JPH0512427B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an electrical contact material, particularly a method for producing an Ag-oxide electrical contact material. (Prior art and its problems) The technology of dispersing oxides in Ag by internally oxidizing the Ag alloy has been widely used in the past, and especially in the field of electrical contacts, Ag-CdO, Ag
-Used in the production of electrical contact materials made of SnO ₂ , etc. Oxides such as CdO and SnO ₂ dispersed in Ag tend to improve adhesion resistance as the amount added increases, but Ag alloys that contain a large amount of solute metal and exhibit significant volumetric expansion due to oxidation may suffer from oxidation cracking. occurs, so Ag
It is not possible to use the so-called post-oxidation method in which the alloy is processed into a contact shape and then internally oxidized. For this purpose, Ag alloy powder, coarse particles, wire rods, plate materials, etc. are internally oxidized, then compressed and sintered, and then processed into electrical contact materials of the desired shape through plastic processing such as extrusion, wire drawing, or rolling. A so-called pre-oxidation method is used for processing. However, when an Ag-Sn alloy is internally oxidized using this pre-oxidation method, SnO ₂
A cohesive layer is formed, no more oxygen enters the interior, and the progress of internal oxidation is stopped. Since most of the Sn is gathered in the agglomerated layer of SnO ₂ , that is, the concentration of Ag-Sn inside the agglomerated layer is very low, plastic processing such as extrusion, wire drawing, or rolling is not possible. Even if the agglomerated layer is destroyed and internal oxidation occurs again, very little SnO ₂ will precipitate, so the SnO ₂ will not be homogeneously dispersed and a broken agglomerated layer will remain, resulting in extremely poor workability and poor electrical contact. When processed, cracks are likely to occur. (Object of the Invention) The present invention was made to solve the above problems, and it is possible to homogeneously disperse an oxide agglomerated layer in Ag, and when processed into an electrical contact,
The object of the present invention is to provide a method for producing an Ag-oxide electrical contact material that can reduce the occurrence of cracks. (Structure of the Invention) The method for producing the Ag-oxide electrical contact material of the present invention involves partially internally oxidizing an Ag alloy to leave the Ag alloy in the inner layer and forming an oxide in the outer layer. Or make a board and then use this
After thermal diffusion treatment is performed at a temperature below the melting point of Ag to disperse oxides in the Ag alloy, compression and sintering are repeated, and the desired shape is obtained by plastic processing such as extrusion, wire drawing, or rolling. It is characterized by the fact that the unoxidized portion is internally oxidized. In the method for manufacturing the Ag-oxide electrical contact material of the present invention, the Ag alloy is first partially internally oxidized to leave the Ag alloy in the inner layer and form the Ag-oxide in the outer layer. This is to leave an unoxidized part without creating an agglomerated layer of material, and the reason why this material is subjected to thermal diffusion treatment is to make the oxide dispersed in the Ag alloy, compress it, and then wire-draw it after sintering. This is to facilitate plastic working such as rolling, to prevent oxidation cracking from occurring during subsequent internal oxidation, and to prevent cracking from occurring when processed into electrical contacts. (Example) The method for producing an Ag-oxide electrical contact material of the present invention will be explained together with an example. First, to explain an example, Ag-Sn9.5wt% powder obtained by the molten metal powder atomization method was
After forming into a billet with a porosity of about 30%, it was internally oxidized at 400° C. under 9 atmospheres of oxygen until the weight ratio of Ag:Sn became about 18:1. The outer layer of each powder of this internally oxidized billet was Ag- _SnO2 . This billet is heated to a temperature below the melting point of Ag in a nitrogen atmosphere.
In this example, thermal diffusion treatment was performed at 500°C to disperse SnO ₂ in Ag-Sn, and then compression and sintering were repeated five times to extrude into a wire rod with a diameter of 6 mm.
After further drawing this wire to a diameter of 2.4 mm,
They were molded into rivet molds with head diameters of 4 mm and 5 mm, and were internally oxidized at 400°C under 9 atmospheres of oxygen so that no unoxidized parts remained, to obtain electrical contact materials. Note that the wire drawing process could be performed using a die within a processing rate of 15 to 20%. Next, to explain a conventional example, Ag-Sn9.5wt% powder obtained by the molten metal spraying method as in the example was molded into a billet with a diameter of 50 mm and a porosity of about 30%, and then heated at 450°C under 9 atmospheres of oxygen. When the billet was internally oxidized so that no unoxidized parts remained, an agglomerated layer of SnO ₂ was formed at the forefront of the oxidation, and no further oxygen entered the interior, and the progress of internal oxidation was stopped.
After extrusion processing into wire rods of 1.0 mm diameter and drawing processing into wire rods of 2.4 mm diameter, the wires were formed into rivet-shaped electrical contact materials with head diameters of 4 mm and 5 mm. Note that the wire drawing process could be performed using a die within a processing rate of 10 to 15%. The occurrence of cracks in 100 pieces of the thus obtained rivet type electrical contact materials of the example and the conventional example were observed, and the results shown in the table below were obtained.

[Table] As is clear from the above table, the rivet-type electrical contact materials of the examples have significantly less cracking than the rivet-type electrical contact materials of the conventional examples. This is an Ag alloy in which oxides are dispersed in the outer layer by partially internally oxidizing the Ag alloy, without creating an agglomerated layer of oxides.
- An oxide is created, leaving an Ag alloy in the inner layer, which is then subjected to thermal diffusion treatment to disperse the oxide in the Ag alloy, making processing easier and allowing oxidation to occur during internal oxidation of unoxidized parts. This is because no cracks occur. (Effects of the Invention) As explained above, the method for producing the Ag-oxide electrical contact material of the present invention involves partially internally oxidizing the Ag alloy, and dispersing the oxide in the outer layer without forming an agglomerated layer of the oxide. The inner layer is made of Ag-oxide, and the Ag alloy is left in the inner layer, which is then heat-diffused to disperse the oxide in the Ag alloy, making wire drawing, rolling, etc. easier, and then unoxidized. Even if a portion is oxidized, oxidation cracking does not occur, and the yield is significantly improved.

Claims (1)

[Claims] 1 Part of the Ag alloy is internally oxidized to leave the Ag alloy in the inner layer and to form a powder, coarse grains, wire or plate material with Ag-oxide formed in the outer layer, and then this is heated at a temperature below the melting point of Ag. Perform diffusion processing
After the oxide is dispersed in the Ag alloy, compression and sintering are repeated, and the desired shape is formed by plastic processing such as extrusion, wire drawing, or rolling, and then the unoxidized portions are internally oxidized. A method for producing an Ag-oxide electrical contact material characterized by: