SEAM-WELDED STEEL PIPE MANUFACTURING METHOD AND ITS MANUFACTURING APPARATUS

摘要

A method for manufacturing an electric resistance steel pipe having a good toughness at a welded portion is provided, the method being capable of stably manufacturing an electric resistance welded steel pipe having a desirable toughness at a welded portion although a steel strip serving as a base material has a dimensional variation. Groove shapes 5a and 5b are applied to edges 4a and 4b of an open pipe 4, an edge shape monitor 11 continuously captures images of the edges 4a and 4b immediately before electric resistance welding, and the captured images are input to an arithmetic processing unit 14 for image processing. Thus, a groove height h is measured, an optimum welding electric power is calculated on the basis of the measurement result, and the welding electric power from electric power generating equipment 6 is adjusted. Furthermore, an ultrasonic flaw detector 15 continuously measures an oxide distribution at the welded portion after the electric resistance welding. The optimum welding electric power is calculated on the basis of the measurement result, and the welding electric power from the welding power generating equipment 6 is adjusted.