Patent ID: 8715430

Claim:
A high strength cold-formed welded pipe excellent in ductile fracture characteristic, by containing, by mass %, C: 0.01 to 0.5%, Si: 0.01 to 3%, Mn: 0.1 to 5%, P: 0.03% or less, and S: 0.03% or less, and a balance of Fe and unavoidable impurities, having a two-phase microstructure containing, by area ratio, more than 5% to no more than 20% of a first phase of ferrite and a balance of a second phase of bainite and martensite, having a maximum value of a {100} accumulation degree of a cross-section rotated 20 to 50° from a plate thickness cross-section about the axis of the rolling direction of 3 or less, and having thickness parallel cracks measured by ultrasonic flaw detection of less than 1 mm.