EFFECTS OF YIELD STRENGTH AND PHOSPHORUS CONTENT ON THE HIGH CYCLE FATIGUE PROPERTIES OF CAST AUSTENITIC MANGANESE STEELS.

High cycle fatigue properties of solution treated cast austenitic manganese steels were investigated, employing five heats of Hadfield steels, having chemical composition in the range (w/o): Mn 11. 9-13. 4, C 0. 8-1. 25, along with Cr, Ni, Mo and V additions. Phosphorus level was varied between 0. 02 to 0. 065 w/o. Fatigue testing was conducted in bending, employing a rotating beam machine in room air, at ambient temperature. The results indicate that in all cases the fatigue limit (95% survival stress at 10**7 cycles) was equal to half of the 0. 2% yield strength. Response curves, which are characteristic of the fatigue transition region were found to be affected by the phosphorus content of the steel. In particular the stress range of this region decreases with increased phosphorus content. Quantitative correlations between yield strength, phosphorus level and response curve equation were established which enable the prediction of fatigue behavior for Hadfield steels. The results of this study demonstrate a need for reducing the phosphorus content of Hadfield steels even below 0. 07 w/o level, which is considered to be harmless when mechanical properties other than fatigue are considered.