| 摘要 |
PURPOSE:To obtain a steel plate having >=1,200MPa yield strength, >=100J Charpy absorption energy and >=150MPasq. rt. m breaking toughness value (K1C) at the temp. of liquid He and having small variance in the mechanical properties in the thickness direction by specifying the content components and component ratios of a steel and specifying the sheet thickness rolling and finishing temp. as well as cooling conditions after rolling to prescribed conditions. CONSTITUTION:A steel ingot is composed, by wt%, of 0.01-0.1 C, 0.01-1 Si, 16-30 Mn, <0.03 P, <0.01 S, 3-10 Ni, 12-20 Cr, 0.1-0.3 N and the balance Fe with inevitable impurities and is so composed as to satisfy the formulas I , II. After such steel ingot is heated to 1,150-1,250 deg.C, the ingot is subjected to forging or blooming which ends at >=950 deg.C, then the steel is allowed to cool. Such billet is heated to 1,150-1,250 deg.C and is then subjected to hot rolling which ends at 950-1,010 deg.C and after holding at an equal temp. for 1-60min at >=800 deg.C or air cooling, the billet is water-cooled down to <=500 deg.C. |
