-64-79302 (1989) discloses a technique that free
machining additives including a MgO-SiO.sub.2 composite oxide
and/or glass powder are contained in reduced iron powder in a
configuration that the additives stay inside of each iron powder
particle (that is, the additives are added to iron powder raw
material before reduction).
[0021] Any of the publications describes that the composite oxide
is preferably added in a range of 0.1 to 1.5 wt %. However,
according to a result of investigation on iron-based powder
containing a lubricant (zinc stearate of 1 wt %) or the like, as an
added amount of the composite oxide is increased, an effect of
improving machining performance is increased, and particularly
large effect is obtained in a range of 0.5 to 1.0 wt %, but on the
other hand, mechanical properties are reduced (Table 3 in
JP-A-1-255604, and FIGS. 6 and 8 in JP-A-64-79302). That is, the
techniques are not necessarily advantageous in a point of quality
of a sintered body.
[0022] It could therefore be helpful to provide an iron-based
powder mixture for powder metallurgy, which has no adverse effect
on furnace environment during sintering a compact, and provides
excellent compaction performance that the powder mixture can be
compacted at high density even in a low temperature region of less
than 100.degree. C.
[0023] Moreover, in consideration of increase in demand for
improving machining performance of a sintered part to reduce
machining cost, it could also be helpful to provide an iron-based
powder mixture for powder metallurgy preferable for machining a
sintered part having excellent machining performance, and
particularly preferable for machining a high-strength sintered
part.
[0024] It could further be helpful to provide a method of
manufacturing an iron-based compacted body using the iron-based
powder mixture as a material and, furthermore, a method of
manufacturing an iron-based sintered body using the iron-based
compacted body as a material.
SUMMARY
[0025] We investigated a particular lubricant, by which when an
iron-based powder mixture is compacted, furnace environment is not
adversely affected, and even if the iron-based powder mixture is
compacted at a relatively low heating temperature of the iron-based
powder mixture, and preferably even if it is compacted without
being heated, a high-density compacted body can be
manufactured.
[0026] As a result, we found that when talc or steatite was used as
a lubricant and, furthermore, fatty acid amide was used,
rearrangement of iron-based powder particles was accelerated during
compaction, consequently even if compaction temperature was low,
that is, about room temperature, an iron-based compacted body
having high compaction density was obtained.
[0027] Moreover, we found that when metallic soap was added, an
extremely high effect of improving machining performance was
obtained by talc or steatite in a low added amount compared with a
previously known amount, which had no adverse influence on
mechanical properties.
[0028] We thus provide: [0029] (1) An iron-based powder mixture,
characterized by containing iron-based powder, and containing as
additives: [0030] at least one selected from talc and steatite, and
[0031] fatty acid amide. [0032] (2) The iron-based powder mixture
according to the above (1), characterized in that the additives
further contain metallic soap. [0033] (3) The iron-based powder
mixture according to the above (1) or (2), characterized in that
the iron-based powder mixture is further blended with alloying
powder. [0034] (4) The iron-based powder mixture according to the
above (3), characterized in that the iron-based powder is
water-atomized alloyed steel powder containing Mo of 0.3 to 0.5
mass %, Mn of 0.1 to 0.25 mass %, and the remainder being Fe and
inevitable impurities, and the alloying powder is Cu powder of 1 to
3 mass % and graphite powder of 0.5 to 1.0 mass %. [0035] (5) An
iron-based powder mixture, characterized in that the iron-based
powder mixture is formed by mixing water-atomized alloyed steel
powder containing Mo of 0.3 to 0.5 mass %, Mn of 0.1 to 0.25 mass
%, and the remainder being Fe and inevitable impurities, Cu powder
of 1 to 3 mass %, graphite powder of 0.5 to 1.0 mass %, at least
one selected from talc and steatite in a range of 0.05 to 0.5 mass
% in total, and fatty acid amide. [0036] (6) The iron-based powder
mixture according to the above (5), wherein the iron-based powder
mixture further contains metallic soap. [0037] (7) A method of
manufacturing an iron-based compacted body, characterized in that
the iron-based powder mixture according to any one of the above (1)
to (6) is filled in a die, and then compacted at a temperature of
less than 100.degree. C. [0038] (8) A method of manufacturing an
iron-based sintered body, characterized in that the iron-based
powder mixture according to any one of the above (1) to (6) is
filled in a die, then compacted at a temperature of less than
100.degree. C., and then an obtained iron-based compacted body is
sintered.
[0039] Each of the content of an alloyed element (including Mo or
Mn) in the iron-based powder, the amount of alloying powder
(including Cu powder and graphite powder) to be added, and the
added amount of talc or steatite refers to percentage of mass of
the iron-based powder mixture.
DETAILED DESCRIPTION
[0040] First, materials of the iron-based powder mixture are
described. The content of each of alloyed elements in the
iron-based powder, and the blending amount of each of the materials
(alloying powder, lubricant and the like) are expressed in a weight
percent of mass (100 mass %) of an iron-based powder mixture
obtained by mixing those, that is, the weight percent is expressed
using a numerical value included in a numerical value of the mass
of the powder mixture. However, such a weight percent is not
significantly different in numerical value from that in the case
that the alloy content (including the amount of partly diffused
alloy) and the like in the iron-based powder is expressed in a
weight percent of mass of the iron-based powder.
Iron-based Powder
[0041] As the iron-based powder, pure iron powder such as atomized
iron powder or reduced iron powder, or alloyed steel powder is
exemplified. As the alloyed steel powder, partly-diffused alloyed
steel powder and prealloyed steel powder (in which alloyed elements
are already contained when melted) are exemplified, and
furthermore, hybrid steel powder is exemplified, in which alloyed
elements are partly diffused in the prealloyed steel powder.
[0042] The content of impurities in the iron-based powder may be
about 3 mass % or less in total. The content of each of typical
impurities is as follows: C is 0.05 mass % or less, Si is 0.10 mass
% or less, Mn (in the case that Mn is not added as an alloy
element) is 0.50 mass % or less, P is 0.03 mass % or less, S is
0.03 mass % or less, 0 is 0.30 mass % or less, and N is 0.1 mass %
or less.
[0043] For the alloyed steel powder, Cr, Mn, Ni, Mo, V, Ti, Cu, Nb
and the like can be alloyed. In particular, Ti, Ni, Mo, Cu and the
like can be added even by diffusion bonding. If the precondition as
the iron-based powder (Fe content is 50 mass % or more) is
satisfied, other alloy elements are not particularly limited in
content.
[0044] Average particle diameter of the iron-based powder is
preferably adjusted to be in a typically used range for powder
metallurgy, that is, in a range of about 70 to 100 .mu.m. The
particle diameter of the powder is shown as a measurement value by
a sieving method according to JIS Z 2510, unless otherwise
specified.
[0045] Hereinafter, a specific composition of alloyed steel powder
particularly preferable for a material of a high-strength sintered
body is exemplified.
Iron-based Powder Example 1
[0046] As a first example, prealloyed steel powder is preferably
shown, which contains Mo of 0.3 to 0.5 mass %, Mn of 0.1 to 0.25
mass %, and the remainder being Fe and inevitable impurities. In
the light of productivity, the steel powder is preferably
water-atomized alloyed steel powder, which is manufactured by
water-atomizing the steel having the above composition.
[0047] The reason for a preferable range of each component is as
follows.
Mo: 0.3 to 0.5 mass %
[0048] Mo is an element that increases strength of a sintered part
by solution hardening or improvement in hardenability (quench
hardenability) of alloyed steel powder. When Mo content is less
than 0.3 mass %, an effect of increasing strength of the sintered
part by Mo is not obtained. On the other hand, when the content is
more than 0.5 mass %, since the effect of increasing strength of
the sintered part is saturated, machining performance is
unnecessarily reduced. Therefore, Mo content is preferably adjusted
to be in a range of 0.3 to 0.5 mass %.
Mn: 0.1 to 0.25 mass %
[0049] Mn is an element that increases strength of a sintered part
by solution hardening or improvement in hardenability of
water-atomized alloyed steel powder. When Mn content is less than
0.1 mass %, an effect of increasing strength of the sintered part
by Mn is not obtained. On the other hand, when the content is more
than 0.25 mass %, oxidation of Mn easily proceeds, leading to
reduction in strength and compressibility of alloyed steel powder.
Therefore, Mn content is preferably adjusted to be in a range of
0.1 to 0.25 mass %.
[0050] The rest of the powder other than the above components
preferably is Fe and inevitable impurities. The inevitable
impurities inevitably gets into the steel in a stage that an ingot
being a material of the water-atomized alloyed steel powder is
produced, or in a stage that water-atomized alloyed steel powder is
manufactured from the ingot.
[0051] A preferable method of manufacturing the water-atomized
alloyed steel powder is described below. An ingot containing a
predetermined composition (that is, the above composition) is
produced, and then the ingot is formed into powder by a water
atomizing method. Furthermore, the obtained powder is subjected to
finish reduction and crushing (or pulverizing) thereby obtaining
water-atomized alloyed steel powder. An apparatus for obtaining
powder from an ingot by the water atomizing method is not limited
to a particular type, and any previously known apparatus may be
used as the apparatus.
Alloying Powder
[0052] As the alloying powder, graphite powder, metal powder of
such as Cu, Mo and Ni, boron powder, cuprous oxide powder and the
like are exemplified. Such alloying powder is mixed to the
iron-based powder, so that strength of a sintered body can be
increased.
[0053] The blending amount of the alloying powder is preferably
adjusted to be about 0.1 to 10 mass % in the iron-based powder
mixture. The reason for this is that the alloying powder is blended
by 0.1 mass % or more, so that strength of an obtained sintered
body is advantageously improved, on the other hand, when it is
blended by more than 10 mass %, dimension accuracy of the sintered
body is reduced.
[0054] In the case of the iron-based powder example 1, particularly
Cu powder of 1 to 3 mass % and graphite powder of 0.5 to 1.0 mass %
are preferably added.
[0055] C being a main component of graphite powder is an element
that increases strength of a sintered part by solution hardening or
improvement in hardenability of water-atomized alloyed steel
powder. When the added amount of graphite powder is less than 0.5
mass %, a desired effect is not sufficiently obtained in the
iron-based powder example 1. On the other hand, when the content is
more than 1.0 mass %, strength of the sintered part is increased
beyond necessity, and consequently machining performance is
unnecessarily reduced. Therefore, the content of graphite powder is
adjusted to be in a range of 0.5 to 1.0 mass %.
[0056] Cu is an element that increases strength of a sintered part
by solution hardening or improvement in hardenability of alloyed
steel powder. Moreover, Cu powder is melted during sintering and
thus changed into a liquid phase, causing adhesion of particles of
the alloyed steel powder to one another. When the added amount of
Cu powder is less than 1 mass %, a desired effect is not
sufficiently obtained in the iron-based powder example 1. On the
other hand, when the amount is more than 3 mass %, since the effect
of increasing strength of the sintered part is saturated, machining
performance is unnecessarily reduced. Therefore, the content of Cu
powder is adjusted to be in a range of 1 to 3 mass %.
[0057] When Cu powder is added, if the added amount is within the
above range, an adding method may be a method where alloyed steel
powder is added with Cu powder and then simply mixed, or a method
of adhering Cu powder on a surface of water-atomized alloyed steel
powder via a binder. Moreover, it is acceptable that the alloyed
steel powder and the Cu powder are mixed and subjected to heat
treatment, so that the Cu powder is diffusion-bonded on a surface
of the alloyed steel powder so as to be formed into partly-diffused
alloyed steel powder (or hybrid alloyed steel powder).
Talc/Steatite
[0058] It is important that at least one selected from talc
(3MgO-4SiO.sub.2) and steatite is blended. Steatite is sometimes
called fired talc, and contains enstatite (MgO-SiO.sub.2) as a main
component.
[0059] When talc or steatite is added together with fatty acid
amide, it exhibits a particularly large effect as a lubricant.
Moreover, while talc or steatite is one of MgO-SiO.sub.2 composite
oxides known as free machining additives, if talc or steatite is
further added together with metallic soap, it exhibits a
particularly large effect even as a free machining additive.
[0060] The talc or steatite is blended as the lubricant, thereby
compressibility of a compacted body is improved, in addition,
ejection force in compaction process is reduced, so that compaction
performance is remarkably improved. The reason for this is
considered as follows.
[0061] That is, it is considered that when talc and steatite are
subjected to shear stress between iron-based powder particles
during compaction, each of the substances tends to be cleaved along
a crystal face, therefore frictional resistance between particles
within a compacted body is reduced, and thus the particles easily
move with respect to each other, as a result, density of the
compacted body is improved. Such an effect is effective in a region
of a relatively low compressive stress. On the other hand, in a
high pressure region, fatty acid amide exhibits an effect that it
thinly enters into a space between the particles so as to reduce
frictional resistance. It is considered that since the frictional
resistance is reduced over all the compressive regions in this way,
a synergetic effect is exhibited for increasing density of the
compacted body.
[0062] Moreover, it is considered that when talc or steatite exists
between a compacted body and a die, since the talc or steatite is
cleaved due to shear stress applied from a die surface during
ejecting the compacted body, slidability of the compacted body on
the die surface is improved, leading to reduction in ejection
force.
[0063] Since the effects are exhibited regardless of temperature of
an iron-based powder mixture, the iron-based powder mixture is not
necessarily heated, and the effects effectively contribute to
increasing density of an iron-based compacted body in compaction
even at normal temperature. Moreover, when the iron-based powder is
heated, since plastic deformation resistance of the iron-based
powder is decreased during compaction, higher density of a
compacted body can be obtained. Therefore, while heating
temperature of the iron-based powder can be appropriately set
depending on a required density of a compacted body, sufficient
heating temperature is less than 100.degree. C. More preferably,
the heating temperature is 80.degree. C. or less.
[0064] While the reason why machining performance is remarkably
improved is not elucidated, it is possibly considered that a metal
component in metallic soap reacts with talc/steatite during
sintering, so that the metal component acts as an auxiliary free
machining additive. A sintered part manufactured by using the
powder mixture for powder metallurgy may have high strength similar
to that of a usual high-strength sintered part, and in addition,
may have extremely excellent machining performance.
[0065] The blending amount of the talc or steatite is preferably
adjusted to be about 0.01 to 0.5 mass % in total in the iron-based
powder mixture. The reason for this is that such a lubricant
blended by 0.01 mass % or more, thereby density of a compacted body
can be adequately increased during compaction, and ejection force
can be adequately decreased during ejecting the compacted body.
Moreover, when an effect of improving machining performance is
intended to be obtained, the lubricant is preferably added by 0.01
mass % or more, too. When alloyed steel powder for a high-strength
sintered body (for example, the iron-based powder example 1) is
used, to secure a stronger effect of improving machining
performance, the added amount of talc and/or steatite is preferably
adjusted to be 0.05 mass % or more in total.
[0066] On the other hand, when the blending amount is more than 0.5
mass % or more, compressibility of the powder mixture is reduced,
which may reduce mechanical strength and the like of a sintered
body obtained by sintering the compacted body. More preferably, an
upper limit of the blending amount is 0.3 mass %, and the upper
limit is preferably adjusted to be 0.2 mass % or less to
substantially eliminate influence on mechanical properties of the
sintered body.
[0067] Preferably, talc has a monoclinic or triclinic crystal
structure and steatite has a monoclinic crystal structure.
[0068] Size of talc or steatite is preferably about 1 to 10 .mu.m
in particle diameter.
Fatty Acid Amide
[0069] At least one of fatty acid amides is blended as a lubricant.
Here, as the fatty acid amide, at least one selected from fatty
acid monoamide (such as stearic acid monoamide), and fatty acid
bisamide (such as ethylene-bis-stearoamide and
methylene-bis-stearoamide) is preferably used.
[0070] Each of them acts as not only a lubricant, but also a
binder. Therefore, by using each of them, segregation or dusting of
the relevant iron-based powder mixture is effectively prevented,
and flowability and compaction performance can be further improved.
While a fatty acid is sometimes mixed in fatty acid amide, this is
not particularly prohibited.
[0071] The blending amount of the fatty acid amide is preferably
adjusted to be about 0.01 to 0.5 mass % in the iron-based powder
mixture. The reason for this is that when the blending amount is
less than 0.01 mass %, the adding effect is poor, and on the other
hand, when the blending amount is more than 0.5 mass %, strength of
a compacted body (or green compact) is decreased. A lower limit of
the blending amount is more preferably 0.03 mass % in the case that
the iron-based powder is pure iron powder, and 0.05 mass % in the
case that it is alloyed steel powder. An upper limit of the
blending amount is more preferably 0.4 mass %, and in the case that
the iron-based powder is pure iron powder, 0.3 mass % is further
more preferable as the upper limit.
Metallic Soap
[0072] Metallic soap can be further blended. According to a
previous common idea, the metallic soap is also counted as a
lubricant.
[0073] As the metallic soap, zinc stearate, lithium stearate,
calcium stearate and the like are listed. Among them, the zinc
stearate and the lithium stearate are particularly preferable.
[0074] The blending amount of the metallic soap is preferably
adjusted to be about 0.01 to 0.5 mass % in the iron-based powder
mixture. The reason for this is that when the blending amount is
less than 0.01 mass %, the adding effect is poor, and on the other
hand, when the blending amount is more than 0.5 mass %, strength of
a compacted body is decreased. A lower limit of the blending amount
is more preferably 0.05 mass % or more, and an upper limit thereof
is more preferably 0.3 mass %.
[0075] The added amount of the fatty acid amide and the metallic
soap in total is preferably adjusted to be 0.1 mass % to 1.0 mass
%. The lower limit is more preferably 0.2 mass %, and the upper
limit is more preferably 0.6 mass %.
[0076] Furthermore, the blending amount of the talc/steatite, the
fatty acid amide, and the metallic soap in total is preferably
adjusted to be about 0.01 to 2.0 mass % in the iron-based powder
mixture. The lower limit is more preferably 0.15 mass %, and the
upper limit is more preferably 0.8 mass %.
Other Materials
[0077] While other additives are not particularly needed for the
iron-based powder mixture, a known additive such as surface
modification agent (including siloxanes) may be further added by
about 0.5 mass % or less.
Method of Manufacturing Powder Mixture
[0078] Next, a method of manufacturing the iron-based powder
mixture is described.
First Method
[0079] Iron-based powder is added with the respective materials
(such as talc, steatite, fatty acid amide, metallic soap, and
alloying powder), and then subjected to primary mixing. Then, a
mixture after primary mixing is agitated while it is heated to a
melting point or higher of at least one of the fatty acid amide and
metallic soap, and then the mixture is gradually cooled while being
mixed. As a result, the alloying powder or other material powder is
adhered on the iron-based powder by an effect of the melted
material.
[0080] That is, the material, which is melted and used for
adhesion, acts even as a binder.
Second Method
[0081] As a method similar to the first method, it is also possible
that the iron-based powder is added with only some of the
materials, and subjected to primary mixing, and then further added
with the rest of the materials, and subjected to secondary mixing.
The material subjected to secondary mixing exists in the powder
mixture in a free state. As a particularly preferable example, a
method is given, in which at least part of the metallic soap is
supplied for the secondary mixing, and the rest of the materials is
supplied for the primary mixing, and fatty acid amide, or a co-melt
of the fatty acid amide with the metallic soap is used for the
binder. According to the method, the added amount of each material
to be blended to the iron-based powder can be minimized.
[0082] Mixing means of the iron-based powder and each material is
not particularly limited, and any of previously known mixers can be
used. In particular, a high-speed mixer, counter current mixer,
plough share mixer, and conical mixer, in each of which the
material powders being easily heated, are particularly
advantageously suited.
Method of Manufacturing Compacted Body and Sintered Body
[0083] Next, a method of manufacturing an iron-based compacted body
using the iron-based powder mixture, and a method of manufacturing
an iron-based sintered body (sintered part) are described.
[0084] The iron-based powder mixture can be made into a compacted
body by a typical compaction method. Specifically, the iron-based
powder mixture is filled into a die, and furthermore subjected to
compaction. As a typically preferable condition of compaction,
pressing force is preferably adjusted to be 400 to 1000 MPa.
Moreover, the die may be heated to 50 to 70.degree. C.
Alternatively, the powder mixture for powder metallurgy and the die
may be heated to 80 to 130.degree. C.
[0085] The iron-based powder mixture can be adequately compacted in
high density even at normal temperature, and preferably compacted
at normal temperature in the light of productivity. However, the
iron-based powder mixture or the die may be advantageously heated,
and the die may be advantageously coated with a lubricant.
[0086] When the powder mixture is compacted in a heated surround,
temperature of the iron-based powder mixture or temperature of the
die is preferably adjusted to be less than 100.degree. C. The
reason for this is that since the iron-based powder mixture is high
in compressibility, the powder mixture exhibits excellent
compaction performance even at a temperature of less than
100.degree. C., and when the temperature is more than 100.degree.
C., there is fear that the powder mixture may be degraded due to
oxidation. More preferably, the temperature is 80.degree. C. or
less.
[0087] Next, the high density, iron-based compacted body obtained
in the above way is ejected from the die, then subjected to
sintering so as to be formed into a high-density sintered body. A
sintering method is not particularly limited, and any of previously
known sintering methods can be preferably used. In the sintering,
preferably, heating temperature is 1100 to 1600.degree. C., and
heating time is 10 to 60 min.
[0088] Sintering is performed in this way, thereby a sintered part
having excellent strength and excellent machining performance
(particularly, a high-strength sintered part in the case of using
alloyed steel powder) is obtained.
[0089] After sintering, a sintered part can be subjected to heat
treatment such as carburizing and quenching (gas carburizing heat
treatment), bright hardening, induction hardening, and
carbonitriding heat treatment, so that strength of the (high
strength) sintered part can be further increased. Furthermore,
tempering may be performed.
EXAMPLES
[0090] Table 1 shows various types of iron powder for powder
metallurgy (each having an average particle diameter of about 80
.mu.m) used as the iron-based powder in examples 1 to 4.
Particularly, in the case of alloyed steel powder, whether the
alloyed steel powder is prealloyed steel powder, partly alloyed
steel powder, or hybrid steel powder in which the prealloyed steel
powder is partly diffused with an alloyed element is distinctively
shown.
TABLE-US-00001 TABLE 1 Category of alloyed steel Symbol Type of
iron-based powder powder A Atomized pure iron powder -- B Reduced
pure iron powder -- C Fe--2%Cu Partly alloyed steel powder D
Fe--4%Ni--1.5%Cu--0.5%Mo Partly alloyed steel powder E
Fe--2%Ni--1%Mo Partly alloyed steel powder F Fe--0.5%Ni--0.5%Mo
Prealloyed steel powder G Fe--0.6%Mo Prealloyed steel powder H
(Fe--0.6%Mo)--[0.2%Mo] Hybrid steel powder* I Fe--0.45%Mo
Prealloyed steel powder J (Fe--0.45%Mo)--[0.15%Mo] Hybrid steel
powder* K (Fe--1.5%Mo)--[2%Ni] Hybrid steel powder* *inside of
parenthesis: composition of prealloyed steel powder inside of
bracket: composition being diffusion-bonded to the prealloyed steel
powder
Example 1
[0091] Various types of iron-based powder as shown in Table 2, and
natural graphite powder (average particle diameter of 5 .mu.m)
and/or copper powder (average particle diameter of 25 .mu.m) were
added with various types of lubricant powder (primary additives),
then heated to 140.degree. C. while being mixed by a high-speed
mixer, and then cooled to 60.degree. C. or lower, and further added
with various types of lubricant powder (secondary additives), and
agitated for 1 min at 500 rpm. Then, a powder mixture was
discharged from the mixer. A type and blending amount of each of
the primary and secondary additives are collectively shown in Table
2. The added amount (part by mass) of a lubricant is expressed in
percentage of total mass of 100% of the iron-base powder, natural
graphite powder, and copper powder. While the percentage is
expressed using a numerical value being not included in that of the
total mass, the percentage is approximately the same as in the case
that it is expressed using a numerical value being included in that
of the total mass. Average particle diameter of the talc powder and
average particle diameter of the steatite powder were 6 .mu.m and 4
.mu.m respectively.
[0092] For comparison, powder mixtures were prepared (refer to
Table 3) in a way that various types of powder having the same
components as the above, each including the iron-based powder, and
natural graphite powder and/or copper powder, were added with zinc
stearate of 0.8 mass %, then the powder was mixed by a
V-container-turning mixer. Each of the comparative materials has a
composition typically used in normal compaction.
[0093] Next, each of the obtained iron-based powder mixtures was
filled in a superhard tablet-shaped die having an inner diameter of
11 mm, and compacted at 490 MPa and 686 MPa. In such compaction,
when a compacted body was ejected from the die, ejection force was
measured, and green density of each of obtained compacted bodies
was measured.
[0094] Separately from this, the obtained iron-based powder
mixtures were subjected to compaction for preparing test pieces for
a machining test (outer diameter of 60 mm, inner diameter of 20 mm,
and length of 30 mm). In the compaction, pressing force was 590
MPa. Sintering was performed in an RX gas atmosphere, wherein
heating temperature was 1130.degree. C., and heating time was 20
min. In evaluation of machining performance, while a cermet cutting
tool was used, a machining test was performed with cutting speed of
200 m/min, feed of 0.1 mm per unit, depth of cut of 0.3 mm, and a
cutting distance of 1000 m, and flank wear width of the cutting
tool was measured. Smaller flank wear width of the cutting tool
shows more excellent machining performance of a sintered body.
[0095] Obtained results are shown in Table 4.
TABLE-US-00002 TABLE 2 Primary additive Secondary additive
Iron-based powder Natural Copper powder lubricant* lubricant*
Blending graphite Blending Blending Blending amount powder amount
amount mount type (mass %) (mass %) type (mass %) type (mass %)
type (mass %) Inventive C 99.4 0.6 -- 0 STAM 0.1 Steatite 0.1
example 1 EBS 0.1 STZN 0.02 -- -- EBS 0.08 -- -- STLI 0.1 Inventive
A 97.2 0.8 Electrolytic 2.0 STAM 0.1 STZN 0.1 example 2 copper
powder EBS 0.1 EBS 0.02 Steatite 0.1 STLI 0.08 Inventive A 97.9 0.6
Atomized copper 1.5 STAM 0.1 STZN 0.02 example 3 powder EBS 0.1 EBS
0.08 Steatite 0.1 STLI 0.1 Inventive B 97.2 0.8 Electrolytic 2.0
STAM 0.1 Steatite 0.1 example 4 copper powder EBS 0.1 STZN 0.02 --
-- EBS 0.08 -- -- STLI 0.1 Inventive D 99.7 0.3 -- 0 STAM 0.1 STZN
0.02 example 5 EBS 0.1 EBS 0.08 Steatite 0.1 STLI 0.1 Inventive F
99.5 0.5 -- 0 STAM 0.1 Steatite 0.1 example 6 EBS 0.1 STZN 0.02 --
-- EBS 0.08 -- -- STLI 0.1 Inventive G 97.5 0.5 Electrolytic 2.0
STAM 0.1 Talc 0.1 example 7 copper powder EBS 0.1 STZN 0.02 -- --
EBS 0.08 -- -- STLI 0.1 Inventive H 99.5 0.5 -- 0 STAM 0.1 Talc 0.1
example 8 EBS 0.1 STZN 0.02 -- -- EBS 0.08 -- -- STLI 0.1 Inventive
I 97.2 0.8 Atomized copper 2.0 STAM 0.1 Steatite 0.1 example 9
powder EBS 0.1 STAM 0.04 -- -- EBS 0.04 STZN 0.02 -- -- STLI 0.1
*EBS: ethylene-bis-stearoamide, STZN: zinc stearate, STAM: stearic
acid monoamide, STLI: lithium stearate
TABLE-US-00003 TABLE 3 Iron-based powder Copper powder Blending
amount Natural graphite powder Blending amount Added type (mass %)
(mass %) type (mass %) lubricant* Comparative C 99.4 0.6 -- 0 0.8
mass % STZN example 1 Comparative A 97.2 0.8 Electrolytic copper
2.0 0.8 mass % STZN example 2 powder Comparative A 97.9 0.6
Atomized copper 1.5 0.8 mass % STZN example 3 powder Comparative B
97.2 0.8 Electrolytic copper 2.0 0.8 mass % STZN example 4 powder
Comparative D 99.7 0.3 -- 0 0.8 mass % STZN example 5 Comparative F
99.5 0.5 -- 0 0.8 mass % STZN example 6 Comparative G 97.5 0.5
Electrolytic copper 2.0 0.8 mass % STZN example 7 powder
Comparative H 99.5 0.5 -- 0 0.8 mass % STZN example 8 Comparative I
97.2 0.8 Atomized copper 2.0 0.8 mass % STZN example 9 powder
*STZN: zinc stearate
TABLE-US-00004 TABLE 4 Green density (Mg/m.sup.3) Ejection force
(MPa) Cutting tool Iron-based powder 490 MPa 686 MPa 490 MPa 686
MPa Flank wear Type compaction compaction compaction compaction
width (mm) Inventive example 1 C 6.99 7.25 13 18 0.15 Inventive
example 2 A 7.01 7.26 13 18 0.20 Inventive example 3 A 7.00 7.26 13
17 0.18 Inventive example 4 B 6.86 7.09 11 20 0.21 Inventive
example 5 D 7.00 7.25 13 17 0.48 Inventive example 6 F 6.91 7.19 14
18 0.15 Inventive example 7 G 6.96 7.21 12 18 0.05 Inventive
example 8 H 6.98 7.22 11 18 0.12 Inventive example 9 I 6.98 7.22 12
20 0.03 Comparative example 1 C 6.96 7.11 11 19 0.35 Comparative
example 2 A 6.97 7.12 12 18 0.55 Comparative example 3 A 6.97 7.12
12 17 0.48 Comparative example 4 B 6.81 6.99 10 18 0.58 Comparative
example 5 D 6.94 7.15 13 18 0.98 Comparative example 6 F 6.84 7.09
14 19 0.43 Comparative example 7 G 6.85 7.08 13 19 0.22 Comparative
example 8 H 6.85 7.09 12 19 0.31 Comparative example 9 I 6.85 7.09
13 20 0.11
[0096] As clear from a comparison between the inventive examples 1
to 9 and the compareative examples 1 to 9 as shown in Tables 2 to
4, the lubricants are used as lubricants, thereby a high-density
compacted body can be obtained without significantly increasing
ejection force even in the case of normal temperature compaction,
and furthermore, machining performance is remarkably improved.
Example 2
[0097] Various types of iron-based powder as shown in Table 5, and
natural graphite powder and/or copper powder were added with
various lubricants (primary additives), then heated to 140.degree.
C. while being mixed by a high-speed mixer, and then cooled to
60.degree. C. or lower, and further added with various lubricants
(secondary additives), and agitated for 1 min at 500 rpm. Then, a
powder mixture was discharged from the mixer. A type and blending
amount of each of the primary and secondary additives are
collectively shown in Table 5. Used materials are those described
in Table 1 as in the example 1.
[0098] For comparison, powder mixtures were prepared in a way that
various types of powder having the same components as the above,
each including the iron-based powder, and natural graphite powder
and/or copper powder, were added with ethylene-bis-stearoamide of
0.6 mass %, then the powder was mixed by a V-container-turning
mixer (comparative materials).
[0099] Next, each of the obtained iron-based powder mixtures was
filled in a superhard tablet-shaped die having an inner diameter of
11 mm, which was heated beforehand such that temperature of a
cavity wall surface was increased to 80.degree. C., and then the
powder mixture was compacted at 490 MPa and 686 MPa. In such
compaction, when a compacted body was ejected from the die,
ejection force was measured, and green density of each of the
obtained compacted bodies was measured.
[0100] Moreover, each of the comparative materials was compacted at
a typical compaction condition of warm compaction, that is, the
comparative material was heated to 120.degree. C., then filled into
a superhard tablet-shaped die having an inner diameter of 11 mm and
which was heated to 130.degree. C., and then compacted at 490 MPa
and 686 MPa. In such compaction, when a compacted body was ejected
from the die, ejection force was measured, and green density of
each of the obtained compacted bodies was measured.
[0101] Moreover, test pieces for a machining test were prepared by
compaction as in the example 1, so that machining performance was
examined.
[0102] Obtained results are shown in Table 6.
TABLE-US-00005 TABLE 5 Primary additive Secondary additive
Iron-based powder Natural Copper powder lubricant* lubricant*
Blending graphite Blending Blending Blending amount powder amount
amount amount type (mass %) (mass %) type (mass %) type mass %)
type (mass %) Inventive A 97.2 0.8 Electrolytic 2.0 STAM 0.1 Talc
0.1 example 10 copper powder EBS 0.1 STZN 0.02 -- -- EBS 0.08 -- --
STLI 0.1 Inventive D 99.7 0.3 -- 0 STAM 0.1 STZN 0.02 example 11
EBS 0.1 EBS 0.08 Steatite 0.1 STLI 0.1 Inventive H 99.35 0.65 -- 0
STAM 0.1 Talc 0.1 example 12 EBS 0.1 STZN 0.02 -- -- EBS 0.08 --
STLI 0.1 Inventive E 99.4 0.6 -- 0 STAM 0.05 Steatite 0.1 example
13 EBS 0.05 STZN 0.02 -- -- EBS 0.08 -- -- STLI 0.1 Inventive J
99.35 0.65 -- 0 STAM 0.1 Steatite 0.1 example 14 EBS 0.1 STAM 0.04
-- -- EBS 0.04 -- -- STZN 0.02 -- -- STLI 0.1 Inventive K 99.7 0.3
-- 0 STAM 0.05 Steatite 0.1 example 15 EBS 0.05 STAM 0.04 -- -- EBS
0.04 -- -- STZN 0.02 -- -- STLI 0.1 Comparative A 97.2 0.8
Electrolytic 2.0 0.6 mass % EBS example 10 copper powder
Comparative D 99.7 0.3 -- 0 0.6 mass % EBS example 11 Comparative H
99.35 0.65 -- 0 0.6 mass % EBS example 12 Comparative E 99.4 0.6 --
0 0.6 mass % EBS example 13 Comparative J 99.35 0.65 -- 0 0.6 mass
% EBS example 14 Comparative K 99.7 0.3 -- 0 0.6 mass % EBS example
15 *EBS: ethylene-bis-stearoamide, STZN: zinc stearate, STAM:
stearic acid monoamide, STLI: lithium stearate
TABLE-US-00006 TABLE 6 Iron-based powder Green density (Mg/m.sup.3)
Ejection force (MPa) Type 490 MPa compaction 686 MPa compaction 490
MPa compaction 686 MPa compaction Inventive example 10 A 7.10 7.30
14 15 Inventive example 11 D 7.05 7.30 16 17 Inventive example 12 H
7.01 7.26 18 19 Inventive example 13 E 7.04 7.29 15 18 Inventive
example 14 J 7.02 7.27 18 20 Inventive example 15 K 6.99 7.24 18 21
Comparative example 10 A 7.11 7.30 15 16 Comparative example 11 D
7.11 7.32 16 18 Comparative example 12 H 7.03 7.27 17 20
Comparative example 13 E 7.09 7.30 15 19 Comparative example 14 J
7.02 7.27 17 19 Comparative example 15 K 6.98 7.23 19 22
[0103] As clear from a comparison between the inventive examples 10
to 15 and the comparative examples 10 to 15 as shown in Tables 5 to
6, the primary and secondary additives were added as lubricants,
thereby the die was simply heated to a relatively low temperature
of less than 100.degree. C., so that even if the powder mixture was
not heated, a compacted body having high density, which was similar
to that of a typical warm compacted body, was able to be obtained
without causing increase in ejection force.
[0104] Flank wear width (mm) of each inventive example was reduced
to about 20 to 40% of that of a comparative example in the same
grouping (number), showing remarkable improvement even in machining
performance.
Example 3
[0105] Various types of iron-based powder as shown in Table 7, and
natural graphite powder and/or copper powder were added with
various lubricants (primary additives), then heated to 140.degree.
C. while being mixed by a high-speed mixer, and then cooled to
60.degree. C. or lower, and further added with various lubricants
(secondary additives), and agitated for 1 min at 500 rpm. Then, a
powder mixture was discharged from the mixer. A type and blending
amount of each of the primary and secondary additives are
collectively shown in Table 7. Used materials are the same as in
the example 1.
[0106] For comparison, powder mixtures were prepared in a way that
each of various types of powder was added with
ethylene-bis-stearoamide having a respective weight, then mixed by
a V-container-turning mixer.
[0107] Next, each of the obtained iron-based powder mixtures was
heated to 60.degree. C., then filled in a superhard tablet-shaped
die having an inner diameter of 11 mm, which was heated beforehand
such that temperature of a cavity wall surface was increased to
80.degree. C., and furthermore coated with lithium stearate powder
on its wall surface, and then the powder mixture was compacted at
490 MPa and 686 MPa. In such compaction, when a compacted body was
ejected from the die, ejection force was measured, and green
density of each of the obtained compacted bodies was measured.
[0108] Moreover, each of the comparative materials was compacted at
a typical compaction condition of warm compaction, that is, the
comparative material was heated to 120.degree. C., then filled into
a superhard tablet-shaped die having an inner diameter of 11 mm and
which was heated to 130.degree. C., and then compacted at 490 MPa
and 686 MPa. In such compaction, when a compacted body was ejected
from the die, ejection force was measured, and green density of
each of the obtained compacted bodies was measured.
[0109] Moreover, test pieces for a machining test were prepared by
compaction as in the example 1, so that machining performance was
examined.
[0110] Obtained results are shown in Table 8.
TABLE-US-00007 TABLE 7 Primary additive Secondary additive
Iron-based powder Natural Copper powder lubricant* lubricant*
Blending graphite Blending Blending Blending amount powder amount
amount amount type (mass %) (mass %) type (mass %) type (mass %)
type (mass %) Inventive example 16 A 97.2 0.8 Electrolytic 2.0 STAM
0.2 Steatite 0.2 copper powder EBS 0.2 STZN 0.04 -- -- EBS 0.16
Inventive example 17 G 99.35 0.65 -- 0 STAM 0.1 Talc 0.1 EBS 0.1
STZN 0.02 -- -- EBS 0.08 -- STLI 0.1 Comparative example 16 A 97.2
0.8 Electrolytic 2.0 0.8 mass % EBS copper powder Comparative
example 17 G 99.35 0.65 -- 0 0.6 mass % EBS *EBS:
ethylene-bis-stearoamide, STZN: zinc stearate, STAM: stearic acid
monoamide, STLI: lithium stearate
TABLE-US-00008 TABLE 8 Green density (Mg/m.sup.3) Ejection force
(MPa) Iron-based powder Compaction temperature 490 MPa 686 MPa 490
MPa 686 MPa Type Powder (.degree. C.) Die (.degree. C.) compaction
compaction compaction compaction Inventive example 16 A 60 80 6.90
7.19 8 11 Inventive example 17 G 60 80 7.04 7.29 15 19 Comparative
example 16 A 120 130 6.94 7.2 9 12 Comparative example 17 G 120 130
7.00 7.26 16 19
[0111] As clear from a comparison between the inventive example 16
and the comparative example 16, and a comparison between the
inventive example 17 and the comparative example 17 as shown in
Tables 7 to 8, the primary and secondary additives were added as
lubricants, thereby the die and the powder were simply heated to a
relatively low temperature of less than 100.degree. C., so that a
compacted body having high density, which was similar to that of a
typical warm compacted body, was able to be obtained with an
extremely low ejection force.
[0112] Flank wear width (mm) of each inventive example was reduced
to about 25 to 35% of that of a comparative example in the same
grouping (number), showing remarkable improvement even in machining
performance.
Example 4
[0113] Various types of iron-based powder as shown in Table 9, and
natural graphite powder and/or copper powder were added with
various lubricants (primary additives), then heated to 140.degree.
C. while being mixed by a high-speed mixer, and then cooled to
60.degree. C. or lower, and further added with various lubricants
(secondary additives), and agitated for 1 min at 500 rpm. Then, a
powder mixture was discharged from the mixer. A type and blending
amount of each of the primary and secondary additives are
collectively shown in Table 9. Used materials are the same as in
the example 1. A comparative example 20 was subjected to processing
where the relevant powder was added with steatite powder in place
of the primary and secondary additives, then mixed by the
high-speed mixer at the same condition as in the above.
[0114] Next, each of the obtained iron-based powder mixtures was
filled in a superhard tablet-shaped die having an inner diameter of
11 mm, and compacted at 490 MPa and 686 MPa. In such compaction,
when a compacted body was ejected from the die, ejection force was
measured, and green density of each of obtained compacted bodies
was measured.
[0115] Separately from this, the obtained iron-based powder
mixtures were subjected to compaction for preparing tensile test
pieces according to Japan Powder Metallurgy Association JPMA
M04-1992, and test pieces for a machining test (outer diameter of
60 mm, inner diameter of 20 mm, and length of 30 mm). In the
compaction, pressing force was 590 MPa. Sintering was performed in
an RX gas atmosphere, wherein heating temperature was 1130.degree.
C., and heating time was 20 min. An evaluation method of machining
performance was the same as in the example 1.
[0116] Obtained results are shown in Table 10.
TABLE-US-00009 TABLE 9 Primary additive Secondary additive
Iron-based powder Natural Copper powder lubricant* lubricant*
Blending graphite Blending Blending Blending amount powder amount
amount amount type (mass %) (mass %) type (mass %) type (mass %)
type (mass %) Comparative D 99.4 0.6 -- 0 STAM 0.1 STLI 0.1 example
18 EBS 0.1 STZN 0.02 -- -- EBS 0.08 Inventive D 99.4 0.6 -- 0 STAM
0.1 Steatite 0.05 example 18 EBS 0.1 STLI 0.1 -- -- STZN 0.02 -- --
EBS 0.08 Inventive D 99.4 0.6 -- 0 STAM 0.1 Steatite 0.1 example 19
EBS 0.1 STLI 0.1 -- -- STZN 0.02 -- -- EBS 0.08 Inventive D 99.4
0.6 -- 0 STAM 0.1 Steatite 0.2 example 20 EBS 0.1 STLI 0.1 -- --
STZN 0.02 -- -- EBS 0.08 Inventive D 99.4 0.6 -- 0 STAM 0.1
Steatite 0.3 example 21 EBS 0.1 STLI 0.1 -- -- STZN 0.02 -- -- EBS
0.08 Comparative D 99.4 0.6 -- 0 STAM 0.1 Steatite 0.6 example 19
EBS 0.1 STLI 0.1 -- -- STZN 0.02 -- -- EBS 0.08 Inventive I 97.2
0.8 Electrolytic 2.0 STAM 0.1 Steatite 0.1 example 22 copper EBS
0.1 STLI 0.1 powder STZN 0.1 -- -- Comparative I 97.2 0.8
Electrolytic 2.0 Steatite 0.1 -- -- example 20 copper powder
Inventive I 97.2 0.8 Electrolytic 2.0 STAM 0.2 Steatite 0.1 example
23 copper EBS 0.2 -- -- powder Comparative I 97.2 0.8 Electrolytic
2.0 STZN 0.2 Steatite 0.1 example 21 copper STLI 0.2 powder *EBS:
ethylene-bis-stearoamide, STZN: zinc stearate, STAM: stearic acid
monoamide, STLI: lithium stearate
TABLE-US-00010 TABLE 10 Green density (Mg/m.sup.3) Ejection force
(MPa) Sintered body Cutting tool Iron-based powder 490 MPa 686 MPa
490 MPa 686 MPa Tensile strength Flank wear Type ompaction
compaction compaction compaction (MPa) idth (mm) Comparative D 6.99
7.24 14 18 630 0.92 example 18 Inventive D 6.99 7.25 13 17 625 0.65
example 18 Inventive D 7.00 7.25 12 16 610 0.54 example 19
Inventive D 6.97 7.23 13 17 590 0.51 example 20 Inventive D 6.95
7.21 13 18 550 0.45 example 21 Comparative D 6.94 7.20 15 19 490
0.43 example 19 Inventive I 6.99 7.23 12 18 620 0.03 example 22
Comparative I Compaction is disabled due to galling. example 20
Inventive I 6.98 7.22 13 19 630 0.05 example 23 Comparative I 6.96
7.20 20 20 610 0.06 example 21
[0117] As clear from a comparison between the inventive examples 18
to 21 and the comparative examples 18 and 19 as shown in Tables 9
to 10, in the iron-based powder mixture in which steatite and the
like are added within a range of the disclosure, a high-density
compacted body can be obtained without increasing ejection force.
In the comparative example 19 in which steatite and the like are
added in a range of more than 0.5 mass %, mechanical properties are
significantly reduced. Furthermore, it is known from the inventive
examples 18 to 21 that the added amount of steatite and the like is
more preferably 0.2 mass % or less in the light of the mechanical
properties.
[0118] As clear from a comparison between the inventive examples 22
and 23 and the comparative examples 20 and 21, fatty acid amide and
the like need to be added with steatite and the like to obtain a
high-density compacted body without increasing ejection force.
Moreover, it is known that metallic soap is further added, thereby
machining performance of a sintered body can be remarkably
improved.
Example 5
[0119] Water-atomized alloyed steel powder having a composition
shown in Table 11 was manufactured by a water-atomizing method. The
rest of the powder other than Mn and Mo is Fe and inevitable
impurities. The water-atomized alloyed steel powder was added with
Cu powder, graphite powder, talc, and steatite in a ratio as shown
in the Table 11. Each of Mo content and Mn content (mass %) in the
water-atomized steel powder, or each of the added amount (mass %)
of the Cu powder, graphite powder, talc, and steatite to be added
to the water-atomized steel powder is shown in percentage of mass
of a powder mixture for powder metallurgy, the percentage being
expressed using a numerical value included in a numerical value of
mass of the powder mixture.
[0120] Furthermore, a lubricant was added in a ratio as shown in
Table 11. The added amount (part by mass) of the lubricant is shown
in percentage of mass (100 part by mass) of a powder mixture for
powder metallurgy obtained by mixing the water-atomized alloyed
steel powder and additives, the percentage being expressed using a
numerical value being not included in a numerical value of moss of
the powder mixture (but, the percentage is approximately the same
as in the case that it is expressed using a numerical value
included therein).
[0121] Next, the materials were mixed by a V blender, then an
obtained powder mixture for powder metallurgy was filled in a die
so as to be subjected to compaction for preparing tensile test
pieces according to Japan Powder Metallurgy Association JPMA
M04-1992, and test pieces for a machining test (outer diameter of
60 mm, inner diameter of 20 mm, and length of 30 mm). In the
compaction, pressing force was 590 MPa. Sintering was performed in
an RX gas atmosphere, wherein heating temperature was 1130.degree.
C., and heating time was 20 min.
[0122] Tensile strength obtained by a tensile test was as shown in
Table 11.
[0123] In evaluation of machining performance, while a cermet
cutting tool was used, a machining test was performed with cutting
speed of 200 m/min, feed of 0.1 mm per unit, depth of cut of 0.3
mm, and a cutting distance of 1000 m, and flank wear width of the
cutting tool was measured. Results of the measurement are as shown
in Table 11. Smaller flank wear width of the cutting tool shows
more excellent machining performance of a sintered body.
[0124] In Table 11, inventive examples use a powder mixture for
powder metallurgy that satisfies the desired range, and comparative
examples use a powder mixture for powder metallurgy that departs
from that range. In a prior-art example of No. 22, a powder mixture
for powder metallurgy using Fe-4Ni-1.5Cu-0.5Mo water-atomized
alloyed steel powder, which is previously practically used, is
blended with a conventional lubricant. Numerical values added to
respective alloy elements of No. 22 are expressed in mass %.
TABLE-US-00011 TABLE 11 Cutting Powder mixture for powder
metallurgy (mass %) *.sup.1 Lubricant 1 Lubricant 2 Sintered tool
Water-atomized Added Added body Flank alloyed steel amount amount
Tensile wear powder Cu Graphite Type (part by Type (part by
strength width No Mo Mn powder powder Talc Steatite *2 mass)
*.sup.3 *2 mass) *.sup.3 (MPa) (mm) Remarks 1 0.45 0.21 0.0 0.8 0.1
-- EBS 0.4 -- -- 380 0.04 Inventive example 2 0.45 0.21 1.5 0.8 0.1
-- EBS 0.4 -- -- 520 0.08 Inventive example 3 0.45 0.21 2.0 0.8 0.1
-- EBS 0.4 -- -- 630 0.08 Inventive example 4 0.45 0.21 3.0 0.8 0.1
-- EBS 0.4 -- -- 650 0.15 Inventive example 6 0.45 0.05 2.0 0.8 --
0.1 STAM 0.2 STZN 0.2 480 0.02 Comparative example 7 0.45 0.12 2.0
0.8 -- 0.1 STAM 0.2 STZN 0.2 550 0.02 Inventive example 8 0.45 0.19
2.0 0.8 -- 0.1 STAM 0.2 STZN 0.2 640 0.04 Inventive example 10 0.2
0.20 2.0 0.8 0.1 0.1 STAM 0.4 -- -- 430 0.07 Inventive example 11
0.3 0.20 2.0 0.8 0.1 0.1 STAM 0.4 -- -- 540 0.07 Inventive example
12 0.5 0.20 2.0 0.8 0.1 0.1 STAM 0.4 -- -- 630 0.07 Inventive
example 14 0.45 0.21 2.0 0.4 0.1 -- EBS 0.5 -- -- 410 0.05
Inventive example 15 0.45 0.21 2.0 0.6 0.1 -- EBS 0.5 -- -- 530
0.05 Inventive example 16 0.45 0.21 2.0 0.9 0.1 -- EBS 0.5 -- --
620 0.10 Inventive example 18 0.45 0.21 2.0 0.8 -- -- EBS 0.3 STLI
0.15 650 0.30 Comparative example 19 0.45 0.21 2.0 0.8 -- 0.3 EBS
0.3 STLI 0.15 640 0.02 Inventive example 20 0.45 0.21 2.0 0.8 --
0.5 EBS 0.3 STLI 0.15 600 0.02 Inventive example 21 0.45 0.21 2.0
0.8 -- 0.7 EBS 0.3 STLI 0.15 460 0.01 Comparative example 22
Fe--4Ni--1.5Cu--0.5Mo 0.6 -- -- EBS 0.5 EBS 0.5 590 0.48 Prior-art
example *.sup.1 percentage of mass of powder mixture for powder
metallurgy (by a numerical value included in a numerical value of
the mass) *2 EBS: ethylene-bis-stearoamide, STZN: zinc stearate,
STAM: stearic acid monoamide, STLI: lithium stearate *.sup.3
percentage of mass of powder mixture for powder metallurgy (by a
numerical value not included in a numerical value of the mass)
[0125] As obvious from Table 11, particularly, any of sintered
bodies obtained from the powder mixtures for powder metallurgy of
the inventive examples are excellent in mechanical properties and
machining performance. The prior-art example is particularly
significantly bad in machining performance of a sintered body.
[0126] When the water-atomized alloyed steel powder contains Mo of
0.3 to 0.5 mass % and Mn of 0.1 to 0.25 mass %, and the powder
mixture contains Cu powder of 1 to 3 mass % and graphite powder of
0.5 to 1.0 mass %, a sintered body can be obtained, which has a
tensile strength of 500 MPa or more, and is excellent in machining
performance.
INDUSTRIAL APPLICABILITY
[0127] An iron-based powder mixture can be obtained, which gives
high compaction density and small ejection force even if the powder
mixture is compacted at low temperature of about room temperature.
Moreover, according to a preferred aspect, a powder mixture for
powder metallurgy can be obtained, which is preferable for
machining a sintered part having excellent machining performance,
particularly, preferable for machining a high-strength sintered
part.
[0128] Moreover, the iron-based powder mixture is used as a
material, thereby an iron-based compacted body having high
compaction density can be obtained, and furthermore, an iron-based
sintered body can be obtained, which has high sintering density, or
has further excellent machining performance.
* * * * *