| 摘要 |
PROBLEM TO BE SOLVED: To provide steel having adequate strength as a structure member to which the strength of HRC 45 or higher is required, and superior toughness. SOLUTION: This steel material includes 0.02% or less P (including 0%) and 0.02% or less S (including 0%), each of which is restricted, along with each of 0.3-1.2% C and 0.15-2.0% Mn. It comprises martensite as a main structure, Rockwell C hardness of 45-64, and a half peak width HWα(200) ofα-Fe(200) peak in a X-ray diffraction which satisfies the following expression (1); HWα(200)>-0.94+3.94×10-2×HRC...(1).
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