TACK WELDING METHOD FOR PRODUCTION OF SPIRAL WELDED STEEL PIPE

摘要

PURPOSE:To obtain a tack welding which has a sufficiently joint strength and a good external beat shape, by welding spirally steel band plates, which have edges of a specific shape, with a high frequency current. CONSTITUTION:Edges of steel bands 1 and 1' to be welded having a thickness (t) (mm.) are generally projected with root faces (f) provided in their edge parts, and steel plates 1 and 1' are butted while overlapping partially to obtain an X edge having included angles theta. The steel band 1 which is preliminarily subjected to the edge preparation actually is wound up spirally and advances in the direction of an arrow 5 as a pipe 2. A high frequency current is applied through contact chips 3 and 4 of the steel band 1 and the pipe 2, and both edge parts are subjected to the butt tack welding at a welding point (a) while overlapping partially. The X edge having the angle theta of 45-120 deg. and the root face (f) of 0.1t-0.5t (mm.) is required for obtaining a good tack welding.