JPH06172029A - Carbon-metal composite material and its production - Google Patents

Abstract

PURPOSE:To provide a carbon-metal composite material, excellent in bending strength and abrasion resistance and suitable as sliding plates for pantographs. CONSTITUTION:A raw material for a carbon material composed of a carbon aggregate; a binder pitch, etc., is mixed with dendritic electrolytic copper powder at 10-40vol.% blending ratio. The resultant mixture is then hot press formed at 500-600 deg.C temperature and burned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding collector material, particularly a carbon / metal composite material having excellent bending strength and abrasion resistance, which is suitable for a pantograph sliding plate for railways, and a method for producing the same.

[0002]

2. Description of the Related Art Recently, as a pantograph sliding plate for railways, a carbon / metal composite material is being adopted which makes good use of the excellent sliding characteristics of carbon and the electrical conductivity of metal. Then, such a carbon-metal composite material is used as a carbon sliding plate (1).
It is attached to a pantograph boat with a sheath and a bolt, (2) brazing, and (3) an organic adhesive.

As the carbon / metal composite material used as a carbon slide plate for a pantograph, a material in which pores of a carbon material are impregnated with a specific metal under pressure (see Japanese Patent Publication No. 56-14732), coke powder, etc. The carbon-metal composite material obtained by mixing the carbon aggregate of No. 3, pitch and metal fiber, press-heating and molding at a temperature of about 500 ° C., and firing (Japanese Patent Laid-Open No. Sho 61-61).
No. 245957, etc.) is known.

[0004]

However, the carbon / metal composite material used as the conventional sliding plate for a pantograph and the method for producing the same have the following problems. In the case of carbon-metal composite materials produced by the metal impregnation method, high temperature and high pressure are used to impregnate porous carbon with metal, so that equipment and processing cost are high, and generally large pores are required. Since it has the above, there is a problem that the strength of the material itself is remarkably reduced when the metal flows out due to the high heat received by the arc during use.

On the other hand, carbon aggregate such as coke powder,
After mixing the pitch and the metal fiber, press-heating molding,
The present inventors have previously proposed a method of firing (Japanese Patent Laid-Open No. 61-61160).
-245957). In this method, the decrease in strength due to the arc is small because the pores are small. However, since the metal fiber diameter is usually as large as 50 μm or more, the abrasion of the sliding plate is large, cracks are likely to occur at the fiber-carbon interface, and the bending strength has not been sufficiently high.

In view of the above problems of the carbon / metal composite material used as a carbon slide plate for a pantograph, the present invention is a carbon / metal composite material having excellent strength characteristics such as bending strength and abrasion resistance, and a method for producing the same. Is to propose.

[0007]

The present invention is based on the above-described method of mixing carbon aggregate such as coke powder, pitch and metal fiber and press-molding at a temperature of about 500 ° C. It has been found that bending strength and wear resistance can be remarkably improved by using dendritic electrolytic copper powder for the added metal instead of the metal fiber.
A carbon-metal composite material containing a metal powder in a carbonaceous matrix, characterized in that the metal powder is a dendritic electrolytic copper powder, and as a method for producing the same, carbon composed of carbon aggregate and binder pitch. The raw material is mixed with dendrite-shaped electrolytic copper powder at a mixing ratio of 10 to 40% by volume, and 500 to 600
It is characterized in that it is heated and molded at a temperature of ° C and then fired.

[0008]

As the carbon aggregate in the present invention, hard carbon such as coke powder obtained by carbonizing petroleum coke or pitch coke, and resin charcoal obtained by carbonizing resin,
It is preferable in terms of wear resistance. The coke particle size is not particularly limited, but if too much coarse particle is present, the flexural strength will decrease, so that the average particle size is usually 10 to 20 μm.

As the binder pitch, there is a flow such as a high softening point pitch obtained by heat treating coal tar under reduced pressure or a high softening point pitch obtained by polymerizing an aromatic compound such as naphthalene in the presence of an acid catalyst. Those having excellent properties and low volatile content are preferable in terms of adhesiveness and carbonization rate. The mixing ratio of the binder pitch is suitably 10 to 40% by volume. When it is less than 10% by volume, the strength becomes low, while when it exceeds 40% by volume, leakage of raw materials during molding is likely to occur, which is not preferable.

Next, the reason why the dendritic electrolytic copper powder is used as the additive metal to be mixed with the carbonaceous material is as follows. Although various metal fibers and metal powders can be considered as the additive metal of the carbon-metal composite material, fine metal powders are superior to metal fibers in terms of wear resistance. As the material of the metal powder, pure copper, which has good electric conductivity and arc resistance, is most preferable. Here, as the copper powder, a spherical powder obtained by the atomizing method, a flat powder obtained by the pulverizing method,
There are dendritic powders obtained by the electrolysis method. Among them, dendritic electrolytic copper powders are most preferable in terms of abrasion resistance and bending strength of the composite material. The reason is that, in the case of electrolytic copper powder, the surface is rich in undulations, so that the carbonaceous matrix and the copper powder are firmly bonded by the anchor effect. For this reason, in the present invention, dendritic electrolytic copper powder is used as the additive metal mixed with the carbon material raw material.

FIG. 1 is a photomicrograph of tree-shaped electrolytic copper powder,
FIG. 2 is a micrograph of crushed copper powder. That is, in the case of tree-shaped electrolytic copper powder, the thickness is about 10 μm and the length is several tens of μm.
The resin shape (tree shape, grape tuft shape, or a structure in which these are connected) is obtained, and as described above, a composite material having excellent bending strength and abrasion resistance can be obtained. On the other hand, the ground copper powder shown in FIG. 2 is better than the copper fiber, but is inferior in bending strength and wear resistance to the tree-shaped electrolytic copper powder.

From the viewpoint of wear resistance, the smaller the compounding ratio of the electrolytic copper powder, the better, but the higher the bending strength and the electric resistance, the better. Therefore, in the present invention, as a blending ratio that can satisfy the bending strength and the wear resistance,
Limited to volume%. That is, when the compounding ratio of the electrolytic copper powder to the carbon material raw material is less than 10% by volume, sufficient bending strength cannot be obtained, while when it exceeds 40% by volume, wear resistance deteriorates.
Further, the weight is increased and the exercise performance of the pantograph is deteriorated.

As pressure and heat molding conditions, heating under pressure in a temperature range in which the binder pitch is solidified, that is, a temperature range of 500 ° C. or higher is preferable for developing strength and wear resistance. On the other hand, press molding in a temperature range exceeding 600 ° C. at which the solidification of the binder pitch is completed is meaningless in terms of sintering, and on the contrary, cracks are likely to occur in the molded body due to thermal stress accompanying rapid heating, The upper limit of the pressure heating temperature is 600 ° C.

The molding pressure is preferably 50 kg / cm ² at least at room temperature to a part of the maximum pressure heating temperature.
That is all. If the molding pressure is lower than 50 kg / cm ² , the binding force between the binder and the electrolytic copper powder decreases, and the abrasion resistance tends to deteriorate.

Firing of the molded body is preferably carried out by raising the temperature at a slow temperature rising rate under normal pressure. The firing temperature is 90 from the viewpoint of sufficiently developing the strength of carbon.
0 ° C. or higher is preferable, while the upper limit temperature is such that the melting point of copper is 10
Since the temperature is 83 ° C., it is preferable to set the temperature not to exceed this, and the firing is usually performed at about 1000 to 1050 ° C.

The carbon of the present invention thus obtained
The metal (copper) composite material is not only excellent in bending strength and wear resistance, but also has high brazing strength and is excellent as a sliding plate for pantographs, as compared with the case of mixing conventional metal fibers and metal powders. It exhibits excellent performance.

As the metal plate which is brazed to the carbon / metal (copper) composite material of the present invention, various materials such as aluminum, iron and copper which are commonly used as materials for pantographs can be used.

As the brazing material used for joining, either a high melting point hard brazing material such as silver brazing or a low melting point soft brazing material such as aluminum solder can be used. When cooling from the brazing temperature, the stress between the carbon / metal composite material and the metal plate, which is generated due to the difference in the thermal expansion coefficient between the carbon / metal composite material and the metal plate, becomes large, causing peeling of the joint surface and Problems such as warpage of metal composite materials and metal plates are likely to occur. Therefore, it is preferable to use soft brazing that can be joined at a low temperature.

When aluminum is used for the metal plate which is brazed to the carbon-metal composite material, tin-zinc type or aluminum-zinc type is suitable as the brazing material. When surface joining of carbon / metal composite material and aluminum plate is performed using these brazing materials, the brazing material is melt-plated in a film shape on each of the carbon / metal composite material and the aluminum plate, and the brazing material welding surfaces are joined together. It can be brazed by pressing and heating it to a temperature above the melting point of the brazing material and then cooling it.

Here, in order to remove the oxide film on the joint surface and to improve the jointability, a flux is usually used, but in the case of the above brazing material, the flux is often unnecessary for aluminum. The carbon sliding plate and the metal boat body joined by such soft brazing do not have problems such as warping or peeling even during cooling after brazing, and have good joining strength.

When the metal plate is made of copper, iron, or the like, it is possible to join it with a tin-lead type solder used for general electric wiring.

[0022]

【Example】

Example 1 A commercially available calcined petroleum coke was pulverized with a vibrating ball mill to an average particle size of 15 μm, and the obtained coke powder was used as a carbon aggregate for molding. As the binder pitch, coal tar pitch having a softening point of 250 ° C. measured by a Koka type flow tester, which is obtained by heat treating coal tar at 440 ° C. under a reduced pressure of 60 mmHg for 1 hour, is crushed to 60 mesh or less. I was there. As the copper powder, dendritic electrolytic copper powder was used, and for comparison, ground copper powder, atomized copper powder, copper fiber, copper-impregnated carbon, steel fiber, and graphite material were used. The compositions of these are summarized in Table 1.

Next, the forming raw material shown in Table 1 was added with the added metal:
Coke powder: binder pitch (a) 10: 60: 3
0, (b) 20:50:30, (c) 40:30:30
Were mixed in three kinds of mixing ratios (volume ratios), charged into stainless steel molds each having an inner diameter of 100 mmφ, and subjected to pressure heating molding. The volume ratio of the blend was calculated from the blend volume calculated by dividing the blend weight of the raw material by the true specific gravity. Pressurized heat molding is performed at a temperature rising rate of 10 ° C./Hr at a temperature of 550 from room temperature.
The test was performed by pressing at 200 kg / cm ² up to ° C, holding at 550 ° C for 1 hour, and then cooling to room temperature while pressing.

Then, the obtained composite material was packed in powder coke and heated in a nitrogen atmosphere at a temperature rising rate of 12 ° C./hr to 1040 ° C.
The temperature was raised to 2, the temperature was maintained for 2 hours and then cooled. About the obtained composite material, (a) Bending strength measurement (3-point bending method, test piece size 10 mm x 10 mm x 60 mm, span 40 m
m), (b) Abrasion test with copper plate (sliding speed 200 km /
Hr, sliding surface 1 × 1 cm, pressing force 2 kgf).
The measurement results of (a) and (b) above are shown in Table 2 (addition metal content ratio 10%), Table 3 (addition metal content ratio 20%), and Table 4 (addition metal content ratio 40%).

From the results shown in Tables 2, 3 and 4, the present invention in which the dendritic electrolytic copper powder A is blended is the same crushed copper powder B, atomized copper powder C and copper fiber D regardless of the blending ratio. It can be seen that the flexural strength and the wear resistance are excellent even when compared with the one in which

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

Example 2 Test No. of Example 1 A brazing test piece (2
5 mm × 25 mm × 2.5 mm thickness) was prepared, and an iron plate and a copper plate having the same dimensions as the test piece were used as mating materials, and brazing was performed.

In this example, solder for aluminum (SP-27 manufactured by Nippon Aluminum Co., Ltd.) was used as the brazing material, and SDG flux manufactured by Nippon Aluminum Co., Ltd. was used as the flux. At that time, SDG flux was applied to the surface of the metal plate to be brazed with the composite material, and the SDG flux was put into a horizontal electric furnace in a nitrogen atmosphere kept at 350 ° C., and after 5 minutes, SP was applied to the surface to which the flux was applied. -Solder 27 solder (bar shape with a diameter of about 2 mm) and melt it,
It was covered with P-27 solder and taken out of the furnace. Next, combine the solder-coated surfaces of the composite material and the metal plate, and
A weight of g was put on the horizontal electric furnace kept at 350 ° C., and after holding for 10 minutes, the weight was taken out of the furnace and was cooled. This brazing object is divided into 4 in the plane and 10 mm x 1
Four 0 mm x 5 mm thick test pieces for measuring shear strength were prepared and subjected to a shear test by applying the test pieces to a tensile tester.
The bonding strength of the brazing surface was measured.

Brazing was also performed on the copper plate using a soft brazing material. As the soft solder, tin-lead solder (1.5 mm in diameter) containing resin for electrical wiring is cut into a length of 3 cm, bent into a ring shape, sandwiched between a copper plate and a test piece, and a 100 g weight is placed thereon at 300 ° C. Heated to
It was placed in a horizontal electric furnace in a nitrogen atmosphere and held for 10 minutes to melt the solder. Then, the brazing test piece, the copper plate, and the weight were taken out of the furnace as they were, and cooled on the heat insulating material.
Four pieces of this brazed material were prepared, and a shear test was carried out on this test piece using a tensile tester to measure the joint strength of the brazed surface.

As is clear from Table 5, it was confirmed that soldering for electric wiring and aluminum solder could also be used for soldering and high bonding strength could be obtained.

[0034]

[Table 5]

[0035]

As described above, the carbon of the present invention
The metal composite material has excellent bending strength and wear resistance, and can adopt a brazing method for joining with a copper plate or an iron plate, and is therefore extremely suitable as a carbon sliding plate for a pantograph. Also, as the manufacturing method thereof, since it can be manufactured based on a method of pressurizing and heating a mixture of a carbon material raw material and an additive metal at a temperature of about 500 ° C., the manufacturing cost does not increase and the manufacturing cost is relatively high. It is possible to provide a high-quality carbon-metal composite material at low cost.

[Brief description of drawings]

FIG. 1 is a photograph showing a microscopic particle structure of a tree-shaped electrolytic copper powder according to the present invention.

FIG. 2 is a photograph showing a microscopic particle structure of commonly used ground copper powder.

Claims (2)

[Claims] 1. A carbon / metal composite material containing a metal powder in a carbonaceous matrix, wherein the metal powder is a dendritic electrolytic copper powder. 2. A method for producing a carbon-metal composite material containing a metal powder in a carbonaceous matrix, wherein 10-40% by volume of dendritic electrolytic copper powder is added to a carbon material raw material composed of carbon aggregate, binder pitch and the like. Mix at the mixing ratio of 500 to 60
A method for producing a carbon / metal composite material, which comprises press-molding under heating at 0 ° C. and then firing.