| 摘要 |
PURPOSE:To obtain a steel pipe of superior low temp. toughness by forming a steel pipe from steel plate which contains specific ratios of C, Si, Mn, P, S, Nb and is hot rolled under prescribed conditions and subjecting the pipe to an aging treatment at prescribed temps. CONSTITUTION:The steel contg., by weight, <=0.15% C, <=0.7% Si, 0.5-2.5% Mn, <=0.025% P, <=0.005% S, 0.01-0.15% Nb, <=0.07% Al, and further if necessary, contg. 0.01-0.15% V, 0.005-0.15% Ti, 0.005-0.15% Zr, etc. is produced by melting and a slab having the thickness from 300mm. up to three times the thickness of the final product is cast continuously from said steel. At the point of the time when the surface temp. of the slab attains 1,000-800 deg.C, rough rolling is begun. Within 60sec after the end of the rough rolling, final finishing is begun at 950- 750 deg.C and the steel is subjected to finish rolling at >=60% draft and Ar3 transformation point -650 deg.C temps. Such hot rolled steel strip is coiled at 750-450 deg.C and is formed to a steel pipe. The steel pipe is subjected to an aging treatment at 100-400 deg.C. |
