Residual Stress Development In Heat Treated Steel Bars Due to Straightening Processes

Distortion of heat treated components is a serious problem since its compensation is a substantial factor in time and expense. The compensation of distorted components is usually done after heat treatment in a straightening process which is a well-defined bending procedure causing plastic deformation in the material. In addition to the aim of gaining a straight component bending also causes microstructural changes in the material which lead to a change of the residual stress state.

The material investigated is high strength quenched and tempered as well as normalized steel. By using X-ray diffraction the residual stress distribution along the bending height and in the outer layers of steel bars is investigated at bending loading. Furthermore, the residual stress development of cylindrical specimens under tensile and compressive loading is examined. It is focused how micro and macro residual stresses as well as the integral width develop at homogeneous tensile/ compressive and inhomogeneous bending loading when a component is straightened.

Keywords: straightening, residual stress, high strength steel, four-point bending, tension-compression