| 摘要 |
PURPOSE:To manufacture a high tensile hot rolled steel plate with low plane plastic anisotropy suitable for deep drawing without requiring a cold rolling process by hot rolling a low carbon steel contg. a specific amt. of Nb under combined hot rolling conditions. CONSTITUTION:A steel ingot is cast contg. C; 0.03-0.20%, Mn; 0.30-2.0%, Si; 0.05-1.0%, N; 0.0005-0.01%, sol. Al; 0.005-0.10% and Nb; 0.01-0.10% or further contg. one or more out of Cu; 0.20-0.50%, Ni; 0.05-0.30% and Cr; 0.10 -1.50%. The ingot is heated at 1200-1320 deg.C, rough hot rolled, and finish hot rolled into a below 6mm thick plate. The reduction ratio of the finish hot rolling is regulated to below 50% at below the lowest limit temp. of austenite recrystallization determined by the Nb content, the rolling is finished at 800-950 deg.C, and the result- ing plate is coiled at 500-680 deg.C. Thus, fine ferrite grains are grown to form a fine grain structure, enhancing the strength and toughness of the plate. |
