JPH07188873A - Valve seat made of iron base sintered alloy for internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain a valve seat excellent in wear resistance by constituting of an iron base sintered alloy in which the specified amount of silicides of Zr, Cr, Mo and W are uniformly dispersed in a base metal of steel of a specified composition. CONSTITUTION:The valve seat is constituted of the iron base sintered alloy having a structure in which >=1 kind of the cilicides of Zr, Cr, Mo and W of 5-20wt.% at the rate of occupation to the whole in a base metal which consists of Cr, Mo and Ni of respectively 0.5-5.0wt.%, 2-10wt.% Co, 0.6-1.5wt.% C and the balance Fe. Even when this valve seat is used for the intake side of engine, the adhesion of the siliside grain dispersed in the base metal to the base metal of the iron base alloy is good, so wear due to the separation of a hard siliside grain is suppressed, attackability to partner of the valve of the partner member is remarkably reduced and wear resistance is improved.

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 such as a diesel engine or an LPG engine, and more preferably, an iron-based sintered alloy exhibiting excellent wear resistance when used as a valve seat on the intake side. It relates to valve seats.

[0002]

2. Description of the Related Art Conventionally, as a valve seat for an internal combustion engine,
For example, as described in JP-A-3-158444, in% by weight (hereinafter,% indicates% by weight), Cr:
0.5-3%, Mo: 0.5-3%, Ni: 0.5-3
%, Co: 2 to 10%, C: 0.6 to 1.5%, and Cr: 25 to 45%, W: 20 to 30 in the Fe-based alloy base material, the balance of which is Fe and inevitable impurities. %,
Co: 20-30%, C: 1-3%, Si: 0.5-
2%, Nb: 0.2-2%, and a Fe-based calcination having a structure in which 10 to 25% of Cr-based alloy hard particles having the composition of the balance of Fe and unavoidable impurities are dispersed. A valve seat made of Fe-based sintered alloy, which is made of bonded gold and has excellent wear resistance, has been proposed.

[0003]

However, recent internal combustion engines have been designed to have high output due to high speed rotation and the like, and the conventional iron-based sintered alloy valve seats, particularly diesel engines and LPG, have been used. When used as a valve seat on the intake side of an engine, the intake side of these engines is
Since the mechanical load is large, under such conditions, the hard particles dispersed in the Fe-based alloy base material do not have sufficient adhesion to the base material, and the wear progress of the valve seat itself due to the separation of the hard particles occurs. There is a problem that speeding up and the separated hard particles also promote wear of the valve, which is a mating member.

[0004]

Therefore, the present inventors have
From the above viewpoints, especially diesel engines and LPs
Focusing on the above-mentioned conventional iron-based sintered alloy valve seats used for intake side valve seats of G engines, etc., as a result of research to improve this wear resistance, as a result, Cr:
0.5-5%, Mo: 0.5-5%, Ni: 0.5-5
%, Co: 2 to 10% and C: 0.6 to 1.5%, and the balance is 5 to 20% of Zr in the base material having a composition of Fe and inevitable impurities.
An iron-based sintered alloy having a structure in which one or more of silicides of Cr, Mo and W are uniformly dispersed.
When the valve seat is constructed, the resulting iron-based sintered alloy valve seat, even when used on the intake side of the engine,
Since the adhesion of the silicide particles dispersed in the matrix to the Fe-based alloy matrix is extremely good, the wear caused by the separation of hard silicide particles is suppressed, and the counterpart attack of the valve that is the counterpart member Therefore, it has been found that the wear resistance is improved, the wear resistance is improved, and the life is greatly improved.

The present invention has been made on the basis of such findings, and Cr: 0.5-5%, Mo: 0.5-
5%, Ni: 0.5 to 5%, Co: 2 to 10% and C: 0.6 to 1.5%, with the balance being Fe and inevitable impurities. A valve seat for an internal combustion engine, which is composed of an iron-based sintered alloy having a structure in which one or more of Zr, Cr, Mo and W silicides in a proportion of 5 to 20% are uniformly dispersed. It has characteristics.

Next, the reason why the component composition of the iron-based sintered alloy constituting the valve seat of the present invention is limited as described above will be explained.

(A) C C component combines with Mo and Cr to form a carbide,
It has the effect of improving hardness and wear resistance, but if its content is less than 0.6%, the desired effect cannot be obtained on the other hand, while its content exceeds 1.5%. Then, the hardness of the base material becomes very high and the valve, which is the mating material, is worn away. Therefore, the value is set to 0.6 to 1.5%, preferably 0.8 to 1.2%.

(B) Cr The Cr component has the function of forming a solid solution in the base material to improve the heat resistance, and the function of forming carbides to improve the wear resistance. If the content is less than 5%, the desired effect cannot be obtained, while if the content exceeds 5%, the sinterability deteriorates.
%, Preferably 1.0 to 3.0%.

(C) Mo The Mo component has an action of forming a solid solution in the matrix to form a carbide and improving wear resistance, but if the content thereof is less than 0.5%, the above action is desired. The effect cannot be obtained, and on the other hand, when the content exceeds 5%, the material strength decreases, so the value is 0.5 to 5%, preferably 1.0 to 3.0.
Set to%.

(D) Ni The Ni component has a function of forming a solid solution in the matrix and strengthening it, but if the content is less than 0.5%, the desired effect cannot be obtained on the above-mentioned function. However, even if the content exceeds 5%, the above action is saturated, and it is uneconomical. Therefore, the value is 0.5 to 5%, preferably 1.0.
˜3.0%.

(E) Co The Co component has a function of forming a solid solution in the matrix to strengthen it, but if the content is less than 2%, the desired effect cannot be obtained for the above-mentioned function, while Even if the content exceeds 10%, the above effect is saturated, and it is uneconomical. Therefore, the value is set to 2 to 10%, preferably 3 to 8%.

(F) Silicide Since the silicide has excellent adhesion to the Fe-based alloy substrate, even if it is used as a valve seat of a high-power diesel engine or LPG engine, the detachment from the substrate is significantly suppressed. However, when the content is less than 5%, the desired effect cannot be obtained, and when the content exceeds 20%, the strength is improved. And since the toughness will decrease,
The content was set to 5 to 20%, preferably 10 to 15%.

[0013]

EXAMPLES Next, the iron-based sintered alloy valve seat of the present invention will be specifically described based on Examples. As a raw material powder, all have a particle size: -100 mesh Fe-1%
Cr powder, carbonyl Ni powder, Co powder, Mo powder,
W powder, Si powder, No powder and natural graphite powder are prepared, and further ZrSi ₂ powder, Cr ₃ Si ₂ powder, MoSi ₂ having a predetermined average particle diameter within the range of 30 to 100 μm.
Powder and W ₃ Si ₃ powder are prepared, and these raw material powders are
6-6.5t / cm ² after blending and mixing at a predetermined ratio
Press-molded into a green compact at a pressure of, the oil is deoiled under the condition of being held at 500 ° C. for 30 minutes, and the temperature is maintained at 1140 to 1180 ° C. for 1 hour in an N ₂ -5% H ₂ atmosphere. Under the conditions
Sintered, having the composition of components shown in Tables 1 and 2, and having an outer diameter of 34 mm, an inner diameter of 27 mm, and a height of 7.2 mm, the valve seat made of an iron-based sintered alloy of the present invention ( Hereinafter, the present invention valve seats) 1 to 15 and conventional iron-based sintered alloy valve seats (hereinafter referred to as conventional valve seats) 1
~ 15 were produced.

[0014]

[Table 1]

[0015]

[Table 2]

Then, the valve seats 1 to 15 of the present invention and the conventional valve seats 1 to 15 are respectively evacuated to a displacement of 2000.
cc built into the intake side of a 4-cylinder diesel engine,
A wear test was performed for 100 hours, and the maximum wear depths of the valve seat and the valve that was a mating member were measured. The results are shown in Tables 1 and 2.

[0017]

As is clear from the results shown in Tables 1 and 2, the valve seats 1 to 15 of the present invention in which the silicide is dispersed in the base material are all compared with the conventional valve seats 1 to 15. It is clear that even when it is used as the intake side valve seat of a diesel engine which is an internal combustion engine, it shows a significantly excellent wear resistance with a small opponent attack.

As described above, the valve seat made of the iron-based sintered alloy of the present invention has excellent wear resistance when used as a valve seat on the intake side of high-power internal combustion engines such as diesel engines and LPG engines. It has industrially useful properties such as long-term performance.

Claims (1)

[Claims] 1. By weight%, Cr: 0.5-5%, Mo: 0.5-5%, Ni: 0.5-5%, Co: 2-10%, C: 0.6-1. 1% of a silicide of Zr, Cr, Mo and W in an amount of 5 to 20% by weight in the total amount in a base material having a composition containing 0.5% by weight and the balance of Fe and inevitable impurities. A valve seat made of an iron-based sintered alloy for an internal combustion engine, comprising two or more kinds of iron-based sintered alloys having a uniformly dispersed structure.