METHOD OF MANUFACTURING HIGH TENSILE STRENGTH STEEL PLATES

摘要

METHOD OF MANUFACTURING HIGH TENSILE STRENGTH STEEL PLATES The steel plate having a high tensile strength is manufactured from a steel consisting essentially of 0.04- 0.16% by weight of C, 0.02 - 0.50% by weight of Si, 0.4 -1.2% by weight of Mn, 0.2 - 5.0% by weight of Ni, 0.2-1.5% by weight of Cr, 0.2 -1.0% by weight of Mo, 0.01 - 0.10% by weight of acid soluble A?, 0.030.15% by weight of one or more of V, Ti and Nb, 0.015% or less by weight of P, 0.006% or less by weight of S and the balance of iron and inherent impurities. The steel is heated to a temperature above a temperature at which carbo-nitrides of V and Nb and carbides of Ti become complete solid solution state, rolled with total reduction of 40% or more below 950.degree.C, quenched by simultaneous cooling immediately after completion of the rolling from a temperature above (A3 - 50).degree.C and tempered at a temperature lower than Ac1 temperature. the density of cooling water (W) for the quenching is determined by the following equation (I) or (II) in accordance with the plate thickness (t): (I) for the plate over 40mm thickness W = 0.7 to 1.5 m3/min?m2 (II)for the plate over 25mm and under 40mm thickness W = 0.7 to m3/min?m2.