JPH04338A - Copper-base sintered alloy excellent in wear resistance at high temperature - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 room temperature and high temperature, especially at high temperature, and is used for valve guide members of internal combustion engines or turbochargers. This bearing relates to a copper-based sintered alloy used for sliding members such as members.

[Conventional technology]

Conventionally, iron-based materials such as chilled castings, Cu-28 (by weight), have been used as members for manufacturing various mechanical parts of internal combustion engines.
%Zn-6%A, copper-based alloy having a typical composition of Q,
or Cu-1 shown in JP-A No. 1-42537
Copper-based sintered alloys are known in which a solid lubricant such as graphite is added to a typical composition of 0%5n-0, 3%P-3%N+.

[Problem to be solved by the invention]

However, as the output of modern internal combustion engines has increased, the temperature inside the combustion chamber has become higher than before. Turbocharger bearings are also exposed to higher temperatures than before. The wear resistance and seizure resistance of such sliding members decrease as the temperature increases, and
There is a significant difference between the temperature inside the combustion chamber of an internal combustion engine and the temperature outside, and sliding members installed from the inside to the outside of the combustion chamber of an internal combustion engine, such as valve guides or turbocharger bearings, also The exposed parts in the vicinity are exposed to higher temperatures than before, and in particular, the diameter of the valve guide near the combustion chamber expands even more than before due to thermal expansion, which creates a gap between the valve guide and the valve. As a result, (a) engine oil will crowd into the combustion chamber and will no longer meet the standards set by exhaust gas regulations; (b) if a gap is created between the valve guide and the valve, the valve guide will not function properly. There were also problems such as the valve vibrating during operation, resulting in a decline in valve function.

To solve these problems, iron-based materials such as the above-mentioned chill castings,
Because of their low thermal conductivity, low seizure resistance, and low conformability, when used as sliding members that are partially exposed near the combustion chamber of an internal combustion engine, such as valve guides or turbocharger bearings, Due to its low thermal conductivity, a large amount of thermal expansion occurs in the partially exposed portion near the combustion chamber of the internal combustion engine, which is undesirable because it creates a gap with the valve or bearing. Also, Cu-28%Zn6%A
A copper-based alloy with a typical composition of Heat resistance is insufficient, and since there are no pores, seizure resistance and conformability are also insufficient. Therefore, copper-based sintered alloys to which solid lubricants such as graphite are added have come to be used. Although these copper-based sintered alloys have few problems with thermal conductivity, seizure resistance, and conformability, , lacks wear resistance and heat resistance.

[Means to solve the problem]

Therefore, in order to solve the above-mentioned problems, the present inventors have developed materials for valve guides or turbochargers that have excellent wear resistance, seizure resistance, and thermal conductivity at room and high temperatures, especially at high temperatures. As a result of research conducted to obtain a copper-based sintered alloy that can be used as a component, the bearing was found to contain 10 to 40% by weight of Zn, with the remainder consisting of Cu and unavoidable impurities. , boride having an average particle size of 1 to 1 otIn is uniformly dispersed in an amount of 1 to 15% by volume, and the number of pores is 1 to 15% by volume.
The copper-based sintered alloy, which has a structure distributed by ~15% by volume, has excellent thermal conductivity and excellent seizure resistance and wear resistance at high temperatures. Or, when the bearing of a turbocharger is used as a member, especially when this copper-based sintered alloy is used as a valve guide member of an internal combustion engine, the valve guide has excellent thermal conductivity, so it is placed near the combustion chamber of the internal combustion engine. Even if the valve guide is heated to a high temperature in It was found that there was no deterioration in function as a valve guide as shown in (a) and (b), and the valve guide exhibited excellent effects over a long period of time.

The present invention has been made based on this knowledge, and the copper-based sintered alloy of the present invention contains 1 boride having an average grain size of 1 to 10 μs in the base material having the above composition.
~15% by volume, uniformly distributed, 1~15% by volume of pores
It is characterized by a copper-based sintered alloy having a distributed structure.

The boride is at least Ti boride, Zr boride, C
It is necessary to contain one or more types of rborides.

Next, the reason why the borides 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 at high temperatures, and has the effect of improving seizure resistance at high temperatures and wear resistance at room and high temperatures. If the content exceeds 40% by weight, the thermal conductivity will decrease and the seizure resistance at high temperatures will decrease.

Therefore, the Zn content was set at 10 to 40% by weight.

(b) Void Vacancies are distributed on the sliding surface and play the role of oil reservoirs, contributing to improvements in seizure resistance and conformability due to the deformation of the pores at high temperatures, but 1% by volume On the other hand, if the amount is less than 15% by volume, the strength will not only decrease, but also the heat resistance will deteriorate due to the decrease in thermal conductivity, and the seizure resistance at high temperatures will deteriorate. This is not preferable because it also reduces wear resistance.

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

(c) Boride Boride is uniformly dispersed in the copper-based sintered alloy base of this invention and suppresses the growth of adhesive parts at room temperature and high temperature, thereby improving wear resistance and reducing thermal deformation. It has the effect of improving wear resistance at high temperatures by preventing and improving heat resistance, but it is not effective when the average particle size is less than 1 tm and 1% by volume, and on the other hand, when the average particle size exceeds 10 tm, it is coarse. If the content exceeds 15% by volume, the strength and toughness of the alloy will decrease, and the aggressiveness of the alloy will increase, which is undesirable. Therefore, the boride was determined to have an average particle size of 1 to 1 oun and a total of 1 to 15% by volume. The boride uniformly dispersed in the copper-based sintered alloy base of this invention is at least T
It is necessary to use one or more types of boride (I), boride (Z), and boride (C).

Note that the copper-based sintered alloy of the present invention may contain P, Mg, Sn, and Pb as inevitable impurities;
If the total content is 1.5% or less, the alloy properties are not impaired in any way, so the content can be tolerated.

Contains Zn of this invention: 10 to 40% by weight, and the remainder is C.
It has a structure in which borides having an average grain size of 1 to 10 um are uniformly dispersed in a volume percent of 1 to 15% in a Cu alloy matrix having a composition consisting of u and inevitable impurities, and pores are distributed in a range of 1 to 15 volume%. To produce a copper-based sintered alloy, a Cu-Zn alloy powder obtained by water atomizing a Cu-Zn master alloy in which boride is dispersed in a Cu-Zn alloy in advance is used as a raw material powder. This raw material powder has fine borides firmly bound in the matrix. Alternatively, a mixed powder obtained by mixing a Cu-Zn alloy powder in which fine boride is firmly bonded to a normal Cu-Zn atomized powder may be used.

Furthermore, a boride with an average particle size of 10 mm or less is added to and mixed with a commonly used fixed lubricant such as zinc stearate, and the resulting mixed powder is mixed with a normal Cu-Zn atomized powder.
The copper-based sintered alloy of the present invention can also be obtained by molding and pressing this into a green compact and molding this green compact. Alternatively, wet mixing may be performed using an organic solvent such as acetone or alcohol.

〔Example〕

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

First, a Cu-Zn master alloy in which borides with an average grain size of 1 to 101 m are uniformly dispersed is prepared, and this Cu-Zn master alloy is water atomized to obtain a composition that is almost the same as the Cu-Zn master alloy described above. These raw material powders were press-molded into a green compact at a predetermined pressure within the range of 5 to 7 tons/cd, and heated to 85% in hydrogen gas with a dew point of -0°C to -30°C.
Sintering is carried out at a predetermined temperature within the range of 0 to 950°C for 1 hour, and then sintered at a predetermined temperature within the range of 300 to 600°C as necessary to control the amount of pores.
After holding for a minute, by applying pressure again, the Cu-based sintered alloys 1 to 19 of the present invention and the comparative Cu-based sintered alloys 1 to 9 having the pore amount and boride average particle size shown in Table 1 were prepared. Vertical: 10m 111% Width: 10mm, length = 4
A block with dimensions of 5 mm was made.

Furthermore, TI boride, Zr boride, and Cr boride having an average particle size of 5 nm are blended into a normal Cu-Zn alloy atomized powder, mixed, and press-molded to form a green compact. Made of sintered Cu-based sintered alloy of the present invention 20 to 22, length = 10 mm, width = 10 mm, length: 45 mm
A block with the dimensions was fabricated.

Cu-based sintered alloys 1 to 2 of the present invention produced in this way
The thermal conductivities of blocks consisting of Comparative Cu-based Sintered Alloys 1 to 2 and Comparative Cu-based Sintered Alloys 1 to 9 were measured, and the results are shown in Table 1. The above comparative Cu-based sintered alloys 1 to 9 are those in which any of the component content, boride average particle size, or pore content is out of the scope of the present invention (marked with a ridge in Table 1). ).

On the other hand, 5U, which is commonly known as a valve material for internal combustion engines, was used as a partner material for the block-on-ring type wear test.
H3 steel material, outer diameter: 40mm 1 inner diameter: 30■■, thickness:
A ring having dimensions of 15 m+s was made, and using the above blocks and rings, as shown in Fig. 1, block 1 was assembled so as to be in contact with ring 2, and refrigeration oil was applied as lubricant around ring 2. After that, block 1
A load of 2 kg was applied to the ring 2, and the ring 2 was rotated at a sliding speed of 1.2 m/sec in an atmosphere at room temperature and temperature of 2600°C until the coefficient of friction suddenly increased and seizure was determined. A block-on-ring type wear tester was used, which continued to rotate and measured the time until seizure occurred and the amount of wear on block 1 at the time of seizure, as well as observing the surface condition of ring 2. Accelerated wear tests were conducted and the measured values and observations are shown in Table 1. The observation results of the ring surface are shown in Table 1 as 0 when the surface of the ring 2 after the test is substantially smooth, Δ when it is a rough surface, and X when it is an adhesive surface.

〔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. 22 have excellent thermal conductivity and much better wear resistance and seizure resistance than conventional Cu-based prepared alloys, and as seen in comparative Cu-based sintered alloys 1 to 9. However, if any of the constituent components, boride average particle size, or pore content falls outside the scope or conditions of the present invention, the thermal conductivity, wear resistance at high temperatures, seizure resistance, or attack resistance against others may deteriorate. It is clear that at least one of these properties 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 can withstand exposure 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 the valve guide can be used at high temperatures. 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.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a block-on-ring type wear test method. 1...Block, 2...Su°ng.

Claims (2)

[Claims] (1) Boride having an average grain size of 1 to 10 μm: 1 to 15 volume % is uniformly distributed in a Cu alloy matrix having a composition of Zn: 10 to 40 weight %, and the remainder consisting of Cu and unavoidable impurities. A copper-based sintered alloy having excellent wear resistance at high temperatures and having a structure in which pores are dispersed in pores and have a distribution of 1 to 15% by volume. (2) The boride includes at least one or more of Ti boride, Zr boride, and Cr boride, and the total amount of these borides is 1 to 15% by volume. A copper-based sintered alloy having excellent wear resistance at high temperatures according to claim 1.