JPH09287422A - Manufacture for sintered alloy connection type valve sheet and connection type valve sheet sintered alloy material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a sintered alloy material which is free from the generation of cracks, has an extension of 1% and is excellent in abrasion resistance. SOLUTION: A sintered alloy connection type valve sheet contains 0.5 to 1.7wt.% of C, 0.5 to 2.5wt.% of Ni, 3.0 to 8.0wt.% of Cr, 1.0 to 3.8wt.% of W and 4.5 to 8.5wt.% of Co. Then the residual part comprises an unavoidable impurity material and Fe. Then at the same time, the sintered alloy material includes 8 to 14v.% of not more than 250 mesh C-Cr-W-Co-Fe particles. Then the sintered hole is infiltrated with copper alloy, and the base material comprises austenite, bainite, and particle parlite. Then the sintered alloy connection type valve sheet is such that C-Cr-W-Co-Fe particles and Fe-Mo particles are dispersed in a base. Iron-type alloy sintered material infiltrated with copper alloy in a hole is heated to a temperature of Ac3 or Acm transformation point or more and 1200 deg.C or less followed by cooling the material to 650 deg.C or less at a cooling speed of 4.5 deg.C/min or less and cooling the material with air. The melting infiltration treatment for melting and infiltration copper alloy in holes may be performed when the material is heated to a transformation point of Ac3 and Acm or more and 1200 deg.C or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve seat for an internal combustion engine, and more particularly to a sintered alloy valve seat that can be joined to a cylinder head.

[0002]

2. Description of the Related Art A valve seat is used by being press-fitted into a cylinder head of an engine and plays a role of sealing combustion gas and cooling a valve. Therefore, it is hit by the valve, worn by slippage, heated by combustion gas, corroded by fuel and additives contained in the fuel and its combustion products, and thermal metabolites.

Sintered alloys are alloy powders that are mixed and kneaded, filled in a mold, compression-molded, and then sintered in a predetermined temperature and atmosphere, and alloys that are difficult to obtain by ordinary melting methods are easily manufactured. it can. In addition, since it is easy to combine functions, it is possible to manufacture parts with unique functions, and it is suitable for manufacturing porous materials, difficult-to-machine materials, etc., and for manufacturing mechanical parts with complicated shapes. In recent years, this sintered alloy has been applied to valve seats requiring wear resistance.

For example, Japanese Patent Laid-Open No. 59-25959 discloses C,
Contains a large amount of Ni, Cr, Mo, W and Co, and contains C-Cr
Disclosed are sintered alloy materials for valve seats in which hard particles of -W-Co-Fe particles and Fe-Mo particles are dispersed and continuous pores are infiltrated with a copper alloy. This sintered alloy material for valve seats has excellent strength, rigidity, and excellent wear resistance. After being molded and sintered, it is commercialized by oil quenching and tempering, and is then inserted into the cylinder head by press fitting and used. ing.

However, recently, in order to increase the speed and weight of automobiles, the number of valves in internal combustion engines is increasing, and a plurality of intake / exhaust ports are arranged close to each cylinder. . Due to such recent trends, the degree of freedom in design, such as reducing the distance between valves, increasing the diameter of the intake / exhaust ports, etc., or improving the heat-releasing properties of valves and valve seats, For the purpose of reducing the load and the like, a joint type valve seat in which a valve seat is joined to a cylinder head has been considered.

However, when the above-mentioned conventional sintered alloy material for valve seats is applied to the joining type valve seats, cracks occur in the valve seats when the valve seats are joined or the engine is operated. However, there is a problem that the sealing property of the valve seat is deteriorated. For such a problem, for example, Japanese Patent Application Laid-Open No. 7-189628
Japanese Patent Laid-Open Publication No. 2003-242242 proposes a joining-type valve seat in which a Cu-based alloy or an austenite-based iron-based alloy is joined to a cylinder head by resistance welding.

[0007] However, this valve seat does not cause cracks during joining or during operation, but it is economically disadvantageous because it contains an expensive alloying element, or is low in strength and rigidity. There was a problem of poor wear resistance.

[0008]

DISCLOSURE OF THE INVENTION The present invention advantageously solves the above-mentioned problems and is made of a sintered alloy having excellent elongation / toughness and wear resistance, which does not cause cracks even in a joined type valve seat. It is an object of the present invention to propose a method for manufacturing a bonded valve seat and a sintered alloy material.

[0009]

DISCLOSURE OF THE INVENTION The present inventors believe that an iron-based sintered alloy material that has been subjected to a sealing treatment by copper infiltration is optimum for valve seats in terms of strength and thermal conductivity. In order to solve the above problems, as a result of diligent study on iron-based sintered alloy materials, the conventional iron-based sintered alloy material is a material with low ductility and toughness that is infiltrated with copper, and occurs during bonding. Although it cannot withstand a large amount of thermal stress (tensile stress) and cracks occur, we found that if the elongation of the material can be 1.0% or more, cracks do not occur at the time of joining even with iron-based sintered alloy materials, The invention has been constructed.

According to the present invention, C: 0.5 to 1.7% by weight,
Ni: 0.5-2.5%, Cr: 3.0-8.0%, W: 1.0-3.8
%, Co: 4.5 to 8.5%, the balance consisting of inevitable impurities and Fe, and C-Cr-W- of 250 mesh or less.
Bonding type made of sintered alloy, which has 8 to 14% by volume of Co-Fe particles, the sintered pores are infiltrated with copper alloy, and the matrix structure consists of austenite, bainite and granular pearlite. It is a valve seat.

In the present invention, C: 0.5-1.% By weight.
7%, Ni: 0.5-2.5%, Cr: 3.0-8.0%, Mo: 0.1
.About.0.9%, W: 1.0 to 3.8%, Co: 4.5 to 8.5%, the balance consisting of inevitable impurities and Fe, and C--Cr--W--Co--Fe particles and Fe--Mo particles of 250 mesh or less. And 8% to 14% by volume, the sintered pores are infiltrated with a copper alloy, and the matrix structure consists of austenite, bainite and granular pearlite. is there.

Still further, the present invention provides, by weight percent, C: 0.5.
~ 1.7%, Ni: 0.5-2.5%, Cr: 3.0-8.0%, W:
C containing 1.0 to 3.8%, Co: 4.5 to 8.5%, the balance consisting of inevitable impurities and Fe, and having 250 mesh or less
-Cr-W-Co-Fe particles having a content of 8 to 14% by volume, or a weight% of C: 0.5 to 1.7%, Ni: 0.5 to
2.5%, Cr: 3.0 to 8.0%, Mo: 0.1 to 0.9%, W: 1.
0-3.8%, Co: 4.5-8.5%, the balance consisting of inevitable impurities and Fe, and C- of 250 mesh or less
Cr-W-Co-Fe particles and Fe-Mo particles in 8% to 14% by volume
After heating the sintered body having the copper alloy for infiltration to the melting point of the copper alloy or higher, infiltrating the copper alloy into the pores, and further heating to a temperature not lower than the _Ac3 or A _cm transformation point and not higher than 1200 ° C. , A method for producing a sintered alloy material for a bonded valve seat having excellent elongation characteristics and wear resistance, which comprises cooling to 650 ° C. or less at a cooling rate of 4.5 ° C./min or less and then air cooling. The present invention heats the sintered body together with a copper alloy for infiltration at a temperature not lower than A _C3 or A _cm transformation point and not lower than the melting point of the copper alloy and not higher than 1200 ° C. to heat the copper alloy for infiltration treatment and heat treatment. And may be performed at the same time.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The component composition of the sintered alloy material for valve seats of the present invention will be described. C: 0.5 to 1.7% C is an element necessary for adjusting the matrix to have a predetermined structure and hardness and for forming C-Cr-W-Co-Fe particles. The amount of ferrite becomes excessive, the matrix strength decreases, and the amount of hard particles becomes insufficient. On the other hand, if it exceeds 1.7%, the amount of cementite in the matrix increases and the machinability deteriorates. Therefore, C is set to the range of 0.5 to 1.7%. Further, it is more preferably 1.0 to 1.5%.
C is preferably added as graphite powder and C-Cr-W-Co-Fe alloy powder.

Ni: 0.5 to 2.5% Ni is an element that forms a solid solution in the matrix to improve heat resistance,
If it is less than 0.5%, its effect is small, and if it exceeds 2.5%, the hardenability deteriorates. Therefore, Ni is 0.5% to 2.5%.
Range. Further, it is more preferably 0.8 to 2.3%. Ni is preferably added as Ni powder or pre-alloyed in iron powder.

Cr: 3.0 to 8.0% Cr is an element that improves wear resistance, and is C-Cr-W-
It is added as a Co-Fe alloy powder. If Cr is less than 3.0%, the amount of hard particles is insufficient and wear resistance and heat resistance deteriorate.
If it exceeds 8.0%, the amount of hard particles becomes excessive and the strength of the sintered body decreases. Therefore, Cr is limited to the range of 3.0 to 8.0%. Incidentally, it is more preferably 3.5 to 7.5%.

Mo: 0.1 to 0.9% Mo can be used even if it is not added, but when Mo is added, the wear resistance can be further improved. In the present invention, Fe-Mo particles are formed and dispersed as hard particles in the matrix to contribute to the improvement of wear resistance.
If the Mo content is less than 0.1%, the amount of Fe-Mo particles is small and the wear resistance is not so improved. Further, if it exceeds 0.9%, the amount of Fe-Mo particles becomes excessive and the strength of the sintered body becomes insufficient. Therefore, Mo is limited to the range of 0.1 to 0.9%. Further, it is more preferably 0.3 to 0.7%. Mo is preferably added as Fe-Mo powder or low C-Fe-Mo powder.

W: 1.0-3.8% W is formed by forming C-Cr-W-Co-Fe particles,
Improves wear resistance. If it is less than 1.0%, the amount of hard particles is insufficient and wear resistance is deteriorated, and if it exceeds 3.8%, the amount of hard particles is excessive and the strength of the sintered body is insufficient. Therefore, W is 1.
It was limited to the range of 0 to 3.8%. In addition, more preferably 1.
3 to 3.3%. W is preferably added as a C-Cr-W-Co-Fe alloy powder.

Co: 4.5-8.5% Co is formed by forming C-Cr-W-Co-Fe particles.
Improves wear resistance. Further, Co has the effect of strengthening the bond between the hard particles and the matrix, and forming a solid solution in the matrix to improve the heat resistance. If it is less than 4.5%, the effect is not recognized, and if it exceeds 8.5%, the hard particles become excessive and the strength of the sintered body becomes insufficient. Therefore, Co is set in the range of 4.5 to 8.5%. It is more preferably 5.0 to 8.0%.
Co is preferably added as a C-Cr-W-Co-Fe alloy powder and a Co powder. Instead of Co powder, a part may be alloyed in iron powder and added.

The balance of the sintered alloy material for a valve seat of the present invention is substantially Fe. Sintered alloy material for valve seats of the present invention has the above composition, further, as hard particles, 250
C-Cr-W-Co-Fe particles below the mesh, or C-
Cr-W-Co-Fe particles and Fe-Mo particles in volume% of 8 to
Contains 14%. If a coarse powder of more than 250 mesh is used as the hard particles, the compression moldability of the mixed powder will decrease, and further, the hard particles will fall out in the sintered alloy and wear resistance will decrease due to non-uniformity. No more than 250 mesh.

When the amount of hard particles is less than 8% by volume, the hard particles are insufficient and wear resistance is deteriorated. On the other hand, if the content exceeds 14% by volume, the hard particles become excessive and the compression moldability of the mixed powder deteriorates, resulting in insufficient strength of the sintered body. As the iron powder as a base, any iron powder such as atomized iron powder or reduced iron powder can be preferably applied. The iron powder may be pre-alloyed with an alloy element.

C-Cr-W-Co-Fe particles which are hard particles have C: 2.0 to 3.0%, Co: 7.0 to 15%, W: 15 to 25%.
%, Fe: 1.0 to 8.0% and the balance is preferably Cr as an alloy powder. Fe-Mo which is a hard particle
The particles are preferably added as ferromolybdenum powder with Mo: 50-70%.

To obtain the sintered alloy material for a valve seat of the present invention, pure iron powder is mixed with a single powder of Ni and Co, or pure iron powder is prealloyed with C, Ni and Co. Further, alloy powder and C powder, which become hard particles, are blended and kneaded so as to have the above composition. In addition, you may mix zinc stearate etc. as a lubricant. Next, these powders are filled in a mold and compressed / molded by a molding press to obtain a green compact. Next, the green compact is sintered to obtain a sintered body.

The sintering condition is that the green compact is 1100 in a protective atmosphere.
It is desirable to heat and sinter in the temperature range of up to 1200 ° C.
If it is less than 1100 ° C, the sintering diffusion is insufficient, and if it exceeds 1200 ° C, the hard particles and the matrix are overdiffused to deteriorate the wear resistance. The sintered body is further heated together with the copper alloy for infiltration at a temperature equal to or higher than the melting point of the copper alloy, and the pores are infiltrated with the copper alloy. This infiltration treatment may be performed simultaneously with the heat treatment of the sintered body described later.

Next, in the present invention, the sintered body having the above composition is subjected to infiltration treatment, or is not subjected to infiltration treatment and is subjected to heat treatment of heating and cooling. In the present invention, the elongation of the sintered alloy material is 1.0% or more, and the structure of the sintered alloy material is austenite + bainite + granular pearlite structure in order to improve the elongation characteristics. Therefore, the heat treatment conditions are limited.

The heating temperature of the heat treatment is not lower than the A _c3 or A _cm transformation point of the sintered body and not higher than 1200 ° C. Heating temperature is A _c3
On the other hand, below the A _cm transformation point, an austenite + bainite + granular pearlite structure having excellent elongation properties cannot be obtained, and tempered martensite + pearlite structure cannot be obtained, and improvement in elongation value cannot be expected. On the other hand, when the temperature exceeds 1200 ° C., the crystal grains become coarse, and the hard particles and the matrix are excessively diffused, and the ductility, toughness and wear resistance are deteriorated. For this reason, the heating temperature of the heat treatment is set to a temperature equal to or higher than the _{Ac 3} or A _cm transformation point, and preferably equal to or lower than 1200 ° C. Preferably, it is 750 ° C or more and 1200 ° C or less. In addition, for the sintered body not subjected to the infiltration treatment, the infiltration treatment may be simultaneously performed by heating the infiltrating copper alloy together with the copper alloy for infiltration at a temperature higher than the melting point of the copper alloy.

After heating to the above heating temperature, 4.5 ° C./min
Cool to 650 ° C or less at the following cooling rate and then air cool. When the cooling rate up to 650 ° C is less than 4.5 ° C / min, an austenite + bainite + granular pearlite structure having excellent elongation properties cannot be obtained, and a martensite + bainite structure cannot be obtained, and a high elongation value cannot be obtained. When the cooling rate is controlled to a temperature higher than 650 ° C, a structure having excellent predetermined elongation properties cannot be obtained.

After the above heat treatment, tempering may be performed if necessary. By combining the above-mentioned composition and heat treatment, the elongation characteristics of the sintered alloy material are improved, and even if the sintered alloy material of the present invention is applied to a joint type valve seat,
No cracks are found. Further, it is preferable to apply copper plating to at least the joint surface of the joint valve valve made of the sintered alloy of the present invention from the viewpoint of improving the jointability.

The joint type valve seat is formed by processing a sintered alloy material into a predetermined shape and is joined to the cylinder head by resistance welding, friction welding, electron beam welding or the like.

[0029]

[Examples] First, tests No. 1 to No. 7 and No. 13 were used as raw material powders in% by weight, C powder (-325 mesh) 1.2%,
Co powder (5 μm or less) 6.0%, Ni powder (-325 mesh)
2.0%, Fe-60% Mo powder (-250 mesh) 1.0%, 2.5
% C-1.0% Co-19% W-63.5% Cr-5% Fe alloy powder (-250 mesh) 11.5% and the balance atomized pure iron powder were mixed with 1% zinc stearate and kneaded. Test No. 8 ~
No. 12 is a raw material powder in% by weight, C powder (-325 mesh) 1.2%, Co powder (5 μm or less) 6.0%, Ni powder (-325 mesh) 2.0%, 2.5% C-1.0% Co-19 % W
-63.5% Cr-5% Fe alloy powder (-250 mesh) 11.5%,
The balance atomized pure iron powder was mixed with 1% of zinc stearate and kneaded. These mixed raw material powders were compacted at a pressure of 6 ton / cm ² and sintered in a reducing atmosphere at 1110 ° C for 60 minutes, and a copper alloy for infiltration was placed on this and subjected to infiltration treatment at 1130 ° C for 60 minutes. . Some of the sintered bodies (Test No. 7 and No. 12) were not subjected to the above infiltration treatment.

Then, the sintered body was heat-treated under the heating and cooling conditions shown in Table 1. In tests No. 7 and No. 12, the copper alloy for infiltration was placed at the time of heating and the infiltration treatment was simultaneously performed.

[0031]

[Table 1]

The compositions of the sintered alloy materials of Test No. 1 to No. 7 are C: 1.3%, Ni: 2.0%, Cr: 7.5%, Mo: 0.6.
%, W: 2.2%, Co: 7.5%, balance impurities and Fe, and the hard particles dispersed in the matrix were 13% by volume.
The compositions of the sintered alloy materials of Test No. 8 to No. 12 are C:
1.3%, Ni: 2.0%, Cr: 7.5%, W: 2.2%, Co:
7.5%, the balance impurities and Fe, and the hard particles dispersed in the matrix was 12% by volume. Copper alloy was infiltrated into 10 to 15% of the sintered pores. The transformation point (A _cm ) of this sintered alloy material was 735 ° C. After the heat treatment, a tensile test was performed on the sintered alloy material to measure the elongation. Table 1 shows the measurement results
It is described together.

Tests No. 1 to 3, No. 5 of the application example of the present invention
Nos. 7, 8 to 9 and Nos. 11 to 12 have elongations of 1.0% or more, while Comparative Examples Nos. 4 and 10 have elongations of 0.8% and 0.6%, respectively, and the conventional example. The growth of No. 13 is 0.3%
And less than 1.0%, it can be seen that the application examples of the present invention have excellent elongation characteristics. Test No. 1 of the application example of the present invention,
After processing under the same composition and processing conditions as Test No. 13 of the conventional example and processing into a valve seat, the cylinder head (material: A
It was joined to DC4) by resistance welding. Due to the thermal stress at the time of joining, no crack was observed in the valve seat of Test No. 1 of the application example of the present invention. However, radial cracks occurred in the valve seat of Test No. 13 of the conventional example. Within the scope of the present invention, even when applied to a joint-type valve seat, no crack is generated due to thermal stress at the time of joining.

The heat-treated sintered alloy materials shown in Table 1 were
It was processed into a normal press-fitting type valve seat and its wear resistance was confirmed by a single rig wear test. The test conditions are as follows. Test temperature: 350 ° C (seat surface) Number of contacts: 1.6 × 10 ⁶ times Cam rotation speed: 3000 rpm Valve rotation speed: 20 rpm Spring load: 30 kgf (when lifted) Valve material: SUH35 (Stellite No. 6 heavy metal) Lift amount: The results of the 7.2 mm test are shown in FIG.

Test Nos. 1 to 3 and No. 5 of the application example of the present invention
In Nos. 7, Nos. 8 to 9 and Nos. 11 to 12, the valve seat wear amount was 9 to 11 μm, and the wear resistance was equivalent to that of No. 13 of the conventional example.

[0036]

EFFECTS OF THE INVENTION According to the present invention, a sintered alloy material having excellent elongation and toughness and excellent wear resistance can be obtained, and a joint type valve seat using the sintered alloy material can be cracked. It is possible to obtain the effect that the high sealing property can be maintained.

[Brief description of drawings]

FIG. 1 is a graph showing a wear amount of a valve seat after a single rig test.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C22C 38/52 C22C 38/52

Claims (6)

[Claims] 1. By weight%, C: 0.5-1.7%, Ni: 0.5
~ 2.5%, Cr: 3.0 ~ 8.0%, W: 1.0 ~ 3.8%, Co:
It contains 4.5 to 8.5%, the balance is unavoidable impurities and Fe, and has 8 to 14% by volume of C-Cr-W-Co-Fe particles of 250 mesh or less, and the sintered pores are copper alloy. A joint type valve seat made of a sintered alloy, which is infiltrated with a matrix structure consisting of austenite, bainite and granular pearlite. 2. C: 0.5 to 1.7% and Ni: 0.5 by weight.
~ 2.5%, Cr: 3.0 ~ 8.0%, Mo: 0.1 ~ 0.9%, W:
C containing 1.0 to 3.8%, Co: 4.5 to 8.5%, the balance consisting of inevitable impurities and Fe, and having 250 mesh or less
-Cr-W-Co-Fe particles and Fe-Mo particles in volume% of 8 to 14
%, The sintered pores are infiltrated with a copper alloy, and the matrix structure is composed of austenite, bainite, and granular pearlite. 3. C: 0.5-1.7%, Ni: 0.5 by weight.
~ 2.5%, Cr: 3.0 ~ 8.0%, W: 1.0 ~ 3.8%, Co:
A sintered body containing 4.5 to 8.5%, the balance being unavoidable impurities and Fe, and having 8 to 14% by volume of C-Cr-W-Co-Fe particles of 250 mesh or less was infiltrated with copper. The alloy is heated above the melting point of the copper alloy to infiltrate the voids with the copper alloy, and further heated to a temperature above the _{Ac 3} or A _cm transformation point and below 1200 ° C, and then at a cooling rate of 4.5 ° C / min or less. 65
A method for producing a sintered alloy material for a joint type valve seat, which is excellent in elongation characteristics and wear resistance, characterized by cooling to 0 ° C or less and then air cooling. 4. By weight%, C: 0.5-1.7%, Ni: 0.5
~ 2.5%, Cr: 3.0 ~ 8.0%, Mo: 0.1 ~ 0.9%, W:
C containing 1.0 to 3.8%, Co: 4.5 to 8.5%, the balance consisting of inevitable impurities and Fe, and having 250 mesh or less
-Cr-W-Co-Fe particles and Fe-Mo particles in volume% of 8 to 14
% Of the sintered body is heated together with the copper alloy for infiltration to a temperature not lower than the melting point of the copper alloy to infiltrate the copper alloy into the pores, and further, A _c3
Alternatively, a joining type having excellent elongation characteristics and wear resistance, which is characterized by heating to a temperature not lower than the A _cm transformation point and not higher than 1200 ° C, then cooling to not higher than 650 ° C at a cooling rate of not higher than 4.5 ° C / min and then air cooling. A method for manufacturing a sintered alloy material for a valve seat. 5. By weight%, C: 0.5-1.7%, Ni: 0.5
~ 2.5%, Cr: 3.0 ~ 8.0%, W: 1.0 ~ 3.8%, Co:
A sintered body containing 4.5 to 8.5%, the balance being unavoidable impurities and Fe, and having 8 to 14% by volume of C-Cr-W-Co-Fe particles of 250 mesh or less was infiltrated with copper. It is characterized in that it is heated together with the alloy to a temperature not lower than the A _c3 or A _cm transformation point and not lower than the melting point of the copper alloy and not higher than 1200 ° C., then cooled to 650 ° C. or lower at a cooling rate of 4.5 ° C./min or lower and then air-cooled. A method of manufacturing a sintered alloy material for a bonded valve seat, which has excellent elongation characteristics and wear resistance. 6. C: 0.5-1.7%, Ni: 0.5 by weight%
~ 2.5%, Cr: 3.0 ~ 8.0%, Mo: 0.1 ~ 0.9%, W:
C containing 1.0 to 3.8%, Co: 4.5 to 8.5%, the balance consisting of inevitable impurities and Fe, and having 250 mesh or less
-Cr-W-Co-Fe particles and Fe-Mo particles in volume% of 8 to 14
% Of the sintered body together with the copper alloy for infiltration at a temperature not lower than the _{Ac 3} or A _cm transformation point and not lower than the melting point of the copper alloy and not higher than 1200 ° C, and then 650 ° C at a cooling rate of not higher than 4.5 ° C / min.
A method for producing a sintered alloy material for a joint type valve seat, which is excellent in elongation characteristics and wear resistance, characterized by cooling to the following and then air cooling.