| 摘要 |
PURPOSE:To obtain a high tensile steel plate having high resistance to hydrogen induced cracking by subjecting a meterial wherein the MnS obtained by a Ca treatment of low C-low Mn-B steel is decreased considerably to controlled rolling under specific conditions. CONSTITUTION:The steel ingot contg., by weight, 0.005-0.05% C, 0.005-0.80% Si, 0.6-1.2% Mn, 0.005-0.03% Ti (where Ti%>=3.4N%), 0.003-0.0020% B, 0.0005-0.0050% Ca, 0.005-0.100% Al, contg. >=1 kind among <=0.5% Cu, <=0.8% Cr, and <=1.0% Ni, contg. >=1.30 value of (Mn%+Cr%+Cu%+Ni%), contg. the following impurities, <=0.008% S, <=0.0020% P, <=0.05% Mo, <=0.008% N or further contg. >=1 kind 0.001-0.080% Nb and 0.002-0.200% V, and consisting of the balance Fe is heated to 900-1,150 deg.C and is then subjected to rolling at >=50% draft at <=900 deg.C, then the rolling is completed at 800-650 deg.C. |
