Method for manufacturing electric-resistance-welded steel pipe

摘要

A method for manufacturing an electric-resistance-welded steel pipe, comprises the steps of; (a) preparing a hot-rolled steel sheet consisting essentially of 0.005 to 0.2 wt.% C, 0.1 to 0.35 wt.% Si, 0.5 to 2 wt.% Mn, 0.01 wt.% or less P, 0.003 wt.% or less S, 0.001 to 0.1 wt.% Nb, and 0.001 to 0.006 wt.% Ca; (b) forming continuously an open pipe from the hot-rolled steel sheet using a multi-stage forming rolls; (c) heating both edges of the open pipe facing each other using electric resistance; and (d) pressure-welding both of the edges which were heated by electric resistance by applying irradiation of laser beam while controlling the upset using a set of squeezing rolls.