| 摘要 |
PURPOSE:To produce inexpensively a hot-worked steel material contg. ultrafine ferrite particles and having high strength by subjecting a steel material contg. a specific compsn. and amt. of C, Si, Mn, Cr, Cu, Ni, etc. to a high rolling reduction by hot working at a specific temp. then cooling quickly the material. CONSTITUTION:A steel material contg. 0.08-0.4% C, <=2% Si, 0.5-5% in total of >=1 kind among Mn, Cr, Cu and Ni, <=1% in total of other alloy elements, and consisting of the balance unavoidable impurities and Fe is subjected to working at a draft of >=40% in one pass or >=60% within one second of >=2 passes of cumulative working at 680-1,000 deg.C in the final stage of hot working. The steel material is thereafter forcibly cooled to at least <=620 deg.C, more preferably <=350 deg.C at a cooling rate of >=50 deg.C/sec within two seconds. The high- strength and hot-worked steel material consisting of the fine structure contg. 1-50vol% cubic ferrite texture of <=5mu average grain size and the balance at least one kind of bainite or martensite, having >=70kg/mm.<2> strength and having good ductility, toughness and processability is obtd.
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