| 摘要 |
PURPOSE:To obtain a high toughness, refined steel with superior low temp. toughness by hot rolling a billet of a specific compsn. contg. C, Si, Mn and N as basic components in the recrystallization and unrecrystallized austenite zone, followed by rapid cooling and rolling in the ferrite zone below Ar1 transformation point. CONSTITUTION:A billet or ingot consisting of C; 0.01-0.20%, Si; 0.005-0.50%, Mn; 0.30-6.0%, N; 0.001-0.015% and the balance iron as basic components, contg. sol. Al; 0.001-0.015% or Nb, V or Ti; 0.005-0.10%, and optionally contg. Cu<=2%, Ni<=10%, Cr<=1%, Mo<=1%, etc. is heated to a temp. above 1000 deg.C to dissolve carbonitride well and hot rolled at a temp. of 1000-800 deg.C and a total reduction ratio more than 60% to let coarse austenite disappear. The hot rolled material is then rapidly cooled to a temp. below Ar1 point at a cooling rate over air cooling, rolled at a total reduction ratio more than 10% in the ferrite zone, heated to a temp. above Ac1 point, quench hardned, and tempered to give a refined, high tensile steel of super fine austenite grain size for low temp. use. |
