JPS59118287A - Electrode material for electric resistance welding - Google Patents

Abstract

PURPOSE:To provide an electrode material for electric resistance welding which is so formed as to withstand the use under high welding current by dispersing a specific amt. of >=1 kind among metallic carbide, metallic oxide and metallic nitride in a copper-bismuth alloy having a prescribed compsn. CONSTITUTION:An electrode material for electric resistance welding is formed by dispersing 0.1-10wt% >=1 kinds among metallic carbide such as TiC, metallic oxide such as Al2O3 or ZrO2, and metallic nitride such as ZrN in a matrix of a copper-bismuth alloy contg. 0.1-10wt% bismuth. Outstanding effects such as an improvement in welding resistance, increased hardness, a less increase in the surface area thereof in welding under high welding current or the like are obtainable with such electrode material, although conductivity decreases.

Description

Detailed Description of the Invention (a) Technical Field The present invention relates to an electrode material for resistance welding, and more specifically to an electrode tip used in electric resistance spot welding and a disc-shaped electrode used in electric resistance seam welding. This relates to electrode materials such as.

(B) Background Art The present applicant has filed a patent application as an alternative to electrode materials such as chromium copper that belong to the class λ of conventional RWMA. Bismuth 0. / - / We have proposed an electrode material for electric resistance welding made by casting or forging a copper alloy containing 0% by weight.

This electrode is characterized by the following points.

cL) Hismuth forms a solid solution with copper at high temperatures, but at room temperature it does not form a solid solution with copper and forms an amorphous form at copper grain boundaries when added up to about 7% by weight, and forms cells in the copper grain boundaries when added in higher amounts. They are dispersed in the matrix and precipitated finely. Therefore, this copper alloy can have high electrical conductivity.

b) Bismuth dispersed and precipitated in the copper matrix is gradually oxidized from the tip under heating of the electrode and partial pressure of oxygen in the steel to form a refractory oxide. As a result, the tip of the electrode has fire resistance, and welding to the material to be welded is prevented.

C) In addition, even if partial wetting occurs between the material to be welded and the electrode, or even if the electrode tip picks up the material to be welded, the electrode tip will peel off into fine powder due to the presence of bismuth oxide. Since it does not adhere to the material to be welded, the material to be welded will not be contaminated, and the tip of the electrode will self-shape without shaving for a considerable period of time.

In this case, the lower limit of the amount of bismuth added is 0.7% by weight, and if the amount is less than this, the above-mentioned effects and effects are difficult to be observed. Moreover, the upper limit is 70% by weight, and if the amount is more than this, the alloy becomes brittle.

(C) Disclosure of the Invention The present invention relates to an improvement of an electrode material for electric resistance welding made of the above-mentioned copper-bismuth alloy. The alloy is characterized in that a refractory metal powder is dispersed in the matrix without forming a solid solution with the alloy.

Examples of such refractory metal powders include:
Metal carbides such as T i C, yL/! 40s and ZrO2
It is a powder of one or more of metal oxides such as ZrN and metal nitrides such as ZrN, and if it is contained in an amount of 0.7% by weight or more, it increases the hardness and melting point of the electrode material. Therefore, welding of the electrode material under high welding current is prevented. Further, the upper limit thereof is approximately 20% by weight, preferably 10% by weight or less, and if the amount exceeds this amount, the electrical conductivity of the electrode material will be too low.

2) Example Cu-B1j (weight M%) alloy powder was sintered and this alloy powder was sintered with 3 wt% At203 powder, and this was extruded using a hot press to form a spot welding electrode tip with a diameter of 6 mm. The material was obtained and processed into a pointed electrode tip with a diameter of 6.35 mm. Furthermore, a pointed electrode tip similar to the above is obtained by separately mixing 3% by weight of TiC powder, 3% by weight of ZrCh powder, and 3% by weight of ZrN powder into the Cu-B1 alloy powder instead of the kt20s powder. I got it.

These electrode tips are similarly pointed-shaped electrode tips (conductivity IAC 8fo%, hardness HRF ~ 7) obtained by casting or forging a molten alloy containing 1.3' weight%
Compared to No. 0), although the electrical conductivity was lower, the hardness was approximately 70 to 20% higher, and it was recognized that it was suitable for welding under high welding current.

(e) Effects of the invention As mentioned above, this invention adds metal carbide, oxide, or nitride in a dispersed manner to an electrode material for electric resistance welding made of a copper-bismuth alloy containing 0.7 to 10% by weight of bismuth. According to the electrode material of the invention, although the electrical conductivity is reduced, its fire resistance and therefore its welding resistance are improved, and its hardness is also increased, making it an excellent material with less increase in surface area even during welding under high welding current. It has the advantage of providing the desired effect.

Patent applicant: Chugai Electric Industry Co., Ltd. 1-

Claims (1)

[Claims] Electricity characterized by being made by dispersing at least 7 or more of metal carbides, metal oxides, and metal nitrides in an amount of 007 to 20% by weight in a copper-bismuth alloy containing 0.1 to 10% by weight of bismuth. Electrode material for resistance welding.