METHOD FOR ELECTRIC RESISTANCE WELDED STEEL TUBE

摘要

A method for manufacturing an electric resistance welded steel tube including: forming a steel tube material into an almost cylindrical open pipe, the steel tube material being a steel sheet wherein Ti and N satisfy (N/14)<(Ti/47.9); forming an electric resistance welded steel tube by bonding ends of the open pipe to each other by induction resistance welding with heat input controlled so that the bond width is 30 to 65 mum; heating the electric resistance welded steel tube to a temperature equal to or higher than the Ac3 transformation temperature; and diameter-reducing rolling the heated electric resistance welded steel tube with rolling reduction expressed by an outer diameter ratio greater than (1-25/the bond width before diameter-reducing rolling (mum))×100% such that the bond width is 25 mum or less.