| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material which can stably show a superior toughness in a weld heat-affected zone even when having been welded with a large quantity of heat input. SOLUTION: The steel material superior in the toughness of the weld heat-affected zone includes, by mass%, 0.03 to 0.20% C, 0.01 to 0.3% Si, 0.5 to 2.5% Mn, 0.005 to 0.025% (40 to 250 ppm) Ti, 0.02% or less P, 0.01% or less S, 0.01% or less N, 0.040% or less Al, 0.001 to 0.020% (10 to 200 ppm) Zr, 0.001 to 0.010% (10 to 100 ppm) O (oxygen), 0.001% or less Mg, and the balance Fe with impurities. The Ti in an amount of 0.004 to 0.020% exists as a solid solution Ti, and the Zr in an amount of 0.005% or less exists as a solid solution Zr. The steel material may further contain one or more components of Cu, Ni, Cr, Mo, Nb, V and B. COPYRIGHT: (C)2010,JPO&INPIT
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