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Metallurgical influences on the fatigue strength of an induction hardened microalloy steel

Abstract:

Component bending fatigue results obtained from production crankshafts have clearly indicated that factors beyond the hardness and/or strength of the induction hardened regions of the crankpins have an influence on fatigue strength. Both the sulfur level of the base material, and the residual stress level present in the induction hardened case have a significant effect on the resultant fatigue strength of the component. Residual stress relaxation has in turn been shown to be a function primarily of tempering temperature and secondarily of steel composition. These results confirm that the application of the lower carbon and sulfur level TMS-80 to production crankshafts has resulted in at least a 15 percent improvement in component fatigue life over that of the standard 1548 grade, at an equivalent hardness level.