| 摘要 |
PURPOSE:To obtain a low-Mn high-tensile steel having no strain aging embrittlement by subjecting a steel having a prescribed component compsn. to hot rolling at a specific finishing temp. after heating then cooling the steel at the regulated average cooling rate in prescribed temp. range and specifying the temp. decreasing condition from said temp. down to room temp. CONSTITUTION:A steel consisting, by weight, of 0.1-0.2% C, <=0.5% Si, 0.6- 1.1% Mn, 0.01-0.08% sol.Al, and <=0.0030% N and the balance Fe and unavoidable impurities is prepd. The steel is heated to 900-1,200 deg.C to accomplish substantially formation of gamma iron and uniform solutionization of carbide and thereafter the steel is subjected to hot rolling at the finishing temp. of 900- 750 deg.C to improve toughness. The above-described steel after the hot-rolling is quickly cooled at 10-60 deg.C/sec average cooling rate in 800-500 deg.C temp. range to about <=300 deg.C. The steel after the quick cooling is cooled by taking >=5min in 300-100 deg.C temp. range to precipitate solid solution of C and solid solution of N and thereafter the temp. is decreased down to room temp., by which the intended low-Mn high-tensile steel is obtd. |
