STEEL PIPE OF WELDED THIN SHEET AND MANUFACTURING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a thin-wall steel pipe having high strength and satisfactory workability, particularly superior in hydroforming workability, and a manufacturing method therefor. SOLUTION: The steel pipe has a welded and joined structure of a thin sheet comprised of either a TRIP steel, a DP steel, an IF steel, a BH steel, a stainless steel or a plated steel sheet. The steel pipe has such maximum and minimum thickness that the difference between them in a circumferential direction is 2% of the average thickness or less excluding the weld. The weld has width of HAZ of 2 mm or less. The method for manufacturing the steel pipe is characterized by forming the cut steel sheet into a shape of a pipe with press forming, and joining the butting parts with laser welding.