| 摘要 |
PURPOSE:To obtain an alloy steel for an unrefined bolt or the like having superior toughness by hot working a low-alloy steel having a specified composition and by cooling it under specified conditions. CONSTITUTION:An ingot of a low-alloy steel contg., by weight, 0.05-0.20% C, <0.05% Si, 1.0-2.0% Mn, <0.015% S, 0.01-0.05% Al and at least one among <0.15% V, <0.1% Nb and 0.05-0.50% Cr is heated to 950-1,150 deg.C and worked into a wire rod for a bolt by hot rolling. The wire rod is finish- rolled and cooled to <=500 deg.C at <=10 deg.C/sec cooling rate to form a dense ferrite- pearlite structure. A steel material having the desired strength and toughness and suitable for use as a material for an unrefined bolt or the like is obtd.
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