JPH04207903A - Production of carbon material for sliding current collection - Google Patents

Abstract

PURPOSE:To obtain a carbon series sliding current collecting material having high strength, low electric resistance and high resistance to brittle fracture by a method wherein a carbonaceous powder material is admixed with specific quantity of metallic fibers and then it is molded and sintered and further subjected to heat treatment. CONSTITUTION:Metallic fibers are admixed by 5-60vol.%, preferably 10-45vol.%, for the total of a carbonaceous powder material and the metallic fibers. When it is lower than 5vol.% electric resistance does not decrease sufficiently whereas when it is higher than 60vol.% the carbonaceous powder material is not sintered sufficiently thus causing decrease of strength. Thus obtained mixture material is then molded or subjected to cold hydrostatic press and sintered at a temperature lower than the melting point of the metallic fiber under an environment of inert gas such as argon or nitrogen thus carbonizing the mixture material. It is further subjected to heat treatment for quenching the metallic fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a carbon-based sliding current collector material. More specifically, the present invention relates to a method for manufacturing a carbon-based sliding current collector material that can be applied to vantakraft sliding plates, current collecting materials for electric motors, and the like.

[Conventional technology]

Currently, there are two main types of sliding current collector materials: metallic materials such as cast alloys and sintered alloys, and carbon-based materials.

Metal-based sliding current collector materials have extremely low electrical resistance and high strength, but the disadvantage is that they generate more arcs than carbon-based sliding current collector materials, and their high strength increases the amount of wear on the mating material. have.

Conventionally, the materials for current collector punk rough plates have mainly been copper, cast alloys such as copper-iron alloys or copper-tin-zinc alloys,
Metal-based sliding current collector materials such as copper-based or iron-based sintered alloys are used.In recent years, due to the increase in current collection capacity due to vehicle cooling, etc., and the increase in vehicle operating speed, current collection The environment in which pantograph sliding plates are used is becoming increasingly harsh. Recently, as the speed of rolling stock has increased, the wire loss rate has increased, resulting in an increase in the amount of mechanical wear and arc wear, as well as problems such as abnormal wear caused by freezing of trolley wires in cold regions, and sliding problems. Problems such as loud noise pollution have also arisen. Therefore, in order to prevent such wear, there is a need to develop a current collecting material with good sliding properties that reduces wear not only on the sliding plate itself but also on mating materials such as trolley wires and electromotive rails. . Further, arc generation is viewed as a problem because it causes not only arc wear but also radio wave interference.

By the way, carbon-based materials are expected to be able to compensate for the drawbacks of these metal-based sliding current collector materials. This carbon-based sliding current collector material has good self-lubricating properties, relatively low electrical resistance, and excellent arc resistance.
It has the characteristics of being lightweight and having low sliding noise, and can overcome the drawbacks of the above-mentioned metal-based sliding current collector materials.

However, this carbon-based sliding current collector material has considerably higher electrical resistance and extremely low strength than metal-based sliding current collector materials, so it cannot be used in locations where large forces are directly applied. In addition, these carbon-based sliding current collector materials are currently widely used in fields such as motor brushes,
Even in fields that use carbon-based sliding current collector materials,
The conditions for their use are becoming increasingly strict, and there is an even greater demand for improved wear resistance and lower electrical resistance. In addition, carbon-based sliding current collector materials are easily broken due to their brittleness when carbon is used alone, and if they break, the current collecting material will scatter, which is dangerous, and in the worst case, current collection may become impossible. Vehicles may also stop.

Currently, studies are being carried out in various fields to solve the drawbacks of these carbon-based sliding current collector materials.

For example, (1) a method of impregnating a carbon-based sliding current collector material with metal (Japanese Patent Publication No. 52-822), and (2) adding metal powder to raw material powder of carbon material to lower electrical resistance and A method of improving strength (Japanese Patent Laid-Open No. 1983-
238.402) has been proposed, and (3
) A method of blending metal fibers with carbon material raw materials, molding and firing (Japanese Patent Application Laid-open No. 197.352/1982) and (4)
) After mixing metal fibers with carbon material raw materials and extrusion molding,
Method of firing and impregnating with metal (Japanese Patent Application Laid-Open No. 61-245,
No. 957) and the like have also been proposed.

However, although the above-mentioned methods (]) and (2) can be expected to be effective to some extent in improving strength, they have low efficiency in lowering electrical resistance, and cannot be expected to be very effective in preventing brittle fracture. In addition, in method (3), although the efficiency of reducing electrical resistance is high due to the use of metal fibers,
It is difficult to sufficiently reduce electrical resistance. Furthermore, in method (4), the metal fibers are oriented in one direction by extrusion molding, but with this method, cracks tend to occur in the direction parallel to the direction of fiber orientation, and the metal fibers become weaker in certain directions. Tend.

・[Problems to be Solved by the Invention] The purpose of the present invention is to create a high-strength carbon material that has lower electrical resistance than conventional carbon-based sliding current collector materials and is resistant to brittle fracture. An object of the present invention is to provide a method for manufacturing a sliding current collecting material.

[Means to solve the problem]

The present inventors focused on the fact that by dispersing metal fibers in a carbon material, the electrical resistivity is significantly lowered, and the flaws of carbon materials such as brittleness and ease of chipping are improved. The present invention has been completed based on the discovery that the physical properties can be improved by improving the properties and then applying heat treatment.

The present invention provides a carbonaceous powder raw material with an OI of 5 volX or more and 60 vOI
This is a method for producing a carbon material for a sliding current collector, in which metal fibers of less than X are added and mixed, then molded, fired, and further heat treated.

The present invention will be explained in further detail below.

The carbonaceous powder raw materials used in the present invention include pitch coke,
It is a powder mainly composed of carbon such as graphite or coal, preferably pitch coke or a powder mainly composed of pitch coke. Pitch coke is produced by heat-treating petroleum-based, coal-based pitch, etc. at 400 to 550°C in a non-oxidizing atmosphere, and the raw coke is further calcined at 1,000 to 1,400°C. However, raw coke itself contains a binder component, so it is not only excellent in moldability, but also excellent in that it can contain a large amount of metal fibers. When using raw coke, the volatile content should be 5 to 17 wt% to reduce the probability of cracking and blistering during firing and to increase yield.
, preferably 8 to 14 wt%. When using a carbonaceous powder raw material such as calcined coke that does not contain a binder component, a binder such as binder pitch or phenolic resin is required.

When it is desired to further improve the sliding properties, it is effective to use graphite powder as part of the carbonaceous powder raw material. When raw coke is used, graphite powder may be added at the raw material pitch stage before heat treatment, or after heat treatment, and when calcined coke and binder pitch are used, these three may be added. Even when kneading,
It may be carried out after kneading and pulverizing these three materials. The graphite powder used for this purpose may be either natural graphite powder or artificial graphite powder, and its particle size is in the range of 0.5 to 30°, preferably 10 to 150. The amount added is 0.3 to 30 wt%, preferably 0.5 to 10 wt%, in the carbonaceous powder raw material in order to bring out the effect of adding graphite powder and not inhibit the sintering of the carbonaceous matrix. When it is desired to add a large amount of graphite powder, it is preferable to use raw coke with a large volatile content or to replenish a binder component such as binder pitch.

When the carbonaceous powder raw material does not contain a binder component or is insufficient, a binder is added in order to improve its moldability and sinter it. Examples of this binder include binder pitch and resins such as phenol resin. The amount of binder added varies depending on the type of binder, but when using binder pitch and using carbonaceous powder that does not contain a binder component such as calcined coke or calcined coke and graphite powder, The amount added is 5 parts by weight per 1.00 parts by weight of carbonaceous powder.
The amount is 0 to 120 parts by weight, preferably 70 to 100 parts by weight, and when using materials that contain or lack a binder component, such as raw coke and graphite powder, the amount added is 1.0 parts by weight of carbonaceous powder. It is preferably about 10 to 50 parts by weight, preferably about 25 to 35 parts by weight.

Metal fibers include iron, iron-based alloys, nickel alloys, beryllium copper, phosphor bronze, nickel silver, or mixtures thereof, or mixtures with copper, copper-based alloys, etc., and are not particularly limited. Metals with high strength (or low electrical resistivity) are desirable. However, when heat treatment is applied, the properties of the metal may not change, or the strength or impact resistance may drop significantly, or the electrical resistance may change. Materials that undergo unfavorable changes such as an extreme increase in resistance are not suitable as sliding current collector materials.Also, materials that are extremely harder than the sliding material will increase the amount of wear on the material and have a low melting point. With these metals, the firing temperature cannot be set high because the metal dissolves during firing, and both are unfavorable.

The shape of the metal fiber is not particularly limited, but the fiber diameter is 1 + r + n for reasons such as not inhibiting sintering of the carbonaceous matrix and making blending uniform and easy.
It is preferable that the fiber length is 10= or less. In addition, when a metal fiber prepared by the chatter cutting method, which has a square cross-sectional polygonal cross-sectional shape, is used, it is possible to easily obtain a good molded product during compression molding.

The amount of metal fiber added is in the range of 5 vol. or more and less than 60 vol.X, preferably 10 to 45 vol.X, based on the total of the carbonaceous powder raw material and the metal fiber. If the amount of metal fiber added is less than 5 volX, the electrical resistance will not decrease sufficiently;
If the amount exceeds 60 vol, the sintering of the carbonaceous raw material will not proceed sufficiently, resulting in a decrease in strength.

The carbonaceous powder raw material and the metal fibers may be mixed by a method such as a rocking mixer or a shaking method that can be dispersed almost uniformly and randomly, and there is no particular limitation. , a large shure acts during mixing,
Mixing methods that cause the metal fibers to be bent or cut are not preferred.

The mixed raw material obtained as described above is molded by a method such as molding or cold isostatic pressing (CIP), and then heated to a temperature below the melting point of the metal fiber in an inert gas atmosphere such as argon or nitrogen. It is carbonized by firing at a temperature of, for example, 800 to 1,500°C.

In order to obtain the material of the present invention, the metal fibers are further subjected to heat treatment for hardening or the like. Since the matrix of this heat treatment is carbon, if the heat treatment is carried out in a temperature range where carbon may be oxidized and consumed, it must be carried out in an inert gas atmosphere such as argon or nitrogen.
Normal heat treatment conditions suitable for each metal and alloy may be used. For example, if it contains iron fibers, it may be quenched by rapid cooling from the austenitizing temperature, or further tempered, and if it contains phosphor bronze fibers, it may be quenched or tempered. , 225-27
Bake at a low temperature of 5℃. When holding materials containing iron fibers at the quenching temperature, it is done in an inert gas atmosphere, and when rapidly cooling, the material is filled with calcined coke particles crushed into a few millimeters or less. It is best to avoid direct contact with the atmosphere and to rapidly cool the calcined coke to prevent the carbon matrix from being oxidized and consumed.

Alternatively, the molded product may be placed directly into a refrigerant to be rapidly cooled, and then the surface of the molded product that has been consumed by oxidation may be cut.

In the sliding current collector material of the present invention, the metal fibers contained therein are not oriented in a specific direction, but in particular, when manufactured by cold isostatic press molding, they are almost uniformly oriented, and can be used in any direction. However, it has characteristics such as high strength and low electrical resistivity. In addition, because it is reinforced with metal fibers, it is resistant to brittle fracture, and even if it breaks, it is less likely to scatter because it is connected by the metal fibers, making it a safe, high-strength, and high-impact-resistant current collector sliding material. becomes. Furthermore, since the sliding current collector material according to the present invention is heat-treated,
For example, when iron fiber is added and quenched, it has a feature of higher strength compared to conventional materials. The carbon material for sliding current collector according to the present invention can be applied not only to pantograph sliding plates but also to current collecting brushes for electric motors as a current collecting material, and can be widely applied.

〔Example〕

The present invention will be specifically described below based on Examples and Comparative Examples.

Example 1 Raw coke with a volatile content of 12 wt% crushed into 8 average particle diameters was mixed with fibers having a diameter of 60 IJIn obtained by the chatter cutting method.
Added 27volX iron fiber with a fiber length of 3M, and added 2.0
Width 40mm x length 120mm with molding pressure of 00 kg/cnr
After molding into a size of 20 mm x 20 mm, the temperature was raised to 1,000° C. at 3° C./hr in a nitrogen atmosphere and fired. Next, after heating at 900° C. for 1 hour in an argon atmosphere, the material was placed in ice water and subjected to a quenching treatment to produce a sliding current collector material.

Example 2 Example 1 except that the amount of iron fiber added was 5vol%
A sliding current collector material was prepared in the same manner as described above.

Example 3 A sliding current collector material was produced in the same manner as in Example 1, except that the amount of iron fiber added was 10 volX.

Example 4 A sliding current collector material was produced in the same manner as in Example 1, except that the amount of iron fiber added was 20 volN.

Example 5 A sliding current collector material was produced in the same manner as in Example 1, except that the amount of iron fiber added was 40vol%.

Example 6 In the raw raw coke used in Example 1, an average particle size of 10
A sliding current collector material was prepared in the same manner as in Example 1, except that a carbonaceous powder raw material was prepared by adding 1 wtX of natural graphite to this raw coke, and this carbonaceous powder raw material was used. did.

Comparative Example 1 Raw coke with a volatile content of 12wtX crushed to an average particle size of 8 was mixed with fibers having a diameter of 60IJIR1 obtained by the chatter cutting method.
Add 27 volN of iron fiber with a fiber length of 3 to 2°000
After molding into a size of 40 mm width x 120 m length x 20 mm thickness at a molding pressure of kg/c, it was heated at 3°C under a nitrogen atmosphere.
The temperature was raised to 1,000° C./hr and fired to produce a sliding current collector material.

Comparative Example 2 A sliding current collector material was produced in the same manner as Comparative Example 1, except that the amount of iron fiber added was 5 volX.

Comparative Example 3 A sliding current collector material was produced in the same manner as in Comparative Example 1, except that the amount of iron fiber added was 1 OvolX.

Comparative Example 4 A sliding current collector material was produced in the same manner as in Comparative Example 1, except that the amount of iron fiber added was 20vol%.

Comparative Example 5 A sliding current collector material was produced in the same manner as Comparative Example 1, except that the amount of iron fiber added was 40vol%.

Comparative Example 6 2,000 kg of raw coke pulverized to an average particle size of 8
/cnf molding pressure to a width of 40M x length of 120mm x thickness of 20mm, and then heated at 3°C/hr under a nitrogen atmosphere.
The temperature was raised to 1,000°C and fired to produce a sliding current collector material.

The bulk density, electrical resistivity, bending strength, and Charpy impact value of the sliding current collector carbon materials prepared in each of the above Examples and Comparative Examples were measured. The results are shown in Table 1.

As is clear from the results in Table 1, the sliding current collector carbon material obtained by the method of the present invention has higher strength and lower electrical resistance than conventional carbon materials. Moreover, it is found that the impact resistance is also high.

Table 1 (Note) *1: g/c resistance *2: μΩ・Cm *3: k
gf/crI*4: kgf-cm/crd [Effects of the Invention] As described above, the present invention provides a carbon-based sliding material that is lightweight and has excellent performance in terms of lubricity, arc resistance, low noise, etc. It is possible to produce an extremely useful carbon material for sliding current collectors that inherits the characteristics of current collector materials, has excellent low electrical resistance, and also has good impact resistance.

Patent applicant: Nippon Steel Chemical Co., Ltd. Same as above Nippon Steel Corporation

Claims (1)

[Claims] (1) After adding and mixing 5 vol% or more and less than 60 vol% of metal fibers to the carbonaceous powder raw material, molding and firing,
A method for producing a carbon material for a sliding current collector, characterized by further heat treatment.