超急速加熱による表面メゾ組織創製がもたらすエコ鋼材の高疲労信頼性

概要

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To improve the fatigue reliability for Mn-Si-C Steel by an environmentally sound surface modification, the influence of the modification on fracture mechanism was studied experimentally. The fatigue properties of Mn-Si-C Steel are found to be obviously improved by a Super-Rapid Induction Quenching, so that they can no longer be estimated by using a concept of "S-N Globe" which has successfully been applied to many surface-treated materials. The detailed observations have revealed that fatigue crack initiation in a Super-Rapid Induction Quenched specimen occurs in a hardened region near surface not in a subsurface region with virgin microstructure. The fatigue crack was induced by slip in the ferritic matrix. And the fatigue crack propagation in the hardened reagion was restricted by the presence of the martensite phase and compressive residual stress. Such a crack initiation mechanism is different from that previously observed in other surface treated materials, explaining the reason why the S-N Globe concept can not be applied to the present case.
一般社団法人日本機械学会の論文
2000-05-25