Consequences of Bend Straightening Processes on Residual Stresses and Strength of Quenched and Tempered Steels

Abstract

AbstractBend straightening is a typical process step applied after heat treatment of e. g. axles and shafts. From a materials science perspective it is an elastic-plastic bending operation with a characteristic inhomogeneous deformation over the cross section of the component. Due to the local amount and distribution of plastic deformation alterations of residual stress fields result and phase transformations are possible. Consequently, bend-straightened components have inhomogeneous materials properties. In particular an anisotropy of strength exists which can be attributed to the position-dependent microstructure and sign of the residual stress state. In addition, a Bauschingereffect is possible which also has considerable impact on the deformation characteristic of the considered component. In the present paper the above mentioned aspects are demonstrated for quenched and tempered steel bars and shafts. Typical examples of residual stress states before and after straightening are presented as well as alterations of retained austenite distributions. Finally, the deformation behavior and strength of bend-straightened components is outlined and discussed.