| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a welded steel pipe excellent in formability. SOLUTION: In this method for producing a welded steel pipe excellent in formability, a welded steel pipe containing, by mass, 0.05 to 0.25% C and >=0.3% Si is rapidly heated to a ferrite + austenite two phase region temperature, is held, is thereafter cooled to <=550 deg.C for <=30 sec and is subsequently cooled to 250 deg.C for >=10 sec. The welded steel pipe excellent in formability and workable to a complicated shape such as that of an automotive subframe can be produced at high productivity by heat treatment in a short time.
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