A New ERW-SAW Process for Spiral Pipe Manufacture

A new welding process which combines ERW and SAW has been developed to improve the productivity and product quality of spiral pipe manufacturing lines. The features of this process are as follows.(1) Construction of a compact and highly efficient spiral pipe mill is made possible by the combination of ERW and SAW in one welding line.(2) Lap type ERW is applied in which the pipe-side edge and the strip-side edge approach each other in the vertical direction.(3) High-speed cosmetic SAW is applied with the use of multiple twin wire system to cover the weld from both inside and outside after ERW.The features of the cosmetic SAW are low heat input, high-efficiency deposit and high oblate ratio of heat source shape to prevent formation of undercuts.(4) The welding speed of the new ERW-SAW process is 5-6m/min, compared with the 3m/min maximum of the conventional process, and the joint performance is equal to or higher than that by the conventional SAW process.