PRODUCTION OF LARGE-DIAMETER WELDED STEEL PIPE

摘要

PURPOSE:To obtain a large-diameter welded steel pipe having a satisfactory size correcting effect and high working accuracy by relieving the residual stress generated in the weld zone and near the same after inside and outside normal welding of the steel pipe then expanding the pipe. CONSTITUTION:A steel plate is formed to a tubular body and the joint part thereof is subjected to tack welding and inside and outside normal welding. The steel pipe 5 after the normal welding is passed through a device for relieving residual stress in the weld zone consisting of a roll stand 2, a boom stand, etc. and is directly rolled by an outside bead rolling roll 21, an inside bead rolling roll 31, etc. to relieve the residual stress generated in the weld zone and near the same by plastic working. The pipe is then expanded. The large-diameter welded steel pipe of which the out of roundness in the axial line direction and the out of roundness in the circumferential direction are corrected within a prescribed size range is obtd. by the above-mentioned method.