爆発硬化した高マンガンオーステナイト鋳鋼繰返し衝撃材の残留応力

Abstract

Explosion hardened high manganese austenitic cast steel is being tried for rail crossing recently. From the previous studies, it became clear that high tensile residual stress was generated in the hardened surface layer by explosion and the surface tensile residual stress changed into the compressive stress of about 500MPa after the repetition of impact.In this study, the distribution of biaxial residual stress in the explosion hardened high manganese austenitic cast steel subjected to repeated impact loads was examined and compared with those of original and shot peened steels.The results obtained are summarized as follows.(1) The residual stress distributions in the impact surface layer of the original, explosion hardened and shot peened steels were similar qualitatively as given in the following. The surface compressive stress changes into tension at the depth of 0.01mm and the tensile stress in the surface layer shows a remarkable variation as the depth increases and changes into compressive stress in the inner layer.(2) It seems that the residual stress distribution mentioned above is produced by the combined effects of surface hardened layer, the transverse deformation in impact surface and uneven deformation at hardened layer.(3) The high tensile residual stress in the explosion hardened surface layer did not increase by repeated impact loading, and no macrocrack was osberved in the impact surface layer.