| 摘要 |
The present invention provides a high strength bolt superior in delayed fracture resistant property having a bolt tensile strength of 1200 N/mm<2> or more and a steel material for the same. <??>A high strength bolt comprised of a head portion and shaft portion formed by a steel material, wherein the relation between a bolt tensile strength TS (N/mm<2>) and tempering temperature T ( DEG C) satisfies the following expression (1), the relation between the bolt tensile strength TS (N/mm<2>) and the carbon equivalent Ceq (%) calculated from the chemical composition of the steel material used for the high strength bolt satisfies the following expression (2), and the tensile strength of the bolt is refined to a range of 1200 N/mm<2> to 1600 N/mm<2> by quenching and tempering: <DF NUM="(1)">TS≤.1T+850 </DF> <DF NUM="(2)">TS≤550Ceq+1000 </DF> where, <DF>Ceq=C+(Mn/6)+(Si/24)+(Ni/40) +(Cr/5)+(Mo/4)+(V/14) </DF> <IMAGE>
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