U.S. patent application number 09/983821 was filed with the patent office on 2002-07-04 for iron-based sintered alloy material for valve seat and valve seat made of iron-based sintered alloy.
This patent application is currently assigned to NIPPON PISTON RINGCO., LTD. Invention is credited to Kakiuchi, Arata, Sato, Kenichi, Takahashi, Teruo.
Application Number | 20020084004 09/983821 |
Document ID | / |
Family ID | 18805703 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020084004 |
Kind Code |
A1 |
Takahashi, Teruo ; et
al. |
July 4, 2002 |
Iron-based sintered alloy material for valve seat and valve seat
made of iron-based sintered alloy
Abstract
An iron-based sintered alloy material for a valve seat, in which
hard particles are dispersed in a base matrix phase, is
characterized in that the base matrix phase is comprised of 5 to 40
vol. % of a pearlite phase and 10 to 40 vol. % of a high-alloy
diffused phase and particles having hardness of Hv 600 to 1300 and
particle diameter of 10 to 150 .mu.m are dispersed as the hard
particles, by the amount of 10 to 30 vol. %, in the base matrix
phase. The hard particles are preferably at least one type of
particles selected from the group consisting of intermetallic
compound particles of Mo--Ni--Cr--Si--Co; intermetallic compound
particles of Cr--Mo--Co; Fe--Mo alloy particles; and
carbide-precipitated particles.
Inventors: |
Takahashi, Teruo;
(Tochigi-ken, JP) ; Kakiuchi, Arata; (Tochigi-ken,
JP) ; Sato, Kenichi; (Tochigi-ken, JP) |
Correspondence
Address: |
CROWELL & MORING, L.L.P.
P.O. Box 14300
Washington
DC
20044-4300
US
|
Assignee: |
NIPPON PISTON RINGCO., LTD
|
Family ID: |
18805703 |
Appl. No.: |
09/983821 |
Filed: |
October 26, 2001 |
Current U.S.
Class: |
148/320 ;
148/334 |
Current CPC
Class: |
C22C 38/30 20130101;
C22C 38/56 20130101; C22C 38/52 20130101; C22C 38/20 20130101; F01L
2303/00 20200501; B22F 2998/00 20130101; C22C 38/46 20130101; F01L
2301/00 20200501; C22C 38/24 20130101; F01L 3/02 20130101; F01L
2301/02 20200501; C22C 38/36 20130101; C22C 38/42 20130101; C22C
38/44 20130101; C22C 38/22 20130101; C22C 33/0207 20130101; B22F
2998/00 20130101; C22C 33/0228 20130101; C22C 33/0242 20130101 |
Class at
Publication: |
148/320 ;
148/334 |
International
Class: |
C22C 038/00; C22C
038/22 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 27, 2000 |
JP |
2000-328923 |
Claims
What is claimed is:
1. An iron-based sintered alloy material for a valve seat, in which
hard particles are dispersed in a base matrix phase, characterized
in that the base matrix phase is comprised of 5 to 40 vol. % of a
pearlite phase and 10 to 40 vol. % of a high-alloy used phase and
particles having hardness of Hv 600 to 1300 and particle diameter
of 10 to 150 .mu.m are dispersed as the hard particles, by the
amount of 10 to 30 vol. %, in the base matrix phase.
2. An iron-based sintered alloy material for a valve seat, in which
hard particles are dispersed in a base matrix phase, characterized
in that a base portion which includes the hard particles has a
composition comprised of 0.2 to 2.0 wt % of C; 1.0 to 9.0 wt % of
Cr; 1.0 to 9.0 wt % of Mo; 0.1 to 1.0 wt % of Si; 1.0 to 3.0 wt %
of W; 0.1 to 1.0 wt % of V; 3.0 to 15.0 wt %,as the total, of at
least one type of element selected from the group consisting of Cu,
Co and Ni; and the remainder which is substantially Fe, the base
matrix phase is comprised of 5 to 40 vol. % of a pearlite phase and
10 to 40 vol. % of a high-alloy diffused phase and particles having
hardness of Hv 600 to 1300 and particle diameter of 10 to 150 .mu.m
are dispersed as the hard particles, by the amount of 10 to 30 vol.
%, in the base matrix phase.
3. An iron-based sintered alloy material for a valve seat according
to claim 1 or 2, wherein the hard particles are at least one type
of particles selected from the group consisting of intermetallic
compound particles of Mo--Ni--Cr--Si--Co; intermetallic compound
particles of Cr--Mo--Co; Fe--Mo alloy particles; and
carbide-precipitated particles.
4. An iron-based sintered alloy material for a valve seat according
to claim 3, wherein the carbide-precipitated particles have a
composition which is comprised of: 0.2 to 2.0 wt % of C; 2.0 to
10.0 wt % of Cr; 2.0 to 10.0 wt % of Mo; 2.0 to 10.0 wt % of W; 0.2
to 5.0 wt % of V; and Fe and inevitable impurities as the
remainder.
5. An iron-based sintered alloy material for a valve seat according
to claim 4, wherein the content of the carbide-precipitated
particles, as is expressed as the proportion by volume thereof
present in the base matrix phase, is less than 20 vol. %.
6. An iron-based sintered alloy material for a valve seat according
to claim 4 or 5, wherein fine carbides having particle diameter of
1 to 10 .mu.m have been precipitated on said carbide-precipitated
particles.
7. An iron-based sintered alloy material for a valve seat according
to any one of claims 1 to 6, wherein the base matrix phase contains
solid lubricant particles by the amount of 0.1 to 10.0 vol. %.
8. An iron-based sintered alloy material for a valve seat according
to claim 7, wherein the solid lubricant particles made of are at
least one type of compound selected from the group consisting of a
sulfide, a fluoride and graphite.
9. An iron-based sintered alloy material for a valve seat according
to any one of claims 1 to 8, wherein sintered pores are infiltrated
with one of the material selected from the group consisting of Cu,
Cu alloy, Pb and Pb alloy or with a phenol-based resin.
10. A valve seat made of an iron-based sintered alloy,
characterized in that the valve seat is made of the iron-based
sintered alloy material for a valve seat of any one of claims 1 to
9.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sintered alloy material,
and specifically to an iron-based sintered alloy material suitable
for a valve seat used in an internal combustion engine.
[0003] 2. Description of Prior Art
[0004] A sintered alloy is produced by a method including the steps
of: blending and mixing alloy powder; filling the blended alloy
powder in a mold and compression the alloy powder for molding; and
sintering the molding in an atmosphere at a predetermined
temperature. By this method, according to a sintered alloy, a metal
or an alloy which is difficult to obtain by an ordinary melting and
casting method can be easily produced In addition, as the various
functions can be easily imparted to the product in a combined
manner, a member having unique functions can be produced according
to this method. Further, a sintered alloy is suitable for producing
a porous material, a hard-machining material or a mechanical member
having a complicated shape. Due to such reasons, a sintered alloy
has recently been applied to a valve seat of an internal combustion
engine which must have high wear resistance.
[0005] In recent years, in the field of automobile engine, a demand
for improvement, such as prolonging the product life, increasing
the power, purifying exhaustion and enhancing fuel consumption
thereof has been increasing. As a result, a valve seat for an
automobile engine is now required to have a more excellent
durability than is required in the conventional model so that the
valve seat can bear a harsher application environment. Accordingly,
there has increasingly been a demand for further improvement of the
heat resistance property and the wear resistance property of a
valve seat.
[0006] As the sintered alloy material for a valve seat, for
examples, JP-B 51-13093 Laid Open discloses an iron-based sintered
alloy material for a valve seat, which simultaneously exhibits
excellent wear resistance, heat resistance and corrosion resistance
even when lead-free gasoline is used. JP-B 51-13093 Laid-Open
discloses a sintered alloy containing C, Ni, Cr, Mo, Co and W by
relatively large amounts, in which specific alloy particles
comprised of C--Cr--W--Co and ferromolybdenum particles are
dispersed in the pearlite base matrix, and Co and Ni are diffused
around these particles. In other words, in the sintered alloy
described in JP-B 51-13093 Laid-Open, specifically large amounts of
W and Co must be added in order to provide the sintered alloy with
excellent heat resistance, wear resistance, corrosion resistance
and the like. As a result, the valve seat made of such a sintered
alloy is quite expensive and problematic in terms of production
cost.
[0007] Further, JP-A 9-53158 Laid-Open discloses an iron-based
sintered alloy of the hard-phase-dispersion-type. The iron-based
sintered alloy described in JP-A 9-53158 Laid-Open has an
iron-based matrix which contains: 3 to 15 wt % of Ni; 3 to 15 wt %
of Mo; 0.5 to 5 wt % of Cr; 0.5 to 1.2 wt % of C; and Fe as the
remainder. Hard phase particles are dispersed by the amount of 3 to
20 wt % in the iron-based matrix. As the hard phase particles, at
least one type of hard phase particles selected from the group
consisting of: hard phase particles containing 50 to 57 wt % of Cr,
18 to 22 wt % of Mo, 8 to 12 wt % of Co, 0.1 to 1.4 wt % of C, 0.8
to 1.3 wt % of Si, and Fe as the remainder; hard phase particles
containing 27 to 33 wt % of Cr, 22 to 28 wt % of W, 8 to 12 wt % of
Co, 1.7 to 2.3 wt % of C, 1.0 to 2.0 wt % of Si, and Fe as the
remainder; hard phase particles containing 60 to 70 wt % of Mo, no
more than 0.01 wt % of C, and Fe as the remainder, are used.
[0008] JP-A 2000-199040 Laid-Open discloses an iron-based sintered
alloy for a valve seat, in which 3 to 20% of hard particles are
dispersed in a base matrix phase, the base matrix phase being
comprised of 5 to 40% of the pearlite phase; 20 to 60% of the
carbide-dispersed phase including fine carbides dispersed therein;
and 5 to 20% of the high-alloy diffused phase.
OBJECT AND SUMMARY OF THE INVENTION
[0009] However, in the iron-based sintered alloy described in JP-A
9-53158 Laid-Open, Cr, Mo, Ni, Co and W must be added by relatively
large amounts, in order to provide the sintered alloy with
excellent heat resistance property, wear resistance property,
corrosion resistance property and the like. As a result, the valve
seat made of such a sintered alloy is quite expensive and causes a
problem in terms of production cost. Further, in producing this
iron-based sintered alloy, the influence of Ni and Co powder on
human body remains as a problem to be solved.
[0010] As the iron-based sintered alloy described in JP-A
2000-199040 Laid-Open includes the carbide dispersed phase having
relatively high hardness therein by a high proportion the
iron-based sintered alloy is quite hard and causes a problem when
the sintered alloy is utilized in an application in which excellent
toughness is required.
[0011] An object of the present invention is to propose an
iron-based sintered alloy material for a valve seat, as well as a
valve seat made of the iron-based sintered alloy for the use in an
internal combustion engine, which solves the aforementioned
problems in an advantageous manner, does not contain the alloy
elements by large amounts and thus is inexpensive, and exhibits
excellent toughness and wear resistance.
[0012] The inventors of the present invention, as a result of the
keen study for achieving the aforementioned object, have discovered
that, by constituting the base matrix phase of the iron-based
sintered alloy material with the pearlite phase and the high-alloy
diffused phase and dispersing hard particles in the base matrix
phase, the wear resistance of the resulting sintered alloy can be
significantly increased and toughness thereof can be enhanced
without adding a large amount of alloy elements. The present
invention has been completed on the basis of this discovery. In the
present invention, "a high-alloy diffused phase" represents a phase
which is characteristically formed around hard particles due to the
diffusion of the alloy elements of the hard particles, contributes
to the excellent heat resistance, wear resistance and corrosion
resistance of the sintered alloy and has hardness of Hv 350 to
600.
[0013] Specifically, the gist of the present invention is as
follows.
[0014] (1) An iron-based sintered alloy material for a valve seat,
in which hard particles are dispersed in a base matrix phase and
which is characterized in that the base matrix phase is comprised
of 5 to 40 vol. % of a pearlite phase and 10 to 40 vol. % of a
high-alloy diffused phase and particles having hardness of Hv 600
to 1300 and particle diameter of 10 to 150 .mu.m are dispersed as
the hard particles, by the amount of 10 to 30 vol. %, in the base
matrix phase.
[0015] (2) An iron-based sintered alloy material for a valve seat,
in which hard particles are dispersed in a base matrix phase,
characterized in that a base matrix portion which includes the hard
particles has a composition comprised of: 0.2 to 2.0 wt % of C; 1.0
to 9.0 wt % of Cr; 1.0 to 9.0 wt % of Mo; 0.1 to 1.0 wt % of Si;
1.0 to 3.0 wt % of W; 0.1 to 1.0 wt % of V; 3.0 to 15.0 wt %, as
the sum, of at least one type of element selected from the group
consisting of Cu, Co and Ni; and the remainder which is
substantially Fe, the base matrix phase is comprised of 5 to 40
vol. % of a pearlite phase and 10 to 40 vol. % of a high-alloy
diffused phase and particles having hardness of Hv 600 to 1300 and
particle diameter of 10 to 150 .mu.m are dispersed as the hard
particles, by the amount of 10 to 30 vol. %, in the base matrix
phase.
[0016] (3) An iron-based sintered alloy material for a valve seat
described in the aforementioned (1) or (2), wherein the hard
particles are at least one type of particles selected from the
group consisting of: intermetallic compound particles of
Mo--Ni--Cr--Si--Co; intermetallic compound particles of Cr--Mo--Co;
Fe--Mo alloy particles; and carbide-precipitated particles.
[0017] (4) An iron-based sintered alloy material far a valve seat
described in the aforementioned (3), wherein the
carbide-precipitated particles have a composition which is
comprised of 0.2 to 2.0 wt % of C; 2.0 to 10.0 wt % of Cr; 2.0 to
10.0 wt % of Mo; 2.0 to 10.0 wt % of W; 0.2 to 5.0 wt % of V; and
Fe and inevitable impurities as the remainder.
[0018] (5) An iron-based sintered alloy material for a valve seat
described in the aforementioned (4), wherein the content of the
carbide-precipitated particles, as is expressed as the proportion
by volume thereof present in the base matrix phase, is less than 20
vol. %.
[0019] (6) An iron-based sintered alloy material for a valve seat
described in the aforementioned (4) or (5), wherein fine carbides
having particle diameter of 1 to 10 .mu.m have been precipitated on
said carbide-precipitated particles.
[0020] (7) An iron-based sintered alloy material for a valve seat
described in any one of the aforementioned (1) to (6), wherein the
base matrix phase contains solid lubricant particles by the amount
of 0.1 to 10.0 vol. %.
[0021] (8) An iron-based sintered alloy material for a valve seat
described in the aforementioned (7), wherein the solid lubricant
particles made of are at least one type of compound selected from
the group consisting of a sulfide, a fluoride and graphite.
[0022] (9) An iron-based sintered alloy material for a valve seat
described in any one of the aforementioned (1) to (8), wherein
sintered pores are infiltrated with one of the material selected
from the group consisting of Cu, Cu alloy, Pb and Pb alloy or with
a phenol-based resin.
[0023] (10) A valve seat made of an iron-based sintered alloy,
characterized in that the valve seat is made of the iron-based
sintered alloy material for a valve seat of any one of the
aforementioned (1) to (9).
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1(a) is a optical micrograph of a sintered alloy
material (the sintered body No. 3) of an example of the present
invention.
[0025] FIG. 1(b) is a sketch of FIG. 1(a).
[0026] FIG. 2(a) is a optical micrograph of a sintered alloy
material (the sintered body No. 6) of an example of the present
invention.
[0027] FIG. (2b) is a sketch of FIG. 2(a).
[0028] FIG. 3(a) is a optical micrograph of a sintered alloy
material (the sintered body No. 10) of a comparative example of the
present invention.
[0029] FIG. 3(b) is a sketch of FIG. 3(a).
[0030] FIG. 4(a) is a optical micrograph of a sintered alloy
material (the sintered body No. 12) of a comparative example of the
present invention
[0031] FIG. 4(b) is a sketch of FIG. 4(a).
[0032] FIG. 5 is a graph which shows the result of the single piece
wear test on rig of the examples.
[0033] FIG. 6 is a schematic view of a tester of the single piece
wear test on rig.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] The iron-based sintered alloy material of the present
invention is comprising of a base matrix phase, hard particles
dispersed in the base matrix phase, and optionally a solid
lubricant particles dispersed in the hard matrix. The base matrix
phase has a structure which includes a pearlite phase and a
high-alloy diffused phase. The high-alloy used phase is formed of
the alloy elements which have been diffused from the hard particles
to the surrounding of the hard particles.
[0035] In the structure of the base matrix, the pearlite phase
occupies 5 to 40 vol. % and the high-alloy diffused phase occupies
10 to 40 vol. % of the sintered alloy material as a whole.
[0036] When the proportion by volume of the pearlite phase is less
than 5%, hardness of the base matrix phase increases and the
machinability thereof may be deteriorated. On the other hand, when
the proportion by volume of the pearlite phase exceeds 40%,
hardness of the base matrix phase is decreased, whereby the wear
resistance and the heat resistance may deteriorate. The high-alloy
diffused phase contributes to enhancing the heat resistance, the
wear resistance and the corrosion resistance properties, whereby
the properties of the iron-based sintered alloy material as a whole
are improved. When the proportion by volume of the high-alloy
diffused phase is less than 10%, improvement of the aforementioned
properties of the iron-based sintered alloy material is reduced. On
the other hand, when the proportion by volume of the high-alloy
diffused phase exceeds 40%, hardness of the base matrix phase
increases and the machinability thereof may be disturbed.
[0037] The hard particles dispersed in the base matrix phase are
particles having hardness in a range of Hv 600 to 1300 and particle
diameter in a range of 10 to 150 .mu.m.
[0038] When hardness of the hard particles is lower than Hv 600,
the wear resistance deteriorates. On the other hand, when hardness
of the hard particles exceeds Hv 1300, toughness of the resulting
sintered alloy material is reduced and the generation rate of chip
and crack thereof increases. When the particle diameter of the hard
particles is smaller than 10 .mu.m, the components of the hard
particles tend to be diffused in the base matrix phase in an
excessive manner at the time of sintering, whereby hardness of the
particles is lowered. On the other hand, when the particle diameter
of the hard particles exceed 150 .mu.m, the machinability of the
sintered body may be deteriorated and the aggressieness to mated
materials increases.
[0039] The hard particles are preferably at least one type of
particles selected from the group consisting of intermetallic
compound particles of Mo--Ni--Cr--Si--Co; intermetallic compound
particles of Cr--Mo--Co; Fe--Mo alloy particles; and
carbide-precipitated particles. By dispersing parties having the
aforementioned composition, as the hard particles, in the base
matrix phase, the diffusion property during sintering is increased,
whereby the strength, the toughness and the wear resistance of the
sintered alloy material are enhanced.
[0040] The intermetallic compound particles of Mo--Ni--Cr--Si--Co
are made of an intermetallic compound which contains: 20 to 30 wt %
of Mo; 5 to 20 wt % of Ni; 10 to 35 wt % of Cr; 1 to 5 wt % of Si;
and the remainder which is substantially comprised of Co. The
intermetallic compound particles of Cr--Mo--Co are made of an
intermetallic compound which contains: 5.0 to 15.0 wt % of Cr; 20.0
to 40.0 wt % of Mo; and the remainder which is substantially
comprised of Co. The Fe--Mo alloy particles are particles which
contain 50 to 70 wt % of Mo and the remainder which is
substantially comprised of Fe.
[0041] The carbide-precipitated particles are particles which have
a composition comprised of: 0.2 to 2.0 wt % of C; 2.0 to 10.0 wt %
of Cr; 2.0 to 10.0 wt % of Mo; 2.0 to 10.0 wt % of W; 0.2 to 5.0 wt
% of V; and Fe and inevitable impurities as the remainder and on
which fine carbides, preferably having the particle diameter of 1
to 10 .mu.m, have been precipitated. When the particle diameter of
the precipitated carbide is smaller than 1 .mu.m, the carbide
particles fail to make significant contribution to the increase in
hardness and the wear resistance of the sintered alloy material
deteriorates. On the other hand, when the particle diameter of the
precipitated carbide exceeds 10 .mu.m, the aggressieness to mated
materials increases. Preferable examples of the
carbide-precipitated particles include SKI 51 powder which contains
a large amount of carbide forming elements such as V, W, Mo and the
like (the typical composition thereof: 0.9 wt % of C, 4 wt % of Cr,
5 wt % of Mo, 6 wt % of W, 2 wt % of V and Fe as the remainder),
SKH 57 powder and SKD 11 powder.
[0042] In a case in which the carbide-precipitated particles are
used as the hard particles, the content of the carbide-precipitated
particles, as is expressed as the proportion by volume thereof
present in the base matrix phase, is preferably less than 20 vol.
%. When the content of the carbide-precipitated particles is no
less than 20 vol. %, hardness of the sintered alloy material
increases, whereby toughness of the particles deteriorates, the
machinability thereof may be disturbed, and the opposite
aggressieness to mated materials.
[0043] In the present invention, at least one type of the
aforementioned hard particles is dispersed in the base matrix phase
such that the total amount thereof is 10 to 30 vol. %. When the
total content of the hard particles is less than 10 vol. %, the
content of the hard particles is too small and the wear resistance
thereof will deteriorate. On the other hand, when the total content
of the hard particles exceeds 30 vol. %, the strength of the
sintered alloy material is lowered, the aggressieness to mated
materials increases, and the machinability of the sintered alloy
material may be deteriorated.
[0044] The composition of the base matrix portion including the
base matrix phase and the hard particles dispersed in the base
matrix phase is preferably comprised of: 0.2 to 2.0 wt % of C; 1.0
to 9.0 wt % of Cr; 1.0 to 9.0 wt % of Mo; 0.1 to 1.0 wt % of Si;
1.0 to 3.0 wt % of W; 0.1 to 1.0 wt % of V; 3.0 to 15.0 wt %, as
the sum, of at least one type of elements selected from the group
consisting of Cu, Co and Ni; and the remainder which is
substantially Fe.
[0045] Next, the preferable contents of the respective alloy
elements of the base matrix portion will be described
hereafter.
[0046] C: 0.2 to 2.0 wt %
[0047] Carbon is an element which is solid-solved in the base
matrix phase, thereby increasing hardness of the base matrix phase.
In addition, carbon is reacted with other alloy elements and forms
a carbide, thereby increasing hardness of the base matrix phase and
improving the wear resistance thereof When the content of carbon is
less than 0.2 wt %, the base matrix phase cannot have the
predetermined hardness and the wear resistance thereof
deteriorates. When the content of carbon exceeds 2.0 wt %, not only
the resulting carbide becomes gross and the toughness thereof
deteriorates, but also the diffusion of the components of the hard
particles proceeds excessively and hardness of the particles is
lowered. Accordingly, the content of C is preferably restricted to
0.2 to 2.0 wt %.
[0048] Cr: 1.0 to 9.0 wt %
[0049] Cr is an element which is contained in the base matrix phase
and the hard particles and contributes to increasing hardness, the
wear resistance and the corrosion resistance of the sintered alloy
material. When the content of Cr exceeds 9.0 wt %, the content of
the hard particles becomes too high or the hardness of the base
matrix phase increases too high, whereby the aggressieness to mated
materials of the sintered alloy materials increases. On the other
hand, when the content of Cr is less than 1.0 wt %, the content of
the hard particles is not high enough and the wear resistance of
the sintered alloy material deteriorates. Accordingly, the content
of Cr is preferably in a range of 1.0 to 9.0 wt %.
[0050] Mo: 1.0 to 9.0%
[0051] Mo is contained in the base matrix phase and the hard
particles and contributes to enhancing hardness and the wear
resistance of the sintered alloy material. However, when the
content of Mo exceeds 9.0 wt %, the content of the hard particles
becomes too high or the hardness of the base matrix phase increases
too high, whereby the aggressieness to mated materials increases.
On the other hand, when the content of Mo is less than 1.0 wt %,
the content of the hard particles is not high enough and the
hardness of the base portion is lowered, whereby the wear
resistance of the sintered alloy material is likely to be
deteriorate. Accordingly, the content of Mo is preferably in a
range of 1.0 to 9.0 wt %.
[0052] Si: 0.1 to 1.0 wt %
[0053] Si is an element which is contained mainly in the hard
particles and contributes to enhancing the wear resistance of the
sintered alloy material When the content of Si is less than 0.1 wt
%, the content of the hard particles is not high enough and the
effect of improving the wear resistance is not clearly observed. On
the other hand, when the content of Si exceeds 1.0%, the content of
the hard particles becomes too high or the hardness of the base
matrix phase increases too high, whereby the aggressieness to mated
materials increases. Accordingly, the content of Si is preferably
restricted to a range of 0.1 to 1.0 wt %.
[0054] W: 1.0 to 3.0 wt %
[0055] W is an element which is contained in the base matrix phase
and/or the hard particles and contributes to strengthening the base
matrix phase and enhancing hardness and the wear resistance of the
sintered alloy material. When the content of W is less than 1.0 wt
%, the content of the hard particles is not high enough and the
effect of improving the wear resistance is not clearly observed. On
the other hand, when the content of W exceeds 3.0%, the content of
the hard particles becomes too high or the hardness of the base
matrix phase increases too high, whereby the aggressieness to mated
materials increases. Accordingly, the content of W is preferably
restricted to a range of 1.0 to 3.0 wt %.
[0056] V: 0.1 to 1.0 wt %
[0057] V is an element which is contained in the base matrix phase
and/or the hard particles and contributes to strengthening the base
matrix phase and enhancing hardness and the wear resistance of the
sintered alloy material. When the content of V is less than 0.2 wt
%, the effect of improving the wear resistance is not clearly
observed. On the other hand, when the content of V exceeds 1.0%,
the content of the hard particles becomes too high or the hardness
of the base matrix phase increases too high, whereby the
aggressieness to mated materials increases. Accordingly, the
content of V is preferably restricted to a range of 0.1 to 1.0 wt
%.
[0058] At least one type of elements selected from the group
consisting of Cu, Co and Ni: the total content thereof being 3.0 to
15.0 wt %
[0059] Cu, Co and Ni are all contained in the base matrix phase and
the hard particles and contributes to strengthening the base matrix
phase and enhancing hardness and the wear resistance of the
sintered alloy material. However, when the total content of Cu, Co
and Ni is less than 3.0 wt %, the effect thereof is not clearly
observed. On the other hand, when the total content of added Cu, Co
and Ni is too large, the hardness of the base matrix phase
increases too high and the aggressieness to mated material
increases. Accordingly, the total content of Cu, Co and Ni is
preferably in a range of 3.0 to 15.0 wt %.
[0060] In the base matrix portion which includes the base matrix
phase and the hard particles, the remainder other than the
aforementioned components is substantially Fe.
[0061] In the iron-base sintered alloy material of the present
invention, the solid lubricant particles may optionally be
dispersed in the base matrix phase. The solid lubricant particles
are preferably at least one type of compound selected from the
group consisting of sulfide, fluoride and graphite. Examples of the
sulfide include MnS, MoS.sub.2 and W.sub.2S. Examples of the
fluoride include CaF.sub.2 and LiF. By dispersing the solid
lubricant particles in the base matrix phase, the machinability of
the sintered alloy material is facilitated, the wear resistance of
the sintered alloy material is enhanced and the aggressieness to
mated materials decreases.
[0062] It is preferable that the solid lubricant particles is
dispersed in the base matrix phase, by the total amount thereof of
0.1 to 10.0 wt %, with respect to the total amount of the base
matrix phase, the hard particles and the solid lubricant particles.
When the content of the solid lubricant particles is less than 0.1
wt %, the content of the solid lubricant particles is not high
enough, whereby the sliding lubricity of the sintered alloy
material deteriorates and the machinability of the sintered alloy
material may be decreased. Further, when the content of the solid
lubricant particles is less than 0.1 wt %, occurrence of adhesion
is accelerated and the wear resistance of the sintered alloy
material deteriorates. On the other hand, when the content of the
solid lubricant particles exceeds 10.0 wt %, the powder-compression
property(compactibility), the diffusion property during sintering
and the strength of the sintered alloy material deteriorate.
[0063] The particle diameter of the solid lubricant particles is
preferably is in a range of 2 to 50 .mu.m. In a case in which the
particle diameter of the sold lubricant particles is smaller than 2
.mu.m, the aforementioned effect of the solid lubricant particles
cannot be expected. On the other hand, in a case in which the
particle diameter of the solid lubricant particles exceeds 50
.mu.m, the sintering and powder-compression
properties(compactibility) will be adversely affected.
[0064] The iron-based sintered alloy material of the present
invention may contain pores by the proportion by volume of no
higher than 10.0%. When the content of pores exceeds 10.0 vol. %,
the strength at a high temperature and the heat conductivity are
lowered and drop-out resistance of the sintered alloy material
deteriorates.
[0065] In order to obtain the iron-based sintered alloy material of
the present invention, first, at least one type of powder selected
from the group consisting of pure iron powder, alloy iron powder
and alloy elements powder is blended with powder of the hard
particles (and optionally with powder of the solid lubricant
powder) such that the aforementioned composition of the base matrix
portion is satisfied, to prepare raw material powder as the mixture
of the components powders.
[0066] Preferable examples of combination of at least one type of
powder selected from the group consisting of pure iron powder,
alloy iron powder and alloy elements powder include the following
1) to 5). In each of 1) to 5), "%" represents "wt %" with respect
to the total amount of pure iron powder, alloy iron powder, alloy
elements powder, powder of the hard particles and powder of the
solid lubricant.
[0067] 1) 40.0 to 85.0% of pure iron powder and 8.0 to 35.0% of
alloy elements powder which contains at least one type of element
selected from the group consisting of C, Cr, Mo, Si, W, V, Cu, Co
and Ni (i.e., the total content of C, Cr, Mo, Si, W, V, Cu, Co and
Ni is in a range of 8.0 to 35.0%)
[0068] 2) At least one type of alloy iron powder, each type of
alloy iron powder containing at least one type of elements selected
from C, Cr, Mo, Si, W, V, Cu, Co and Ni by the amount of 20% or
less each, as well as Fe and inevitable impurities as the
remainder, the content of each type of alloy iron powder being
adjusted such that the total content thereof is within a range of
70.0 to 95.0%
[0069] 3) 20.0 to 70.0% of pure iron powder and at least one type
of alloy iron powder, each type of alloy iron powder containing at
least one type of elements selected from C, Cr, Mo, Si, W, V, Cu,
Co and Ni by the amount of 20% or less each, as well as Fe and
inevitable impurities as the remainder, the content of each type of
alloy iron powder being adjusted such that the total content
thereof is within a range of 5.0 to 70.0%
[0070] 4) At least one type of alloy iron powder, each type of
alloy iron powder containing at least one type of elements selected
from C, Cr, Mo, Si, W, V, Cu, Co and Ni by the amount of 20% or
less each, as well as Fe and inevitable impurities as the
remainder, and alloy elements powder which contains at least one
type of element selected from the group consisting of Cr, Mo, Si,
W, V, Cu, Co and Ni, the total content of the alloy iron powder(s)
being in a range of 45.0 to 90.0% and the content of the alloy
elements powder, i.e., the total content of the alloy elements
being in a range of 5.0 to 30.0%
[0071] 5) 15.0 to 65.0% of pure iron powder, at least one type of
alloy iron powder, each type of alloy iron powder containing at
least one type of element selected from C, Cr, Mo, Si, W, V, Cu, Co
and Ni by the amount of 20% or less each, as well as Fe and
inevitable impurities as the remainder, alloy elements powder which
contains at least one type of element selected from the group
consisting of Cr, Mo, Sit W, V, Cu, Co and Ni, the total content of
the alloy iron powder(s) being in a range of 5.0 to 65.0% and the
content of the alloy elements powder, i.e., the total content of
the alloy elements being in a range of 5.0 to 25.0%
[0072] The mixed powder as the raw material powder is preferably
prepared by blending and mixing at least one type of powder
selected from the group consisting of the pure iron powder, the
alloy iron powder and the alloy elements powder, with the hard
particles (and optionally with the solid lubricant powder), such
that the content of the added hard particles is in a range of 3 to
20 wt % and the content of the added solid lubricant powder is in a
range of 0.1 to 10 wt % with respect to the total amount of the
pure iron powder, the alloy iron powder, the alloy elements powder,
the hard particles and the solid lubricant powder. As the
lubricant, zinc stearate and the like may further be added.
[0073] The hard particles powder is preferably at least one type of
powder selected from the group consisting of: intermetallic
compound particles of Mo--Ni--Cr--Si--Co; intermetallic compound
particles of Cr--Mo--Co; Fe--Mo alloy particles; and
carbide-precipitated particles. The solid lubricant powder is
preferably at least one type of powder selected from the group
consisting of a sulfide, a fluoride and graphite.
[0074] The mixed powder as the raw material powder prepared as
described above is filled in a mold and subjected to compression
and molding by a molding press, whereby a compressed powder body is
obtained (the molding process), and the compressed powder body is
heated to a temperature in a range of 1,000 to 1,200.degree. C. in
a protective atmosphere and sintered, whereby a sintered body is
obtained (the sintering process). The sintered body may be further
subjected to infiltration or impregnation (the
infiltration-impregnation process). As a result, an iron-based
sintered alloy material for a valve seat is produced.
[0075] When the temperature at the sintering process is below
1,000.degree. C., the diffusion during sintering does not occur in
a sufficient manner and the formation of the base is insufficient.
On the other hand, when the temperature at the sintering process
exceeds 1,200.degree. C., excessive diffusion occurs at the hard
particles and the base matrix, whereby the wear resistance of the
sintered alloy material deteriorates. It is preferable that the
sintering atmosphere is a protective atmosphere and specifically
NH.sub.3 gas, a mixture of N.sub.2 and H.sub.2 gases or the
like.
[0076] The infiltration-impregnation process is optionally carried
out in order to seal the sintered pores (air pores). The pore
sealing process may be carried out by setting a low-melting point
metal such as Cu, Cu alloy, Pb or Pb alloy on the sintered body,
heating the metal and allow the metal to infiltrate the sintered
body. Alternatively, the pore sealing process may be carried out by
allowing a phenol-based resin to impregnate the sintered body.
[0077] The produced sintered body is then subjected to cutting and
grinding, so that a valve seat having a desired dimension and shape
is obtained.
EXAMPLES
[0078] At least one type of powder selected from the group
consisting of the iron powder, the alloy iron powder and the alloy
elements powder was blended and kneaded with powder of the hard
particles (and optionally with the solid lubricant powder) as shown
in Table 1, whereby the mixed powder was obtained. The blended
amount of each component powder was indicated as wt % with respect
to the total amount of the mixed powder.
[0079] The types of the alloy iron powder which was used are: (A)
alloy steel powder containing 1.0% of Cr, 0.5% of Mn, 0.3% of Mo
and Fe as the remainder; (B) alloy steel powder containing 3.0% of
Cr, 0.2% of Mo and Fe as the remainder; (C) alloy steel powder
containing 4.0% of Ni, 1.5% of Cu, 0.5% of Mo and Fe as the
remainder. Here, "%" represents "wt %".
[0080] The types of the hard particles which were used are: (a)
powder of carbide-precipitated particles (the average particle
diameter being 80 .mu.m, the average particle diameter of carbide
being 3 .mu.m) of SKD 11 (1.5% of C, 12% of Cr, 0.8% of V; 1% of Mo
and Fe as the remainder); (b) powder of carbide-precipitated
particles (the average particle diameter being 80 .mu.m, the
average particle diameter of carbide being 3 .mu.m) of SKH 51 (0.8%
of C, 4% of Cr, 5% of Mo, 2% of V, 6% of W and Fe as the
remainder); (c) powder of carbide-precipitated particles (the
average particle diameter being 80 .mu.m, the average particle
diameter of carbide being 4 .mu.m) of SKH 57 (1.2% of C, 4% of Cr,
3% of Mo, 10% of W, 3% of V, 10% of Co and Fe as the remainder);
(d) powder of intermetallic compound particles containing 9% of Cr,
30% of Mo and Co as the remainder (the average particle diameter
being 100 .mu.m); (e) powder of intermetallic compound particles
containing 24% of Mo, 10% of Ni, 24% of Cr, 2% of Si and Co as the
remainder (the average particle diameter being 100 .mu.m); (f)
powder of alloy particles containing 60% of Mo and Fe as the
remainder (the average particle diameter being 100 .mu.m). "%"
represents "wt. %".
[0081] The types of the solid lubricant powder which was used are
MnS (X), CaF.sub.2 (Y) and Graphite(Z).
[0082] The mixed powder as described above was filled in a mold and
subjected to compression and molding by a molding press, whereby a
compressed powder body was obtained. Each compressed powder body
was subjected to sintering in a reducing atmosphere (NH.sub.3 gas)
at a temperature of 1,000 to 1,200.degree. C. for 15 to 45 minutes,
whereby a sintered body was obtained. Some of the sintered body
samples were subjected to the infiltration process in which each
sample was heated with an infiltration agent (lead) at 500.degree.
C.
[0083] The composition of the base matrix portion, as well as the
structural proportions, of each of the obtained sintered body
samples are shown in Table 2.
[0084] FIG. 1(a), FIG. 2(a), FIG. 3(a) and FIG. 4(a) show the
optical micrographs of the sintered body No. 3, the sintered body
No. 6, the sintered body No. 10 and the sintered body No. 12,
respectively. FIGS. 1(b) to 4(b) are sketches of FIGS. 1(a) to
4(a), respectively. "P," represents the pearlite phase, "P"
represents the high-alloy diffused phase, "H" represents the hard
particles (other than the carbide-precipitated particles), "HC"
represents the carbide-precipitated particles (the hard particles),
"ST" represents the solid lubricant particles.
[0085] Next, each sintered body was processed to form a valve seat
(having a dimension of .phi.41.4.times..phi.38.8.times.7.0 mm),
whereby a single piece wear test on rig was carried out as
described below.
[0086] 1) A single piece wear test on rig wear test(an wear
resistance test)
[0087] The wear resistance was investigated by using a single piece
wear test on rig shown in FIG. 6. The single piece wear test on rig
was carried out by: pressingly inserting the valve seat 1 into a
jig 2 which simulated a cylinder head; moving up/down the valve 4
in the vertical direction with heating the valve 4 and the valve
seat 1 by using a heat source (LPG+Ar) 3 provided in the testing
device; and measuring the amount of wear as the amount of sinking
of the valve. The conditions at the test were as follows.
[0088] Temperature: 400.degree. C. (at the seat surface)
[0089] Testing time: 9.0 hr
[0090] Number of cam rotation: 3000 rpm
[0091] Number of valve rotation: 20 rpm
[0092] Load of spring: 35 kgf (at the time of setting)
[0093] Valve material: SUH3
[0094] The result of the single piece wear test on rig are shown in
Tables 2 and FIG. 5.
[0095] Table 1
[0096] Table 2
[0097] The amount of wear of the valve seat in each of the sintered
bodies No. 1 to No. 9, No.14 to No.17 of the present examples was
in a range of 11 to 19 .mu.m. In these examples, the amount of wear
of the mated material was in a range of 4 to 11 .mu.m. The amount
of wear of the valve seat in each of the sintered bodies No. 10 to
No. 13 of the comparative examples, which were beyond the scope of
the present invention, was in a range of 29 to 48 .mu.m. In these
comparative examples, the amount of wear of the mated material was
in a range of 15 to 47 .mu.m. Accordingly, it is understood that
the amount of wear is decreased, the wear resistance is improved
and the aggressieness to mated materials is lowered in the present
examples, as compared with the comparative examples.
[0098] As described above, according to the present invention, a
sintered alloy material which is inexpensive and excellent in
toughness and wear resistance can be obtained. This sintered alloy
material exhibits excellent durability in a harsh operation when
used as a valve seat for an automobile and achieves a significantly
excellent effect in the industrial terms.
1 TABLE 1 Amount to be blended (wt %) Alloy Alloy elements powder
(wt %) Powder of hard particles** Powder of solid Sintered Iron
iron powder* Total Total lubricant particles Infiltration agent
body No. Powder Type wt % C Others amount Type wt % Type wt %
amount Type wt % Type wt % 1 28.5 B 45.0 1.5 Ni:2.0 2.0 b 10.0 d
12.0 22.0 Y 1.0 -- -- 2 31.8 A 50.0 1.2 -- -- b 8.0 d 8.0 16.0 X
1.0 -- -- 3 37.5 C 40.0 1.5 -- -- b 10.0 e 10.0 20.0 X 1.0 -- -- 4
62.8 -- -- 1.2 Ni:2.0, Co:3.0 5.0 a 15.0 e 13.0 28.0 Y 2.0 Pb 1.0 5
59.0 C 10.0 1.0 Cu:2.0 2.0 c 10.0 f 15.0 25.0 X 2.0 Pb 1.0 6 21.8 A
53.0 1.2 -- -- b 8.0 e 15.0 23.0 X 1.0 -- -- 7 29.7 B 45.0 1.3
Ni:2.0 2.0 c 10.0 e 10.0 20.0 Y 2.0 -- -- 8 40.9 C 35.0 1.1 Cu:2.0
2.0 c 10.0 e 10.0 20.0 X 1.0 -- -- 9 30.5 A 40.0 1.0 -- -- b 12.0 d
15.0 27.0 Y 1.5 -- -- 10 28.5 B 34.5 1.5 -- -- b 20.0 e 15.0 35.0 X
0.5 -- -- 11 73.2 C 10.0 1.3 Co:3.0, Ni:2.0 5.0 b 5.0 e 5.0 10.0 Y
0.5 -- -- 12 20.0 A 22.5 -- -- -- b 45.0 e 12.0 57.0 X 0.5 -- -- 13
25.0 C 40.0 -- -- -- a 10.0 e 25.0 35.0 -- -- -- -- 14 32.8 A 40.0
1.2 Co:3.0, Ni:2.0 5.0 a 20.0 -- -- 20.0 Z 1.0 -- -- 15 26.4 C 40.0
1.1 -- -- -- -- d 15.0 15.0 Y 1.0 -- -- 16 28.4 C 45.0 1.1 -- -- --
-- e 25.0 25.0 X 0.5 -- -- 17 28.4 B 40.0 1.1 Co:4.0 4.0 -- -- f
26.0 26.0 Y 0.5 -- -- *Alloy iron powder A: 1.0% of Cr-.5% of
Mn-0.3% of Mo--Fe B: 3.0% of Cr-0.2% of Mo--Fe C: 4.0% of Ni-1.5%
of Cu-0.5% of Mo--Fe **Hard particles a: SKD11
(carbide-precipitated particles) b: SKH51 (carbide-precipitated
particles) c: SKH57 (carbide-precipitated particles) d: An
intermetallic compound containing 9% of Cr-30% of Mo--Co e: An
intermetallic compound containing 24% of Mo-10% of Ni-24% of Cr-2%
of Si--Co f: An alloy containing 60% of Mo--Fe Solid lubricant
agent X: MnS Y: CaF.sub.2 Z: Graphite
[0099]
2TABLE 2 Sintered body Structure of Hard particles the base
Carbide-precipitated matrix phase particles High-alloy Particle
Sintered Composition of the base matrix portion (wt %) Pearlite
phase diffused phase diameter Hardness body No. C Cr Mo Si W V Co,
Ni, Cu (vol %) (vol %) .mu.m* (Hv) vol. % 1 1.6 2.8 4.0 0.3 0.6 0.3
Co:7.2, Ni:2.0 35 36 4 650 10 2 1.3 1.5 2.8 0.2 0.5 0.2 Co:4.8 39
39 3 630 8 3 1.6 2.8 3.1 0.2 0.6 0.2 Co:4.0, Ni:2.6, 38 37 4 650 10
Cu:0.8 4 1.4 4.9 3.3 0.3 -- 0.1 Ni:3.3, Co:8.2 35 33 3 620 15 5 1.1
0.4 9.4 0.1 0.9 0.3 Cu:2.2, Co:0.9, 35 36 4 660 10 Ni:0.4 6 1.3 4.5
4.2 0.3 0.5 0.2 Co:6.0, Ni:1.5 32 38 3 630 8 7 1.4 4.2 2.9 0.2 0.9
0.5 Ni:3.1, Co:4.9 36 37 4 660 10 8 1.2 2.8 2.9 0.2 0.9 0.3 Cu:2.5,
Co:4.9, 37 37 4 660 10 Ni:2.4 9 1.1 2.2 5.0 0.4 0.7 0.2 Co:9.0 26.5
39 3 630 12 10 1.7 5.5 4.7 0.4 1.2 0.5 Co:6.0, Ni:1.5 11.5 45 4 500
20 11 1.4 1.4 1.5 0.1 0.3 0.1 Ni:2.9, Co:5.0, 56.5 30 4 630 5
Cu:0.2 12 0.4 4.9 5.2 0.4 2.6 0.9 Ni:1.2, Co:4.8 9.5 20 2 500 45 13
0.1 7.2 6.3 0.5 -- 0.1 Ni:4.1, 27 30 2 450 10 Co:10.0, Cu:0.6 14
1.6 3.4 0.4 -- -- 0.2 Co:3.0, Ni:2.0 38 38 2 620 20 15 1.1 2.4 8.2
0.7 -- -- Co:13.0, Ni:1.6 39.5 39.5 -- -- -- 16 1.1 6.0 6.2 0.5 --
-- Co:10.0, 36 33.5 -- -- -- Ni:4.3, Cu:0.6 17 1.1 1.2 15.7 -- --
0.1 Co:0.4 32 35.5 -- -- -- Sintered body Hard particles Solid
Single rig Others lubricant Infiltration test Particle particles
agent Void Amount of Sintered diameter Hardness vol. Total amount
Particle vol. vol. rate wear (.mu.m) body No. (.mu.m) HV % (vol. %)
diameter (.mu.m) % % vol. % Seat Valve Note 1 90 750 12 22 15 1.0
-- 6.0 17 8 Present example 2 90 750 8 16 10 1.0 -- 5.0 18 4
Present example 3 80 1000 10 20 10 1.0 -- 6.0 14 7 Present example
4 80 1000 15 28 13 2.0 1.0 1.0 15 5 Present example 5 70 1000 15 25
10 2.0 1.0 1.0 12 7 Present example 6 80 1000 15 23 10 1.0 -- 6.0
18 6 Present example 7 80 1000 10 20 15 2.0 -- 5.0 18 9 Present
example 8 80 1000 10 20 10 1.0 -- 5.0 17 6 Present example 9 90 750
15 27 15 1.5 -- 6.0 11 11 Present example 10 80 1000 15 35 10 0.5
-- 8.0 29 35 Comparative example 11 80 1000 5 10 15 0.5 -- 3.0 48
15 Comparative example 12 80 1000 12 57 10 0.5 -- 13.0 40 38
Comparative example 13 80 1000 25 35 -- -- -- 8.0 35 47 Comparative
example 14 -- -- -- 20 2 1.0 -- 3.0 19 5 Present example 15 90 750
15 15 15 1.0 -- 5.0 13 5 Present example 16 80 1000 25 25 10 0.5 --
5.0 12 6 Present example 17 70 1000 26 26 15 0.5 -- 6.0 18 11
Present example *Particle diameter: Average particle diameter of
carbide
* * * * *