| 摘要 |
PURPOSE:To ensure high strength and toughness in welded metal of pipe and to obtain the aimed bent pipe, by heating the steel pipe having welding metal of a specified compsn. to a specified temp. range, and bending it, while quenching. CONSTITUTION:As welding metal, steel pipe having main compsn. composed of 0.02-0.12wt% C, <=0.6% Si, 1.20-1.60% Mn, <=0.02% P, <=0.15% S, <=0.05% Nb, <=0.02% Al, <=0.010% N, <=0.035% O and the balance Fe with inevitable impurities is bent. Thereat, said pipe is heated to Ac3 point or above, preferably >=Ac3 point-<=about 1,100 deg.C, and bending worked while being quenched. It is preferable to quench said pipe at <=about 60 deg.C/sec cooling rate.
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