| 摘要 |
PURPOSE:To produce a hot rolled thick steel plate having high strength and high toughness by subjecting steel contg. specific ratios of C, Si, Mn, solAl, Nb, and N to quick cooling under specific conditions between rough rolling and finish rolling thereby suppressing precipitation of NbCN. CONSTITUTION:An ingot of steel contg., by weight 0.05-0.15% C, 0.001-0.5% Si, 0.8-2% Mn, 0.001-0.06% solAl, 0.005-0.1% Nb, and 0.002-0.01% N is heated to about >=1,000 deg.C and is roughly rolled at about >=950 deg.C. The rolled steel is subjected to air cooling for adjustment of the rolling temp. in the temp. range of about 900 deg.C. The steel is then quickly cooled at about >=0.5 deg.C/sec cooling rate in the temp. range of about 870-930 deg.C to suppress the precipitation of NbCN prior to finish rolling and thereafter, the steel is subjected to the finish rolling at about >=700 deg.C. The rolled steel is forcibly cooled down to about <=500 deg.C to precipitate fine NbCN, by which the hot rolled thick steel plate is produced.
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