Microstructure Prediction Of Continuous Casting Billet Based On CA-FVM

The quality of the continuous casting billet directly affects the quality of the final steel,and the microstructure determines the quality of the continuous casting billet to a large extent.In the microstructure research method,the computer simulation method can save cost and reduce the workload.Therefore,computer simulation of microstructure has become the main means to study the microstructure of continuous casting billet.Studying the microstructure of continuous casting billet has important research significance for optimizing process parameters and improving the quality of continuous casting billet.In this thesis,continuous casting billet of 60#steel in size of 160mm×160 mm is taken as the research object.The macro-micro coupling model is established based on cellular automaton-finite volume method(CA-FVM),and the coupled model is numerically solved to predict the microstructure of the continuous casting billet.The effects of different process parameters on the microstructure of the continuous casting billet and the position of the columnar-to-equiaxed transition(CET)were analyzed to optimize the continuous casting process.The specific research contents are as follows:(1)The macroscopic temperature field and the solute field model have been established.The thermophysical parameters and kinetic parameters have been selected.According to the initial conditions and boundary conditions,the finite volume method(FVM)has been used to numerically modeled the temperature field and the solute field.(2)The nucleation model and growth model are analyzed and determined.In the nucleation model,when calculating the grain density,the approximate function method and the error function method are compared and analyzed,and the algorithm with higher accuracy is selected to improve the accuracy of grain density calculation.In the dendrite growth,the LGK model and the KGT model are deduced respectively,and the application of the two models is studied.The advantages of the two models are combined to improve the growth model.The method for calculating the curvature of the interface is used to calculate the curvature undercooling for improving the accuracy of growth rate calculations.(3)The macro and micro models are coupled,and the coupled model is numerically solved by CA-FVM method.The calculated macroscopic temperature and concentration are interpolated into the microscopic cells by bilinear interpolation,and the microscopic cells feed back the latent heat of crystallization into the temperature field and change the solute distribution by calculating the solid fraction.(4)The microstructure is predicted by controlling process parameters.The effect of different process parameters on the microstructure of the continuous casting billet and the columnar-to-equiaxed transition(CET)are studied,and the optimized continuous casting process is obtained.By changing the production process parameters of casting temperature,water supply rate and drawing speed,the predicted microstructure and CET position of the continuous casting billet are studied.An optimization scheme is obtained:the quality of the continuous casting billet can be improved by appropriately reducing the pouring temperature,reducing the water supply amount and reducing the pulling speed.