JPH03232940A - 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-Mn contg. Cu alloy base and distributing a specified amt. of 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, 0.1 to 3% Mn 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.% void 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 sufficiently 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%A,Q 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
It was a coarse oxide with an average particle diameter of 20 μs or more (20 to 70 p).

[Problem that the invention attempts to solve]

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 higher the temperature of such sliding members, the lower their wear resistance and seizure resistance.
In addition, there is a significant difference between the temperature inside the combustion chamber of the internal combustion engine and the temperature outside, and sliding members such as valve guides installed from the inside to the outside of the combustion chamber of the internal combustion engine are exposed near the combustion chamber. (a) (b) The valve vibrates during operation, preventing the valve guide from working properly and reducing valve function. There were also problems.

[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 conducted on the basis of In the Cu alloy matrix having the composition, 1 to 15 volume % of oxides having an average grain size of 1 to 10 IErl are uniformly dispersed, and the pores are 1 to 15% by volume.
A copper-based sintered alloy with a structure distributed by ~15% by volume has excellent thermal conductivity and excellent seizure resistance and wear resistance at high temperatures, and this copper-based sintered alloy is used as a valve guide for internal combustion engines. If the valve guide has excellent thermal conductivity, even if it is heated to a high temperature near the combustion chamber of the internal combustion engine, the heat in the valve guide portion exposed near the combustion chamber will escape to the outside and the high temperature will not occur. Therefore, the diameter of the valve guide does not expand due to thermal expansion, and it has been found that 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. It is.

The present invention has been made based on this knowledge, and the copper-based sintered alloy of the present invention has an average particle size of 1 to 10 oxides in the base having the above composition. ~
It is characterized by a copper-based sintered alloy having excellent wear resistance at high temperatures and having a structure in which vacancies are uniformly distributed at 15% by volume and 1 to 15% by volume.

The above oxides include at least AΩ oxide, Sj oxide, Z
It is necessary to contain one or more of r oxide, Cr 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
The content was set at 5 to 35% by weight.

(b) A, Q A, Q form a matrix with high strength and high toughness together with Cu and Zn, and also combine with oxygen to form an oxide, which improves seizure resistance at high temperatures and resistance to corrosion at room and high temperatures. It has the effect of improving the wear resistance under the surface, but if the content is less than 0.1% by weight, it has no effect, while if the content exceeds 3% by weight, the thermal conductivity decreases. At the same time, the seizure resistance at high temperatures decreases, which is not preferable.

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

(c) Mn Mn forms a solid solution in the matrix and has the effect of improving the strength of the alloy, but if its content is less than 0.1% by weight, the desired effect cannot be obtained; If the content exceeds this amount by weight, the heat resistance will decrease, and the seizure resistance and abrasion resistance at high temperatures will decrease, which is not preferable. Therefore, M
The content of n was set at 0.1 to 3% by weight.

(d) Void Void is distributed on the sliding surface and has the effect of improving seizure resistance, especially at high temperatures, but this effect cannot be obtained at less than 1% by volume; If there is too much distribution, not only the strength will decrease, but also the heat resistance will deteriorate due to the decrease in thermal conductivity, and the seizure resistance under high temperature will decrease.
It is also undesirable because it reduces wear resistance.

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

(e) 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. However, if the average grain size is less than 1uy1 or less than 1% by volume, it is not effective.On the other hand, if the average grain size exceeds 10% or becomes coarser or exceeds 15% by volume, the strength of the alloy decreases. 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, and the total thereof was determined to be 1 to 15% by volume. The oxide uniformly dispersed in the copper-based sintered alloy base of this invention is at least A
It is necessary to use one or more of ρ oxide, Si oxide, Zr 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, AΩ: 0. ]~3
% by weight and Mn: 0.1 to 3% by weight, with the remainder consisting of Cu and unavoidable impurities, and 1 to 15% by volume of an oxide having an average grain size of 1 to 10 grains. In order to produce a copper-based sintered alloy having a structure in which pores are uniformly dispersed and distributed by 1 to 15% by volume, oxides are prepared in advance in Cu-ZnA, Q-Mn alloy, Cu-Zn alloy, C
Cu produced by water atomizing a mother alloy dispersed in a uAρ alloy, a Cu-Zn-Aρ alloy, a CuMn alloy, and a Cu-Zn-Mn alloy.
-Zn-AΩ-M1 alloy powder, Cu-Zn alloy powder, C
u-A, & alloy powder, Cu-Zn-AΩ alloy powder, C
U-Mn alloy powder and Cu-Zn-Mn alloy powder are used as raw material powders. This raw material powder has fine oxides firmly bound in the matrix. In addition, Cu-Zn-AΩM in which fine oxides are firmly bonded in the above matrix
You may use the mixed powder which mixed n alloy powder with the usual Cu-Zn-Ap-Ml atomized powder. However, if an oxide powder with an average particle size of 10 or less is added to and mixed with a normal Cu-Zn-Aρ-Mn atomized powder, the resulting mixed powder is press-molded to form a green compact, and this green compact is Even if sintered, the copper-based sintered alloy of the present invention cannot be obtained.

When an oxide powder with an average particle size of 10 or less is added to ordinary CuZn-A (1-Mn atomized powder) and mixed, it is difficult to mix uniformly because the oxide powder is a fine powder. Even when the powder is press-molded and sintered, the oxide powder either aggregates within the pores or exists mechanically non-uniformly in contact with the pores, and easily falls off, resulting in poor wear resistance and attack potential. This is because not only problems arise, but also the disadvantage of easy segregation.

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

〔Example〕

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

First, CuZn-A, Q in which oxides are uniformly dispersed
-Mn master alloy is prepared, and this Cu -Zn-Aρ-Mn
The above Cu-Zn-
A raw material powder with almost the same composition as the AΩ-Mn master alloy was prepared,
These raw material powders are press-molded into a green compact at a predetermined pressure within the range of 5 to 7 tons/c-, and the dew point is 06C to -30C.
Sintering is carried out at a predetermined temperature in the range of 800 to 950°C for 1 hour in hydrogen gas, and then sintered at a temperature in the range of 300 to 600°C as necessary to control the amount of pores. After holding at a predetermined temperature for 1 minute and repressurizing, the present invention C having the pore volume and oxide average particle size shown in Table 1 was obtained.
U-based sintered alloys 1-42 and comparative Cu-based sintered alloys 1-1
2 was produced.

Furthermore, A, Q oxides, Si oxides, and Z
R 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 13 to 17. Comparison C above
U-based sintered alloys 1 to 17 are all those whose content of any one of the constituent components, average oxide particle size, pore content, or manufacturing method are outside the scope of the present invention (Table 1). (indicated with *).

Cu-based sintered alloys 1 to 4 of the present invention produced in this way
2 and comparative Cu-based sintered alloys 1 to 17, the diameter:
1. A pipe with a 5 mm pin, an outer diameter of 14 mm, an inner diameter of 7 mm, and a length of 40 ynm was prepared. 1. Electrical conductivity was measured to evaluate its thermal conductivity, and the results were As shown in Table 1, the following wear test was conducted using the above pin and pipe.

Wear Test I A chromium-plated SUH disc was prepared as a mating material, and the disc was heated to 500°C with a burner from the back side of the disc and rotated at a circumferential speed of 1.6 m/sec, while the diameter of the disc was 1. .Press a 5mm pin against the above disc with a pressing load of 5kg, and slide it for a sliding distance of IOkm while dripping engine oil. Check the occurrence of seizure from the change in generated torque using a torque meter. Furthermore, the presence or absence of abnormal wear of the pins was confirmed, and the results are shown in Table 1.

Wear test ■ Diameter of SUH material treated with tuftride as mating material: f
A round bar with a length of 3.9 mm and a length of BO mm 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 480°C. A certain round bar was pressed with a pressing load of 5 kg, and while dropping 7.5W-40 oil, the above round bar was stroked in the axial direction at 1O + nm, 3000 times/min for 1 hour, and an abrasion test was performed to determine the amount of wear. Measurement, presence or absence of seizure, and surface condition of the mating material were observed, and the results are shown in Table 1.

Regarding the surface condition of the mating material, those with no scratches are marked with ○, those with some scratches due to seizure are marked with Δ, and those with wear scratches on the surface are marked with ×. did.

〔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. 42 have excellent thermal conductivity and much better wear resistance and seizure resistance than conventional Cu-based sintered alloys. As such, if any of the constituent components, average oxide particle size, pores, and manufacturing method deviate from the scope or conditions of this invention, the thermal conductivity, abrasion resistance at high temperatures, seizure resistance, or attack by opponents may deteriorate. It is clear that the quality of at least one of the following is inferior.

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 part, the temperature of the valve guide near the combustion chamber does not rise, therefore, the diameter of the valve guide does not increase, there is no leakage of engine oil, and high output is achieved. It can be used satisfactorily as a structural member of an internal combustion engine, especially as a valve guide, and in practical use, it exhibits excellent performance over a long period of time, resulting in excellent industrial effects.

Claims (2)

[Claims] (1) Zn: 5 to 35% by weight, Al: 0.1 to 3% by weight, Mn: 0.1 to 3% by weight, and the rest is Cu and inevitable impurities in a Cu alloy matrix. , an oxide having an average particle size of 1 to 10 μm: 1 to 15% by volume is uniformly dispersed, and has a structure in which pores are distributed by 1 to 15% by volume, and has excellent wear resistance at high temperatures. Copper-based sintered alloy. (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.