Purity of automobile gear steel

The purity requirement of automobile gear steel mainly refers to the inclusion of oxides and sulfides and the reduction of the content of harmful elements such as N, h, O and s. The inclusions in steel significantly reduce the fatigue performance of gears, especially the contact fatigue strength of gears, deteriorate the process performance of steel, and thus affect the service life of automobile gears.

In addition, in order to improve the purity and reduce harmful inclusions, the addition of titanium in high-quality gear steel is prohibited. In the internal control standard of the former West Germany Lehigh steel plant, it is clearly stipulated that the titanium content must be less than 0.01%. Because the TiCN generated by titanium and N and C in steel has a great impact on the fatigue life of gears.

The influence of oxygen content on gear fatigue life has attracted more and more attention. Foreign research results show that the oxygen content of 20m ncr5 steel ranges from 2.8 × 10-5 to 1.8 × At 10-5, the gear contact fatigue strength can be increased by 27%; The oxygen content of SCM 420h steel is from 4.5 × 10-5 to 2.0 × At 10-5, the contact fatigue strength can be increased by 47%.

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