JPH02160664A - Carbon-metal composite material - Google Patents

Abstract

PURPOSE:To obtain the title composite material excellent in wear and impact characteristics, flexural strength and electrical resistivity, thus suitable for pantograph sliding plates by incorporating a carbonaceous raw material with several kinds of metallic fiber differing in at least one nature selected from length, thickness and material nature from one another. CONSTITUTION:At least two kinds of metallic fiber differing in at least one nature selected from length, thickness and material nature from each other (e.g. steel fiber, copper fiber) are incorporated in a carbonaceous raw material such as coke powder plus pitch, or phenolic resin. Thence, using a hot pressing mold provided with e.g. a top force 3, bottom force 4 and metal frame 5, a raw material to be formed is filled between the top and bottom forces 3, 4, a hot plate 7 being heated with a heater 7-1, followed by pressing with a press head 1 to make a forming. The resultant form is then baked in a non-oxidative atmosphere at temperatures below the melting point of said metallic fiber, thus obtaining the objective composite.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a composite material that can be used mainly for pantograph sliding plates for railways.・Regarding metal composite materials.

Conventional technologyAs a carbon material for current collection, the excellent sliding properties of carbon and the electrical conductivity of metals are used to cope with the increasing speed of vehicles and the increase in power consumption due to air conditioning equipment, etc. Carbon/metal composite sliding plates that take advantage of this are being adopted.

This type of carbon-metal composite material includes, for example: ■ Composite material manufactured by pressurizing and impregnating the pores of a carbon material with a specific metal; Composite material manufactured by a method of carbonizing after molding using a molding method (Japanese Patent Application Laid-Open No. 62-72564), ■ Manufactured by a method of blending metal fibers oriented in one direction with raw materials for carbon materials, then molding and firing. Composite materials (JP-A-62-197
352).

However, the carbon/metal based sliding plates mentioned above are in the transition period from the current sintered metal based sliding plates to the carbon/metal based sliding plates, that is, the transition between the metal sintered and carbon/metal based sliding plates. The drawback is that the sliding plate is subject to a large amount of wear when the trolley wire (made of copper) is slid in a rough condition, which is intended for mixed use.

In order to eliminate such drawbacks, the present inventors have developed a carbon material raw material whose main components are carbon material aggregate powder and binder pitch.
We previously proposed a method for obtaining a carbon-metal composite material with excellent wear resistance by blending metal fibers and metal powder, molding this raw material under pressure and heat, and then firing it (Japanese Patent Application No. 63-26).
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By the way, when using the sliding plate, the sliding plate may hit violently against the trolley wire hanger that has come off due to ice forming on the trolley wire or for some other reason.

At that time, if the impact strength of the sliding plate is low, the first concave plate will break and its fragments will be scattered around, which is extremely dangerous.

Therefore, the sliding plate is required to have not only wear resistance but also impact resistance.

However, the above-mentioned carbon-metal composite materials have a common drawback in that they are significantly inferior in impact strength compared to conventional metal sintered metal composite materials.

The reason for this poor impact strength is basically that the impact strength of carbon is low. Therefore, to compensate for this, impact strength can be improved by increasing the proportion of metal components, but as the amount of metal components increases, more sparks will be generated between the contact wire and the contact wire, resulting in greater wear on the contact wire and sliding plate. Undesirable.

Furthermore, carbon-metal composite materials have a disadvantage in that they have a higher electrical resistivity than conventional metal sintered sliding plates.

If the electric resistivity is high, the temperature of the trolley wire will increase due to Joule heat, and the trolley wire to which high tension has been applied may break, which is extremely dangerous.

The reason why the electrical resistivity of the carbon-metal composite material is high is basically that carbon has a high electrical resistivity. Therefore, it is possible to lower the electrical resistivity by increasing the amount of a metal component with low electrical resistivity, such as copper, but as mentioned above, when the metal component increases, sparks occur between the contact wire and the trolley wire. This is not desirable.

Problems to be Solved by the Invention In view of the actual situation described above, this invention has been developed to easily solve the problems of carbon-metal composite materials, such as the difficulty in achieving both abrasion resistance and impact resistance, and the electrical resistivity. The purpose of this project is to solve the problem of not being able to lower the electrical resistance, and to provide a carbon-metal composite material that has excellent impact resistance and wear resistance, and has low electrical resistivity.

Means for Solving the Problems The inventor has developed a carbon-metal composite material that has both wear resistance and impact resistance without increasing the content of metal fibers in a composite material that combines metal fibers with carbon material raw materials. As a result of various studies on composite materials, we found the following.

Because metal fibers have a large aspect ratio (fiber length/fiber diameter), they have a large reinforcing effect and contribute to improving the static strength and impact strength of composite materials, but compared to the same aspect ratio, the smaller the fiber diameter, the higher the strength. can get.

However, impact strength shows a result contrary to static strength, in that fibers with larger fiber diameters and longer fiber lengths exhibit higher impact strength.

Regarding the aspect ratio, it is well known that the larger the aspect ratio of the same material, the better the static strength and impact strength of the composite material. Fiber balls, or entangled aggregates of fibers, tend to form,
The amount added must be reduced.

As a result of further studies based on the above knowledge, the inventor found that it is effective to blend 52 or more types of fiber hybridization zuna.

For example, it has been found that when metal fibers with a small fiber diameter are mixed with a small amount of metal fibers with a large fiber diameter and a long fiber length, the static strength is slightly lowered, but the impact strength is significantly improved.

It has also been found that the same effect as described above can be obtained by blending fibers with the same diameter but different lengths.

In general, it has been found that hybridization can be applied not only to the size of the fibers but also to the material of the fibers.

For example, it has been discovered that by combining iron-based fibers and copper-based fibers, it is possible to achieve both wear resistance and electrical resistivity.

That is, this invention provides a carbon-metal composite with excellent wear resistance, impact resistance, and electrical resistivity, which is obtained by blending two or more types of metal fibers that differ in length, thickness, and material. The main point is the material.

Function The carbon material raw materials in this invention include self-sintering mesophase powder, binary raw materials consisting of carbonaceous aggregate powder and pitch such as coke powder, thermosetting resins such as phenolic resin, etc. can be used.

Here, carbonaceous aggregates in binary raw materials include coke powder obtained by carbonizing pitch, coal, etc. at about 100°C from the viewpoint of wear resistance, and isotropic carbon obtained by carbonizing phenolic resin. Those with high hardness such as

Regarding the particle size of the carbonaceous aggregate, from the viewpoint of strength and wear resistance, a small particle size is good. It is preferable to use it after pulverizing it to less than 1 ozm.

Binder pitches include coal tar medium pitch,
A high softening point pitch obtained by rough heat treatment of this material can be used.

The pitch is preferably one that exhibits fluidity when heated and has as low a volatile content as possible, since this improves the strength and abrasion resistance of the composite material.

Various metal fibers such as steel fiber, steel wool, copper fiber, etc. can be used as the metal fiber. Among these, low carbon steel fibers are suitable as metal fibers effective for developing wear characteristics, and copper fibers are suitable for lowering electrical resistivity. Therefore, these metal fibers are appropriately selected and used depending on the required properties.

The shape, size, etc. of various metal fibers are not particularly limited, but
Regarding the size, those with a thickness of 0.5 seconds or less and a length of 1M or more have a large strength improvement effect. The shape of the metal fiber can be needle-like, wedge-like, wavy, net-like, or a mixture thereof.

In this invention, the reason why we decided to blend two or more types of metal fibers that differ in length, thickness, and material is because
This is because, as mentioned above, there is a limit to the improvement of the properties of the carbon-metal composite material, such as wear resistance, impact resistance, and electrical resistivity.

In addition, when blending metal fibers with different lengths, it is preferable that the ratio of the lengths is at least twice or more. In consideration of abrasion characteristics and impact strength, it is desirable that the proportion of long fibers be about 10 to 40% of that of short fibers.

The blending amount of all metal fibers is not particularly limited, and high strength and excellent abrasion resistance and impact resistance can be obtained even at a high blending ratio of 50 to 60% by volume, but in consideration of spark properties, 40 to 60% by volume
About 50% by volume is preferable.

The method for molding the carbon-metal composite material according to this invention includes:
Various methods such as cold molding, extrusion molding, pressurized heat molding, etc. can be adopted. Among these, the method of using pitch as a binder and pressurizing and heating molding yields a carbon-metal composite material with the best strength and wear resistance.

The pressure and heat molding conditions are in the temperature range where the binder pitch solidifies, that is, 480°C or higher, preferably 500°C.
Since it is necessary to pressurize and heat in the above temperature range, the maximum pressure and heating temperature is 480°C or higher, preferably 500'C.
The above shall apply.

The pressure of pressurized and heated molding is at least 40 to 94 or higher in a part of the range from normal temperature to the maximum temperature of pressurized heating, preferably 80 kq.
Must be J or higher. This is because if the molding pressure is less than 40 ki4, the bonding force between the binder and the metal decreases, making it impossible to obtain a carbon-metal composite material with good wear characteristics.

The molded body obtained by the pressure and heat molding method is fired in the same manner as ordinary carbon materials.

Example Figure 1 is a schematic diagram showing an example of a pressurized and heated mold.
1) is the upper press head, (2) is the lower press head (fixed), (3) is the upper mold, (4) is the lower mold, (5) is the metal frame, (6) is the molding raw material, (7 ) is a sheathed heater (7-1
) hot plate, (8) is covered with heat insulating material.

That is, after filling the molding raw material (6) between the upper mold (3) and the lower mold (4), the sheath heater (7-1) is energized to heat the hot plate (sword) and press head Pressure is applied according to (1). The mold may be preheated.

The molded body obtained by such a pressure-heat molding method can be fired in a non-oxidizing atmosphere at a temperature below the melting point of the metal fiber.

Next, a carbon-metal composite material manufactured by a pressure and heat molding method using a mold shown in FIG. 1 and a normal firing method will be described.

As the molding aggregate, coke powder with an average particle size of 12 particles was used, which was obtained by carbonizing regular grade petroleum coke at 1000° C. and then pulverizing it in a vibrating mill packed with stainless steel balls of 10 m in diameter.

As a binder pitch, coal tar is used at 60sH (
Coal tar pitch obtained by heat treatment at 430° C. under reduced pressure of J for 2 hours and having a softening point of 270° C. measured with a Koka type flow tester was used, which was pulverized to 60 mesh or less.

The following four types of metal fibers were used.

(a) 0.05 #X O,05MX length 3IrIM
Low carbon steel fiber (b) 0.1m x 0.1 shoe x length 6IrI! r1 low carbon steel fiber (C) 0.5 mX 0.5 shoes x length 25N r1 low carbon steel fiber (d) 0.05 am The molding raw material obtained by mixing raw materials at the compounding ratio shown in Table 1 is molded into a molding material with internal dimensions of 100# width x 200m length.
After charging it into the mold, it was heated at 5°C under a molding pressure of 200 3/cit using a hydraulic press with a pressure capacity of 500 tOn.
The temperature was raised to 500'C at a temperature increase rate of 1 hour, held for 1 hour, and then cooled to obtain a molded article with a width of 100 m, a length of 200 g, and a thickness of 10 shoes.

The obtained molded body was placed in a stainless steel container filled with coke powder and heated at a heating rate of 12°C/Hr in a nitrogen atmosphere.
The temperature was raised to 000°C, held for 4 hours, and then cooled and fired.

From the obtained carbon-metal composite material, width 10m x length 60m
A test piece with a thickness of m (thickness is the same as the thickness after baking) was cut out, and its Charpy impact value, bending strength, and electrical specific resistance value were measured.

The cutting direction of the test piece is 60mm in length. The direction was made to match the direction of the 200 m length of the molded body.

The Charpy impact value was measured with the impact direction perpendicular to the pressing direction during molding.

The bending strength was measured by rolling down the part corresponding to the upper part during molding with a bending span of 40M.

Next, from the same carbon-metal composite material, we made 8 shoes in width x 8 meters in length.
A test piece with a height of 10M was cut out so that the height direction coincided with the pressing direction during molding, and the surface of this test piece that corresponded to the top surface during molding was used as the sliding surface, and a wear test was conducted under the following conditions. After the wear test, the thickness change of the test piece was measured, and the wear volume per sliding pressure of 1i1100- was calculated.

For comparison, Table 1 shows the conditions under which one type of metal fiber was used and
The physical properties of a carbon-metal composite material obtained by pressurizing, heating molding and firing by the same method as the present invention are also shown.

As is clear from Table 1, none of the comparative examples made of one type of fiber were able to achieve both abrasion loss and impact value, whereas the present invention was excellent in both abrasion characteristics and impact characteristics, and A composite material with low resistance was obtained.

Table 1 below shows the Charpy impact value, bending strength, wear amount, and electrical resistivity value described above.

As described in detail, the carbon-metal composite material according to the present invention has improved wear characteristics, impact characteristics, and electrical resistivity by blending two or more types of metal fibers of different sizes and materials. Since it has been improved, it exhibits excellent characteristics as a store board for pantographs, and the effects it brings are enormous.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a pressure-heat molding mold for carrying out the method of the present invention.

Claims (1)

[Claims] A carbon-metal composite material, which is a composite material in which metal fibers are blended into a carbon material raw material, and is characterized in that it contains two or more types of metal fibers that differ in at least one of length, thickness, and material.