Residual stresses in a super duplex stainless steel cast part

This paper describes a methodology capable of predicting residual stresses and distortions in castings with complex geometries. The methodology was developed based on the evaluation of the correlations between the temperature gradients, the solid phase transformations and the mechanical constraints imposed by the mold during the cooling of the liquid metal in the case of a C-ring. First, the thermal model was developed using calibrated curves of interfacial heat transfer coefficients (IHTCs) as a function of temperature. Such curves were determined by an inverse method using experimental data from temperature measurements with thermocouples positioned inside the mold cavity during cooling of the liquid metal. A sequentially coupled thermal-mechanical analysis implemented in Abaqus™ was then used to predict the thermal residual stresses in a duplex stainless steel (DSS) cast part. The approach uses the thermophysical properties of the DSS obtained from the composition of the solid phases as a function of temperature. This is particularly critical for those materials that undergo phase transformations in the cooling range, as the microstructure evolution and properties change, can have a major impact on the level of residual stresses generated. A limited agreement was obtained between the numerical results and the residual stress measurements using the contour method. The present work also addresses the effect of the distribution and volume fraction of phases on the magnitude of residual stresses by means of software OOF2™, which takes into account real images of the microstructure. The described methodology is useful to understanding how residual stresses are induced on complex castings in duplex stainless steels.