Effect of Micro-Segregation on Phase Transformation and Residual Stress

Some factors affecting the residual stresses in a thick plate of hardened steel have been studied. Dilatometry shows that the expansion during phase transformation on cooling is anisotropic and that the behaviour varies with position in the plate, being most marked in the centre and less in the sub-surface regions. This dimensional anisotropy on cooling is due to micro-segregation of the alloy elements. The extent of anisotropy also depends to some extent on conditions of austenitisation and on cooling rate. From the measurements of length change in different regions estimates are made of levels of residual stress in the hardened plates.