| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a thick high-tensile strength steel plate having a thickness of 50 mm or more, which is excellent in low temperature toughness of a multi-layer weld zone and suitably used for a large-size steel structure, and to provide a method for producing the thick high-tensile strength steel plate. <P>SOLUTION: The steel plate contains, by mass, 0.005-0.02% of C, 0.3% or less of Si, 0.5-5.0% of Mn, 0.015% or less of P, 0.005% or less of S, 0.5-5% of Ni, 0.02-3% of Cr, 0.01-0.08% of Al, 0.007% or less of N, 0.0003-0.003% of B, one or more selected from among Cu, Mo, V, Nb, Ca, and REM as occasion demands, and the balance comprising Fe and inevitable impurities. A slab containing the above components is reheated to Ac<SB POS="POST">3</SB>point to 1,150°C, then subjected to hot forging and/or hot rolling at a cumulative rolling reduction of 50% or more so as to have a prescribed thickness, thereafter subjected to direct quenching or reheating quenching, and tempered at 450-650°C. <P>COPYRIGHT: (C)2013,JPO&INPIT |
