| 摘要 |
PURPOSE:To manufacture a high strength hot rolled steel plate with superior workability by subjecting a steel contg. specified percentages of C, Si and Mn to hot rolling, cooling and coiling under specified conditions to form a structure contg. a specified percentage by area of bainite. CONSTITUTION:A steel contg. 0.01-0.12% C, 0.1-1.6% Si and 0.5-2.3% Mn or further contg. >=1 kind among 0.01-0.08 Nb, 0.02-1.5% V, 0.01-0.08% Ti and 0.02-0.18% Zr is hot rolled at 700-900 deg.C finish temp., cooled at 10-40 deg.C/sec average cooling rate, and coiled at 575-350 deg.C. Thus, a steel plate having a polygonal ferrite + bainite structure contg. 3-60% by area of bainite. The Cr content of the steel is restricted to <= about 1%, <= about 0.01% rare earth element, Ca and Mg may be contained in the steel, and the S content is regulated to <= about 0.02%. |
