Heat transfer, solidification, and microstructural evolution in al-33Cu alloy during the starting of twin roll strip casting

Abstract

Numerical simulation of transient fluid flow, heat transfer, and solidification during the starting of high speed twin roll strip casting was carried out to estimate the time required for steady state condition to set in and solidification front speed during the transient stage. The solidification front speed during the transient stage was expected to be higher, leading to different microstructure and thus it is necessary to know it in comparison to that during the steady state. The free surface of the pool was tracked using volume of fluids (VOFs) approach and an enthalpy-porosity method was employed to incorporate the phase change during solidification. Surface tension was incorporated into the momentum transfer equation and all the physical properties were treated as functions of temperature. The filling sequence and temperature profiles in the molten pool, along with the solidification front profile were numerically simulated. From the evolution of temperature profile the transient length of the cast strip was estimated. The prediction of temperature profile in the transient stage was experimentally validated using Jackson-Hunt theory. From the results of simulation the transient length of strip, which needs to be rejected for different casting speeds was estimated. It was found that when the speed is increased beyond 0.7979 up to 3.98 m s-1 the transient length did not increase appreciably. Numerical simulations for high speed twin roll strip casting is carried out to estimate the time which is required for steady state condition to set in and solidification front speed during the transient stage. By using this model it is possible to determine the transient length of the cast strip which needs to be rejected during the starting process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.