| 摘要 |
PROBLEM TO BE SOLVED: To provide a high tensile bolt having a tensile strength of 1,7 00 MPa or more and excellent tensile deformation performance and delayed fracture resistance, and a method of manufacturing the same.SOLUTION: A steel containing, by mass, 0.35-0.70% C, 0.50-2.50% Si, 0.10-1.00% Mn, 0.30-3.00% Cr, 0.50-1.50% Mo, 0.001-0.1% Al and the balance Fe with inevitable impurities, is formed into a bolt shape in such a manner that a shape parameter S (=Ab/Ae, wherein, Ab is an effective cross-sectional area in a shaft part 2 and Ae is an effective cross-sectional area in a screw part) in the shaft part 2, becomes a value of 0.85 to <1.25, and after quenching the steel by austenization in the temperature range of 850-1,050°C, the steel is subjected to a tempering treatment in the temperature range of 500-650°C. |
