| 摘要 |
PURPOSE:To produce a steel sheet having an excellent DWTT characteristic at a low cost by rolling a billet consisting of specifically composed C, Si, Mn, Al, Ti and Fe at the limited draft, finish temp., etc. CONSTITUTION:The billet consisting of 0.01-0.20% C, <=1.0% Si, 0.3-3.0% Mn, 0.002-0.10% Al, 0.03-1.0% Ti and the balance substantially Fe is rolled at <=5% draft for each one pass and <30-50% total draft at <=850 deg.C and is subjected to finish rolling at 700-760 deg.C. The finer crystal grains are thereby formed while the generation of the abnormal stucture and mixed grains is suppressed without adding alloy element. The steel sheet which has excellent DWTT characteristic respectively in the rolling direction, the direction perpendicular thereto and the intermediate direction thereof and is suitable particularly for the thick sheet stock for a spiral steel pipe, is obtd.
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