PRODUCTION OF STEEL PLATE FOR LINE PIPE EXCELLENT IN CO2 CORROSION RESISTANCE AND LOW TEMPERATURE TOUGHNESS

摘要

PURPOSE: To produce a high tensile strength steel plate excellent in CO₂ corrosion resistance and low temp. toughness by subjecting a low carbon steel having a specified compsn. to hot rolling under the conditions of a specified temp. and rolling reduction and thereafter executing water cooling and air cooling. ;CONSTITUTION: A slab having a compsn. contg., by weight, 0.01 to 0.09% C, 0.5% Si, 0.7 to 1.5% Mn, 0.03% P, 0.005% S and specified amounts of Nb, Cr, Cu, Ti and Al so as to satisfy the inequality, and the balance Fe or moreover contg., as strength regulating elements, specified small amounts of at least one kind among V, Ni, Mo, Ca, Zr and rare earth metals is heated to 1000 to 1280°C and is rolled by hot rolling at ≤1000°C and ≥60% cumulative draft in such a manner that the number of times in the rolling reduction of ≥10% per pass is regulated to ≥80% to the whole body and, in the case the plate thickness at the time of the start of the rolling at ≤1000°C is defined as t1, the plate thickness in the process of the rolling as t2 and the final plate thickness as t3, the steel plate temp. at t2 to t1 is regulated to 850 to 1000°C, the steel plate temp. at t3 to t2 is regulated to 700 to 900°C, and the conditions of t11.3 t2, t22.0 t3 and t1t2t3 are satisfied.;COPYRIGHT: (C)1996,JPO