PRODUCTION OF HIGH TENSILE STRENGTH AND HIGH TOUGHNESS FINE BAINITIC STEEL

摘要

PURPOSE: To produce a thick steel plate having a fine bainitic structure and excellent in weldability and low temp. toughness in a non-heat treating state. ;CONSTITUTION: Steel stock contg., by weight, 0.01 to 0.20% C, 0.05 to O.6% Si, 0.6 to 2.0% Mn, 0.005 to 0.08% Nb, 0.005 to 0.03% Ti, 0.0005 to 0.0020% B, ≤0.05% solAl and ≤0.008% N and furthermore contg., at need, Cu, Cr, Mo, V and Ni, and the balance Fe with inevitable impurities is heated to 1000 to 1250°C and is thereafter rolled-down at ≤900°C at ≥50% cumulative draft, and the rolling is completed at the Ar₃ paint to 800°C. Immediately, it is subjected to accelerated cooling to 580 to 450°C and is then isothermally held to the temp. range for 10 to 100S or is gradually cooled in the same temp. range for a given time.;COPYRIGHT: (C)1994,JPO&Japio