| abstract |
PROBLEM TO BE SOLVED: To provide a steel material having sufficient strength and excellent toughness even when used as a structural member requiring high strength of Rockwell C hardness (HRC) 45 or more. SOLUTION: This is a steel material containing C and Mn, each having excellent toughness suppressed to P: 0.02% or less (meaning of mass%, the same applies hereinafter) and S: 0.02% or less, and mainly composed of a martensite structure. And a Rockwell C hardness (HRC) of 45 or more and 400 to 500 calculated from the results of differential scanning calorimetry. A steel material having excellent toughness, wherein the calorific value per unit mass in the range of ° C is 2.0 J / g or less. |