Simulation of casting solidification and its grain structure prediction using FEM

Metal casting is one of the basic manufacturing processes. Numerical simulation of solidification is useful in getting high quality castings and minimising product cost and scrap. Finite element analysis in heat transfer can be used for this purpose. In this study, a program for finite element modelling of casting solidification was developed. The salient features of the program are: facility to incorporate latent heat through enthalpy method, incorporation of air gap by coincident node technique, ability to handle non-linear transient heat conduction through temperature dependent material properties, and object oriented programming. The code was written in C++ language and Gaussian elimination method was used to solve the matrices. This program can handle two-dimensional solidification of pure metals and alloys. Using this program, solidification of infinite slab of water was simulated and the results were compared with the reported literature and ANSYS and were found to be in good agreement. Also, solidification of Al–6 wt.% Si alloy in sand and metal mould was simulated and compared with the experimental findings and simulation results reported in the literature and ANSYS. For a given geometric profile, the solidification time obtained from the present program was 1200 s as against the literature of 1100 s and ANSYS package of 900 s. So it was found to be in good agreement with the research and experimental findings. The program was limited to 2D heat transfer analysis using linear quadrilateral elements. The program could be extended for predicting the grain structure. From the simulation results, the solid–liquid interface velocity (R) and solidification rate (dT/dt) could be calculated and using these values thermal gradient (G) could be found and there by the most probable grain structure could be predicted.