| 摘要 |
PURPOSE:To obtain a high strength steel plate without deteriorating the workability by carrying out a working at a specified temp. and a specified reduction ratio during rapid cooling when steel contg. a specified percentage of C, Mn and other element is annealed after hot rolling and cold rolling. CONSTITUTION:Steel is prepared consisting of 0.03-0.15wt% C, 0.6-1.8wt% Mn as an element stabilizing the austenite phase and the balance Fe with inevitable impurities or further contg. >=1 kinds of other elements such as >=about 0.2wt% Cr and >=0.1wt% Mo stabilizing the austenite phase. The steel is mill-finished by hot rolling, coiled, and continuously annealed by heating at 730-880 deg.C as hot rolled or after cold rolling. During rapid cooling a working is repeated plural times at 250- 520 deg.C intermediate temp. T deg.C and 0.5-3% reduction ratio so as to attain 2-20% total reduction ratio. Thus, a steel plate having a structure composed principally of ferrite phase and low temp. transformation phase is obtd. |
