| 摘要 |
PURPOSE:To produce a spring having excellent resistance to fatigue by adjusting the hardness of a base material for a low alloy steel wire rod to a specific value or above, then subjecting the surface layer part to a heating treatment and coiling the material to a spring shape, and further subjecting the coil to a shot peening treatment. CONSTITUTION:The low alloy steel contg., by wt%, 0.3-1.0% C, 0.15-0.25% Si, 0.3-2.0% Mn, and <3.0% Cr is rolled to produce the base material of the steel wire having >=2.0mm diameter. The base material is subjected to a hardening treatment after heating and is adjusted to >=500 Hv hardness. Such material is subjected to heating by irradiation of a CO2 laser or induction heating at >=200m sec by high-frequency electric power of >=10MHz frequency to 500-700 deg.C, by which the range of 10mum from the surface of the steel wire is heated to soften to <=450 Hv. The hardness in the deep part of >=100mum from the surface is thus maintained at >=500 Hv. The material is coiled to a spring shape and the coil is subjected to the shot peening treatment, by which the spring having the excellent resistance to fatigue is produced. |
