JPH02225636A - Manufacture of electrical contact material - Google Patents

Abstract

PURPOSE:To obtain the electrical contact material having excellent initial deposition resistance by mixing Ag2O powder with MoO3 powder or WO3 powder, subjecting the mixture to reduction under heating into a metallic powder mixture and thereafter executing compacting and sintering. CONSTITUTION:Ag2O powder is mixed with MoO3 powder or WO3 powder so that the amt. of Mo or W is regulated to 10% in an Ag-Mo series or an Ag-W series. The Ag2O-MoO3 mixed powder or Ag2O-WO3 mixed powder is heated to 300 to 500 deg.C in the atmosphere of N2 gas to thermally decompose Ag2O into Ag powder in the first place and is thereafter heated to 500 to 950 deg.C in the atmosphere of reducing gas such as hydrogen to reduce MoO3 or Wo3 into the powder of Mo or W. The Ag-Mo mixed powder or Ag-W mixed powder is repeatedly subjected to compacting and sintering and is thereafter subjected to hot extruding and drawing, by which the electrical contact material free from the defect such as initial deposition can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing an electrical contact material, and particularly to a method for producing an Ag-based electrical contact material produced by a powder metallurgy method.

(Prior art and its problems) Ag and metals that are difficult to dissolve in Ag (Mo, WlTi, Cr)
, Co, etc.) are generally used as electrical contacts, although they are excellent in low contact resistance and wear resistance, they are susceptible to welding resistance, particularly initial welding.

For example, when looking at the welding resistance using the Weibull distribution parameter m, if m is less than 1, it is classified as an early welding type, and this defect was considered to be a fatal defect. Furthermore, the amount of wear during opening and closing of contacts is related to the sintered density, and if the density is insufficient, rapid wear occurs.

The conventional manufacturing method for Ag+ (a metal that is difficult to form a solid solution with Ag) is to mix Ag powder and a metal powder that is difficult to form a solid solution with Ag, and then form it into a wire of the desired shape by compression, sintering, and extrusion. The metal particles in this wire, which are difficult to form a solid solution with Ag, had aggregated to a size of 10 μm to several tens of μm. This is thought to be because the powder has a high surface energy, so the same metal powders aggregate during mixing. In other words, the initial welding occurs because the metal particles, which are difficult to dissolve in Ag in the wire, are not uniformly and finely dispersed.

Also, rapid wear of the blisters and contacts during powder processing and sintering was a problem.

As a result of intensive research, the inventors of the present invention have developed a method for manufacturing electrical contact materials that does not cause initial welding and is less likely to be rapidly worn out when the contacts are opened and closed.

(Means for Solving the Problems) The manufacturing method of the present invention is a method for manufacturing electrical contact materials by powder metallurgy, in which both Ag powder and metal powder that is difficult to dissolve in Ag are mixed as metal oxide powder, and then It is characterized by reducing the metal oxide powder. That is, the aim is to prevent agglomeration by mixing metal powder as oxide powder, and at the same time to take advantage of the brittleness of metal oxide and break up the metal oxide powder during mixing to make the particles finer. Therefore, these effects are not inhibited even if metals other than metals that are difficult to form a solid solution with Ag are added as additives.

The mixing device includes a V-type mixer, a ball mill, a pulverizer, and the like, and these may be used in combination. In addition, it is preferable to reduce the metal oxide powder in stages to avoid rapid sintering shrinkage due to heat generated by H20.
By thermally decomposing silver oxide at 00°C and then reducing molybdenum oxide or tungsten oxide at 500 to 950°C, a sintered body with fewer blisters can be obtained. As a result, we succeeded in suppressing the rapid increase in consumption when opening and closing contacts, which occurs due to insufficient increase in density.

(Comparative Example 1) Ag powder and M003 powder adjusted to form an A g -Mo 10 wt% alloy were premixed for 3 hours using a V-type mixer, and then filled into a crucible with an inner diameter of 50φ and heated to a temperature of 800.
Reduction treatment was carried out in a H2 atmosphere. Next, compression and sintering were repeated, followed by hot extrusion and drawing to produce wire rods in the order of 2.5φ and 2φ. When the cross section of this wire was observed with a metallurgical microscope, all Mo particles were 5 μm or less in size.

(Comparative Example 2) Ag powder and WO1 powder adjusted to form an Ag-W10wt% alloy were premixed for 3 hours using a V-type mixer, then filled into a crucible with an inner diameter of 50φmm and heated to a temperature of 800'C H2.
Reduction treatment was carried out in the atmosphere. Next, compression and sintering were repeated, followed by hot extrusion and drawing to obtain wire rods of 2.5φ and 2φ. When the cross section of this wire was observed with a metallurgical microscope, W
All particles were 5 μm or less.

(Conventional example) 450 g of Ag powder and 50 g of W powder were mixed in a V-type mixer.
After mixing for a while, it is filled into a mold with an inner diameter of 50a*, and the temperature is 80℃.
Heat treatment was performed in a vacuum at 0° C. for 1 hour. Next, compression and sintering were repeated, hot extrusion, and drawing were performed to form 2.5φ and 2φ
■It was made into a wire rod. When the cross section of this wire was observed with a metallurgical microscope, the W particles were in the range of 15 μm to 60 μm.

The wire rods obtained in Examples 1 and 2 and the conventional example were subjected to header processing and had a head diameter of 4 mm, an expanded diameter of 2 电, a total length of 2.7 mm, and 5 μm or less.

(Example 1) After pre-mixing Ag2O powder and MoO* powder, which were adjusted to form an A g -Mo 10 wt% alloy, using a V-type mixer for 3 hours, they were filled into a crucible with an inner diameter of 50 φ.
00t: After thermally decomposing A, g20 in a N 2 atmosphere, the atmosphere was replaced with an H 2 gas atmosphere, and then the temperature was raised to 800° C. for reduction treatment. Next, compression, sintering, sewing, hot extrusion, and drawing process are performed to 2.5φr! 1111 and 2φ city wire rods were used. When the cross section of this wire was observed using a metallurgical microscope, all of the W particles were 5 μm or less in size.

(Example 2) Ag adjusted to form an A g -W lht% alloy
After pre-mixing the zO powder, WO, and powder for 3 hours using a V-type mixer, they were filled into a crucible with an inner diameter of 50φm111 and heated to 400°C.
After thermally decomposing AgzO in a N2 atmosphere, the atmosphere was replaced with a H2 gas atmosphere, and then the temperature was raised to 800°C for reduction treatment. Next, compression and sintering are repeated, hot extrusion, and drawing process.
．． The wire rod had a diameter of 5φ and a diameter of 2φmm.

When the cross section of this wire was observed with a metal M microscope, all of the W particles were 5 μm or less in size.

(Leaving space below) As is clear from the table above, the contact of Example 1.2 has a uniform and fine distribution of metal particles that are difficult to dissolve in Ag compared to the conventional example, so the characteristics It can be seen that the life span was more than doubled, and the Weibull distribution parameter m was 1 or more, indicating that no initial welding occurred.

(Effects of the Invention) As detailed above, the method for manufacturing an electrical contact of the present invention has the excellent effect of preventing the initial welding of metallic electrical contact materials that are difficult to dissolve in Ag-Ag.

Applicant: Tanaka Kikinzoku Kogyo Co., Ltd.

Claims (1)

[Claims] 1. In the powder metallurgical manufacturing method of an electrical contact material in which molybdenum or tungsten metal particles are dispersed in an Ag base, after mixing silver oxide powder and molybdenum oxide or tungsten oxide, and filling this mixed powder into a container, 3
Silver oxide is thermally decomposed at 00°C to 500°C, then 500°C
1. A method for producing an electrical contact material, which comprises reducing molybdenum oxide or tungsten oxide at a temperature of .degree. C. to 950.degree. C. to obtain a preliminary billet, followed by repeated compression and sintering to obtain a billet for extrusion.