| 摘要 |
PURPOSE:To perform grain refining and improve the ductility and toughness by rough-rolling a steel slab contg. specified amts. of C, Si, Mn, Al and Nb at a lowered rolling start temp. and a reduced rate of rolling strain. CONSTITUTION:A steel consisting of, by weight, 0.01-0.2% C, 0.05-0.5% Si, 0.3-2% Mn, 0.005-0.08% Sol.Al, 0.005-0.1% Nb and the balance Fe is manufactured by refining. A hot slab of the steel is optionally heated before transformation is completed and it is rough-rolled twice or more and subjected to controlled rolling. The rough rolling is carried out under conditions of 900-1,050 deg.C rolling start temp., 10<-4>-10<-1>/sec rate of rolling strain and >=5% draft per one pass.
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