| 摘要 |
PURPOSE: Non-heat treated steel and a manufacturing method thereof are provided to obtain free-cutting effect without degradation of processing yield and mechanical properties of steel materials by adding a proper amount of sulfur. CONSTITUTION: Non-heat treated steel comprises C of 0.37-0.44wt.%, Si of 0.15-0.35wt.%, Mn of 0.55-0.90wt.%, S of 0.02-0.03wt.%, Cr of 0.85-1.25wt.%, Mo of 0.15-0.35wt.%, Nb of 0.01-0.05wt.%, and Fe and inevitable impurities of the remaining amount. The non-heat treated steel has tensile strength of 1000-1100MPa, yield strength of 700-710MPa, elongation of 14-16%, and a bainite structure including a microstructure at a sectional area rate of 50% or more. |
