METHOD OF MANUFACTURING WELDED PIPE OF MARTENSITE-BASED STAINLESS STEEL

PROBLEM TO BE SOLVED: To provide a method of manufacturing a welded pipe of martensite- based stainless steel, by which the generation of such welding defects as a blow hole and an insufficient penetration are prevented without lowering productivity. SOLUTION: In the method of manufacturing of the welded pipe of martensite-based stainless steel, by which an open pipe 1 is shaped into a cylindrical form with a shaping roll and welded with a laser beam while an upset pressurizing is performed with a squeeze roll 4, both edges 5 and 5 of the open pipe 1 which face each other are preheated with a high frequency heating method, then the position, which is decided by the amount E.I of preheating, an upset value U, and an angle α formed by both edges 5 and 5 in a part where both edges 5 and 5 in the vicinity of the squeeze roll 4 are butted in a V-shape, is irradiated with a laser beam. Further the position X decided by E.I, U, and αis kept in a predetermined range, and inner and outer beads are cut after pressurized by the squeeze roll.