The properties of the newly developed valve spring steel have been shown to have high resistance to temper softening. Further, this strength does not decrease even during nitriding; valve springs can be produced by the same process as that for conventional SAL9254 steel. The sensitivity to inclusions during fatigue testing is improved and high cleanliness has been realized by the optimum production technology for high-Si steel, resulting in stable and high fatigue strength.The fatigue strength has been improved by 1.4 times as compared with SAE9254 steel, which has made weight reduction and downsizing of valve springs possible, resulting in more power and less fuel consumption in engines.
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