JP2002363681A - Sintered alloy, production method therefor and valve seat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a sintered alloy which can exhibit wear resistance, to provide a production method therefor, and a valve seat having excellent wear resistance. SOLUTION: The sintered alloy has a composition containing, by weight, 4 to 30% Mo, 0.2 to 3% C, 1 to 30% Ni, 0.5 to 10% Mn and 2 to 40% Co, and the balance Fe with inevitable impurities. The sintered alloy has high wear resistance because of its improved density and improved soled lubricating action owing to an oxidation film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered alloy having excellent wear resistance and a method for producing the same. Further, the present invention relates to a valve seat made of a sintered alloy having excellent wear resistance.

[0002]

2. Description of the Related Art An internal combustion engine used for an automobile engine or the like is provided with a valve for intake and exhaust and a valve seat on which the valve is seated.

[0003] Valve seats are required to have high wear resistance. That is, when the valve seat is worn, a valve seat recess occurs in which the valve sinks when seated.

[0004] Valve seats having excellent wear resistance include, for example, sintered alloys in which Co-based hard particles are dispersed in an Fe-based matrix. As a valve seat made of this sintered alloy, for example, there is a valve seat for an internal combustion engine disclosed in Japanese Patent Application Laid-Open No. 9-242516.

A valve seat for an internal combustion engine disclosed in Japanese Patent Application Laid-Open No. 9-242516 is a valve seat for an internal combustion engine in which cobalt-based hard particles are dispersed in a matrix of an iron-based alloy. C as a base component: 0.5 to
1.5% by weight, at least one element selected from the group consisting of Ni, Co and Mo: 2.0 to 20.0% by weight in total, and the balance: Fe-containing at least and cobalt-based hard particles Is contained in an amount of 26 to 50% by weight.

However, this valve seat has insufficient wear resistance for use as a valve seat of a gas engine.

That is, in an engine using a liquid fuel such as gasoline or light oil, lubrication between the valve and the valve seat is maintained by the fuel or a combustion product (for example, C). Wear of the seat is suppressed.

On the other hand, liquefied petroleum gas (LPG: L
equalized Natural Gas (CNG) or compressed natural gas (CNG).
In a gas engine using a gas fuel such as Gas), lubricating properties between the valve and the valve seat cannot be sufficiently ensured due to a small amount of combustion products. Further, in a gas engine, an oxide film contributing to lubrication between solids is less likely to be formed on a sliding surface of a valve seat due to a reducing action of hydrogen contained in a large amount in fuel gas.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a sintered alloy capable of exhibiting sufficient wear resistance, a method for producing the same, and a valve seat having excellent wear resistance. That is the task.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have repeatedly studied a sintered alloy having excellent wear resistance and a method for producing the same. The inventors have found that the above problem can be solved by increasing the density to increase the hardness, and forming a sintered alloy in which Mo forms an oxide film to ensure solid lubricity by the oxide film.

That is, the sintered alloy of the present invention has a total of 1
When the content is set to 00 wt%, 4 to 30 wt% Mo,
0.2 to 3 wt% C, 1 to 30 wt% Ni,
0.5-10 wt% Mn and 2-40 wt% Co
And the balance consists of unavoidable impurities and Fe.

The method for producing a sintered alloy according to the present invention is characterized in that, when the total hard particle powder is 100% by weight, 20 to 60% by weight.
% Mo, 3 wt% or less C, and 5-40 wt% N
i, 1-20 wt% Mn, and 5-40 wt% Co
And the remainder is a mixed powder of a hard particle powder composed of unavoidable impurities and Fe, a carbon powder, a Co powder, and an Fe powder or a low alloy steel powder.
When the content is 00 wt%, it is composed of 10 to 60 wt% of hard particle powder, 0.2 to 2 wt% of carbon powder, 20 wt% or less of Co powder, and the balance of Fe powder or low alloy steel powder. Adjusting the mixed powder, forming the mixed powder to form a green compact, and sintering the green compact.
It is characterized by being a sintered alloy having the composition described in 2.

In the valve seat of the present invention, the hardness is improved by promoting the diffusion of Mn during sintering to increase the density, and the solid lubricity of the oxide film is improved by forming the oxide film with Mo. It has been found that the above problem can be solved by providing a valve seat made of a sintered alloy that is secured.

That is, the valve seat of the present invention has a Mo content of 4 to 30 wt% when the whole is 100 wt%.
And 0.2 to 3 wt% of C and 1 to 30 wt% of Ni
And 0.5 to 10 wt% of Mn and 2 to 40 wt% of C
o, and the balance consists of unavoidable impurities and Fe.

[0015] In the present invention, wt% corresponds to mass%.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION (Sintered Alloy) The sintered alloy of the present invention has a total content of 4 to 30% by weight, assuming 100% by weight.
Mo, 0.2 to 3 wt% C, 1 to 30 wt% Ni, 0.5 to 10 wt% Mn, and 2 to 40 wt%
Of Co, and the balance consists of unavoidable impurities and Fe.

Mo forms Mo carbides to improve the hardness and wear resistance of the sintered alloy, and Mo and Mo carbides dispersed and dissolved in the structure by sintering form a Mo oxide film. The coating improves the solid lubricity.

If the Mo content is less than 4 wt%, the Mo film becomes insufficient and the formation of an oxide film becomes insufficient, so that sufficient solid lubricity cannot be obtained. On the other hand, if Mo exceeds 30% by weight, an oxide film will be formed excessively, and this oxide film will peel off, and the hardness and wear resistance of the sintered alloy will decrease. Further, when Mo exceeds 30% by weight, the yield is lowered when forming the raw material powder for forming the sintered alloy. The production of the raw material powder includes, for example, an atomizing method. Therefore M
o is defined in the range of 4 to 30 wt%.

C combines with Mo to form Mo carbides and improves hardness and wear resistance. C is 0.2wt
%, The amount of Mo carbide formed is small and the wear resistance is insufficient. On the other hand, when C exceeds 3 wt%, the density of the sintered alloy decreases. Therefore, C is 0.2 to 3 wt.
%.

Ni increases the austenite phase, which increases the amount of solid solution of Mo, and improves the wear resistance of the sintered alloy. If the content of Ni is less than 1 wt%, the amount of Mo dissolved becomes insufficient and sufficient wear resistance cannot be obtained. In addition, Ni is 30 wt.
%, The hardness is reduced, so that Ni is 1 to 30%.
It is defined in the range of wt%.

Since Mn diffuses efficiently during sintering,
The density of the sintered alloy is improved by improving the adhesion of the structure constituting the sintered alloy. Further, Mn has an effect of increasing the austenite phase, and thus improves wear resistance.
If Mn is less than 0.5 wt%, the effect of improving the density cannot be sufficiently obtained, and if it exceeds 10 wt%, the above-mentioned effect is saturated. For this reason, Mn is specified in the range of 0.5 to 10 wt%.

[0022] Co increases the austenite phase in the sintered alloy and improves the hardness. Co is 2wt%
If less than 40%, the effect of Co addition is not observed,
If it exceeds, the above-described effect is saturated. For this reason, Co
Is defined in the range of 2 to 40 wt%.

Fe is composed of Mo, C, Ni, Mn and Co.
Disperse.

When the whole is 100 wt%, 5 wt%
% Of Cr and 2 wt% or less of Si.

When the whole is 100 wt%, 5 wt%
% Of Cr is preferred. In addition, 5wt%
The following indicates a range that does not include 0 wt%. Since the sintered alloy of the present invention contains 5 wt% or less of Cr, it is possible to prevent Mo from forming an excessive amount of an oxide film to lower the wear resistance of the sintered alloy. That is, when the sintered alloy is exposed to a high temperature, a large amount of oxide is generated in the sintered alloy, the generated oxide is separated, and the sintered alloy is worn. C
r has a high oxidation start temperature, and by adding this Cr,
Oxide formation in the sintered alloy is suppressed, and the characteristics of the sintered alloy are maintained. On the other hand, when Cr exceeds 5% by weight, the generation of oxides decreases, and the solid lubricity decreases. For this reason, Cr is specified in the range of 5 wt% or less.

When the whole is 100 wt%, 2 wt%
% Or less of Si. In addition, 2wt%
The following indicates a range that does not include 0 wt%. Si improves the adhesion of the oxide film. On the other hand, when Si exceeds 2 wt%, the density of the sintered alloy decreases, and the hardness decreases. For this reason, Si is specified in a range of 2 wt% or less.

The sintered alloy of the present invention preferably has a structure in which hard particles are dispersed in a matrix. That is, in the sintered alloy of the present invention, the hard particles dispersed in the matrix exhibit wear resistance.

The sintered alloy of the present invention has high wear resistance because the density is improved and the solid lubrication effect of the oxide film is improved.

(Method for Producing Sintered Alloy) In the method for producing a sintered alloy of the present invention, when the entire hard particle powder is 100% by weight, 20 to 60% by weight of Mo and 3% by weight or less of C
And 5 to 40 wt% of Ni and 1 to 20 wt% of Mn
And 5 to 40 wt% of Co, with the balance being unavoidable impurities and F
e, a hard powder, a carbon powder, a Co powder, a Fe powder or a low alloy steel powder.
A mixed powder composed of 0 to 60 wt% of hard particle powder, 0.2 to 2 wt% of carbon powder, 20 wt% or less of Co powder, and the balance of Fe powder or low alloy steel powder is prepared and mixed. A method for producing a sintered alloy having the composition according to claims 1 and 2, wherein a powder compact is formed by molding powder, and the compact is sintered.

The hard particles constitute a hard phase that enhances the wear resistance of the sintered alloy. When the content of the hard particles is less than 10 wt%, the wear resistance of the manufactured sintered alloy becomes insufficient. On the other hand, if the content of the hard particles exceeds 60 wt%, the bonding strength of the manufactured sintered alloy becomes insufficient. Furthermore, when the amount of the hard particles is excessive, the aggressiveness of the opponent increases, and the retention of the hard particles is hardly secured. For this reason, the hard particles
It is defined in the range of 10 to 60 wt%.

The carbon (C) constituting the carbon powder diffuses into the matrix of the sintered alloy (Fe or low alloy steel) or hard particles during sintering, and forms a solid solution or carbides (Mo carbides). . It is preferable to use graphite powder as the carbon powder. If the carbon powder is less than 0.2 wt%,
When the ferrite phase increases in the base of the manufactured sintered alloy, the base hardness decreases, and the wear resistance of the sintered alloy becomes insufficient. Further, when the carbon powder exceeds 2 wt%, the cementite phase increases in the matrix of the manufactured sintered alloy, and the toughness of the manufactured sintered alloy decreases. For this reason, the carbon powder is specified in the range of 0.2 to 2 wt%.

The Co powder increases the density of the sintered alloy produced. If the content of Co particles exceeds 20 wt%, the effect is saturated. In addition, 20 wt% or less of the ratio of the Co powder indicates a range not including 0 wt%.

[0033] Fe powder or low alloy steel powder forms the matrix of the sintered alloy. Fe-C-based alloy powder can be used as the low alloy steel powder. For example, when the low alloy steel powder is 100 wt%, an alloy powder having a composition of 0.2 to 5 wt% of C and the balance of unavoidable impurities and Fe can be used.

In the hard particles, Mo becomes M by sintering.
o carbides are formed to improve the hardness and wear resistance of the sintered alloy, and Mo and Mo carbide dispersed and dissolved in the sintered alloy form a Mo oxide film, and the oxide film is formed by the method of the present invention. Improves the solid lubricity of the sintered alloy produced by the method.

If the Mo content of the hard particles is less than 20% by weight, the formation of an oxide film becomes insufficient due to the insufficient Mo, so that sufficient solid lubricity cannot be obtained. Also,
If Mo exceeds 60% by weight, an excessively oxidized film is formed in the manufactured sintered alloy, and the oxidized film causes peeling, thereby lowering the hardness and wear resistance of the sintered alloy. On the other hand, if Mo exceeds 30% by weight, the yield will decrease when hard particle powder is produced by the atomizing method or the like. For this reason, Mo is 20 to 60 wt%.
Is defined in the range.

[0036] In the hard particles, C combines with Mo to form Mo carbides and improves hardness and wear resistance. If C exceeds 3 wt%, the density of the manufactured sintered alloy will decrease. When C is small, C diffused from the carbon powder forms Mo carbide. Therefore, C is specified in a range of 3 wt% or less.

In the production method of the present invention, the hard particles contain C. That is, 3 wt% or less indicating the amount of C in the hard particles indicates a range exceeding 0 wt% and 3 wt% or less.

In the hard particles, Ni increases the austenite phase, which increases the amount of solid solution of Mo, and improves the wear resistance of the sintered alloy. If Ni is less than 5 wt%, Mo
Is insufficient to provide sufficient wear resistance. If the Ni content exceeds 40 wt%, the hardness is reduced. Therefore, the Ni content is defined in the range of 5 to 40 wt%.

In the hard particles, Mn is an element that efficiently diffuses into the matrix at the time of sintering, so that the adhesion between the matrix and the hard particles is improved, and the density of the sintered alloy is improved. Further, Mn has an effect of increasing the austenite phase, and thus improves wear resistance. If Mn is less than 1 wt%, the effect of improving the density cannot be sufficiently obtained, and if it exceeds 20 wt%, the above-mentioned effect is saturated. Therefore, Mn is 1
It is specified in the range of ２０20 wt%.

In the hard particles, Co increases the austenite phase in the sintered alloy and improves the hardness. If Co is less than 5 wt%, the effect of Co addition is not seen, and if Co exceeds 40 wt%, the above-mentioned effects are saturated. Therefore, Co is specified in the range of 5 to 40 wt%.

The mixed powder is 100 wt% of the whole mixed powder.
In this case, it is preferable that Ni powder is mixed at a ratio of 10 wt% or less. In addition, 10 wt% or less means 0 wt%.
Indicates the range not including%. That is, Ni in the mixed powder
By mixing the powder, diffusion of elements during sintering is promoted, and the density of the sintered alloy is improved. On the other hand, when the proportion of the Ni powder exceeds 10% by weight, the retained austenite phase increases, and the wear resistance decreases. For this reason, the Ni powder is specified in a range of 10 wt% or less.

The hard particles consist of 100 w of the entire hard particle powder.
t as%, 10% by weight or less of Cr;
It is preferable to have at least one kind of Si at a ratio of not more than wt%.

The hard particles consist of 100 w of the entire hard particle powder.
It is preferable to have Cr at a ratio of 10 wt% or less when t%. In addition, 10 wt% or less means 0 wt%.
Indicates the range not including. By containing Cr, it is possible to prevent Mo from forming an oxide film in an excessive amount and lowering the hardness of the sintered alloy. That is, when the sintered alloy is exposed to a high temperature, a large amount of oxide is generated in the sintered alloy, the generated oxide is separated, and the sintered alloy is worn. Cr has a high oxidation initiation temperature, and the addition of this Cr suppresses the formation of oxides in the sintered alloy, thereby maintaining the characteristics of the sintered alloy. On the other hand, if Cr exceeds 10% by weight, the generation of oxides decreases, and the solid lubricity decreases. For this reason, Cr is specified in a range of 10 wt% or less.

The hard particles are 100 w
It is preferable to have Si in a ratio of 4 wt% or less when t%. In addition, 4 wt% or less refers to a range that does not include 0 wt%. Si improves the adhesion of the generated oxide film in the sintered alloy. In addition, 4 wt% of Si
%, The density of the sintered alloy decreases and the hardness decreases. For this reason, Si is specified in a range of 4 wt% or less.

In the method for producing a sintered alloy of the present invention, it is preferable to perform a tempering treatment after sintering the green compact. That is, by performing tempering on the sintered alloy, the crystal structure of the sintered alloy is stabilized.

In the method for producing a sintered alloy according to the present invention, it is preferable to perform forging after sintering the green compact.
That is, by performing forging on the sintered alloy, not only can the shape of the sintered alloy be formed into a desired shape, but also it is possible to remove pores generated by sintering, and the density and wear resistance of the sintered alloy are improved. And the like.

According to the method for producing a sintered alloy of the present invention, the cost of the starting material can be reduced, and the compactability of the compact can be improved. This is advantageous for increasing the density of the bonding gold.

According to the method for producing a sintered alloy of the present invention, since the element contained in one of the hard particles and the matrix diffuses into the other during sintering, the adhesion between the hard particle and the matrix is increased. Increase. In particular, Mn contained in the hard particles efficiently diffuses into the matrix, so that the adhesion between the hard particles and the matrix increases. This can improve the density of the sintered alloy, the hardness of the sintered alloy, and the wear resistance of the sintered alloy.

In the method for producing a sintered alloy of the present invention, the method for producing hard particles is not particularly limited. Examples of the method for producing the hard particles include particles produced by atomizing the molten metal and particles obtained by pulverizing a solidified material obtained by solidifying the molten metal by mechanical pulverization. As the atomizing treatment, a material that has been atomized in a non-oxidizing atmosphere (inert gas atmosphere such as nitrogen gas or argon gas or in vacuum) can be used.

The average particle size of the hard particles can be appropriately selected according to the use and the type of the manufactured sintered alloy, but is generally about 20 to 250 μm, and generally 30 to 20 μm.
The thickness is preferably about 0 μm and about 40 to 180 μm. However, the average particle size of the hard particles is not limited to these ranges.

The hardness of the hard particles depends on the amount of Mo carbide and the like, but is generally about Hv 350 to 750,
Hv can be about 450 to 700. However, the hardness of the hard particles is not limited to these ranges, and may be any hardness as long as the hard particles are hard to be used, such as a base of a sintered alloy.

In the method for producing a sintered alloy according to the present invention, the sintering temperature is about 1050 to 1250 ° C., especially 11
About 00 to 1150 ° C can be adopted. The sintering time at the above-mentioned sintering temperature is 30 minutes to 120 minutes, especially 4 minutes.
5 to 90 minutes can be employed. In addition, as the sintering atmosphere,
A non-oxidizing atmosphere such as an inert gas atmosphere is preferred. Examples of the non-oxidizing atmosphere include a nitrogen atmosphere, an argon gas atmosphere, and a vacuum atmosphere.

In the method for producing a sintered alloy of the present invention, since hard particles, carbon powder, Co powder and Fe alloy powder are mixed and sintered, diffusion of the hard particles and elements of the matrix during sintering is performed. Is promoted, and the density of the manufactured sintered alloy is improved. Mo is diffused in a large amount by promoting the diffusion of the element, and the diffused Mo forms a carbide or an oxide film, whereby a sintered alloy having excellent wear resistance and solid lubricity is obtained.

(Valve Seat) The valve seat of the present invention is 4 to 30 wt% when the whole is 100 wt%.
Mo, 0.2 to 3 wt% C, 1 to 30 wt% Ni, 0.5 to 10 wt% Mn, and 2 to 40 wt%
Of Co, and the balance consists of unavoidable impurities and Fe.

Mo constituting the valve seat of the present invention is
Mo carbides are formed to improve the hardness and wear resistance of the valve seat, and Mo and Mo carbides dispersed and dissolved in the structure by sintering form a Mo oxide film, which improves the solid lubricity. Let it.

If the Mo content is less than 4 wt%, the Mo film becomes insufficient, so that the formation of an oxide film becomes insufficient, so that sufficient solid lubricity cannot be obtained. On the other hand, if Mo exceeds 30% by weight, an oxide film will be formed excessively, and this oxide film will peel off, and the wear resistance of the valve seat will decrease. Further, when Mo exceeds 30% by weight, the yield decreases when forming the raw material powder for forming the valve seat. The production of the raw material powder includes, for example, an atomizing method. Therefore M
o is defined in the range of 4 to 30 wt%.

C constituting the valve seat of the present invention is M
Combines with o to form Mo carbides and improves hardness and wear resistance. If C is less than 0.2 wt%, the amount of Mo carbide formed is small and the wear resistance becomes insufficient. Also,
If C exceeds 3% by weight, the density of the valve seat decreases. For this reason, C is defined in the range of 0.2 to 3 wt%.

Ni constituting the valve seat of the present invention is
The austenitic phase which increases the amount of solid solution of Mo is increased, and the wear resistance of the valve seat is improved. Ni is 1w
If it is less than t%, the amount of Mo dissolved will be insufficient and sufficient wear resistance cannot be obtained. When Ni exceeds 30 wt%,
Since the above effects are saturated, Ni is 1 to 30 wt%.
Is defined in the range.

Mn constituting the valve seat of the present invention is
In order to efficiently diffuse during sintering, the adhesiveness of the structure constituting the valve seat is improved, and the density of the sintered alloy is improved. Further, Mn has an effect of increasing the austenite phase, and thus improves wear resistance. Mn is 0.5wt
%, The effect of increasing the density cannot be obtained sufficiently, and
When the content exceeds wt%, the above-described effects are saturated. For this reason,
Mn is specified in the range of 0.5 to 10 wt%.

Co constituting the valve seat of the present invention is
It increases the austenite phase in the valve seat and improves hardness. If Co is less than 2 wt%, the effect of Co addition is not seen, and if Co exceeds 40 wt%, the above-mentioned effects are saturated. Therefore, Co is 2 to 40 wt.
%.

The Fe constituting the valve seat of the present invention is
Serves as a base for dispersing Mo, C, Ni, Mn and Co.

When the whole is 100 wt%, 5 wt%
% Of Cr and 2 wt% or less of Si.

When the whole is 100 wt%, 5 wt%
% Of Cr is preferred. In addition, 5wt%
The following indicates a range that does not include 0 wt%. The valve seat according to the present invention contains 5 wt% or less of Cr,
It is possible to suppress that o forms an excessive amount of the oxide film and lowers the wear resistance of the valve seat. That is, when the valve seat is exposed to a high temperature, a large amount of oxide is generated in the valve seat, the generated oxide is separated, and the valve seat is worn. Cr has a high oxidation start temperature, and by adding this Cr, generation of oxides in the valve seat is suppressed, and the characteristics of the valve seat are maintained. On the other hand, when Cr exceeds 5% by weight, the generation of oxides decreases, and the solid lubricity decreases. Therefore, Cr is 5w
It is specified in the range of t% or less.

When the whole is 100 wt%, 2 wt%
% Or less of Si. In addition, 2wt%
The following indicates a range that does not include 0 wt%. Si improves the adhesion of the oxide film. On the other hand, when Si exceeds 2 wt%, the density of the sintered alloy decreases, and the hardness decreases. For this reason, Si is specified in a range of 2 wt% or less.

The valve seat of the present invention is manufactured by using the manufacturing method according to claims 3 to 5. That is, by mixing and sintering the hard particles, carbon powder, Co powder and Fe alloy powder, the diffusion of the hard particles and the elements of the matrix is promoted at the time of sintering. Density is improved. Further, Mo is diffused in a large amount by promoting the diffusion of the element, and the diffused Mo forms a carbide or an oxide film, whereby a valve seat having excellent wear resistance and solid lubricity is obtained.

The valve seat of the present invention preferably has a structure in which hard particles are dispersed in a matrix. That is,
In the valve seat of the present invention, the hard particles dispersed in the matrix exhibit abrasion resistance.

Since the valve seat of the present invention has an improved density and an improved solid lubricating action by the oxide film, it is a valve seat having high wear resistance and can be sufficiently used for a gas engine. High wear resistance.

[0068]

The present invention will be described below with reference to examples.

(Hard Particles) In this example, alloy powders having the compositions of Samples A to R shown in Table 1 were produced by gas atomization using an inert gas (nitrogen gas). Further, an alloy powder having a composition of S was manufactured by pulverization after melting. These alloy powders were classified into a range of 44 to 180 μm to obtain hard particles.

[0070]

[Table 1]

Samples A to J shown in Table 1 are powders corresponding to hard particles within the scope of the production method of the present invention.
In sample K, Mo was as small as 15 wt%, which corresponds to a comparative material. Sample L does not contain Mn having a high diffusion efficiency, and corresponds to a comparative material. Sample M has a relatively high content of C of 3.5 wt%, and corresponds to a comparative material. Sample N was 45% Ni.
It contains a relatively large amount of wt%, which corresponds to a comparative material. Sample O
Contains a large amount of Cr of 15 wt%, and corresponds to a comparative material. Sample P contains a large amount of 5% of Si,
This corresponds to a comparative material. In Sample Q, Co was as small as 2 wt%, which corresponds to a comparative material. Sample R is a Ni-based alloy that does not contain Mn and Co but contains a large amount of Cr, and corresponds to a conventional material. Sample S is ferromolybdenum (FeMo), does not contain Ni and Mn, and corresponds to a conventional material.

Using the hard particle powders of Samples A to S, each hard particle powder was heated and oxidized in the air, and the temperature at which the weight increase accompanying the oxidation suddenly started was investigated. This temperature was taken as the oxidation start temperature. The measured oxidation onset temperatures are shown in Table 1.

As shown in Table 1, in Samples A to J corresponding to the hard particles specified in the production method of the present invention, the oxidation onset temperature was about 630 to 670 ° C., and the oxidation onset temperature was low. . A low oxidation start temperature indicates that the formation of an oxide film having solid lubricity starts from a low temperature range when used as a sintered alloy. In other words, the start of the formation of the oxide film in the low-temperature region means that the formation of the oxide film is likely to occur, which indicates that a sufficient amount of the oxide film for solid lubricity is formed.

(Sintered Alloy) At the ratios shown in Table 2, the hard particle powders, graphite powder, Ni powder having a particle size of 2 to 60 μm, 100 μm
And a pure Fe powder having a particle size of 150 μm or less,
Were mixed by a mixer to form a mixed powder as a mixed material. As shown in Table 2, in most of the examples, the powder of hard particles was 40 wt%, and the graphite powder was 0.6 wt%.
Ni powder was 6 wt%, and Co powder was 6 wt%.

In Example 11, the ratio of the powder of the hard particles was reduced to 15%. In Example 12, the ratio of the powder of the hard particles was increased to 55%. In Example 13, the proportion of the graphite powder was as small as 0.3%. Example 1
In No. 4, the ratio of the graphite powder was set to be as high as 1.5%. In Example 15, the Ni powder was not added. In Example 16, not only the Ni powder was not added, but also the ratio of the Co powder was set to be as large as 12%. In Example 17, no Co powder was added. In Example 18, the proportion of Co powder was set to be as large as 12%.

[0076]

[Table 2]

Then, using a molding die, the mixed powder mixed as described above was mixed with 78.4 × 10 ⁷ Pa (8 tonf /
A ring-shaped test piece was compression-molded with a pressure of ² cm ² ) to form a green compact. The test piece has a valve seat shape.

Thereafter, each green compact was sintered for 45 minutes in an inert atmosphere (nitrogen gas atmosphere) at 1150 ° C.
Tempering was performed at 00 ° C. for 100 minutes to form a sintered alloy (valve seat) according to the test piece.

In Example 19, after sintering, 137.
2 × 10⁷Pa (14 ton / cm^Two Forging with pressure)
After that, tempering was performed at 600 ° C. for 100 minutes.
In Example 20, sintering was performed at a sintering temperature of 1185 ° C.
I was

Further, Comparative Examples 1 to 13 also
A test piece having a ring shape was compression-molded to produce a sintered alloy (valve seat) according to the test piece.

Further, based on the conditions shown in Table 3, sintered alloys (valve seats) for the test pieces were also manufactured for Comparative Examples 14 and 15. In Table 3, the composition of the entire sintered alloy was shown, and the samples of hard particles and the mixing ratio were also shown.

As shown in Table 3, in Comparative Example 14, a sample S was used as hard particles, and a compact formed by compression-molding a mixed powder obtained by mixing the sample S at 10 wt% was sintered. Comparative Example 15 used Sample R as hard particles,
% Is obtained by sintering a green compact obtained by compression-molding a mixed powder of which the powders have been mixed.

[0083]

[Table 3]

Further, with respect to the sintered alloys as the test pieces of the example and the comparative example, the density of the sintered alloy and the hardness of the sintered alloy were measured. The measured hardness of the sintered alloy is a macro Vickers hardness (load: 10 kgf).
Table 4 shows the results of these measurements.

[0085]

[Table 4]

Next, a wear test was performed on the abrasion resistance of the sintered alloy using the tester shown in FIG. 1 to evaluate the abrasion resistance.

In this wear test, as shown in FIG.
The propane gas burner 5 was used as a heating source, and the sliding portion between the ring-shaped valve seat 3, which is a test piece made of the sintered alloy of the example and the comparative example, and the valve face 4 of the valve 1 was made a propane gas combustion atmosphere. . The valve face 4 is SUH35. Set the temperature of the valve seat 3 to 200
° C, a load of 18 kgf is applied when the valve seat 3 and the valve face 4 come into contact with the spring 6, and the valve seat 3 and the valve face 4 are brought into contact with each other at a rate of 2000 times / min. A wear test was performed.

Further, when the temperature of the valve seat 3 was controlled to 300 ° C., a wear resistance test was similarly performed.
Table 4 shows the amount of wear of each test piece at test temperatures of 200 ° C and 30 ° C.

Next, the workability of the sintered alloy was evaluated.

The workability of the sintered alloy was evaluated by feeding a ring-shaped valve seat made of the sintered alloys of Examples and Comparative Examples at a feed rate of 0.05 mm / rev and a cut of 0.3 m.
The cutting was performed with a carbide tool under the condition of m, and the wear amount of the tool due to the cutting was measured. The measurement results are shown in Table 4.

A more detailed test method is as follows. First, the valve seat is rotated in the circumferential direction around the axis of the ring. At this time, a carbide tool having a blade made of carbide H1 is brought into contact with an inner peripheral edge of the end surface of the ring-shaped valve seat. Thereafter, the cemented carbide tool was moved so that the contacted blade moved radially outward by 0.05 mm when the ring of the valve seat made one rotation in the circumferential direction. The end surface of the valve seat is cut by moving the cemented carbide tool with the end surface of the valve seat in contact with the end surface. When the blade moves to the outside of the valve seat, the blade is returned to the inner peripheral edge of the valve seat, and the same cutting is continued. At this time, the blade is returned 0.3 mm in the axial direction of the valve seat. When this cutting is performed 100 times, the cutting is terminated and the wear amount of the tool is measured.

As shown in Table 4, the sintered alloys of Examples 1 to 20
It turns out that it is excellent in density, hardness, wear resistance and workability.

On the other hand, the sintered alloys of Comparative Examples 1 to 15 shown in Table 4 were inferior in any of density, hardness, wear resistance and workability.

Next, the valve seats of Example 3 and Comparative Examples 14 and 15 were assembled on the exhaust side of the engine. This engine has a displacement of 2,400 c using unleaded gasoline as fuel.
c. A 180-hour durability test was performed using this engine.

The valve seats of Example 19 and Comparative Example 13 were assembled on the intake side of the engine. This engine has a displacement of 1500 cc using CNG as fuel. A 300-hour durability test was performed using this engine.

Then, each valve protrusion amount (m
m), and the amount of increase (mm) in the contact width of the valve seat was measured. As the condition on the intake side, the valve face is SUH1
No. 1 was subjected to a soft nitriding treatment. As the condition on the exhaust side, the valve face is SUH35.

The valve protrusion amount is an amount by which the valve position when the valve is closed is displaced (projects) to the outside of the engine due to wear of the valve seat and wear of the valve face. The contact width increase amount of the valve seat is an amount by which the valve seat is worn due to the contact between the valve seat and the valve face, and the width of the contact portion of the valve seat with the valve face increases. Table 5 shows the measurement results.

[0098]

[Table 5]

As shown in Table 5, Example 3 incorporated on the exhaust side of a gasoline engine showed Comparative Examples 14 and 15
As compared with, the protrusion amount of the valve and the increase amount of the width per valve seat were considerably reduced, and it was found that the abrasion resistance was excellent.

Further, in Example 19 incorporated on the intake side of the gas engine, the amount of protrusion of the valve and the increase in the width per valve seat were considerably reduced as compared with Comparative Example 13, and the wear resistance was excellent. I knew it was there.

That is, it is understood that the valve seat made of the sintered alloy of the example has high hardness and wear resistance.

[0102]

Industrial Applicability The sintered alloy of the present invention has high wear resistance because its density is improved and the solid lubricating action of the oxide film is improved.

In the method for producing a sintered alloy according to the present invention, since hard particles, carbon powder, Co powder, and Fe alloy powder are mixed and sintered, the hard particles and the elements Is promoted, and the density of the manufactured sintered alloy is improved. Further, by promoting the diffusion of the element, M
o is diffused in a large amount, and the diffused Mo forms a carbide or an oxide film to form a sintered alloy having excellent wear resistance and solid lubricity.

Further, since the valve seat of the present invention is made of the sintered alloy of the present invention manufactured by the method of manufacturing a sintered alloy of the present invention, the solid lubricating action of the oxide film is improved, so that the valve seat has a high resistance. It has the effect of having abrasion properties.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an apparatus on which a durability test has been performed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Valve 3 ... Valve seat 4 ... Valve face 5 ... Propane gas burner 6 ... Spring

[Procedure amendment]

[Submission date] July 30, 2002 (2002.7.3)
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0088

[Correction method] Change

[Correction contents]

Further, when the temperature of the valve seat 3 was controlled to 300 ° C., a wear resistance test was similarly performed.
Table 4 shows the amount of wear of each test piece at test temperatures of 200 ° C and 300 ° C.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/00 304 C22C 38/00 304 F01L 3/02 F01L 3/02 F (72) Inventor Hiroyuki Murase Aichi Toyota Motor Co., Ltd., Toyota City, Toyota Prefecture (72) Inventor Tokuyuki Tsuge 1, Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Kunihiko Endo 1, Toyota Town, Toyota City, Aichi Prefecture Toyota (72) Inventor Koji Tomita 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Naoki Ishihara 5-1, Kurisuno Kitsuka, Yamashina-ku, Kyoto, Kyoto Japan powder alloy stock In-company (72) Inventor Masahiro Hayakawa 5-1, Kurisuno Kitsuka, Yamashina-ku, Kyoto-shi, Japan The internal F-term (reference) 4K018 AA10 AA22 AB07 AC01 BA04 BD10 CA07 HA04 KA05 KA10

Claims (7)

[Claims] 1. When the whole is 100 wt%, 4 to
30 wt% Mo, 0.2-3 wt% C, 1-3
0 wt% Ni, 0.5-10 wt% Mn,
A sintered alloy comprising 40 wt% of Co and the balance being unavoidable impurities and Fe. 2. When the whole is 100 wt%, 5 w
2. The sintered alloy according to claim 1, wherein the sintered alloy has at least one of t% or less of Cr and 2 wt% or less of Si. 3. When the total amount of the hard particles is 100% by weight, 20 to 60% by weight of Mo, 3% by weight or less of C,
5-40 wt% Ni, 1-20 wt% Mn, 5
-40% by weight of Co, the balance being unavoidable impurities and Fe,
, A powder of carbon, a powder of Co, and a powder of Fe or low alloy steel.
A mixed powder consisting of wt% Fe alloy powder, 0.2 to 2 wt% carbon powder, 20 wt% or less Co powder, and the remaining Fe powder or low alloy steel powder is prepared, and the mixed powder is prepared. A method for producing a sintered alloy, comprising: forming a green compact by forming a green compact; and sintering the green compact to obtain a sintered alloy having the composition according to claim 1. 4. The mixed powder comprises 10 parts of the whole mixed powder.
The method for producing a sintered alloy according to claim 3, wherein the Ni powder is mixed at a ratio of 10 wt% or less when the content is 0 wt%. 5. The hard particles have a C content of 10% by weight or less when the entire hard particle powder is 100% by weight.
5. The method for producing a sintered alloy according to claim 3, wherein the method comprises at least one of r and 4 wt% or less of Si. 6. When the total content is 100 wt%, 4 to
30 wt% Mo, 0.2-3 wt% C, 1-3
0 wt% Ni, 0.5-10 wt% Mn,
A valve seat comprising 40 wt% of Co and the balance of unavoidable impurities and Fe. 7. When the whole is 100 wt%, 5 w
7. The valve seat according to claim 6, comprising at least one of Cr of t% or less and Si of 2 wt% or less.