GB620227A - Improvements in and relating to spot welding electrodes - Google Patents

Abstract

620,227. Electric welding. MALLORY METALLURGICAL PRODUCTS, Ltd., and HYDE, C. C. Jan. 10, 1947, No. 841. [Class 83 (iv)] A welding tip for a spot welding electrode has a body of relatively soft metal of low electrical resistance and having extending axially therethrough from end to end one or more wires or strips of relatively hard metal of high electrical resistance, the body forming an insert in the working end of the electrode. The tip which may comprise an insert 5 in a truncated conical main body 1 having an axial cooling hole 2, may consist of a soft metal body portion 6 such as of silver or silver alloy or composition containing 75 per cent of silver and also graphite, cadmium oxide or nickel, or of copper or aluminium, with contingent addition of a small proportion such as 3 per cent of chromium, cadmium or beryllium, and one or more relatively hard metal portions such as of tungsten, molybdenum, nickel and chromium alloy or heat-resisting steel, which may consist of one or a number of separate rods or wires 7 embedded in the body 6. The outer end of the insert may be formed with a transversely flattened portion 8 and sloping sides 9 merging into the conical face of the electrode. The total surface area of hard metal is preferably not more than 25 per cent of the whole surface area. The wires 7 may be replaced by a strip of tungsten bent into S-shape or four rectangular strips evenly distributed radially round the axis. The hard metal parts extend throughout the soft metal part and at the operative end may be flush with or extend beyond the soft metal part. The last modification may be initially produced in this manner or may be produced by forming it initially with an insert flush with the soft metal and then subsequently dissolving away part of the soft metal. The insert may be pre-formed before insertion or may be formed in situ in the recess. According to the Provisional Specification the hard metal parts may extend only part of the way through the soft metal part from the operative end.