JPS5937343B2 - High temperature wear resistant sintered alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present description relates to a sintered alloy that has excellent wear resistance at high temperatures and is particularly suitable for valve seat materials for internal combustion engines such as automobiles.

In the past, special cast iron and heat-resistant steel were used for the valve seats of internal combustion engines, but as exhaust gas regulations have been tightened several times to protect the environment, internal combustion engines have also become compliant with these regulations. Improvements have been made to achieve lower fuel consumption and higher performance.

As a result, the conditions under which valve seats are used have become increasingly severe, and not only the conventional materials mentioned above, but also various materials developed in response to the early regulations, have become unusable.

As previously stated in Japanese Patent Application No. 53-144325, the applicant of the present application has developed an sintered structure in which 25 to 75% of the He alloy portion and 75 to 25% of the B alloy portion of the following composition exist in patches with each other. We have developed steel compacts and put them into practical use.

This material has superior abrasion resistance compared to other materials that have already been developed, but under recent harsh usage conditions it sometimes wears out, making it necessary to further strengthen its abrasion resistance. .

In order to improve wear resistance, it is effective to disperse a hard substance into the base material.

The inventors used 45 to 60% Co as a hard substance.
36% Mo-8i and 45-60% Fe-33~
36%M.

-8i ternary intermetallic compound (both are commercially available as alloy powders).

) was added to various base materials to examine its wear resistance, and as a result, it was found that a particularly large effect was exhibited when this hard substance was added to the alloy of the earlier application in an amount of 3 to 15 times.

In an engine bench test, even under test conditions in which the valve seat made of the alloy of the prior application causes abnormal wear, the alloy of the present invention shows only normal wear.

Hereinafter, the present invention will be described in detail with reference to Examples.

Example First, a side alloy powder having a composition excluding carbon from each composition and graphite powder are mixed so that the ratio of the A alloy to the B alloy is 1=1, and then a hard phase C is mixed with the graphite powder. as 55%C
A powder with a composition of o-35% Mo-8i was added from 0 to 20%, formed into a predetermined shape, and sintered at 1200°C for 20 minutes in a protective atmosphere to produce several types of samples with different hard phase contents. It was created.

Next, abrasion tests were conducted on these samples using a Dalian type abrasion tester, and among the obtained data, the hard phase C
The content of is 0. 5. A 10% sample is shown in FIG.

It can be seen from this graph that there is a condition range in which wear is significantly increased, and that even under such adverse conditions, wear is significantly reduced by the addition of a hard phase.

Next, the graph in Figure 2 shows the influence of the hard phase content in the base material on the radial crushing strength and wear resistance.As the hard phase increases, the amount of wear decreases, but the strength also decreases. It shows that.

By the way, since the valve seat is generally attached by simply being press-fitted into a hole provided in the cylinder head or being cooled down, if its strength is insufficient, there is a risk that it will fall off during operation.

Therefore, the content of the hard phase needs to be 3 or more from the viewpoint of wear, and on the other hand, from the viewpoint of strength, it is necessary to keep it to 15 or less.

This is confirmed by the results of the bench durability test.
That is, as shown in FIG. 3, even under test conditions that a base material that does not contain a hard phase would not have, the wear of a material that contains 3% of the hard phase is approximately normal and is sufficiently durable for use.

Note that up to 15 inches, wear decreases as the hard phase increases, but even if the amount is further increased beyond that, no significant difference in wear is observed.

Next, in order to investigate the interrelationship between the material of the base material and the presence or absence of a hard phase, three kinds of base materials were prepared: a base material containing only A alloy, a base material containing only B alloy, and a base material containing equal amounts of both alloys. A sample containing no hard phase C and a sample containing 10 hard phase C were prepared and compared, and the results are shown in the following table.

In other words, compared to the case where the hard phase is added to the base material of only alloy A or alloy B, adding it to the base material where both alloys coexist is more effective in terms of the absolute value of the amount of wear. It is also superior in terms of the degree of wear reduction due to its addition in the base material.

Regarding the ratio of alloy A and alloy B in the base material in the present invention, the latter has better wear resistance than the other alloys.

When A alloy is added to B alloy alone, the wear decreases when A alloy is 25 or more, reaches a minimum value at 40 to 60%, and then increases again, and when it exceeds 75%, B alloy wear decreases. Abrasion resistance is worse than taste.

This is the reason why the ratio of both alloys is set at 25 to 75% for one and the remainder for the other.

Moreover, although the case of hard phase C has been described above, similar effects can be obtained even when part or all of it is replaced with hard phase.

Next, the graph and micrograph in Figure 4 show the relationship between the sintering temperature when sintering the alloy according to the present invention and the wear resistance, radial crushing strength, and metallographic structure of the obtained sintered material. in,
Combining these items, it can be seen that the sintering temperature is preferably centered around 1200°C and within a range of 20°C around it.

The second invention adds solid lubricating effect by infiltrating lead into the pores of the sintered material of the first invention, and is useful when the operating conditions of an internal combustion engine are particularly severe. be.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between friction speed and wear for samples with different hard phase contents, Figure 2 is a graph showing the relationship between hard phase content, wear and radial crushing strength, and Figure 3 is a graph showing the relationship between hard phase content and wear and radial crushing strength. FIG. 4 is a graph showing the results of the bench durability test, and a graph showing the influence of sintering temperature on the wear resistance, radial crushing strength, and metal structure of the sintered material, and a micrograph.

Claims (1)

[Claims] 1. CrO, 5-3%, Co1.3-5.7 by weight
H, Mo 0.2-2.4%, N i O, 1-2.
3%, Vo, 0.5~0.3%, C0.6~1.2%, and the balance of Fe, and the A alloy part 25~ has the following composition.
High-temperature wear resistance characterized in that at least one of the following hard phase C and hard phase is dispersed in a ratio of 3 to 15% in a matrix in which 75% to 25% of alloy portions 75 and B are present in patches. Sintered alloy. A alloy B alloy Cr 2-4% Co 5.5-7.54M
o 0.2-0.4% NiO, 5-3%
VO, 2-0.4% Mo 0.5-3%
CO, 6~1.2chi CO,. 6-1.2% Fe, balance Fe, remainder hard phase C: 45-60% Co-33-36% Mo-8i
Hard phase D = 45-60% Fe-33-36% Mo-8i
2 Cr065-3%, Co1.3-5.7 in weight ratio
H, Mo0.2-2.4%, N i O, 1-2.3
%, Vo, 05 to 0.3%, C0, 6 to 1.2%, and the balance of Fe, and the A alloy part 25 to 7 has the following composition.
A sintered steel in which at least one of the following hard phases C and hard phases is dispersed in a matrix of 3 to 15 degrees in a matrix in which 5 degrees and B alloy portions of 75 to 25 degrees exist in patches, A high-temperature wear-resistant sintered alloy whose pores are impregnated with lead. A alloy B alloy Cr 2-4% Co 5.5-7.5% Mo
0.2-0.4% NiO, 5-3%V
O, 2~0.4% Mo 0.5~3% CO96~
Section 1.2 C0.6~1.2%Fe Balance Fe
Remaining hard phase C: 45-60% Co-33-36% Mo-8
i Hard phase D = 45-60% Fe-33-36% Mo-8
i