Simple macro/microcoupling mathematical model and its predicting on effects of processing factors on solidification structure for 1Cr18Ni9Ti stainless steel twin-roll thin strip

Abstract

Based on the simple macro/microcoupling mathematical model developed in this paper and its predicted results, the effects of processing factors such as pouring temperature, casting velocity and molten pool height on the solidification structure for 1Cr18Ni9Ti stainless steel thin strip with ideal solidification type are investigated. In the developed model, the latent heat is treated by enthalpy method; the grid and nodes are divided by the assumed streamlines. Moreover, the heterogeneous nucleation and columnar-to-equiaxed transition (CET) models are also introduced, together with the revising of dendrite growth dynamic model of Kurz–Giovanola–Trivedi (KGT). With the help of solid fraction, the coupling of macro/micromodels is realised using different grid sizes and time steps, macro and micro, together with the columnar dendrite front tracing. The predicted results of mathematical models indicate that the effects of pouring temperature, casting velocity and melt pool height on the solidification structure of 1Cr18Ni9Ti stainless steel twin-roll thin strips are very different, in that the effects of molten pool height is greatest, then are casting velocity and pouring temperature respectively. Accordingly, for the actual twin-roll thin strip casting, the molten pool height and casting velocity should be controlled strictly in order to obtain ideal solidification structure.