HIGH TENSILE BOLT EXCELLENT IN DELAY BREAKING RESISTANCE CHARACTERISTIC AND ITS STEEL PRODUCT

摘要

PROBLEM TO BE SOLVED: To provide a high tensile bolt excellent in a delay breaking resistant characteristic having bolt tensile strength of more than 1200 N/mm<2> and its steel product. SOLUTION: This high tensile bolt has a head part 1 and a shaft part 2 which are formed of a steel product, and the steel product is refined in a range that a relation of bolt tensile strength TS (N/mm<2> ) and tempering temperature T ( deg.C) satisfies a following (1) expression, a relation of the bolt tensile strength TS and carbon equivalent Ceq (%) to be calculated from its chemical composition satisfies a following (2) expression and the bolt tensile strength is more than 1200 N/mm<2> and less than 1600 N/mm<2> by hardening and tempering. TS<=1.1T+850...(1) TS<=550Ceq +1000...(2) hereby Ceq =C+(Mn/6)+(Si/24)+(Ni/40)+(Cr/5)+(Mo/4)+(V/14).