| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive high strength coil spring which has high impact resistance, and to provide a production method therefor. SOLUTION: The high strength coil spring is obtained by using an oil tempered wire of steel having a composition containing, by weight, 0.6 to 0.7% C, 1.8 to 2.2% Si, 0.7 to 0.9% Mn, 0.5 to 0.8% Cr, and 0.05 to 0.15% V, and the balance Fe with inevitable impurities; wherein, the content of P is controlled to≤0.05%, S to≤0.025%, and Cu to≤0.2%, and in which the maximum size of nonmetallic inclusions is 15μm. By performing coiling, microshot, nitriding treatment at 440 to 475°C, and two-step shot peening thereto, the hardness of the surface layer part (in the vicinity of 0.02 mm from the surface) is controlled to 600 to 800 Hv. In this case, desirably, the tensile strength of the oil tempered wire is controlled to≥1,960 MPa, and reduction of area to≥38%. By the combination of the above conditions, the inexpensive high strength coil spring having high impact resistance can be obtained. COPYRIGHT: (C)2003,JPO
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