JPH10280108A - Wear resistant iron base sintered alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wear resistant iron base sintered alloy capable of corresponding to severe using environments, furthermore improved in wear resistance and capable of reducing or stopping the infiltration of Pb. SOLUTION: This sintered alloy has the total compsn. contg., by weight, 1.4 to 15% Co, 1.5 to 16% Mo, 0.4 to 10.0% Mn, 0.4 to 12% Cr, 0.2 to 6.0% W, 0.4 to 3.2% C, 0.2 to 9.0% Ni, and the balance Fe with inevitable impurities. It is composed of a sintered body in which, into the structure of a matrix contg. 2 to 15% Co, 2 to 10% Mo, 0.4 to 10% Mn, 0.2 to 2% C, <=10% Ni, and the balance Fe with inevitable impurities, hard grains contg. 5 to 20% Mo, 20 to 40% Cr, 5 to 20% W, 0.5 to 5% C, 5 to 30% Fe, and the balance Ni with inevitable impurities are dispersed by 2 to 30%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron-based sintered alloy having excellent wear resistance. INDUSTRIAL APPLICABILITY The present invention is useful for sintered parts such as valve seats, piston rings, and exhaust system collars used in internal combustion engines of vehicles such as automobiles.

[0002]

2. Description of the Related Art A conventional iron-based sintered alloy having wear resistance will be described with reference to a sintered alloy for a valve seat used in an internal combustion engine of a vehicle. Conventionally, as a sintered alloy for a valve seat, a Fe—C—Co—Ni base material,
A material obtained by adding an intermetallic compound such as ferromolybdenum (Fe-Mo) or ferrochrome (Fe-Cr) or an Fe-C-Cr-Mo-V alloy to an Fe-C base material for the purpose of improving wear resistance. Used (JP-A-56-1541).
No. 10).

Further, Fe— containing Cr and Mo
A sintered alloy in which iron-based hard particles composed of Cr, Mo, V, etc. are dispersed in a C base structure to improve abrasion resistance and aggressiveness to a partner (Japanese Patent Laid-Open No. 60-224762), and Fe-C-
Sintered alloys in which hard particles made of FeMo and FeW are dispersed in a Co-Ni base matrix, and a Pb alloy or the like is infiltrated to improve wear resistance (Japanese Patent Laid-Open No. 62-20205)
No. 8) is disclosed.

The characteristics required of the valve seat material include corrosion resistance and heat resistance in addition to wear resistance. Here, the hard particles are mainly responsible for the wear resistance, and the corrosion resistance and heat resistance are mainly responsible for the base structure, and both of them ensure durability.

[0005]

In recent years, in the field of using wear-resistant iron-based sintered alloys, there is an increasing demand for improving the properties of the iron-based sintered alloys. For example,
2. Description of the Related Art In internal combustion engines of vehicles such as automobiles, there is an increasing demand for longer life, higher output, higher rotation, measures for purifying exhaust gas, or measures for improving fuel efficiency. For this reason,
For engine valves and valve seats in internal combustion engines of vehicles, it has become unavoidable to withstand harsh use environments more than ever before, while further improving wear resistance and heat resistance, There is a need to improve corrosion resistance.

Further, Pb infiltrated as a lubricating component is:
Due to their potential impact on the environment, there is a recent demand for alternatives to replace them. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems in the conventional iron-based sintered alloy, and can cope with severe use environments, and has further improved wear resistance, particularly at high temperatures. It is an object to provide an iron-based sintered alloy.

[0007]

Means for Solving the Problems In order to improve wear resistance, corrosion resistance, and oxidation resistance, the present inventor has proposed a chemical composition of a base of an iron-based sintered alloy, the type and amount of hard particles, We conducted intensive research on base organizations. As a result, according to the first to third aspects, as a first feature, Ni-based hard particles having carbides of Mo, Cr, W, and Fe or carbides of Si are dispersed in an iron-based matrix. The second characteristic is that N
By diffusing Ni contained in the i-based hard particles to the matrix around the hard particles, high-temperature strength, heat resistance, and corrosion resistance near the hard particles of the matrix are improved, and the hard particles are prevented from floating from the matrix. And that the falling of hard particles can be suppressed,
The third feature is that the easily oxidizable elements such as Cr and Mn are positively added to the base structure, and the formation of an oxide film on the sliding surface of the iron-based sintered alloy is expected. It has been found that direct contact is suppressed, and the above three main features can maintain good wear resistance of the iron-based sintered alloy for a long period of time. Completed a ferrous iron-based sintered alloy.

The wear-resistant iron-based sintered alloy according to claim 1 has a total composition of 1.4 to 15% by weight of Co;
o: 1.5 to 16%, Mn: 0.38 to 9.5%, C
r; 0.4 to 12%, W; 0.2 to 6.0%, C;
4 to 3.2%, Ni; 0.2 to 9.0%, the balance being unavoidable impurities and Fe, Co; 2 to 15%, M
o: 2 to 10%, Mn: 0.4 to 10%, C: 0.2 to
2%, Ni; 10% or less, the balance being an inevitable impurity and Fe base structure, Mo: 5-20%, Cr;
0 to 40%, W: 5 to 20%, C: 0.5 to 5%, F
e; a sintered body containing 5 to 30% and hard particles composed of unavoidable impurities and Ni dispersed in 2 to 30% in the balance.

The wear-resistant iron-based sintered alloy according to claim 2 has a total composition of Co: 1.4 to 15% by weight, M
o: 1.5 to 16%, Mn: 10% or less, Cr: 0.6
-20%, W; 0.2-6.0%, C; 0.4-3.2
%; Ni; 0.2 to 9.0%; the balance consists of unavoidable impurities and Fe; Co; 2 to 15%, Mo;
0%, at least one of Cr and Mn; 0.4 to 10
%, C: 0.2 to 2%, Ni: 10% or less, and the balance is based on an unavoidable impurity and Fe.
20%, Cr; 20-40%, W; 5-20%, C;
It is characterized by comprising a sintered body containing 0.5 to 5%, Fe; 5 to 30%, and the balance, in which hard particles of inevitable impurities and Ni are dispersed in 2 to 30%.

The wear-resistant iron-based sintered alloy according to claim 3 has a total composition of Co: 1.4 to 15% by weight, M
o: 1.5 to 16%, Mn: 9.5% or less, Cr;
4-20%, W; 0.2-6.0%, C; 0.4-4.
0%, Ni; 0.2 to 9.0%, Si; 0.6% or less, the balance being unavoidable impurities and Fe, Co;
2 to 10%, at least one of Cr and Mn; 0.4 to 10%, C; 0.2 to 2%, Ni;
In the base structure containing 0% or less and the balance being inevitable impurities and Fe, Mo: 5 to 20%, Cr: 20 to 40%,
W: 10 to 20%, C: 0.5 to 4%, Fe; 5 to 30
%, Si; 2% or less, the balance being unavoidable impurities and N
It is characterized by comprising a sintered body in which hard particles composed of i are dispersed by 2 to 30%.

In the present specification, unless otherwise indicated by volume%, it means weight%.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION According to the wear-resistant iron-based sintered alloy according to the present invention, Ni-based hard particles include Mo, Cr, W, Fe or S in addition to C.
i. Therefore, the Ni-based hard particles have carbide and become hard. Since such Ni-based hard particles are dispersed in the iron-based matrix, the wear resistance of the iron-based sintered alloy is ensured.

The floating of the hard particles from the base is not preferable because it induces abrasion of the mating material and falling off of the hard particles.
In this respect, according to the wear-resistant iron-based sintered alloy according to the present invention, N
Since the Ni of the i-based hard particles diffuses to the matrix around the hard particles, high-temperature strength, heat resistance, oxidation resistance, and corrosion resistance are improved near the hard particles of the matrix, and the floating of the hard particles is suppressed. . This reduces excessive wear of the mating material. Furthermore, since the floating of the hard particles from the matrix is suppressed, the falling of the hard particles from the iron-based sintered alloy is suppressed.

According to the wear-resistant iron-based sintered alloy according to the present invention, easily oxidizable elements such as Cr and Mn are positively added to the base structure, so that the sliding surface of the iron-based sintered alloy has a moderate It is expected that a proper oxide film will be formed. Thereby, direct contact between the metal forming the base and the counterpart material is suppressed, and adhesion of the metal forming the base is suppressed. Base Base is 100% by weight, Co: 2
-15%, Mo; 2-10%, Mn and / or Cr;
0.4 to 10%, C: 0.2 to 2%, Ni: 10% or less.

Co: 2 to 15% Co forms a solid solution in the matrix and strengthens it, and has an effect of improving high-temperature strength, heat resistance and corrosion resistance.
If the Co content in the base is less than 2%, the effect is insufficient, while if it exceeds 15%, the effect is further improved but the economy is low. Therefore, considering this point, the content is defined as 2 to 15%.

Mo: 2 to 10% Mo forms a solid solution in the matrix and strengthens it, and also has an effect of improving the strength in a high temperature range. In a sintered body containing carbon, a part of carbides forms carbide. Effective for improving wear resistance. These effects are insufficient if the content is less than 2% in the base, more preferably more than 3%. Even if the content exceeds 10%, the effect is improved, but the iron base constituting the base is not improved. To reduce the compressibility of the alloy powder, its content is defined as 2 to 10%.

Mn and / or Cr: 0.4 to 10% Mn and Cr are easily oxidizable metal elements. Therefore, an oxide film is easily generated even in an environment where the amount of oxygen is small. By the oxide film, direct contact between the metal constituting the matrix and the counterpart material is suppressed. Therefore, adhesion of the base is suppressed, and the wear resistance of the base is improved. Further, since Mn and Cr easily form carbides, in this sense, Mn and Cr can also contribute to improving the wear resistance of the matrix. If Mn and / or Cr is less than 0.4%, the above effect is insufficient. If it exceeds 10%, the effect is improved, but the economic efficiency is reduced.
Stipulated.

C: 0.2 to 2% When the base is defined as 100%, C is 0.1% by weight in the base.
It contains 2 to 2%. As described above, C contributes to carbide formation and contributes to improvement of wear resistance. When C is less than 0.2%, ferrite formation of the matrix is promoted, and when C exceeds 2%, graphite is easily released.

Ni: 10% or less Assuming that the matrix is 100%, the matrix contains 10% or less by weight of Ni diffused from Ni-based hard particles.
This improves the high-temperature strength and corrosion resistance of the base. If Ni in the matrix exceeds 10%, Ni in the hard particles
Is excessively diffused, so the hard particles tend to be thin,
The adhesion of the hard particles becomes weak.

Ni-based hard particles The hard particles according to claim 1 are Mo: 5 to 20%, Cr: 20 to 40 by weight ratio, when the hard particles are 100%.
%, W: 5 to 20%, C: 0.5 to 5%, Fe; 5 to 3
0%, and the balance consists of unavoidable impurities and Ni. The hard particles according to claim 2, when the hard particles are 100%, Mo: 5 to 20%, Cr: 20 to 40% by weight ratio,
W: 5 to 20%, C: 0.5 to 5%, Fe: 5 to 30%
And the balance consists of unavoidable impurities and Ni.

According to a third aspect of the present invention, the hard particles include one hard particle.
Mo: 5% to 20% by weight, Cr;
20-40%, W; 10-20%, C; 0.5-4%,
Fe: 5 to 30%, Si: 2% or less, the balance being unavoidable impurities and Ni. The hard particles are harder than the matrix and contribute to improving the wear resistance of the iron-based sintered alloy. These Ni-based hard particles are hard particles developed by the present inventors, and include C, Mo, Cr,
Contains W, Fe or Si. Mo, Cr, W, Fe or Si combines with C to form a carbide,
It increases the hardness of the hard particles and contributes to the improvement of the wear resistance of the iron-based sintered alloy.

The hard particles contain 5 to 30% of Fe, particularly 1
It can be made 15 to 20% from 2 to 22%. Fe in the Ni-based hard particles is mainly intended to regulate the counter-attack of the iron-based sintered alloy. The reason is that the hardness of Fe carbide is lower than that of other carbides. N
Part of Ni and Fe of the i-based hard particles are diffused into the matrix by sintering, and act to improve the oxidation resistance of the matrix and the retention of the hard particles to the matrix.

The ratio of the Ni-based hard particles is 2 to 100% by weight when the iron-based sintered alloy is 100%.
30% is preferred. Therefore, the hard particles are defined as 2 to 30% when the whole iron-based sintered alloy is 100%. Here, if the Ni-based hard particles are less than 2%, the improvement of the wear resistance is insufficient. It is appropriate that the hard particles have a content of 2 to 30%.

Although the reasons for limiting the composition of the matrix and the Ni-based hard particles have been described above, the reasons for limiting the composition of the matrix and the hard particles in the iron-based sintered alloy basically correspond to these. . C The iron-based sintered alloy has a weight ratio of C
Is contained 0.4 to 3.2% or 0.4 to 4.0%. C forms a solid solution in the matrix and strengthens the matrix, and partly diffuses into the Ni-based hard particles, and M
It combines with o, Cr, W, etc. to form carbides, increases the hardness of Ni-based hard particles, and is effective in improving wear resistance. C
Can be supplied from graphite powder as a raw material powder.

The iron-based sintered alloy according to the present invention is a member requiring wear resistance, particularly a member requiring wear resistance at a high temperature, specifically, an exhaust system and an intake system of an internal combustion engine. Suitable for valve seats. Representative Production Method The iron-based sintered alloy according to the present invention includes iron-based alloy powder (generally, an Fe—Co—Mo alloy), Mn element powder, Cr element powder,
It can be formed by sintering a green compact obtained by compressing the mixed powder by using a mixed powder obtained by mixing a powder of Ni-based hard particles and a graphite powder. The Fe-Co-Mo alloy powder is excellent in compressibility, and therefore is advantageous in increasing the density of the green compact and the iron-based sintered alloy. Mn of the Mn element powder and Cr of the Cr element powder easily diffuse into the matrix during sintering.

Although the sintering temperature of the iron-based sintered alloy of the present invention can be appropriately selected, the temperature is preferably from 1323 K to lower than the melting point of the Ni-based hard particles. If the sintering temperature is lower than 1323K, the progress of sintering is insufficient and wear resistance and strength are insufficient. If the sintering temperature exceeds a temperature lower than the melting point of the Ni-based hard particles, the crystal grains become coarse. This is not preferable because of the conversion.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in comparison with comparative examples to clarify the features of the present invention. (Examples 1 to 7) Examples 1 to 7 intend a sintered alloy that does not infiltrate Pb. In these examples, iron-based spray alloy powders A, D, E, and F are used. The iron-based spray alloy powder A is Mo: 4.9%, Co: 4.6%, and the balance substantially Fe, when the iron-based spray alloy powder A is 100%. The iron-based sprayed alloy powder D is Mo: 1.2% by weight, when the iron-based sprayed alloy powder D is 100%, C:
o: 4.7%, the balance being substantially Fe. The iron-based spray alloy powder E is Mo: 2.2%, Co: 4.6%, and the balance substantially Fe, when the iron-based spray alloy powder E is 100%. 2. The iron-based spray alloy powder F is Mo by weight when the iron-based spray alloy powder F is 100%;
1%, Co; 4.5%, the balance being substantially Fe. Each of the iron-based spray alloy powders A, D, E, and F described above has a particle size of 177 μm or less.

Further, an element powder of Mn and an element powder of Cr are used. Each of these element powders has a particle size of 177 μm or less. Further, powder of Ni-based hard particles B (spray alloy powder, particle size of 149 μm or less) and powder of Ni-based hard particles C (spray alloy powder, particle size of 149 μm or less) are used. The hard particles B are, assuming that the hard particles B are 100%, by weight: Cr: 35.2%, W: 12.5%, Mo: 8.7%,
Fe: 18.7%, C: 2.6%, Si: 0.6%, the balance being substantially Ni. When the hard particles C are 100% of the hard particles C, the weight ratio is Cr: 26.7%, W: 1
6.2%, Mo; 13.3%, Fe; 17.0%, S
i: 0.6%, C: 2.7%, and the balance is substantially Ni.

The above alloy powders (A, D, E, F)
), The element powder of Mn, the element powder of Cr, the hard particles, and the graphite powder are appropriately weighed so as to have the composition shown in Table 1. These were mixed by a V-type mixer to obtain a mixed powder. In addition, Table 1 shows mixed powder [except for the lubricant that evaporates during sintering, that is, alloy powder (A, D, E, or F) + (Mn element powder and / or Cr element powder) + Hard particles + graphite powder] as 100% by weight.

As shown in Table 1, 0.8% by weight of lubricating zinc stearate was added as a lubricant to the mixed powder excluding the lubricant.

[0031]

[Table 1] Thereafter, the mixed powder was compressed at a molding pressure of 7 tonf / cm ² to form a green compact. The obtained green compact was sintered in a decomposed ammonia gas atmosphere at a temperature of 1393 K for 30 minutes, thereby producing Examples 1 to 7 and Comparative Examples 1 and 2.

In each of the test pieces of Examples 1 to 7, carbide is dispersed in the matrix, and further, Ni-based hard particles in which the carbide is formed are dispersed in the matrix. The representative metal structure of the matrix of the iron-based sintered alloy according to the present embodiment is determined to be a structure in which pearlite, austenite, and bainite are mixed. Table 2 shows the alloy composition of the manufactured iron-based sintered alloy. The ratio in Table 2 indicates that the iron-based sintered alloy is 1 in weight ratio.
This is the ratio when 00% is set.

[0033]

[Table 2] For the test pieces of Examples 1 to 7 and Comparative Examples 1 and 2,
Using a valve-valve seat test machine simulating an actual machine, the wear resistance of each test piece at high temperature was evaluated. In this test, each test piece was used as a ring-shaped valve seat 10 as shown in FIG. This test device reproduces the beating wear of the valve face 20c of the valve 20 and the valve seat 10 by a mechanism that heats the valve 20 and the valve seat 10 by burning propane gas and opens and closes the valve 20 by driving a cam. It is.

In the above test, the material of the valve 20 as the mating member was JIS-SUH35, and the temperature of the valve 20 was 1
120K, the temperature of the valve seat 10 was controlled to be maintained at 670K, the rotation speed of the cam was set to 2200 rpm, and the operation was performed for 20 hours. When the valve 20 as a test piece was closed before the test shown in FIG. (T-T), which is the difference between the dimension T from the base 40 to the valve end 20e from the base 40 and the dimension t from the base 40 to the valve end 20e when the valve is closed after the test, is calculated. The wear amount of the valve seat 10 was evaluated based on the valve sink amount.

FIG. 2 shows the test results. The greater the valve sinking amount, the greater the amount of wear. As can be understood from FIG. 2, in Comparative Examples 1 and 2, the valve sink amount is considerably large. Especially in Comparative Example 1, the number is considerably large. Furthermore, in Comparative Examples 1 and 2, the contact surface of the valve seat 10 was rough due to adhesion. In Comparative Examples 1 and 2, it is assumed that Cr and Mn were not present in the matrix.
On the other hand, in Examples 1 to 7, the valve sink amount is small. Further, in Examples 1 to 7, the contact surface of the valve seat 10 was in a smooth state. From the test results, in the iron-based sintered alloy according to the present example, the wear resistance is secured without infiltrating Pb.

[0036]

According to the abrasion-resistant iron-based sintered alloy according to each claim, the Ni-based hard particles include Mo, Cr, W,
It has Fe or Si. Therefore, the Ni-based hard particles have carbide. Since such Ni-based hard particles are dispersed in the iron-based matrix, wear resistance is ensured.

According to the abrasion-resistant iron-based sintered alloy according to each claim, Ni of the Ni-based hard particles diffuses into the matrix around the hard particles, so that high-temperature strength and heat resistance near the hard particles of the matrix are obtained. , Oxidation resistance, and corrosion resistance are improved, and the floating of hard particles with respect to the matrix is suppressed. This reduces excessive wear of the mating material. Further, since the floating of the hard particles is suppressed, the falling of the hard particles from the iron-based sintered alloy is suppressed. Also in this sense, the wear resistance of the iron-based sintered alloy is improved.

According to the abrasion-resistant iron-based sintered alloy according to each claim, Cr and Mn, which are easily oxidized, are positively added to the base structure so that the sliding surface of the iron-based sintered alloy has an appropriate resistance. The formation of an oxide film is expected. Thereby, direct contact between the metal forming the base and the counterpart material is suppressed, and adhesion of the metal forming the base is suppressed. Therefore, the wear resistance of the iron-based sintered alloy is improved.

As described above, according to the wear-resistant iron-based sintered alloy according to each claim, since the wear resistance is improved without infiltrating Pb, the method of infiltrating Pb can be reduced or eliminated. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a valve sinking amount.

FIG. 2 is a graph showing valve sink amounts of an example of the present invention and a comparative example in a wear test.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshio Fuwa 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (3)

[Claims] 1. The total composition is Co; 1.4 to 15 in weight ratio.
%, Mo; 1.5 to 16%, Mn; 0.38 to 9.5
%, Cr: 0.4 to 12%, W: 0.2 to 6.0%,
C: 0.4 to 3.2%, Ni: 0.2 to 9.0%, the balance being unavoidable impurities and Fe, Co; 2 to 15%, Mo: 2 to 10%, Mn; 0.4 ~
10%, C: 0.2 to 2%, Ni: 10% or less, the balance being a base structure composed of unavoidable impurities and Fe, Mo: 5 to 20%, Cr: 20 to 40%, W; 20
%, C: 0.5 to 5%, Fe: 5 to 30%, the balance being 2 to 30% of hard particles composed of unavoidable impurities and Ni.
A wear-resistant iron-based sintered alloy comprising a dispersed sintered body. 2. The total composition by weight is Co;
%, Mo; 1.5 to 16%, Mn; 10% or less, Cr;
0.6-20%, W; 0.2-6.0%, C; 0.4-
3.2%, Ni; 0.2 to 9.0%, the balance consists of unavoidable impurities and Fe; Co; 2 to 15%, Mo; 2 to 10%, at least one of Cr and Mn; 0.4 to 10%, C: 0.2 to 2%,
Ni: contains 10% or less, and the balance is composed of an unavoidable impurity and Fe. Mo: 5 to 20%, Cr: 20 to 40%, W: 5 to 20
%, C: 0.5 to 5%, Fe: 5 to 30%, the balance being 2 to 30% of hard particles composed of unavoidable impurities and Ni.
A wear-resistant iron-based sintered alloy comprising a dispersed sintered body. 3. The total composition is Co; 1.4 to 15 in weight ratio.
%, Mo; 1.5 to 16%, Mn; 9.5% or less, C
r; 0.4 to 20%, W: 0.2 to 6.0%, C;
4 to 4.0%, Ni; 0.2 to 9.0%, Si; 0.6
%; The remainder consists of unavoidable impurities and Fe; Co: 2 to 15%, Mo: 2 to 10%, at least one of Cr and Mn; 0.4 to 10%, C: 0.2 to 2% %,
Ni: contains 10% or less, and the remainder has an inevitable impurity and Fe as a base structure. Mo: 5 to 20%, Cr: 20 to 40%, W: 10 to 2
0%, C: 0.5-4%, Fe: 5-30%, Si; 2
% Of a hard particle comprising hard particles composed of inevitable impurities and Ni dispersed in an amount of 2 to 30%.