JPS5942065B2 - Sliding body with excellent wear resistance - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for producing a novel copper alloy sliding body with excellent wear resistance, and particularly to a current collector with excellent wear resistance as a sliding plate for a train pantograph. Concerning a method for manufacturing a sliding body.

[Background of the Invention] Conventionally, so-called bearing base metals such as copper-based alloys, tin-based alloys, lead-based alloys, aluminum-based alloys, iron-based alloys, and cadmium-based alloys have been used for bearings or mechanical sliding parts. However, these alone cannot provide a lubricating effect, so graphite, P
Contains a solid lubricant of low friction material such as b.

Taking the current collector pantograph sliding plate as an example, PB is used as a lubricant for iron-based alloys, and graphite is used for copper-based alloys.

Generally speaking, the main characteristics required for a sliding plate material are good conductivity and wear resistance, but in recent years, as electric cars have become faster and the amount of power collected has increased, there has been a growing demand for improvements in wear resistance and strength. It's here.

The amount of wear on sliding plates for electric vehicles increases as the operating conditions become more severe, such as as the speed of electric vehicles increases and the amount of collected power increases.

In order to meet these demands, copper-based alloys contain appropriate amounts of iron, nickel, chromium, phosphorus, etc. to strengthen the base in addition to being used as lubricants, but they do not have sufficient wear resistance under harsh usage conditions. There wasn't.

Graphite-dispersed copper-based sintered alloys are common as copper-based alloys, and the volume percentage of graphite particles in the alloy is considered in terms of the relationship between improvement of wear resistance and strength. Although there are restrictions, attention is paid to the particle size of graphite particles in order to enable uniform mixing.

On the other hand, from the viewpoint of improving wear resistance, the graphite content is 5.
~50% by volume is required, and in order to obtain uniform dispersion, it is said that the particle size of graphite particles is preferably 200 μm or less.

Furthermore, recently, graphite dispersed alloys using casting methods have been studied, and in this case, in order to disperse graphite in the molten alloy, the graphite particle size must be 200 μm or less, especially 40 to 120 μm.
It is said that a range of .

However, despite the appropriate content and particle size of graphite, and despite the reinforcement of the base metal, these conventional alloys do not have a uniform dispersion of graphite, resulting in insufficient wear resistance. I couldn't find sex.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a copper alloy sliding body with excellent wear resistance in which graphite particles are uniformly dispersed.

[Summary of the invention]

In the present invention, a molten copper alloy containing not more than 20% tin, not more than 20% zinc, not more than 20% lead, and not more than 5% chromium, and having a particle size of 0.25 to 7 A method for manufacturing a copper alloy sliding body is characterized by dispersing dragon graphite particles, casting a molten copper alloy containing dispersed graphite particles into a mold, and solidifying it under pressure.

Tin, zinc, and chromium are elements necessary to improve the strength of the copper alloy, and each contains up to 20% by weight of tin, up to 20% by weight of zinc, and up to 5% by weight of chromium.

Contents exceeding the respective values of each element should be avoided as they reduce the ductility of the alloy matrix.

In particular, the addition of chromium has the important effect of reacting with graphite to form chromium carbide on the surface of graphite, causing wetting between the molten copper alloy and graphite. Floating is prevented and graphite can be uniformly dispersed in the copper alloy.

Lead, like graphite, acts as a solid lubricant.
The lead particles, which are finer than graphite and are in close contact with the copper alloy, have an important lubricating effect, and their content is 20% by weight.
It is as follows.

Addition of more than 20% by weight should be avoided from the viewpoint of ductility and strength.

When the particle size of the graphite particles is 0.25 to 7 mrn, the wear resistance is significantly improved.

It has excellent wear resistance, especially when energized.

Generally, it is said that the wear resistance is better as the graphite particle size becomes smaller, ie, 100 μm or less.

However, the present inventors conversely found that the particle size was larger than 0.2
It has been found that the abrasion resistance decreases when the wear resistance is between 5 and 7.

The content of graphite is preferably 1 to 50% by volume from the viewpoint of the abrasion resistance of the copper alloy and the abrasion resistance in an energized state.

The manufacturing method of the present invention involves pouring a molten copper alloy in which graphite particles are dispersed into a mold, and then solidifying the molten metal under pressure.

By dispersing graphite particles in the molten copper alloy, a desired content of graphite particles can be uniformly dispersed in the copper alloy.

By pouring the molten metal into a mold and solidifying it under pressure, the molten metal can be rapidly cooled, thereby preventing graphite particles from floating.

As mentioned above, if graphite particles with a larger particle size than those conventionally used are used, the graphite particles, which are lighter than the copper alloy, tend to float in the molten metal, making it difficult to obtain uniform dispersion.

However, if the molten metal solidifies rapidly after pouring, it can be prevented from floating.

The method for producing a copper alloy sliding body of the present invention has particularly high sliding abrasion resistance when energized, and is extremely useful as a sliding plate for puncture graphs. When it has the highest electrical abrasion resistance.

[Embodiments of the invention]

Example I Cu-5%Sn-5%Zn 4%Pb-0,8
%Cr (weight composition) alloy was melted, and Cu-plated graphite powder was added thereto.

The amount of Cu plating was determined by measuring the change in graphite weight before and after plating and was 20% by weight.

Assuming that the specific gravity of graphite is 2.0, the amount of graphite necessary to make the volume of graphite in the alloy 20% was determined and added to the molten metal at 1030°C.

The graphite particle size was sieved and classified within the range of 4011m to 107nrIL.

After stirring the classified graphite of each particle size into the molten copper alloy,
The molten metal was poured into a carbon steel mold with a diameter of 50m, and immediately solidified under pressure from the top with a carbon steel plunger to a diameter of 50m.
An ingot with a length of 120 mm was obtained.

The pressing force in this case was kept constant at 6301y/ffl.

As a result of observing the macrostructure of the longitudinal section of the ingot thus obtained, it was confirmed that the graphite particles were uniformly dispersed.

Further, as a result of observing the microstructure, chromium carbide was formed on the graphite surface.

A wear test piece with a diameter of 10 mrn and a length of 25 m71 L was cut from this ingot, and the mating material was carbon steel 545C (hardness Hv2) at a surface pressure of 500 ky/i and an average sliding speed of 0.2 m/s
05), a reciprocating sliding abrasion test was conducted under dry conditions.

The results are summarized in the relationship between wear dimension (μm) and graphite particle size (μm) in FIG. 1.

This figure shows that when the particle size is less than 200 μm, the amount of wear is large, and when the particle size is larger than that and 77 nrft or less, the wear is significantly less.

Example 2 A 1OX25X50TLr/L specimen was cut out from the ingot of Example 2, and a dry current wear test was conducted using a hard copper wire as the mating material at 40 krIl/h and a pressing load of 3.5 kg.

The current is 20OA DC.

FIG. 2 shows the relationship between the wear dimension and graphite particle size after running at 100 Ian.

From this figure, the abrasion resistance during energization is also 0.25 to 7.0 mm in particle size.
It is clear that it is significantly superior when .

〔Effect of the invention〕

As described above, according to the method for manufacturing a copper alloy sliding body of the present invention,
Graphite particles with a grain size of 0.25 to 7 mm are uniformly dispersed in the copper alloy base, and it has extremely high wear resistance.It has particularly excellent current-carrying wear resistance as a sliding plate that conducts electricity while sliding, such as a Punk graph. The excellent results obtained were demonstrated.

[Brief explanation of the drawing]

Figures 1 and 2 are copper-5% tin-5% zinc-4% Pb.
FIG. 2 is a diagram showing the relationship between wear amount and graphite particle size for a composite in which 20% graphite by volume is dispersed in a -0.8% chromium (weight composition) alloy.

Claims (1)

[Claims] 1. By weight, 20% or less of tin, 20% or less of zinc, and 20% of lead.
Graphite particles with a particle size of 0.25 to 77n7rt are dispersed in a molten copper alloy containing 5% or less of chromium and 50% or more of copper, and the molten copper alloy in which the graphite particles are dispersed is molded into a mold. A method for manufacturing a copper alloy sliding body, which is characterized by casting and solidifying under pressure. 2. The method for manufacturing a copper alloy sliding body according to claim 1, wherein the content of sheath graphite is 1 to 50% by volume.