| 摘要 |
PROBLEM TO BE SOLVED: To produce a Cr-Mo seamless steel pipe free from the dispersion of strength and excellent in toughness by a simplified producing process. SOLUTION: In the case of heating a billet contg. 0.10 to 0.25% C, <=1.0% Si, 0.2 to 2.0% Mn, <=0.020% P, <=0.010% S, 0.2 to 1.5% Cr, 0.1 to 0.5% Mo, 0.005 to 0.020% Ti, 0.01 to 0.10% V and <=0.006% N, if required, contg. one or >= two kinds among <=1.0% Ni, <=0.5% Cu and <=0.01% Nb and the balance Fe with inevitable impurities, punching rolling the billet and thereafter, finish rolling composed of drawing and sizing the billet, under the condition of >=900 deg.C finishing temp., large working distortion is provided by finishing the billet at >=40% reduction rate in the cross section area. Moreover, after the finish rolling, without executing cooling, the billet is directly soaked to the temp. range of 900 to 1,000 deg.C, quenched and tempered so that the heat treatments are continuously executed online.
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