JPS6411698B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sintered electrical contact material (hereinafter referred to as "electrical contact material"). Conventionally, as electrical contact materials, silver-metal oxide type, silver-nickel type, silver-tungsten type, silver-graphite type, etc. have been used. In particular, silver-nickel electrical contacts are widely used because of their good contact performance and workability. Conventionally, 10% to 30% nickel by weight is often used.
The reason for this is the contact resistance required for electrical contacts,
This is because the overall evaluation of welding resistance and abrasion resistance is excellent. If it is less than 10%, it has not been used in the past because the contact performance is almost the same as that of silver, but as mechanical parts have recently become smaller, the contact force and separation force have become smaller, resulting in higher contact resistance or This causes instability and ultimately leads to poor conduction, causing mechanical parts to malfunction. The reason for this is that silver and nickel hardly dissolve in solid solution, so silver powder and nickel powder are mixed, compressed,
Manufactured using a powder metallurgy method called extrusion. Therefore, silver powder and nickel powder are mechanically mixed and bonded, and when this material is used as an electrical contact, the nickel aggregates due to the electrical contact heat and arc heat during opening and closing, and the nickel oxidizes. It is to become nickel. However, in the past, this problem could be solved by improving the mechanical parts, such as by increasing the contact force and separation force, but as mentioned at the beginning, with the miniaturization of the mechanical parts, it became impossible to deal with this problem. In view of the above circumstances, the present invention was made with the object of stabilizing the contact resistance of silver-nickel electrical contact materials. Another object of the present invention is to provide an electrical contact material that has stable contact resistance without impairing the advantages of silver-nickel electrical contact materials, such as good workability, good welding resistance, and wear resistance. shall be. The present invention is an electrical contact material comprising, by weight, 5 to 10% nickel and at least one of tungsten carbide, chromium carbide, or molybdenum carbide, with the balance being silver in a total of 0.4 to 2%. Tungsten carbide, chromium carbide, and molybdenum carbide all have extremely high hardness and are poorly compatible with silver and nickel. Therefore, the present invention attempts to uniformly disperse at least one of these carbides in a silver-nickel alloy material to prevent agglomeration of nickel and improve contact performance. Here, the reason why the weight percent of nickel is limited to 5 to 10% is because if it is less than 5%, the welding resistance and abrasion resistance will deteriorate, and if it is more than 10%, the agglomeration and oxidation of nickel will become severe. Also tungsten carbide,
Chromium carbide or molybdenum carbide acts equally on the silver-nickel alloy in the range of 0.4 to 2%, and either carbide stabilizes contact resistance without impairing welding resistance or abrasion resistance. However, if it is less than 0.4%, it will not be possible to prevent the agglomeration of nickel due to the heat of the dure and arc when electrical contacts are opened and closed, and if it exceeds 2%, the workability will deteriorate and the wear and tear during opening and closing will be significant, so the total amount of these carbides should be reduced to 0.4%. It was limited to ~2%. Next, in order to clarify the effects of the electrical contact material according to the present invention, specific examples and conventional examples thereof will be described. Example 1 Silver powder, nickel powder, and tungsten carbide powder each having a particle size of about several tens of microns were mixed in a weight ratio of 90:8:2. This mixed powder was repeatedly compressed and sintered, then hot extruded and cold wire drawn. and,
By header processing this wire, we obtained a movable contact with a head diameter of 2.8 mm and a fixed contact with a head diameter of 3.5 mm. Example 2 Silver powder, nickel powder, tungsten carbide powder, and molybdenum carbide powder with a particle size of about 100 microns were mixed in weight ratio.
They were mixed at a ratio of 94:5:0.5:0.5. A movable contact and a fixed contact were obtained using this mixed powder in the same manner as in Example 1. Example 3 Silver powder, nickel powder, and chromium carbide powder each having a particle size of about 100 microns were mixed in a weight ratio of 89.6:10:0.4. A movable contact and a fixed contact were obtained using this mixed powder in the same manner as in Example 1. Conventional Example 1 Silver powder and nickel powder with a particle size of several tens of microns were mixed at a weight ratio of 90:10. This mixed powder was repeatedly compressed and sintered, then hot extruded and cold wire drawn. Then, by header processing this wire, a movable contact with a head diameter of 2.8 mm and a fixed contact with a head diameter of 3.5 mm were obtained. Conventional example 2 Silver powder and nickel powder with a particle size of about 100 microns are
They were mixed at a ratio of 70:30. A movable contact and a fixed contact were obtained using this mixed powder in the same manner as in Conventional Example 1. Therefore, nine sets of rivet-type electrical contacts of Examples 1 to 3 and Conventional Examples 1 to 2 were subjected to opening/closing tests under the following test conditions, and the welding resistance and contact resistance were investigated, and the results are shown in the table below. I got it. Test conditions Voltage AC100V 50Hz Current 5A Opening/closing frequency 20 times/min Load Resistance Number of opening/closing Until welding occurs

[Table] As is clear from the results in the table above, the electrical contacts made using the electrical contact material of the present invention have more stable contact resistance than conventional electrical contacts, and the welding resistance is the same as that of conventional electrical contacts. I can see that it is excellent. As is clear from the above description, the electrical contact material of the present invention can be said to be an epoch-making invention that has superior stability in contact resistance compared to conventional electrical contact materials.

Claims (1)

[Claims] 1. A sintered electrical contact material comprising, by weight, 5 to 10% nickel, a total of 0.4 to 2% of at least one of tungsten carbide, chromium carbide, and molybdenum carbide, and the balance being silver.