| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a steel material excelling in toughness of a weld heat-affected zone. <P>SOLUTION: This steel material excelling in toughness of a weld heat-affected zone contains, by mass, 0.01-0.2% of C, 0.005-0.15% of Si, 0.3-2.5% of Mn, ≤0.05% of P, ≤0.008% of S, 0.0005-0.0030% of Al, ≤0.010% of N and 0.0010-0.0050% of O, wherein the residual part comprises Fe and impurities; the content of Mg, Ca, REM and Ti as the impurities satisfies the following formula (A) (Mg+Ca+REM+Ti/10) ≤0.001% (wherein, each elemental symbol of Mg, Ca, REM, Ti in the expression represents the content (mass%) of each element included in the steel material); the average composition of oxide particles dispersed in the steel material satisfies, by mass, Al<SB POS="POST">2</SB>O<SB POS="POST">3</SB>≥50% and MnO ≥5%; and the average dispersion density of the oxide particles each having a size of 0.4-10 μm by circle-equivalent diameter is ≥50 per 1 mm<SP POS="POST">2</SP>. <P>COPYRIGHT: (C)2012,JPO&INPIT |
