PURPOSE: To manufacture an electric welded pipe having a welded part excellent in toughness by forming and welding an electric welded pipe and successively sizing it after heat-treating its welded part, and finally straightening its shape by at least one stand.
CONSTITUTION: In a manufacturing line of an electric welded pipe, a blank pipe obtained by forming and welding a blank material is drawn into a prescribed outside diameter, and a sizing which requires an intense drawing for straightening a bend and making an internal stress uniform, etc. is performed and successively a post annealing for heat-treating a welded part is performed. Thereafter, a shape correction of the out of roundness by reforming rolls is performed in a cold or hot state while performing air cooling or water cooling, etc., and the pipe is cut while running to obtain an electric welded pipe. Thus the sizing is performed without damaging the toughness of the welded part, and the post annealing is performed without causing a peaking of pipe, accordingly the out of roundness is obtained by straightening the shape without performing drawing.
ISHIRO SABUROU
YASUGI SEIJIROU
SUGAMASA TETSUAKI
KURODA TAKASHI
NAGAHAMA YUTAKA
KONAWA TSUTOMU
SUGIMOTO YUUZOU
Next Patent: DEVICE FOR TREATING COILED WIRE ROD END