Measurement and Prediction of Residual Stresses in Heat Treated Large Forgings

High residual stresses induced by heat treatment are often the cause of immature failures of large forgings with diameters greater than 1 meter.  Experimental measurement of residual stresses in such large forgings is extremely difficult and cost prohibitive, if not impossible.  This study attempts to develop a validated approach for the prediction of residual stresses in large forgings.

Two cylinders that are 600 mm in diameter and 1800 mm in length are heated and subsequently quenched in difference cooling media, and then tempered.  Residual stresses in the cylinders are experimentally measured utilizing the Sach’s method.  The development of residual stresses during heat treatment processes are also predicted from coupled and integrated thermo-metallo-mechanical analyses based on commercial FEA analysis packages DEFORM and ABAQUS.  The experimentally measured and numerically predicted residual stresses are found in good agreement.  Similar agreements are also obtained between the model predicted residual stresses in heat treated cylinders of various sizes and materials presented in open publications.  With the confidence in the computational models built upon experimental validations, the coupled and integrated thermo-metallo-mechanical model are extended to predict residual stresses in a heat treated back-up roll with 1.3 meter diameter.  Microstructural evolution and development of residual stresses in the heat treatment of large forgings are presented and disseminated.