| 摘要 |
PURPOSE:To produce titled high tensile steel by heating a steel ingot contg. specific contents of C, Si, Mn, Al, S at a temp. higher than specific temp., and combining specific controlled rolling and cooling after rolling thereby reducing abnormal structure by central segregation. CONSTITUTION:A steel ingot is composed, by weight, of 0.005-0.2 C, 0.1-0.5 Si, 0.6-2 Mn, 0.005-0.08 Al and <0.008 S, and if necessary, 1 or >=2 kinds among 0.01-0.1 V, 0.003-0.04 Ti, <0.05 Cu, Cr, Ni, Mo, and 0.005-0.01 FEM are contained therein, and the balance Fe and unavoidable impurities are contained therein. Such ingot is heated to >=1,000 deg.C and is rolled at >=50% draft in a temp. region from Ar3+70 deg.C up to Ar3 then at >=20% draft in a temp. region from Ar3 to Ar3-70 deg.C. Right after the rolling reduction, the rolled steel is cooled to <=500 deg.C at 2-15 deg.C/sec cooling rate. Thus the non-tempered high tensile steel for low temp. service of 40-60kgf/mm.<2> grade having excellent low temp. toughness, weldability and characteristics in thickness direction is produced. |
