HIGH-STRENGTH TOUGH STEEL FOR PRESSURE VESSEL

摘要

PURPOSE:To obtain a steel having both high strength, especially superior strength characteristic at high temp. and superior toughness by adding Cr, sol. Al and B to an Mn-1/2Mo steel or further adding Cu and Ni. CONSTITUTION:This steel consists of, by wt., 0.07-0.22% C, 0.05-0.50% Si, 1.00-1.60% Mn, 0.10-1.00% Cr, 0.45-0.60% Mo, 0.010-0.10% sol. Al, 0.00015- 0.0030% B and the balance Fe with inevitable impurities or further contains 0.10-0.50% Cu and/or 0.10-1.00% Ni. Cr enhances the hardenability during normalizing and prevents carbide from coarsening during annealing and use, and the lower and upper limits of Cr are decided with respect to the effect and the weldability, respectively. The lower limit or more of sol. Al is required with respect to the deoxidation, yet more than the upper limit of sol. Al reduces the toughness. B increases the hardenability of the normalized steel to ensure high strength and toughness, yet less than the lower limit of B produces an insufficient effect, and more than the upper limit of B deteriorates the toughness of the weld heat-affected zone. Cu and Ni enhance the strength furthermore.