| 摘要 |
PROBLEM TO BE SOLVED: To produce a seamless steel pipe produced with both characteristics of high strength and high toughness needed to the steel pipe for oil well. SOLUTION: When a seamless steel pipe is produced by heating a blank composed by wt.% of 0.15-0.5% C, 0.1-1.0% Si, 0.1-1.5% Mn, <=0.02% P, <=0.002% S, 0.1-1.5% Cr, 0-0.5% Ti, 0-0.01% B, 0.005-0.5% Al, <=0.01% N, <=0.01% O and the balance Fe with inevitable impurities and by piercing in the hot-state, the working in the finish-rolling process is executed at <=40% compressed cross- section reduction and >=1,050 deg.C finishing temp. Successively, this formed steel pipe is kept to >=930 deg.C and directly quenched under the condition that the average short diameter in the austenitic grain before quenching is >=40μm.
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