| 摘要 |
PROBLEM TO BE SOLVED: To provide a Cr-Mo steel sheet excellent in strength, toughness, low-temperature cracking resistance upon welding and reheat cracking resistance, and a method for producing the same.SOLUTION: The steel sheet has steel composition including, by mass, 0.03-0.12% C, 0.01-0.8% Si, 0.45-1.0% Mn, 0.05-0.6% P, S, and Cu, 0.2-1.5% Ni, 0.8-1.5% Cr, 0.3-0.8% Mo, 0.005-0.040% Sol.Al, and 0.0005-0.005% Ca, wherein N, O, Cu+Ni≥0.55%, and 1≤Ca/S≤10, 0.0003% or less B, and 0.005% or less Ti, wherein XB=10000B-7700×(N-0.292Ti)<0, and if necessary, at least one of Nb, Mg, and REM, with the balance comprising Fe and unavoidable impurities. The steel of the composition is reheated to a temperature of at least 880°C, then cooled to a temperature of 300°C or less at an average cooling rate of at least 1°C/s, and then subjected to tempering treatment at a temperature of at least 600°C. |
