JPH11209855A - Valve seat made of Fe-based sintered alloy that exhibits excellent wear resistance under conditions of high surface pressure - Google Patents

Abstract

(57) [Problem] To provide a valve seat made of an Fe-based sintered alloy which exhibits excellent wear resistance under high surface pressure application conditions. SOLUTION: The valve seat is C: 0.7% by weight.
To 1.4%, Si: 0.2 to 0.9%, Co: 15.1
-26%, Mo: 6.1-11%, Cr: 2.6-4.
7%, Ni: 0.5 to 1.2%, Nb: 0.2 to 0.7
%, The balance being Fe and inevitable impurities, and wear-resistant Co-based alloy hard particles made of a Co-Mo-Cr-based alloy dispersed in a base material of an alloy steel at a rate of 10 to 24 area%. It is made of a Fe-based sintered alloy having a distributed structure and a porosity of 5 to 15%, and is further infiltrated with copper or a copper alloy, or lead or a lead alloy as necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve seat as a structural member of an internal combustion engine such as a diesel engine or a gasoline engine, and more particularly to an Fe-based sintering bond which exhibits excellent wear resistance under high surface pressure applied conditions. It relates to a gold valve seat.

[0002]

2. Description of the Related Art Conventionally, as a valve seat for an internal combustion engine such as a diesel engine or a gasoline engine, for example, Japanese Patent Application Laid-Open Nos. 55-16463 and 58-178 have been proposed.
As described in, for example, Japanese Patent Application Laid-Open No. 073, etc., many proposals have been made of Fe-based sintered alloys having a structure in which hard particles are dispersed and distributed in a base material.

[0003]

On the other hand, in recent years, the output and the size of the internal combustion engine have been remarkably increased, and accordingly,
The spring constant of the valve spring tends to be high in order to prevent outgassing of the combustion gas, so that the seating load applied to the valve contact surface of the valve seat is further increased, and thus the valve seat has a high surface pressure. Although operation under additional conditions is inevitable, when many other valve seats, including the above-described conventional Fe-based sintered alloy valve seats, are used under high surface pressure additional conditions, the wear progresses rapidly. At present, the service life is reached in a relatively short time.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
In view of the above, research has been conducted to develop a valve seat that exhibits excellent wear resistance, especially in practical use under high surface pressure application conditions. % For composition indicates weight), C: 0.7 to 1.4%, Si: 0.2 to 0.9%, Co: 15.1 to 26%, Mo: 6.1 to 11%, Cr : 2.6-4.7%, Ni: 0.5-1.2%, Nb: 0.2-0.7%, the balance being the overall composition of Fe and unavoidable impurities, A Co-based alloy hard particle composed of a Co-Mo-Cr-based alloy was observed on an optical microstructure photograph, and was dispersed and distributed at a rate of 10 to 24 area% in total, and 5 to 15% of the base material. If it is composed of an Fe-based sintered alloy having a porosity, the resulting valve seat made of an Fe-based sintered alloy has In particular, since the hard particles act to significantly suppress wear progress under high surface pressure applied conditions, they exhibit excellent wear resistance even when applied to large and high output internal combustion engines, Research results show that infiltrating this with copper or copper alloy improves thermal conductivity and strength, and infiltrating lead or lead alloy improves lubricity, vibration damping, and machinability. I got it.

The present invention has been made on the basis of the above research results, wherein C: 0.7-1.4%, Si: 0.2-0.9%, Co: 15.1-26. %, Mo: 6.1 to 11%, Cr: 2.6 to 4.7%, Ni: 0.5 to 1.2%, Nb: 0.2 to 0.7%. Abrasion-resistant Co-based alloy hard particles made of a Co-Mo-Cr-based alloy were observed in an optical microstructure micrograph to show a total composition of Fe and unavoidable impurities and a base material of an alloy steel of 10 to 24% by area. It is composed of an Fe-based sintered alloy having a structure dispersed and distributed at a ratio and a porosity of 5 to 15%, and further infiltrated with copper or a copper alloy, or lead or a lead alloy as necessary. It is characterized by a valve seat made of Fe-based sintered alloy that exhibits excellent wear resistance under conditions of high surface pressure. Than it is.

[0006] The valve seat of the present invention, as a base forming alloy powder, C: 0.8-2.1%, Ni: 0.6-1.7%, Cr: 1.2-3.6. %, Nb: 0.3 to 0.9%, Co: 4.3 to 13%, Mo: 1.4 to 4.2%, with the balance being Fe and inevitable impurities. Mo: 20-35%, Cr: 5-10%, S
i: 1 to 4%, the balance being C made of a Co-Mo-Cr alloy having a composition of Co and inevitable impurities.
o-based alloy powder, as a raw material powder, these raw material powders are blended in a predetermined ratio, mixed under the following ordinary conditions, pressed into a predetermined shape, sintered, and further, if necessary, copper or Manufactured by infiltrating copper alloy, or lead or lead alloy. Further, as for the raw material powder for forming a base, in place of the alloy steel powder, an element powder or an element powder and an alloy powder are used, and these are blended so as to have the same composition as the alloy steel powder. It may be used as a raw material powder.

Next, the reason why the overall composition of the Fe-based sintered alloy, the ratio of the hard particles, and the porosity in the valve seat of the present invention are limited as described above will be described. (A) Ingredient composition (a) C In addition to solid solution in the base material to strengthen the C component, it also forms carbides dispersed in the base material to improve the wear resistance of the base material, and further improves hard particles. However, if the content is less than 0.7%, a desired improvement effect cannot be obtained in the above-mentioned effect, while the content is 1.4%. If it exceeds, the opponent's aggressiveness rapidly increases, so that the content is 0.7 to 1.4.
%, Preferably 1.0 to 1.3%.

(B) Si The Si component has the effect of forming a solid solution in the base material to increase its hardness and thereby improve the abrasion resistance. However, if the desired effect is not obtained, on the other hand, if the content exceeds 0.9%, the strength is reduced, so that the content is 0.2 to 0.9%, preferably 0.4 to 0.9%. It was determined to be 0.7%.

(C) Mo The Mo component has a function of improving the strength and abrasion resistance of the base by forming a carbide which dissolves in the base and disperses in the base, and has a hard particle together with Co and Cr. In practical use under high surface pressure application conditions, there is an effect of improving the wear resistance. However, if the content is less than 6.1%, a desired effect of improving the effect cannot be obtained. If the content exceeds 11%, the aggressiveness of the opponent increases, so the content is set to 6.1 to 11%, preferably 6.5 to 10%.

(D) Co In the Co component, besides strengthening the solid solution, Mo and C
However, when the content is less than 15.1%, a desired effect cannot be obtained in the above-mentioned effect. If the amount exceeds 26%, the abrasion resistance of the valve seat itself decreases, so the content is reduced to 15.1 to 1.5%.
26%, preferably 16 to 24%.

(E) Cr The Cr component has a function of improving the strength and abrasion resistance of the base by forming carbides and intermetallic compounds dispersed in the base while forming a solid solution in the base. M
When hard particles are formed together with o to improve wear resistance in practical use under high surface pressure application conditions, if the content is less than 2.6%, the desired effect cannot be obtained. On the other hand, if the content exceeds 4.7%, the sinterability deteriorates, and it becomes impossible to secure a desired strength to the valve seat. Therefore, the content is desirably 2.6 to 4.7%. Was determined to be 3 to 4.3%.

(F) Ni The Ni component has the effect of forming a solid solution in the base material and the hard particles and strengthening it. If the content is less than 0.5%, the desired effect can be obtained. On the other hand, if the content exceeds 1.2%, the abrasion resistance decreases, so the content is 0.5 to 1.2%, preferably 0.1 to 0.2%.
It was determined to be 7 to 1%.

(H) Nb The Nb component has a function of improving the heat resistance of the Nb component in solid solution and contributing to the improvement of the high-temperature wear resistance, but its content is less than 0.2%. Does not provide the desired effect in the above-mentioned effects, whereas when the content exceeds 0.7%, the aggressiveness to the opponent increases, so that the content is 0.2 to 0.1%.
7%, preferably 0.5 to 0.6%.

(B) Proportion of Hard Particles If the proportion of the hard particles is less than 10 area%, the desired wear resistance cannot be secured, while if the proportion exceeds 24 area%, the aggressiveness of the opponent sharply increases. Not only do the strength but also decrease the strength.
24% by area, preferably 14 to 22% by area.

(C) Porosity If the porosity is less than 5%, not only the lubricity improving effect due to the oil retaining effect cannot be expected, but also the infiltration of copper and copper alloy or lead and lead alloy becomes non-uniform. The effect of infiltration cannot be fully exhibited, while the porosity is 15%
If the porosity exceeds the limit, the porosity is set to 5 to 15%, and preferably 7 to 13%, since a decrease in strength and wear resistance cannot be avoided.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the valve seat of the present invention will be specifically described with reference to embodiments. First, base material forming alloy powders M-1 to M-15 and hard particle forming alloy powders H-1 to H-6 having average particle diameters and component compositions shown in Tables 1 and 2, respectively, are used as raw material powders. Are prepared, and these raw material powders are blended in a predetermined ratio in a combination shown in Table 3, zinc stearate: 1% is added, and 3% is added by a mixer.
After mixing for 0 minutes, the mixed powder was pressed into a green compact at a predetermined pressure within the range of 5 to 7 ton / cm ² , and the green compact was held at 500 ° C. for 30 minutes to degrease, and the ammonia decomposition gas was removed. After sintering in an atmosphere at a predetermined temperature in the range of 1170 to 1250 ° C. for 1 hour, then −100 to −150
C. for 30 minutes at a given temperature in the range of
By performing a tempering treatment at a predetermined temperature in the range of ~ 700 ° C for 1 hour, the composition has the overall composition shown in Tables 4 and 5 and the proportion of hard particles (100
(Measured by an image analyzer based on a photograph of the optical microscope structure at × 2 magnification) and a Fe-based sintered alloy having a porosity, outer diameter: 42 mm × minimum inner diameter: 34.5 mm × thickness: 6.
Inventive valve seats 1 to 15 and comparative valve seats 1 and 2 each having a size of 5 mm were produced. In each of the comparative valve seats 1 and 2, the ratio of the hard particles is out of the range of the present invention, whereby the overall composition is also out of the range of the present invention.

Further, the valve seats 1 to 15 of the present invention are provided.
And comparative valve seats 1 and 2 as a main body, and pure copper and a Cu-3% Co alloy (hereinafter, Cu
Alloy-1) or Cu-3% Fe-2% Mn-2%
An infiltrant of a Zn alloy (hereinafter, referred to as Cu alloy 2) was placed in a combination shown in Table 6, and in this state, copper or copper alloy was held in a methane-modified gas atmosphere at a temperature of 1100 ° C. for 15 minutes. The copper infiltration valve seats 1 to 15 of the present invention and the comparative copper infiltration valve seat 1,
2 were each manufactured. Also, the valve seats 1 to 15 of the present invention and the comparative valve seats 1 and 2 were used as main bodies, and pure lead, Pb-4%
Sb alloy (hereinafter referred to as alloy a) or Pb-5% S
In a heating bath of an infiltrant of n alloy (hereinafter, referred to as alloy b),
The lead-infiltrated valve sheets 1 to 15 of the present invention and the lead-infiltrated valve according to the present invention are subjected to infiltration treatment of lead or a lead alloy under a condition of immersion for 1 hour in a nitrogen atmosphere while applying a pressure of 8 kg / cm ² to the bath surface. Immersion valve seats 1 and 2 were manufactured respectively.

Next, with respect to the various valve seats obtained as a result, using a wear tester on a valve seat base, the material of the valve: Stellite-1 Number of seating of the valve: 2400 times / min, atmosphere: light oil combustion gas, Heating temperature (water cooling) of the valve seat: 300 to 400 ° C, seating load: 60 kg, operation time: 8 hours in a row, a high surface pressure additional wear test was conducted. The maximum wear depth of the valve seat and the valve as the mating material Was measured for maximum wear depth. Tables 6 to 8 show these measurement results.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

[Table 4]

[0023]

[Table 5]

[0024]

[Table 6]

[0025]

[Table 7]

[0026]

[Table 8]

[0027]

From the results shown in Tables 6 to 8, the valve seats 1 to 15 of the present invention and the copper infiltrated valve seats 1 to 1 of the present invention are shown.
5 and the lead-infiltrated valve seats 1 to 15 of the present invention each have low aggressiveness against a mating member and show excellent wear resistance under high surface pressure applied conditions.
2. As can be seen in the comparative copper infiltrated valve seats 1 and 2 and the comparative lead infiltrated valve seats 1 and 2, when the proportion of the hard particles of the Fe-based sintered alloy constituting them is out of the range of the present invention. It is clear that the abrasion resistance decreases and the opponent aggression increases. As described above, the valve seat made of an Fe-based sintered alloy according to the present invention is made of a hard particle made of a Co-Mo-Cr-based alloy dispersed and distributed in a base material of an alloy steel. In this case, it exhibits excellent wear resistance, and therefore can sufficiently cope with an increase in the size and output of the internal combustion engine.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masaaki Sakai 3-1 Koganecho, Niigata City, Niigata Prefecture Mitsubishi Materials Corporation Niigata Works (72) Inventor Kunio Hanada 1-5-1 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Terial Co., Ltd. Processing Business Division

Claims (2)

[Claims] C: 0.7 to 1.4%, Si: 0.2 to 0.9%, Co: 15.1 to 26%, Mo: 6.1 to 11%, Cr : 2.6 to 4.7%, Ni: 0.5 to 1.2%, Nb: 0.2 to 0.7%, the balance being Fe and unavoidable impurities. An abrasion-resistant Co-based alloy hard particle composed of a Co-Mo-Cr-based alloy was observed on an optical microscope micrograph to disperse and distribute at a rate of 10 to 24 area%, and 5 to 15% A valve seat made of an Fe-based sintered alloy having excellent wear resistance, comprising a Fe-based sintered alloy having a porosity. 2. In% by weight, C: 0.7 to 1.4%, Si: 0.2 to 0.9%, Co: 15.1 to 26%, Mo: 6.1 to 11%, Cr : 2.6 to 4.7%, Ni: 0.5 to 1.2%, Nb: 0.2 to 0.7%, the balance being Fe and unavoidable impurities. An abrasion-resistant Co-based alloy hard particle composed of a Co-Mo-Cr-based alloy was observed on an optical microscope micrograph to disperse and distribute at a rate of 10 to 24 area%, and 5 to 15% Fe-based sintered alloy having a porosity, and excellent in wear resistance characterized by infiltrating copper or copper alloy, or lead or lead alloy
Base sintered alloy valve seat.