| 摘要 |
PURPOSE:To improve the delayed fracture resistance of a steel for a high tension steel bolt by reducing the P content of the steel to a specified value or below. CONSTITUTION:The P content of a steel for a high tension steel bolt having a composition contg. 0.10-0.50% C, 0.30-2.5% Mn and 0.005-0.060% sol. Al is reduced to <=0.0010%. The composition may further contain 0.1-2.0% Si and/or one or more among 0.01-2.0% Ni, 0.01-2.0% Cr, 0.01-2.0% Mo and 0.0001- 0.0050% B. A steel for a high tension steel bolt having superior delayed fracture resistance in a high strength range of >=110kg/mm.<2> is obtd.
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