METHOD FOR HEAT-TREATING WELDED PART OF MARTENSITIC HIGH-CHROMIUM ELECTRIC RESISTANCE WELDED STEEL PIPE AND METHOD FOR MANUFACTURING MARTENSITIC HIGH-CHROMIUM ELECTRIC RESISTANCE WELDED STEEL PIPE

摘要

PROBLEM TO BE SOLVED: To surely prevent cold cracking in a welded part when a martensitic high-chromium steel pipe is manufactured by an electric resistance welded pipe manufacturing process.;SOLUTION: A martensitic high-chromium steel sheet which contains, by mass, 0.1-0.5% C, 7-18% Cr, ≤0.5% Si, ≤2% Mn, ≤0.03% P, ≤0.05% S, ≤0.1% Al, ≤0.1% N and the balance of Fe and inevitable impurities is subjected to roll molding, the roll-molded steel sheet is subjected to electric resistance welding to obtain an electric resistance welded steel pipe, the welded part of the electric resistance welded steel pipe is cooled to ≤100°C and the cooled welded part is reheated to the temperature that exceeds Ac₁ and is reheated so as to be equal to or lower than 1/2(Ac₁+Ac₃).;COPYRIGHT: (C)2011,JPO&INPIT