JPH03232939A - Copper-base sintered alloy excellent in wear resistance at high temperature - Google Patents

Abstract

PURPOSE:To improve the thermal conductivity and wear resistance at a high temp. in a copper-base sintered alloy by uniformly dispersing oxides having specified grain size into a Zn-Al contg. Cu alloy base and distributing a specified amt. of void therein. CONSTITUTION:By volume, 1 to 15% oxides having 1 to 10mum average grain size are uniformly dispersed into a Cu alloy base constituted of, by weight, 5 to 35% Zn, 0.1 to 3% Al and the balance Cu with inevitable impurities to form a Cu-base sintered alloy. Furthermore, its structure is formed into a one in which 1 to 15vol.% are distributed. As the oxides, at least one or more kinds among Al oxides, Si oxides, Zr oxides, Cr oxides and W oxides are used, and the total is regulated to 1 to 15vol.%. This Cu-base sintered alloy has excellent thermal conductivity, wear resistance at a high temp., seizing resistance or attackability on a mate, so that it can satisfactorily correspond as a structural member of a high output internal combustion engine.

Description

Detailed Description of the Invention [Field of Industrial Application] This invention relates to a copper-based sintered alloy that has excellent wear resistance at high temperatures, and is particularly applicable to copper-based sintered alloys for valve guides of internal combustion engines or bearings of turbochargers. It relates to sintered alloys.

[Conventional technology]

BACKGROUND ART Conventionally, a copper-based alloy or sintered alloy having a typical composition of Cu-28%Zn6%A11 in weight percent has been used as a member for manufacturing various mechanical parts for internal combustion engines. Copper-based sintered alloys in which oxide powder is dispersed are also known, but the oxides dispersed in the matrix of this alloy are
Average particle size: It was a coarse oxide with an average particle size of 20 or more (20 to 70 t!n).

[Problem to be solved by the invention]

In recent internal combustion engines, as the output has increased, the temperature inside the combustion chamber has become higher than before. Therefore, the sliding members that are partially exposed near the combustion chamber, such as the valve guide, are also higher than before. exposed to higher temperatures. The wear resistance and seizure resistance of such sliding members decrease as the temperature increases, and a significant difference occurs between the temperature inside the combustion chamber of the internal combustion engine and the temperature outside. Sliding members attached to the engine, such as valve guides, are also exposed to higher temperatures than before in the vicinity of the combustion chamber, and the diameter of the valve guide in the vicinity of the combustion chamber is expanded further than before due to thermal expansion. As a result, a gap is created between the valve guide and the valve, which may cause (a) engine oil to crowd into the combustion chamber, which will no longer meet the standards set by exhaust gas regulations, or (b) the valve to vibrate during operation, causing the valve to become damaged. Problems also arose, such as the guide's function not working sufficiently and the valve's function also deteriorating.

[Means to solve the problem]

Therefore, the present inventors recognized that the above-mentioned problems could be solved by using a material for the valve guide that has excellent wear resistance and seizure resistance at room temperature and high temperature, and excellent thermal conductivity. As a result of research based on , average particle size: 1-10. 1 to 15% by volume of the oxide having a size of
The copper-based sintered alloy, which has a structure with a 15% volume distribution, has excellent thermal conductivity and excellent seizure resistance and wear resistance at high temperatures, and this copper-based sintered alloy has been used as a valve guide for internal combustion engines. In this case, the valve guide has excellent thermal conductivity, so even if it is heated to a high temperature near the combustion chamber of an internal combustion engine, the heat in the exposed part of the valve guide near the combustion chamber escapes to the outside and does not reach a high temperature. First, we have obtained the knowledge that the diameter of the valve guide does not expand due to thermal expansion, and the function as a valve guide does not deteriorate as shown in (a) and (b) above, and it exhibits excellent effects over a long period of time. be.

The present invention was made based on this knowledge, and the copper-based sintered alloy of the present invention has an oxide having an average particle size of 1 to IO- in the base having the above composition. ~
The copper-based sintered alloy has a structure in which pores are uniformly dispersed by 15% by volume and pores are distributed by 1 to 15% by volume, and has excellent wear resistance at high temperatures.

The above oxides include at least HeΩ oxide, S1 oxide, Z
It is necessary to contain one or more of r oxide, C oxide, and W oxide.

Next, the reason why the oxides and pores of the copper-based sintered alloy for a valve guide of the present invention are limited as described above will be explained.

(a) Zn Zn forms a matrix together with Cu and has the effect of improving the strength and toughness of the alloy, and also combines with oxygen to form an oxide, improving seizure resistance at high temperatures and at room and high temperatures. It has the effect of improving wear resistance, but if it is less than 5% by weight, it has no effect, while if it is contained in more than 35% by weight, the thermal conductivity decreases and the seizure resistance at high temperatures decreases. become. Therefore, the Zn content is 5
It was set at ~35% by weight.

(b) Al Al not only forms a matrix with high strength and toughness together with Cu and Zn, but also combines with oxygen to form an oxide, which improves seizure resistance at high temperatures and resistance at room and high temperatures. It has the effect of improving wear resistance, but its content is 0.
．． If the content is less than 1% by weight, there is no effect, while if the content exceeds 3% by weight, the thermal conductivity and seizure resistance at high temperatures will decrease, which is not preferable.

Therefore, the content of Al was set at 0.1 to 3% by weight.

(c) Void Vacancies are distributed on the sliding surface and have the effect of improving seizure resistance, especially at high temperatures, but this effect cannot be obtained when the volume is less than 1% by volume. When distributed in large amounts, not only the strength decreases, but also heat resistance deteriorates due to a decrease in thermal conductivity, seizing resistance at high temperatures decreases, and wear resistance also decreases, which is not preferable.

Therefore, the distribution amount of pores was determined to be 1 to 15% by volume.

(d) Oxide The oxide is uniformly dispersed in the copper-based sintered alloy base material of the present invention, improves wear resistance at room temperature and high temperature, and improves wear resistance at high temperature by improving heat resistance. If the average grain size is less than 1tHr1 or less than 1% by volume, it will not be effective.On the other hand, if the average grain size becomes coarser than 10% or more than 15% by volume, the strength of the alloy will be improved. This is undesirable because it reduces toughness and increases the aggressiveness of the opponent. Therefore, the average particle size of the oxide was determined to be 1 to 10 parts, and the total thereof was determined to be 1 to 15% by volume. The oxides uniformly dispersed in the copper-based sintered alloy base of the present invention include at least AΩ oxide, St oxide, Z” oxide, Cr oxide,
and W oxide.

The copper-based sintered alloy of the present invention may contain P, Mg, Sn, and Pb as unavoidable impurities, but if the total content is 1.5% or less, the alloy properties will not be impaired in any way. Since it is not a substance that can be used as a substance, its content can be tolerated.

Zn of this invention: 5 to 35% by weight and AΩ: 0.1 to
3% by weight, with the remainder consisting of Cu and unavoidable impurities, in which 1 to 15% by volume of oxides having an average grain size of 1 to 10 mm are uniformly dispersed and 1 to 1 pores are present. In order to produce a copper-based sintered alloy having a structure distributed by ~15% by volume, an oxide is preliminarily added to a Cu-Zn-AΩ alloy.
Cu-Zn alloy or Cu-AJ) obtained by water atomizing a mother alloy dispersed in the alloy
ZnAΩ alloy powder, Cu-Zn alloy powder, and Cu-
AΩ alloy powder is used as the raw material powder. This raw material powder has fine oxides firmly bound in the matrix. In addition, Cu-Zn in which fine oxides are firmly bonded in the above matrix
A mixed powder obtained by mixing -Al alloy powder with normal Cu-Zn-AΩ atomized powder may also be used. but,
Oxide powder with an average particle size of 10 μm or less is added to and mixed with ordinary CuZn-A, Ill atomized powder, the obtained mixed powder is press-molded to form a green compact, and this green compact is sintered. However, the copper-based sintered alloy of this invention cannot be obtained. Average particle size of ordinary Cu-Zn-AJII atomized powder:
If 10 or less oxide powders are added and mixed, it is difficult to mix them uniformly because the oxide powders are fine powders, and even if this mixed powder is press-formed and sintered, the oxide powders will be empty. This is because they aggregate in the pores or exist non-uniformly in contact with the pores, and tend to fall off, causing problems in wear resistance and attackability, as well as being easily segregated.

Therefore, the average particle size of the oxides dispersed in the matrix of conventional copper-based sintered alloys was 20 mm or more.

〔Example〕

Next, the copper-based sintered alloy of the present invention will be specifically explained with reference to Examples.

First, a Cu-Zn-A & master alloy made of uniformly dispersed oxides is prepared, and this Cu-Zn-1 master alloy is water-atomized to create a composition that is almost the same as the Cu-Zn-A, IJ master alloy mentioned above. These raw material powders were press-molded into a green compact at a predetermined pressure within the range of 5 to 7 tons/cJ, and then heated at 80°C in hydrogen gas with a dew point of 0°C to -30°C.
Sintering is carried out under conditions of holding at a predetermined temperature within the range of 0 to 950°C for 1 hour, and then in order to control the amount of pores,
If necessary, after holding the temperature at a predetermined temperature within the range of 300 to 600°C for 1 minute and repressurizing it, the material having the component composition, amount of pores, and average oxide particle size shown in Table 1 can be prepared. Invention Cu-based sintered alloys 1 to 38 and comparative Cu-based sintered alloys 1 to 11 were produced.

Furthermore, the usual Cu-Zn-Aj! Average particle size in alloy atomized powder: 5mm A, 17 oxide, St oxide,
Zr oxide, Cr oxide, and W oxide were blended, mixed, and press-molded to form a green compact, and this green compact was sintered to produce Comparative Cu-based sintered alloys 12 to 16. The above Comparative Cu-based sintered alloys 1 to 1G are all those in which the content of any one of the constituent components, average oxide particle size, pore content, or manufacturing method is outside the scope of the present invention (No. In Table 1, it is indicated with 0 * mark).

Cu-based sintered alloys 1 to 3 of the present invention produced in this way
8 and comparative Cu-based sintered alloys 1 to 16, the diameter:
1.5m pin, and outer diameter: 14mm, inner diameter near m
m, length: A pipe with dimensions of 40+nm was made and the electrical conductivity was measured to evaluate its thermal conductivity,
The results are shown in Table 1, and the following wear tests were conducted using the above pins and pipes.

Wear Test I A chromium-plated SUH disc was prepared as a mating material, and while heating the disc to 540°C with a burner from the back side of the disc, the disc was rotated at a circumferential speed of 1 and 7 m/see, while the diameter of the disc was 1. .5m pin pressing load:
6kg was pressed against the above disk, and without dripping engine oil, the disk was allowed to slide for a sliding distance of 10km, and the presence or absence of seizing was confirmed by the change in generated torque using a torque meter, and the presence or absence of abnormal wear of the pins was confirmed. The results were confirmed and shown in Table 1.

1 Wear test ■ Diameter of SUH material treated with tuftride as the mating material:
A round bar with a length of 6.9+++ m and a length of 60 mrn was prepared.

Insert the round bar that is the mating material into the hole of the pipe that is the sample, heat one end of the round bar that is the mating material with a burner, and set the atmospheric temperature at one end to 520°C. Press the bar with a load of 5 kg, 7.5W-4
A wear test was performed by stroking the above round rod in the axial direction at 10 mm and 3000 times/min for 1 hour while dropping 0.0 oil, and observing the amount of wear, the presence or absence of seizure, and the surface condition of the mating material. The results are shown in Table 1.

Regarding the surface condition of the mating material, those with no scratches were marked with 01, those with scratches due to partial seizure were marked with Δ, and those with wear scratches on the surface were marked with ×. .

〔Effect of the invention〕

From the results shown in Table 1, Cu-based sintered alloys 1 to 1 of the present invention
All of No. 38 have excellent thermal conductivity compared to conventional Cu-based sintered alloys, and also have far superior wear resistance and seizure resistance, and are superior to comparative Cu-based sintered alloys No. 1 to 16. As described above, if any of the constituent components, average oxide particle size, pores, and manufacturing method are outside the scope or conditions of this invention, the thermal conductivity, abrasion resistance at high temperatures, and oxidation resistance may deteriorate. It is clear that at least one of the following qualities will be inferior: or the opponent's aggressiveness.

As mentioned above, the Cu-based sintered alloy of the present invention has thermal conductivity, wear resistance at high temperatures, seizure resistance, or attack resistance, so it cannot be exposed to high temperatures associated with high output. Even when used as a structural member of an internal combustion engine, especially a valve guide member, the temperature of the valve guide near the combustion chamber does not increase, the diameter of the valve guide does not increase, there is no leakage of engine oil, and high-output internal combustion It can be used satisfactorily as a structural member of an engine, especially a valve guide, and in practical use, it exhibits excellent performance over a long period of time, resulting in excellent industrial effects.

5

Claims (2)

[Claims] (1) Zn: 5 to 35% by weight, Al: 0.1 to 3% by weight, in a Cu alloy base having a composition with the remainder consisting of Cu and unavoidable impurities, and having an average grain size of 1 to 10 μm. A copper-based sintered alloy with excellent wear resistance at high temperatures, characterized by having a structure in which oxides: 1 to 15% by volume are uniformly dispersed and pores are distributed by 1 to 15% by volume. (2) The above oxide contains at least one or more of Al oxide, Si oxide, Zr oxide, Cr oxide, and W oxide, and the total number of these oxides is 1 to 1.
2. The copper-based sintered alloy having excellent wear resistance at high temperatures according to claim 1, wherein the content is 15% by volume.