ROLL FOR FORMING WELDED STEEL PIPE AND METHOD FOR MANUFACTURING WELDED STEEL PIPE

摘要

PROBLEM TO BE SOLVED: To provide a roll for forming a welded steel pipe and a method for manufacturing the welded steel pipe which curb the generation of defects to a low level in a warm temperature zone. SOLUTION: A steel strip is preheated to the warm temperature zone and, while a sintered hard alloy is built up on a surface of a caliber which has an internal water-cooled structure and a caliber bottom is separated from a caliber flange, is continuously formed into an open pipe with an idle forming roll by the caliber flange. Thereafter both edges of the open pipe are heated and opposition-contacted them by a squeeze roll. A lubricant containing a boric acid material and a water-soluble polymer is preferably supplied to a forming roll.