| 摘要 |
PROBLEM TO BE SOLVED: To realize a steel material with an excellent HAZ toughness in which an austenite particle enlargement by heating at a high temperature for a long time is greatly suppressed even in welding with a large amount of heat input of 200 kJ/cm2 or more. SOLUTION: The steel material excellent in heat-affected zone toughness, is characterized in that in a steel having required components, oxide particles in circular equivalent diameter of 0.005-2.0μm, preferably 0.1-2.0μm, are contained, and oxide particles having at least Ca and Al, or Ca, Al and Mg as the composition, wherein the mass ratio of elements excepting O, is Ca: 5% or above and Al: 5% or above, or Ca: 5% above, Al: 5% above and Mg: 1% or above, are contained in 100-5,000 pieces/mm2.
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