JPH033441B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a copper-based sintered current collector sliding material. Conventional technology and its problems Characteristics required for current collector sliding materials include, for example, low aggression against the mating material, the trolley wire, sufficient abrasion resistance, and mechanical strength. However, it has low electrical resistance. Especially when considering the maintenance and lifespan of the trolley wire, the most important characteristic is that it is less aggressive. To reduce aggressiveness, lower the hardness of the material,
Abundant lubricity is an absolutely necessary condition.
It is advantageous that the material is soft and has good lubricity, since these tend to coincide. That is, when a lubricant is added, the softer the material, the more likely the lubricant will protrude, and the more opportunities for the lubricant to come into contact with the mating material. Conventional sintered alloys for current collector sliding are made of a matrix mainly composed of Fe or Cu, with various metals added to improve wear resistance. However, in all of these sintered alloys, the metal diffuses significantly into the base, and as the material hardens, the lubricity inevitably decreases, resulting in increased aggressiveness against the trolley wire. Furthermore, since the electrical resistance increases with the addition of metal, the amount of elements used as lubricants added to these materials is limited to a fairly small amount, resulting in further deterioration of lubricity. Furthermore, together with the increase in electrical resistivity, these elements extremely reduce the mechanical strength, especially the impact value. Elements used as lubricants also act in a similar manner, so the amount added is also limited from the viewpoint of mechanical properties. That is,
Metals added mainly for the purpose of improving wear resistance improve aggressiveness to trolley wires, electrical resistivity,
It has a negative effect on most factors such as impact value, and this is the reason why it has been thought that it is contradictory to have both wear resistance and lubricity in sintered current collector sliding materials. Means for Solving the Problems The present invention aims to solve these problems by making the Cu-based base as soft as possible to reduce its attack on the trolley wire, and to provide a current collector with excellent wear resistance. The purpose is to provide materials for active use. In other words, the present invention is characterized in that only the minimum amount of metal is added to maintain the mechanical properties and electrical properties at predetermined values, and the improvement in wear resistance is mainly obtained by using titanium or ferrotitanium that has been nitrided in advance. Concerning copper-based sintered current collector sliding materials. In the present invention, titanium or ferrotitanium is added after being nitrided in advance. Titanium or ferrotitanium is easily nitrided, but these nitrides are stable, and once nitrided, the nitridation does not progress to the inside, so the nitrided powder particles have a thickness of about 2μ or less from the surface. It is made of a very hard nitride layer and a soft interior made of pure titanium or pure ferrotitanium. FIG. 1 shows a model of the sliding condition of the product of the present invention to which these nitrides are added as an anti-wear agent. As shown in the figure, the part that actually acts as an anti-wear agent is the hatched area where the nitride layer contacts the mating material. Therefore, the proportion of the area occupied by the titanium and ferrotitanium nitride layers on the sliding surface is extremely small.Furthermore, during sliding, these nitride layers become abrasion powder and break off, and nitridation occurs as the sliding surface moves. Because the layer is extremely thin, approximately 2μ at most, it is less likely to attack the mating material. The wear resistance of the product of the present invention will be shown in Examples later, but it exhibits sufficient wear resistance. As mentioned above, it is the nitride layer of titanium or ferrotitanium, rather than the nitride of titanium or ferrotitanium, that improves the wear resistance. Although the exposed area of these nitride layers on the sliding surface is extremely small, the reason why they exert a remarkable effect on wear resistance is firstly that the nitride layer is extremely hard, and secondly.
This is due to the fact that these nitride layers are microscopically continuous from the sliding surface to the inside. The second cause will be explained in more detail. The nitrided layer exists on the very surface of the titanium or ferrotitanium powder particles with a substantially uniform thickness and in the form of an eggshell. When the product of the present invention is in a sliding state, in order for this nitride layer to wear out, a shearing stress sufficient to destroy the so-called egg shell is required, but this nitride layer is made of pure titanium or pure ferrotitanium inside. Naturally, it is firmly connected to the sliding surface, and it is difficult to break it and remove it from the sliding surface. Furthermore, when the sliding surface of the mating material is rough, there is a risk that the so-called "chip-off phenomenon" will occur, in which the entire wear-resistant particles separate from the matrix, rather than wear that gradually destroys the nitrided layer. This is solved by using ferrotitanium nitride as the wear-resistant particle. When ferrotitanium is nitrided, Ti, which is easily nitrided, is preferentially nitrided, and Fe is not nitrided, so when it is added to a base mainly composed of Cu, only the Fe in ferrotitanium diffuses into the matrix, making the bond stronger. Because it will be. Since titanium nitride hardly diffuses into the matrix, and the same applies to ferrotitanium as described above, the matrix itself hardly shows any hardening due to metal solid solution. A major feature of the product of the present invention is that the thin nitride layer is used primarily as an anti-wear agent and the soft matrix does not attack the mating material. titania,
Oxides such as silica are also known to be hard substances, just like titanium nitride layers, but when these are used as wear-resistant particles, the entire particle is hard, so the phenomenon of breakage and wear is due to "chip-off" phenomenon. Abrasion is more likely to occur, and in either case, the abrasion powder is hard and coarse and attacks the mating material, and cannot be expected to be effective as an anti-wear agent because it cannot be bonded to the matrix. As the titanium or ferrotitanium nitride in the present invention, it is preferable to use particles of about 100 to 200 mesh, for example. Furthermore, since the part that actually acts as an anti-wear agent is limited to the very surface of the particles, desired wear-resistant properties can be obtained by adjusting the particle size. The amount of titanium or ferrotitanium is approx.
0.5-10% by weight is preferred. In this range, sufficient wear resistance, lubricity, and mechanical strength can be obtained. The sintered current collecting sliding material of the present invention is characterized by containing the above-mentioned titanium or ferrotitanium nitride layer, and the other configurations may be the same as those of the usual copper-based sintered current collecting sliding material. Therefore, Cu or Cu-based alloys such as bronze,
Known base components such as brass can be used.
Further, in the present invention, metals and the like that are normally added to sintered current collector sliding materials can be added in the minimum amount that maintains the mechanical properties and electrical properties at predetermined values. Examples of these metals include Ni, Mo,
Metals such as Cu, Fe, Cr, p, and alloys of these metals, typical examples include FeMo, FeCr, CuCr, etc., and at least one or more of these can be added, usually in a range of about 0.3 to 15 wt%. However, in the present invention, the amount of these metals can be reduced compared to conventional ones, and is usually about 0.3 to 10 wt%.
It is particularly preferable to use the range. In the present invention, in addition to the above, WS ₂ ,
It is also possible to add lubricants such as MoS ₂ , C (graphite), and boron nitride, and antiwear agents such as Mo, Cr, FeMo, and FeCr. The sintered current collector sliding material of the present invention is obtained by adding titanium or ferrotitanium to a mixture of the base component, metal component, and other additives as necessary, which has been nitrided in advance, and molding and sintering the material. It will be done. To perform the nitriding treatment, as mentioned above, the temperature is about 600 to 1300°C in an atmosphere containing nitrogen or ammonia, such as nitrogen gas, a mixed gas of nitrogen and hydrogen, ammonia gas, or ammonia decomposition gas, especially in a neutral or reducing atmosphere. It is best to heat it with Preferably, the molding is carried out at about 2.5 to 7.5 ton/cm ² and the sintering is usually carried out at about 750 to 900°C. The sintering may be performed in an atmosphere containing a gas such as nitrogen, ammonia gas, argon, hydrogen, or helium, or in a vacuum atmosphere. In the sintered current collector sliding material of the present invention obtained as described above, the hardness of the matrix can be any value greater than that of pure copper sintered material, but the mechanical strength, lubricity, and mating material Considering various requirements such as aggressiveness to trolley wires (for example, trolley wires), a Brinell hardness of about 50 to 95, particularly about 60 to 80 is preferred. Within these hardness ranges, the added lubricant can sufficiently exhibit its effect. Effects of the Invention The current collector sliding material of the present invention has excellent properties such as excellent abrasion resistance and low aggressiveness against trolley wires. Examples The present invention will be explained below with reference to Examples. Examples 1 to 2 and Comparative Example 1 Table 1 shows the composition of samples containing Cu as a main component.
In addition, the numerical values in the table indicate weight %. Samples were prepared by mixing the components shown in the table, molding at 4 tons/cm ² , and sintering in ammonia decomposition gas at a sintering temperature of 860° C. for 90 minutes. However, nitrides (FeTi
-N) is prepared by preparing FeTi in ammonia at 1000℃ for 1
The one in which nitrides were generated by holding for a certain period of time was used. The physical properties of the obtained sintered body are shown in Table 2, and the results of the wear resistance test are shown in Table 3.

【table】

【table】

[Table] The wear test was performed using the obtained slider material with dimensions and shape of 10×
A piece of 25 x 90 mm was cut out and used as a test piece for current collector sliding wear. The test conditions were a pressing force of 5Kg/cm ² and an AC current.
(21V) 100A, sliding speed was set at 50 and 100km/h. The mating trolley wire is made of hard copper wire, and the diameter
The wire structure is wrapped around 385mm and has a contact sliding surface with a width of 6mm. In this case, the eccentricity of the slider plate should be set to 10mm.
The conditions for using pantographs on trains are similar to those for pantographs on trains. Among the test items, the friction coefficient was calculated from torque fluctuations, and the amount of wear on the slide plates was measured by removing them for each test and measuring the remaining weight and remaining dimensions using a micrometer. Evaluation of the sample surface condition and trolley surface condition is as follows. ◎ Very good 〇 Good △ Slightly poor × Poor As is clear from Tables 1 to 3 above, adding titanium or ferrotitanium nitride to the copper matrix causes damage to the trolley wire when used as a current collector sliding material. It has become clear that the wear resistance can be improved without increasing the wear resistance, and the effect is significant. Example 3 and Comparative Example 2 Compositions shown in Table 4 (numbers in the table represent weight %)
The components were mixed, molded at 4 tons/cm ² , and sintered at 880° C. for 2 hours in a nitrogen atmosphere to obtain a copper-based sintered body.
Note that FeTi-N in the table was prepared by previously holding FeTi in ammonia at 1000° C. for 1 hour to form nitrides. Table 5 shows the physical properties and wear resistance test results of the obtained sintered body. The test method was the same as in Examples 1 and 2 and Comparative Example 1, except that in the wear test, the sliding speed was 100 Km/h and the current was 200 A AC.

【table】

[Table] As is clear from Table 5, no nitriding treatment was performed.
It can be seen that when FeTi is used, the impact strength and abrasion resistance are inferior.

[Brief explanation of drawings]

FIG. 1 is a model of the sliding situation of the sintered current collector sliding material of the present invention, 1... mating material, 2... sliding surface,
3...Nitride layer, 4...Pure titanium or ferrotitanium, 5...Matrix.

Claims (1)

[Claims] 1. A copper-based sintered current collector sliding material containing approximately 0.5 to 10% by weight of titanium or ferrotitanium that has been nitrided in advance.