| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material excellent in the toughness of an HAZ (heat-affected zone) by suppressing the formation of coarse TiN. SOLUTION: The steel material satisfies a prescribed chemical component composition, and in the steel material, when the size of each inclusion is defined as the length of the widest portion in the direction perpendicular to the maximum length of the projection of the inclusion as observed with a microscope, inclusions each characterized in that the size is ≥2 μm are dispersed. Each inclusion satisfies the relations of following formulas (1): 0.01≤[Ca]/[Al]≤0.50 and (2): 0.08≤([CaO]+[CaS])/([Al<SB>2</SB>O<SB>3</SB>])≤1.80 (wherein, [Ca], [Al], [CaO], [CaS], and [Al<SB>2</SB>O<SB>3</SB>] represent the contents (mass%) of Ca, Al, CaO, CaS, and Al<SB>2</SB>O<SB>3</SB>, respectively in the inclusion). COPYRIGHT: (C)2010,JPO&INPIT
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