Study on Fatigue Strength of Ferritic Stainless Steel SUS 430 by Shot Peening Process

摘要

A Ferritic stainless steel SUS 430 was evaluated experimentally using a rotating bending fatigue test after shot peening, and the factors that influence fatigue strength improvement through shot peening were determined by measuring mainly hardness and residual stress at the surface and adjacent areas. The results are as follows. (1) A work hardening layer on the surface after the shot peening was observed at a depth of approximately 250 mum, and the top surface approximately 80 mum deep was hardened by the fine structure of ferritic phase. The underlying layer, which was approximately from 80 to 250 mum deep, was considered to be work-hardened by the hardening of the ferritic phase itself. (2) The fatigue limit of SUS 430 was improved by approximately 25 percent by the shot peening. It was considered that compressive residual stress affects the improvement of the fatigue strength of this steel. Furthermore, the improvement of hardness by the work hardening greatly contributes to the improvement of the fatigue strength.