Production mannered null mass of 60 kilo class high tension steel which is superior in tenacity after the weldability and

摘要

PROBLEM TO BE SOLVED: To provide a method for producing 60 kilo class reheated, quenched and tempered steel excellent in weldability and toughness after strain aging and having excellent low temp. toughness even after cold working such as bending. ;SOLUTION: Steel contg., by weight, 0.06 to 0.10% C, 0.1 to 0.5% Si, 1.2 to 1.8% Mn, 0.1 to 0.5% Cr, 0.01 to 0.05% Nb, 0.002 to 0.070% sol. Al and 0.001 to 0.004% N, moreover, added with Mo, Cu, Ni, V, Ti and Ca in accordance with desired performance capacities and also satisfying P cm≤0.20%, Ceq (WES)≤0.42% and 0.50≤Si+3Cr≤1.25% is reheated and quenched from ≥Ar3 and is thereafter tempered at 400 to 630°C, where Pcm=C+Mn/20+Si/30+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B, and Ceq (WES)=C+Mn/6+Si/24+ Ni/40+Cr/5+Mo/4+V/14.;COPYRIGHT: (C)2001,JPO