JPH1046298A - Wear resistant sintered alloy for valve seat of internal combustion engine excellent in corrosion resistance and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve seat material for an internal combustion engine having corrosion resistance to scavenger and lead compounds and suitable wear resistance and more inexpensive than the conventional one. SOLUTION: This wear resistant sintered alloy is the one in which the compsn. of the whole body is composed of, by weight, 2.75 to 5.79% W, 1.58 to 13.5% Ni, 0.75 to 7.0% Cr, 0.21 to 2.2% No, 0.015 to 0.3% Si, 0.55 to 2.0% C, and the balance Fe with inevitable impurities. Then, its metallic structure shows the structure composed of (1) to (3) of (1) baintic phases or mixed phases of bainite and sorbite, (2) austenitic phases or mixed phases of austenite and ferrite having the nuclei of hard phase mainly composed of Cr carbides and high in the concns. of Ni and Cr surrounding the nuclei and (3) martensitic phases furthermore surrounding the environs of (2), and on which fine W carbides are uniformly dispersed into the matrix excepting the hard phases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant sintered alloy particularly suitable for a valve seat of an internal combustion engine and a method for producing the same.

[0002]

2. Description of the Related Art Sintered alloys for valve seats are required to have high-temperature abrasion resistance in order to cope with higher performance and higher output of automobile engines.
High temperature strength is required, and the present applicant has patent No. 1043124.
Has provided sintered alloys for valve seats, etc., by the manufacturing method registered under No. Furthermore, in response to higher performance and higher output in recent years, and especially to higher combustion temperatures due to lean burn, Japanese Patent Application Laid-Open No.
-10244, JP-A-7-233454, and the like. However, these materials are expensive materials because expensive elements such as Co are frequently used in the base material components in order to improve the performance at high temperatures.

[0003] In areas where high-performance internal combustion engines are used for leaded gasoline in high-temperature environments, not only lead oxide, but also lead scavengers contained in leaded gasoline (lead components can be effectively contained in exhaust gas). Adhesion of components that help discharge and lead compounds such as lead sulfate, lead bromide, and lead chloride) to valves and valve seats causes corrosion and abrasion, which tends to show an extreme decrease in durability. Corrosion resistance to chemicals and lead compounds is also required.

[0004]

However, recently, due to improvements in engine design technology, high-performance and expensive materials such as those disclosed in Japanese Patent Application Laid-Open Nos. 62-10244 and 7-233454 have been developed. Even without it, it can be used as a valve seat. In particular, since the ambient temperature of the valve seat on the intake side is lower than that of the exhaust side, Japanese Patent Application Laid-Open Nos. 62-10244 and 7-23345.
The materials disclosed in No. 4 and the like have excessive quality.
In recent years, automobile development has shifted from performance-oriented automobile development aiming at even higher performance to economic emphasis of developing cost-effective and inexpensive automobiles. Therefore, as a sintered alloy for valve seats in the future, it is required not to have the conventional excessive wear resistance, but to have appropriate wear resistance and to be inexpensive. .

[0005] In addition, the use of different materials for the valve seat according to the fuel conditions of the internal combustion engine complicates the production line and causes an increase in cost. Therefore, due to the characteristics of current international automobile products, various conditions differ depending on the destination. Therefore, a valve seat material that can cope with a wide range is desired.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a sintered alloy for a valve seat for an internal combustion engine, which has a corrosion resistance to a lead scavenger and a lead compound, a suitable abrasion resistance, and is less expensive than a conventional one. It is intended to provide a manufacturing method.

[0007]

Means for Solving the Problems In order to achieve the above object, among the present invention, the wear-resistant sintered alloy of the first invention has a total composition of W: 2.75 to 5.79% by weight. , Ni: 1.
58-13.5%, Cr: 0.75-7.0%, Mo:
0.21-2.2%, Si: 0.015-0.3%,
C: 0.55 to 2.0%, the balance being Fe and unavoidable impurities, and its metal structure is, as shown in the schematic diagram of the metal structure shown in FIG. 1, a bainite phase or a mixed phase of bainite and sorbite; It has a hard phase nucleus made of carbide, Ni, which surrounds the nucleus, an austenitic phase having a high Cr concentration or a mixed phase of austenite and ferrite, and a martensite phase which further surrounds the periphery, and a fine phase. The structure shows that the W carbides are uniformly dispersed in the matrix except for the hard phase. The sintered alloy of the second invention further contains V: 2.12% or less by weight in the first invention alloy, and fine V carbides are more uniformly dispersed in the matrix excluding the hard phase. Presenting organization. In particular,
By weight ratio, W: 2.75 to 5.79%, V: 2.123
% Or less, Ni: 1.58 to 13.5%, Cr: 0.75
To 7.0%, Mo: 0.21 to 2.2%, Si: 0.0
15 to 0.3%, C: 0.55 to 2.0%, and the balance being Fe and unavoidable impurities, the metal structure of which is a bainite phase or a mixed phase of bainite and sorbite as shown in the schematic diagram of FIG. Ni, Cr having a hard phase nucleus mainly composed of Cr carbide and surrounding the nucleus
A high-concentration austenite phase or a mixed phase of austenite and ferrite, and the above-mentioned martensite phase further surrounding the periphery, and fine W carbide and V carbide are uniformly dispersed in the matrix except for the hard phase. Presenting organization.

The sintered alloy according to the third aspect of the present invention further comprises Mn:
0.762% or less and S: 0.438% or less,
A structure in which 1.2% or less of MnS particles are dispersed in the matrix excluding the hard phase. A sintered alloy according to a fourth aspect of the present invention is the wear-resistant sintered alloy according to the first or second aspect, wherein any of acrylic resin, lead or a lead alloy, copper or a copper alloy is contained in pores of the sintered alloy. Distributed.

The method for producing a sintered alloy according to the first aspect of the present invention is described as follows: W: 3.5 to 6.0% by weight, and Fe-based alloy powder comprising the balance of Fe and unavoidable impurities.
Cr: 25 to 35%, Mo: 7 to 11%, Si: 0.5
-1.5%, C: 1.5-3.0%, and Ni-based alloy powder consisting of the balance Ni and unavoidable impurities: 3-20
% And a graphite powder: 0.5 to 1.4%. As a method for producing the sintered alloy of the second invention, the Fe-based alloy powder in the production method of the first invention may further contain V:
The main part is to include 2.2% or less.

The method for producing the sintered alloy according to the third aspect of the present invention includes the Fe method according to the first or second aspect of the present invention.
In the base alloy powder, Mn: 0.790 by weight ratio
%, And S: 0.454% or less. Further, as another method for producing the sintered alloy of the third invention, the mixed powder in the production method of the first or second invention further comprises MnS having a weight ratio of 1.2% or less.
The main part is to add powder. As a method for producing the sintered alloy according to the fourth invention, an acrylic resin, lead or a lead alloy is formed in the pores of a sintered body molded and sintered using the mixed powder according to the production method according to the first to third inventions. Or infiltrating or infiltrating any of copper or a copper alloy.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The metal structure and each component of the present invention will be described below. First, when considering corrosion resistance, it is effective to contain a large amount of corrosion-resistant components such as stainless steel.However, when considering the compressibility of powder, high alloying deteriorates because the powder becomes harder. , Mechanical properties and wear resistance are reduced. On the other hand, when the alloy component is added as a simple powder, the compressibility does not decrease, but the diffusion of the alloy element becomes non-uniform, and corrosion proceeds from a portion having low corrosion resistance, which is not effective. Further, high alloying is not preferable in terms of economy. Therefore, in the present invention, in order to obtain the corrosion resistance to the scavenger component in the leaded gasoline with a small amount of the alloy component, Fe-W or Fe-W-V
A base alloy powder was used as a base. At the same time, W and V
Is an excellent carbide-generating element, so that these fine carbides are dispersed in the matrix to improve the wear resistance of the matrix.

When a mixed structure of (Fe-based alloy powder) or more is obtained, W given as a solid solution in the Fe-based alloy powder is:
Reacts with added graphite to form W carbide in the matrix.
Since the formed carbide is finely and uniformly dispersed in the matrix, it contributes to improving the wear resistance of the matrix. In addition, W that does not form carbides diffuses into the base and improves the corrosion resistance to the lead-cleaning components (H2SO4, HCl) present in the leaded gasoline. At this time, if the W content is 3.5% or less, most of the solid solution forms in the matrix, carbides do not precipitate, and the wear resistance decreases. On the other hand, if the content exceeds 6.0%, the Fe-based alloy powder becomes hard, adversely affecting the powder properties such as compressibility and fluidity, and eventually lowers the mechanical strength and wear resistance. Therefore, in the present invention (the fifth and sixth inventions), F
The amount of W in the e-base alloy powder was limited to 3.5 to 6.0%.

V is provided as a solid solution together with W in an Fe-based alloy powder, and reacts with the added graphite to form V carbide in the matrix. The formed V carbide is dispersed in the matrix and contributes to improving the wear resistance of the matrix. In addition, V that does not form carbides diffuses into the base and improves the corrosion resistance to the lead-cleaning components (H2SO4, HCl) present in the leaded gasoline. At this time, if the V content exceeds 2.2%, the Fe-based alloy powder becomes hard, which has an adverse effect on powder characteristics such as compressibility and fluidity, resulting in a decrease in mechanical strength and wear resistance. Therefore, the present invention (sixth invention)
In this example, the V content in the Fe-based alloy powder was limited to 2.2% or less.

The above Fe-W or Fe-WV Fe
When the base alloy powder contains 0.1 to 1% of C, Fe
It is preferable because W or V in the base alloy powder forms a carbide, the amount of alloy components in the matrix of the powder decreases, and the compressibility of the powder improves. If the amount of C in the Fe-based alloy powder is less than 0.1%, the amount of carbide formed in the Fe alloy powder is small, and does not contribute to the improvement of the compressibility, and is formed if it exceeds 1%. The amount of carbides becomes too large, which impairs the compressibility.

(Ni-based alloy powder) In order to improve the abrasion resistance while securing the corrosion resistance, Cr, which forms a hard carbide based on Ni, which has a corrosion resistance to a lead-cleaning agent component,
A Ni-based alloy powder containing Mo was added to form a hard phase. That is, Cr carbide, Mo carbide, Cr-Mo
The hard phase made of eutectic carbide or the like has a function of suppressing the plastic flow of the matrix generated when the valve is seated by the pinning effect. Further, Ni and Cr of the Ni-based alloy powder are
It diffuses into the e-base alloy powder, improves the hardenability of the matrix, converts it to martensite, and improves the wear resistance. At the same time, the high concentration of Ni and Cr around the hard phase is soft,
It forms white austenite or a mixed phase of austenite and ferrite, has an effect of alleviating the impact when the valve is seated and preventing the hard phase from falling off.

If the amount of the Ni-based alloy powder is less than 3%, it does not contribute to the improvement of the wear resistance. If it exceeds 20%, the compressibility is reduced, the mechanical properties are reduced, and the amount of the hard phase is increased. This increases the aggressiveness of the valve, causing the valve to wear. Therefore, in the present invention, the addition amount of the Ni-based alloy powder is set to 3
Limited to ~ 20%.

Cr provided as a solid solution in the Ni-based alloy powder reacts with C in the Ni-based alloy powder to form a hard and wear-resistant Cr carbide and a eutectic carbide with Mo described later. Form. It also improves the hardenability of the matrix by diffusing it into the matrix, transforms the matrix structure into martensite, improves wear resistance, and forms austenite or a mixed phase of austenite and ferrite around the hard phase with a high Cr concentration. In addition, the shock when the valve is seated is reduced, and the hard phase is prevented from falling off. At this time, the amount of Cr is 25
If it is less than 35%, sufficient carbides cannot be obtained, and if it exceeds 35%, the amount of carbides increases and the aggressiveness of the partner increases, causing the valve to wear. Therefore, in the present invention, the amount of Cr in the Ni-based alloy powder is limited to 25 to 35%.

Mo, which is provided as a solid solution in the Ni-based alloy powder, reacts with C in the Ni-based alloy powder to form a hard carbide having excellent wear resistance and a eutectic carbide with Cr. . At this time, if the Mo content is less than 7%, a sufficient carbide cannot be obtained, so that it does not contribute to the wear resistance.
If it exceeds, the amount of carbides increases and the aggressiveness of the partner increases, causing the valve to wear. Therefore, in the present invention, the amount of Mo in the Ni-based alloy powder is limited to 7 to 11%.

Si is also provided as a solid solution in the Ni-based alloy powder, acts as a deoxidizing agent, and has the effect of increasing the adhesion between the Ni-based alloy powder and the Fe-based alloy powder. However, if the amount of Si in the Ni-based alloy powder is 0.5% or less, the deoxidizing effect is insufficient to improve the fixability of the powder. The acid effect cannot be expected, and the Ni-based alloy powder itself is hardened, so that the compressibility is reduced, which causes a decrease in mechanical strength and wear resistance. Therefore, in the present invention, the amount of Si in the Ni-based alloy powder is set to 0.5 to 1.5%.

It is also possible to improve the adhesion of both powders by adding a small amount of C or Fe, which easily diffuses into the Fe-based alloy powder, to the Ni-based alloy powder. C
Is provided in order to improve wear resistance by forming a hard carbide by reacting with Cr and Mo in a solid solution in a Ni-based alloy powder. Also, C is given as graphite powder,
It contributes to the precipitation of W and V carbides in the base, the formation of martensite in the base, and the strengthening of the base into bainite. If the amount of C provided as a solid solution in the Ni-based alloy powder is less than 1.5%, the amount of carbides precipitated will be small, and the effect of improving wear resistance will be poor, while exceeding 3.0%. And the amount of carbide that precipitates is too large, which increases valve attack,
Since the powder becomes hard, the compressibility is reduced, and the density of the compact is reduced. As a result, the strength is reduced. For this reason, in the present invention, Ni
The amount of C in the base alloy powder was set to 1.5 to 3.0%.

(Graphite powder) C added as graphite powder
If the amount is less than 0.5%, the amount of precipitation of W and V carbides will be small, and the amount of C dissolved in the matrix will be small, and will not contribute to strengthening of the matrix and improvement of wear resistance. 1.
If it exceeds 4%, C is supersaturated in the matrix to form a solid solution, resulting in a decrease in toughness and machinability, and a liquid phase is likely to be generated during sintering, which impairs the dimensional accuracy. For this reason, in the present invention, the amount of C added as graphite powder is 0.5 to
It was set to 1.4%.

When it is desired to improve the machinability of the sintered alloy of (MnS particles or Mn, S) or more, it is effective to disperse the MnS particles uniformly and finely in the structure as in the third invention. is there. That is, since the MnS particles have a chip breaker function, they are effective in improving machinability,
At the time of machining, it adheres to the tool blade surface to protect the cutting edge and prolong tool life. As a method of dispersing the MnS particles in the matrix, a method of blending MnS powder is simple and effective. However, since MnS powder inhibits sintering, Fe
It is more preferable that Mn and S are added to the base alloy powder in a state of being reacted during sintering and finely dispersed in the matrix. When the amount of MnS particles dispersed in the matrix is more than 1.2% in both cases of adding MnS powder and forming a solid solution in Fe-based alloy powder to form a reaction, mechanical properties and wear resistance are exceeded. Is reduced, MnS powder addition, MnS
When the upper limit of the amount of S powder to be added is given as 1.2% in the form of an Fe-based alloy powder, the amounts of Mn and S in the Fe-based alloy powder are set to M
n: 0.76% or less, S: 0.44% or less.

(Acrylic resin, etc.) In order to improve machinability in the above sintered alloy, impregnation or infiltration of acrylic resin, lead or lead alloy, copper or copper alloy into pores of the sintered body is required. Is effective. When acrylic resin, lead or lead alloy, copper or copper alloy is present in the pores,
The cutting mode at the time of cutting is changed from intermittent cutting to continuous cutting, the impact given to the tool is reduced, the damage to the tool edge can be prevented, and the machinability can be improved. In addition, since lead or lead alloys, copper or copper alloys are soft, they adhere to the tool blade surface to protect the cutting edge of the tool, improve machinability and tool life, and when used, use the valve seat and valve face. It acts as a solid lubricant between the surfaces and serves to reduce wear on both sides. In addition, copper or a copper alloy has a high thermal conductivity, has the effect of releasing heat generated at the cutting edge during cutting to the outside, preventing heat buildup at the cutting edge, and reducing damage to the cutting edge.

[0024]

The present invention will be further described below with reference to examples. In Examples, Fe-based alloy powders (powder numbers 1 to 21) having the component compositions shown in Table 1 were used, and hard layer forming powders, graphite powders, MnS powders, and molding lubricants (zinc stearate) were used. After blending at the ratios listed in Table 2 and mixing the blends for 30 minutes, the molding pressure was 6.5.
It was molded at ton / cm2.

The above compacts were sintered in an ammonia decomposition gas atmosphere at 1175 ° C. for 60 minutes to obtain alloys 1 to 29 of the present invention shown in Table 3 (sample numbers 1 to 29).
And any of the comparative alloys 1 to 12 in which any component deviates from the present invention.
(Sample numbers 1 to 12) were obtained.

It should be noted that the alloys 18 to 20 of the present invention, after sintering,
Further, the pores were impregnated or infiltrated with acrylic resin, Pb, and Cu. Comparative alloy 13 in Tables 2 and 3 is a conventional alloy for valve seats described in Japanese Patent No. 1043124 as a conventional alloy.

Composition of Fe-based alloy powder used

[Table 1]

The alloy (1 to 29) of the present invention and the comparative alloy (1 to 29)
13) Compounding ratio

[Table 2]

The alloys of the present invention (1-29) and the comparative alloys (1-29)
13) Overall composition

[Table 3]

An apparent hardness test was performed on the above sintered alloy,
A radial crushing strength test, a machinability test, a wear resistance test, and a corrosion resistance were performed. The results are listed in Table 4. The machinability test uses a tabletop drilling machine, drills holes in the sample with the load of the rotating part's own weight and only the additional weight, and compares the number of processed holes. In this test, the load was 1 .
8 kg, the drill used was a φ3 mm carbide drill, and the thickness of the sample was set to 5 mm.

In the wear resistance test, a sintered alloy worked into a valve seat shape was press-fitted into an aluminum alloy housing,
The valve face is moved up and down by the rotation of the eccentric cam driven by the motor, so that the valve face and the seat face collide repeatedly, and this is performed for a certain period of time, and the abrasion amount of the valve seat and the valve face face generated at that time is measured. Was evaluated. During the test, the temperature is controlled by heating the umbrella of the valve with a burner. In this test, the rotational speed of the eccentric cam was 3000 rpm, the test temperature of the valve seat portion was 250 ° C., and the repetition time was 10 minutes.
Set to time. For the corrosion resistance, a mixed powder of a Pb compound is used as a corrosive agent, a sample is placed in the mixed powder, heated in an air atmosphere, kept at 300 ° C. for 5 hours, and then the thickness of a corroded layer generated on the outermost surface of the sample is measured. Was evaluated.

The alloy (1 to 29) of the present invention and the comparative alloy (1 to 29)
13) Evaluation

[Table 4]

The following can be seen from the above evaluations in Table 4. 2 to 8 are graphs of the abrasion resistance (amount of wear) and corrosion resistance (corrosion depth) of the above evaluation, and FIGS. Number). △ indicates a valve, ○ indicates a valve seat,
The symbol □ plots the total wear of the valve and the valve seat, and the conventional alloy (Comparative 13) is also shown by the total wear of the valve and the valve seat. FIG. 8 shows the machinability (the number of processed holes) when the pores of the sintered alloy are impregnated with acrylic resin, Pb, and Cu. In the drawings, for example, the alloy 1 of the present invention is indicated as invention 1 and the comparative alloy 1 is indicated as comparison 1.

By comparing the alloys 1, 2, 17, 29 of the present invention and the comparative alloys 1, 2, 3, when the amount of W in the Fe-based alloy powder is changed, the effect is examined as follows. As the amount of W in the Fe-based alloy powder increases, FIG.
As shown in the figure, the wear amount of the valve seat is reduced. on the other hand,
The wear amount of the valve increases as the W amount increases. The total wear of the valve seat and the valve is 3.5
It is stable and low at ~ 6%. The amount of wear at this time is lower than that of the comparative alloy 13 of the related art. This is presumed to be due to an increase in the amount of W carbide in the base as the amount of W increased, resulting in a decrease in valve seat wear, but an increase in valve wear due to an increase in aggressiveness against the valve. You. Further, when the amount of valve wear increases, the amount of wear of the valve seat itself also increases due to the effect of abrasion powder. Therefore, when the W amount is 6% or more, the total wear amount is conversely large. Further, as the corrosion resistance increased with the increase in the amount of W in the Fe-based alloy powder, the amount of W dissolved in the matrix increased, and as a result, the corrosion depth decreased, indicating good corrosion resistance. From the above, the amount of W in the Fe-based alloy powder is
It can be seen that both abrasion resistance and corrosion resistance are good in the range of 3.5 to 6%.

The effects of changing the amount of V in the Fe-based alloy powder by comparing the alloys 3 to 6, 17, 28 of the present invention and the comparative alloys 4, 5 are as follows. In addition,
The alloys 3 to 6, 17, and 28 of the present invention relate to claims 1 and 2,
Among them, the alloy 3 of the present invention has a V content of 0% in the Fe-based alloy, and corresponds to claim 1. As shown in FIG. 3, up to 2% of the V content in the Fe-based alloy powder, the valve seat abrasion slightly decreases, but when it exceeds 2%, the abrasion increases. On the other hand, the valve wear amount gradually increases as the V amount increases. The total wear amount of the valve seat and the valve is almost constant up to the V amount of 2%, increases when the V amount exceeds 2%, becomes approximately the same as 0% at 2.2%, If it exceeds 2.2%, the amount of wear is rather large. This is because V carbide in the base increases as the V amount increases, and the wear resistance of the valve seat is improved. However, the valve aggressiveness is increased, so that the valve wear amount is increased. Is estimated to increase. In addition, the corrosion resistance is improved as the corrosion depth decreases with an increase in the amount of V. From the above, it can be seen that when the V content in the Fe-based alloy powder is 2.2% or less, good wear resistance and corrosion resistance are exhibited.

When the alloys 7, 17, 25 to 27 of the present invention and the comparative alloys 6, 7 are compared (FIG. 4), the addition of 3% of the Ni-based alloy powder sharply reduces the amount of wear of the valve seat. The amount of wear gradually decreased up to the addition amount of 20%. On the other hand, the valve wear gradually increases as the amount of the Ni-based alloy powder added increases, and when it exceeds 20%, the wear rapidly increases. Thereby, the total wear amount is reduced by adding 3% of the Ni-based alloy powder,
%, It is lower than that of the comparative alloy 13 (conventional alloy) and shows a substantially constant value, but when it exceeds 20%, the wear amount rapidly increases. This is because the addition of the Ni-based alloy powder forms a hard phase composed of a hard intermetallic compound,
A soft austenite or a mixed phase of austenite and ferrite is formed around the hard phase and a martensite phase effective for abrasion resistance is formed around the soft phase, improving wear resistance by intermetallic compounds, and austenite or a mixed phase of austenite and ferrite. The amount of wear is reduced due to the effect of preventing the intermetallic compound from falling off, reducing the impact when the valve is seated, and improving the wear resistance by the martensite phase.
Excessive addition of the Ni-based alloy powder increases the amount of the intermetallic compound and the amount of the martensite phase, thereby increasing the valve attack, and increasing the austenite or the mixed phase of austenite and ferrite, thereby increasing the base strength. It is inferred that the abrasion resistance sharply decreases in combination with the decrease. On the other hand, the corrosion resistance is almost constant irrespective of the addition amount of the Ni-based alloy powder, and shows a good value lower than that of the comparative alloy 13 (conventional alloy). From the above, it can be understood that the addition amount of the Ni-based alloy powder has a great effect on the wear resistance when it is in the range of 3 to 20%.

When the alloys 8, 9, 17, 23, 24 of the present invention and the comparative alloys 8, 9 are compared, as shown in FIG. 5, the wear amount of the valve seat is sharply increased by adding 0.5% of graphite powder. , The wear amount further decreases until the graphite powder addition amount: 1.4%, and when it exceeds 1.4%, the valve seat wear amount sharply increases. On the other hand, the valve wear amount gradually increases as the amount of graphite powder added increases. Thus, the total wear amount is stable at a value lower than that of the comparative alloy 13 (conventional alloy) in the range of 0.5 to 1.4%. This is because, as the amount of graphite powder added increases, the amount of carbides in the matrix increases, and as a result, the valve seat wear decreases, but the valve aggressiveness increases, so the valve wear gradually increases, and the graphite increases. If the amount of powder exceeds 1.4%, the valve seat will also wear due to the valve wear,
It is presumed that the total wear increased rapidly. Also,
The corrosion resistance is almost constant up to the graphite powder addition amount of 1.4%, and shows good corrosion resistance lower than that of the comparative alloy 13 (conventional alloy). Based on the above, the amount of graphite powder added was 0.1.
It turns out that there is a great effect on abrasion resistance in the range of 5 to 1.4%.

According to the invention alloys 10 to 12, 14, 17, and 21 and the comparative alloys 10 and 12, Mn was added to the Fe-based alloy powder.
Of MnS amount when solid solution of S and S is given (FIG. 6), and MnS amount when MnS powder is added and given by invention alloys 10, 13, 15, 16, 22 and comparative alloy 11. (FIG. 7). That is, Mn
In both cases where S is given by dissolving Mn and S in Fe-based alloy powder and when MnS powder is added, the amount of wear in the valve seat up to the MnS content of 1.2% in the overall composition. Is gradually increased, and when it exceeds 1.2%, the strength of the matrix is reduced, and as a result, the amount of wear is increased. In both cases, the corrosion resistance shows a good value lower than that of the comparative alloy 13 (conventional alloy). From the viewpoint of the addition form of MnS, when Mn and S are given as a solid solution in the Fe-based alloy powder,
The amount of wear is lower than that given by adding S powder and Mn
The rate of increase in the amount of wear due to the increase in the S amount is also low. This is presumed to be because when the MnS powder is added and given, the MnS powder inhibits diffusion and bonding due to sintering of the base powder, and lowers the base strength. Therefore, the corrosion resistance is also MnS
In the case of the addition of powder, there is a tendency that the amount is slightly reduced, although there is no problem. On the other hand, the machinability is M
Although improved with an increase in the amount of nS, the effect of improving the machinability is greater when the solid solution is applied to the Fe-based alloy powder and the MnS amount is the same because the metal is uniformly dispersed in the matrix. . From the above, the machinability is improved by MnS irrespective of the form of addition, but when the amount of MnS in the entire composition exceeds 1.2%, the wear resistance rapidly deteriorates. Therefore, the upper limit of the amount of MnS added is set to 1.2%. In addition, MnS powder may be added in the form of addition, but it can be seen that the effect is higher when Mn and S are dissolved in Fe-based alloy powder and given.

When the alloys of the invention 17, 18, 19, and 20 were compared with the comparative alloy 13, the machinability was Mn in the Fe-based alloy.
An alloy in which 0.9% MnS is dispersed in the entire composition by dissolving S and S in solid solution is superior in wear resistance, corrosion resistance and machinability to the conventional alloy, but as shown in FIG. , Pb, and Cu can be impregnated or infiltrated to further improve machinability without impairing wear resistance and corrosion resistance.

[0040]

As is apparent from the above description, according to the wear-resistant sintered alloy for a valve seat of the present invention and the method for producing the same, since an expensive element such as Co is not used, it is inexpensive, and the internal combustion engine is inexpensive. It has sufficient wear resistance for practical use as a sintered alloy for valve seats.
A sintered alloy having excellent corrosion resistance to the compound b is obtained. In particular, in the case of the third and fourth aspects and the manufacturing method thereof, an excellent sintered alloy having further improved machinability is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view of a metal structure of a sintered alloy of the present invention.

FIG. 2 is a graph showing the results of evaluation of the amount of wear and the corrosion depth when the amount of W in the matrix-forming alloy powder is changed in Examples of the present invention.

FIG. 3 is a graph showing the results of evaluation of the amount of wear and the corrosion depth when the amount of V in the matrix-forming alloy powder is changed in Examples of the present invention.

FIG. 4 is a graph showing an evaluation result of a wear amount and a corrosion depth when the addition amount of a hard phase forming powder is changed in Examples of the present invention.

FIG. 5 is a graph showing an evaluation result of a wear amount and a corrosion depth when the amount of graphite powder is changed in Examples of the present invention.

FIG. 6 shows an example of MnS in the overall composition in an example of the present invention.
It is a graph which shows the wear amount when changing the amount, the corrosion depth, and the evaluation result of the number of processing holes.

FIG. 7 is a graph showing the results of evaluation of the amount of wear, the corrosion depth, and the number of processed holes when the amount of added MnS powder was changed in Examples of the present invention.

FIG. 8 is a graph showing the evaluation results of the number of working holes when the sintered alloy is impregnated with acrylic resin, Pb, and Cu in the example of the present invention.

Claims (9)

[Claims] 1. The composition according to claim 1, wherein the weight ratio is W: 2.75 to
5.79%, Ni: 1.58 to 13.5%, Cr: 0.
75-7.0%, Mo: 0.21-2.2%, Si:
0.015 to 0.3%, C: 0.55 to 2.0%, and the balance is Fe and inevitable impurities, and its metal structure is mainly composed of a bainite phase or a mixed phase of bainite and sorbite, and Cr carbide. Ni, which has a hard phase nucleus and surrounds the nucleus, has a high austenitic phase or a mixed phase of austenite and ferrite having a high Cr concentration, and a martensite phase further surrounding the periphery. A wear-resistant sintered alloy for a valve seat of an internal combustion engine having excellent corrosion resistance, which exhibits a structure in which the hard phase is uniformly dispersed in a matrix except for the hard phase. 2. The composition as a whole has a weight ratio of W: 2.75 to 2.75.
5.79%, V: 2.123% or less, Ni: 1.58-
13.5%, Cr: 0.75 to 7.0%, Mo: 0.2
1 to 2.2%, Si: 0.015 to 0.3%, C: 0.2%
55-2.0%, with the balance being Fe and unavoidable impurities, the metal structure of which has a nucleus of a bainite phase or a mixed phase of bainite and sorbite and a hard phase nucleus mainly composed of Cr carbide, and Ni surrounding the nucleus An austenite phase having a high Cr concentration or a mixed phase of austenite and ferrite; a martensite phase further surrounding the periphery; and fine W carbides and V carbides are uniformly dispersed in the matrix except the hard phases. A wear-resistant sintered alloy for a valve seat of an internal combustion engine having excellent corrosion resistance, characterized by exhibiting a texture that changes. 3. The wear-resistant sintered alloy according to claim 1, further comprising a weight ratio of M in the overall composition.
n: 0.762% or less and S: 0.438% or less, and 1.2% or less of Mn in the matrix excluding the hard phase
An abrasion-resistant sintered alloy for a valve seat of an internal combustion engine having a structure in which S particles are dispersed and having excellent corrosion resistance. 4. A wear-resistant sintered alloy according to claim 1, wherein acrylic resin, lead or a lead alloy, or copper or a copper alloy is dispersed in pores of the sintered alloy. Wear resistant sintered alloy for valve seats of internal combustion engines with excellent corrosion resistance. 5. An Fe-based alloy powder comprising 3.5 to 6.0% by weight of W and the balance of Fe and unavoidable impurities in a weight ratio of Cr: 25 to 35% by weight and Mo: 7 to 11 by weight. %, S
i: 0.5 to 1.5%, C: 1.5 to 3.0%, and a Ni-based alloy powder composed of the balance of Ni and unavoidable impurities:
The wear-resistant sintering for a valve seat of an internal combustion engine having excellent corrosion resistance according to claim 1, wherein a mixed powder containing 3 to 20% and graphite powder: 0.5 to 1.4% is used. Gold manufacturing method. 6. The weight ratio of W: 3.5-6.0%, V:
2.2% or less, Fe: 25 to 35% by weight, Mo: 7 to 11%, S:
i: 0.5 to 1.5%, C: 1.5 to 3.0%, and a Ni-based alloy powder composed of the balance of Ni and unavoidable impurities:
The wear-resistant sintering for a valve seat of an internal combustion engine having excellent corrosion resistance according to claim 2, wherein a mixed powder containing 3 to 20% and graphite powder: 0.5 to 1.4% is used. Gold manufacturing method. 7. An Fe-based alloy powder according to claim 5 or 6, further comprising, by weight ratio, Mn: 0.790% or less and S: 0.454% or less. The method for producing a wear-resistant sintered alloy for a valve seat of an internal combustion engine having excellent corrosion resistance according to claim 3. 8. A valve seat for an internal combustion engine having excellent corrosion resistance according to claim 3, wherein a MnS powder having a weight ratio of 1.2% or less is further added to the mixed powder according to claim 5 or 6. Manufacturing method of wear resistant sintered alloy. 9. Pores of a sintered body molded and sintered using the mixed powder according to claim 5 and impregnated with any one of acrylic resin, lead or a lead alloy, or copper or a copper alloy The method for producing a wear-resistant sintered alloy for a valve seat of an internal combustion engine having excellent corrosion resistance according to claim 4, which is infiltrated or infiltrated.