The Cu precipitation enhanced extremely thick steel null where low temperature tenacity

摘要

PURPOSE:To make a steel material thick-walled and also to improve the weldability and toughness at low temp. of a steel material, by specifying respective contents of C, Si, Mn, Ti, Nb, B, Cu, Al, and N and also by precipitating fine Ti in a steel so that it comprises a proportion in a specific range. CONSTITUTION:An extreme thick steel material has a composition consisting of, by weight ratio, 0.005-0.10% C, 0.05-0.60% Si, 0.5-2.0% Mn, 0.004-0.015% Ti, 0.005-0.10% Nb, 0.0005-0.0020% B, 0.7-2.0% Cu, 0.010-0.10% Al, =0.0050% Ni, and the balance Fe with inevitable impurities. In the above composition, at least a part of Ti is regulated so that it comprises 0.004-0.015% of the steel in the form of a fine precipitate of 0.01-0.06mu. If necessary, =1.5% Ni, =1.0% each of Mo and Cr, and =0.05% REM are incorporated to the above composition. In this way, a Cu precipitation strengthening-type thick steel material having superior weldability can be made high-strength and high- toughness.