Analysis of the Distortion Potential within Bearing Rings

Abstract: Causes for distortion phenomena during heat treatment are inhomogeneous or asymmetric distributions of mass, alloying elements, microstructure, residual stresses, and temperature. These causes generate a distortion potential within the work piece which can be released during the final heat treatment. For a calculation of the distortion potential it is necessary to know the interrelationships between the physical mechanisms which lead to strains, the distribution of these strains within the work piece, and the changes in dimensions and shape. In a recently published paper the functional interrelationship between strains and distortion was given for cylindrical rings and the important role of the geometry was highlighted. For thin walled bearing rings made of the through-hardening bearing steel SAE 52100 an important part of the distortion potential can be attributed to transformation-induced plasticity. This distortion mechanism is caused by an interaction of stresses and phase transformations. In this contribution the physical mechanism will be investigated in a more detailed manner. Experimental results gathered during the Collaborative Research Centre “Distortion Engineering” at the University of Bremen were compared with the theoretical description of the distortion potential. Keywords: bearing ring, SAE 52100, distortion mechanism, distortion potential, transformation plasticity