| 摘要 |
PROBLEM TO BE SOLVED: To produce a high strength seamless steel pipe having excellent toughness by an on-line working-heat treatment without adding expensive alloy steel. SOLUTION: (1) This method for producing the high strength seamless steel pipe having excellent toughness comprises steps of finish-rolling in which the steel material containing 0.04-0.5% C, 01.-1.0% Si, 0.2-1.5% Mn, 0.1-1.5% Cr, 0.01-1.0% Mo, <=0.03% P, <=0.003% S and 0.005-0.5% Al and, if necessary, further containing arbitrary elements is used as a base material, subsequent reheating at <=Ac1-100 deg.C charging temperature into a reheating furnace and at 850-1000 deg.C reheating temperature and immediate quenching thereafter. (2) In the above (1) preheating method, the charging temperature into the reheating furnace is preferably adjusted by changing the time from rolling completion to the charge into the reheating furnace by changing carrying conveyor speed and/or tray moving speed on the basis of the roll finishing temperature of the steel tube measured after the finish-rolling.
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