JPH04340A - Copper-base sintered alloy excellent in wear resistance at high temperature - Google Patents

Abstract

PURPOSE:To obtain a Cu-base sintered alloy for a bearing excellent in wear resistance at a high temp. and seizing resistance by subjecting the powder of a Cu-Zn alloy in which specified Mo-Si series intermetallic compounds are uniformly dispersed to compacting and sintering. CONSTITUTION:By volume, 1 to 15% of at least one kind among the fine powder of Mo-Si series intermetallic compounds such as Mo-Fe-Si, Mo-Ni-Si and Mo-Co- Si having 1 to 50mum average grain size is added to the molten metal of a Cu-Zn alloy contg. 10 to 40wt.% Zn, and this mixture is thereafter pulverized by a water atomizing method. This Cu-Zn alloy powder uniformly contg. the fine powder of the Mo-Si series intermetallic compounds is compacted and is thereafter sintered. The Cu-base sintered alloy in which fine pores performing the role of a lubricating oil sump are present in the ratio of 1 to 15vol.% and excellent in wear resistance at a high temp. and seizing resistance as a bearing material can be obtd.

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, in terms of weight percent, have been used as members for manufacturing various mechanical parts of internal combustion engines.
Copper-based alloy having a typical composition of 8% Zn-6% Al,
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. etc. are also exposed to higher temperatures than before.

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 cylinder, such as valve guides or turbocharger bearings, are exposed to higher temperatures than before, and in particular, the diameter of the valve guide near the combustion chamber is subject to thermal expansion. This causes the valve to expand further than before, creating a gap between the valve guide and the valve, which results in (a)
(b) If there is a gap between the valve guide and the valve, the valve guide will not function properly and the valve will vibrate during operation. However, there were also problems such as 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 the 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 1 is used, but this copper-based alloy lacks wear resistance and heat resistance as a component for valve guides or turbocharger bearings, and it also has pores. do not have! 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 conducting research to obtain a copper-based sintered alloy that can be used as a component, the bearing is made of a Cu alloy base containing Zn: 10 to 40% by weight, with the remainder consisting of Cu and unavoidable impurities. , M having an average particle size of 1 to 50 m.
A copper-based sintered alloy with a structure in which o-5i intermetallic compounds are uniformly dispersed in an amount of 1 to 15% by volume and pores are distributed in a range of 1 to 15% by volume has excellent thermal conductivity and is resistant to seizure at high temperatures. Therefore, when this copper-based sintered alloy is used as a component for the valve guide of an internal combustion engine or the bearing of a turbocharger, When used as a component, 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 valve guide portion exposed near the combustion chamber will escape to the outside. The knowledge that the temperature does not reach high temperatures, therefore 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. I got it.

This invention was made based on this knowledge, and the average particle size: 1 to 50
- It is characterized by a copper-based sintered alloy having a structure in which MO-8i intermetallic compounds within the range of 1 to 15% by volume are uniformly dispersed and vacancies are distributed by 1 to 15% by volume. .

The above Mo-5i intermetallic compound is MoFe51゜M
At least one or two or more of oNiSi and MoCo5I.

Next, the reason why the Mo-5i intermetallic compound and the pores of the copper-based sintered alloy 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.It also improves adhesion resistance, seizure resistance at high temperatures, and resistance at room and high temperatures. It has the effect of improving wear resistance, but if it is less than 1% by weight, it has no effect. On the other hand, if it is contained in more than 15% by weight, the thermal conductivity decreases and the seizure resistance at high temperatures decreases. It becomes like this.

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 deformation of the pores especially at high temperatures, but 1% by volume If it is less than I55 capacity, the effect cannot be obtained, and on the other hand, if it is distributed more than I55 capacity, not only the strength will decrease, but also the heat resistance will deteriorate due to the decrease in thermal conductivity, and the seizure resistance at high temperatures will decrease. However, it 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) Mo-S I-based intermetallic compound The Mo-5i-based intermetallic compound is uniformly dispersed in the copper-based sintered alloy base of the present invention to suppress the growth of adhesive parts at room temperature and high temperature. It has the effect of improving wear resistance, preventing thermal deformation, and improving wear resistance at high temperatures by improving heat resistance, but it is not effective when the average particle size is less than 1 and 1% by volume. On the other hand, the average particle size is 5ot! If the content exceeds n and becomes coarse, or 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 Mo-5i intermetallic compound has an average particle size of 1 to 51 ha++ and a total of 1 to 5% by volume. The Mo-5i intermetallic compound uniformly dispersed in the copper-based sintered alloy base of this invention includes MoFeSi,
MoNiSi.

One or more types of M o Co S I.

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.

Contains Zn of this invention: 10 to 40% by weight, and the remainder is C.
MO8i-based intermetallic compounds having an average grain size of 1 to 50 nodes are uniformly dispersed in a Cu alloy matrix having a composition consisting of U and inevitable impurities, and 1 to 15% by volume, and 1 to 15 pores are dispersed.
In order to produce a copper-based sintered alloy having a structure with a volume % distribution, a Cu-Zn alloy in which a Mo-5i intermetallic compound having an average particle size of 1 to 50 ta is dispersed in advance is used.
Cu- obtained by water atomizing n master alloy
Zn alloy powder is used as the raw material powder. In this raw material powder, fine Mo-5i intermetallic compounds are firmly bound in the matrix. Alternatively, a mixed powder obtained by mixing a Cu-Zn alloy powder in which a fine Mo-5i intermetallic compound is firmly bonded to a normal Cu-Zn atomized powder may be used.

Furthermore, a Mo-5i intermetallic compound with an average particle size of 50 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. , press this to form a green compact,
The copper-based sintered alloy of the present invention can also be obtained by 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, Mo-8i intermetallic compound powder + MoFeSi powder, MoN15f powder, and MoCoSi powder with an average particle size within the range of 1 to 50-50 are prepared, and these Mo
-5i-based intermetallic compound powder, Zn: 10 to 40% by weight
Mc)-8i based intermetallic compound:
MoFe5I.

A Cu-Zn master alloy in which one or two of MoNiSt and MoCoSi are uniformly dispersed is prepared, and this Cu-Zn master alloy is water-atomized to produce a raw material having almost the same composition as the above-mentioned Cu-Zl master alloy. Make a powder,
These raw material powders are press-molded into a compact at a predetermined pressure within the range of 5 to 7 tons/c-, and the dew point is 20℃ to -30''.
Sintering is carried out in hydrogen gas at a temperature of 850 to 950 degrees Celsius for one hour, and the temperature is 300 to 600 degrees Celsius as necessary to control the amount of pores. The Cu-based sintered alloys 1 to 1 of the present invention having the pore volume and Mo-8i intermetallic compound average particle size shown in Table 1 were prepared by holding at a predetermined temperature for 1 minute and then repressurizing.
25 and comparative Cu-based sintered alloys 1 to 10, blocks having dimensions of vertical: 10 m + *, width: 1 Onns and length: 40 mm were produced.

Furthermore, a Mo-5i intermetallic compound: MoFeSi with an average particle size of 25 was added to the normal Cu-Zn alloy atomized powder.
, MoNiSi, and MoCoSi, mix them, press-form them to form a green compact, and sinter this green compact to produce a freshly prepared product made of comparative Cu-based sintered alloys 26 to 30. A block having dimensions of: 10+n, width: 10 length, and length: 401 was produced.

Cu-based sintered alloys 1 of the present invention prepared in this manner
The thermal conductivities of blocks consisting of No. 30 and Comparative Cu-based sintered alloys 1 to 10 were measured, and the results are shown in Table 1. The above comparative Cu-based sintered alloys 1 to 10 have a component content of Mo-
Either the average particle size or the pore content of the 5i-based intermetallic compound is outside the scope of the present invention (indicated by a brown mark 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 outer diameter: 40m+s, inner diameter: 30mm, thickness:
A ring having a size of 15 mm 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 engine 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 = 600°C, and the ring 2 was rotated until seizure occurred and the coefficient of friction rapidly increased. Accelerated wear was then carried out using a block-on-ring type wear tester that measured the time until seizure occurred, the amount of wear on block 1 at the time of seizure, and observed the surface condition of ring 2. 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 △ when the surface of the ring 2 after the test is substantially smooth, when it is an O1 rough surface, and as × 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. 30 have excellent thermal conductivity and much better wear resistance and seizure resistance than conventional Cu-based sintered alloys, and are also seen in comparative Cu-based sintered alloys 1 to 10. As such, if any of the constituent components, the average particle size of the Mo-3i gold metal compound, and the amount of pores deviates from the scope or conditions of the present invention, the thermal conductivity, wear resistance at high temperatures, and seizure resistance will deteriorate. It is clear that at least one of the following characteristics, sexual or aggressiveness, will be 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 is suitable for 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, and there is no leakage of engine oil. It can be used satisfactorily as a structural member of a high-output 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 drawings]

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

Claims (2)

[Claims] (1) Mo-Si based intermetallic compound having an average particle size of 1 to 50 μm in a Cu alloy matrix having a composition of Zn: 10 to 40% by weight, and the remainder consisting of Cu and unavoidable impurities: 1 to 15% by volume is uniformly dispersed, and the number of pores is 1 to 1.
A copper-based sintered alloy with excellent wear resistance at high temperatures, characterized by having a structure with a 15% volume distribution. (2) The Mo-Si based intermetallic compound is MoFeSi
2. The copper-based sintered alloy having excellent wear resistance at high temperatures according to claim 1, wherein the total amount of at least one or two or more of , MoNiSi, and MoCoSi is 1 to 15% by volume.