Three-dimensional Numerical Simulation of Metal Flow and Solidification in the Multi-cavity Casting Moulds of Automotive Components

The liquid metal flow and the solidification behaviours in a multi-cavity casting mould of two automotive cast parts were simulated in three dimensions. The commercial code, FLOW-3D® was used because it can track the front of the molten metal by a Volume of Fluid (VOF) method and allows complicated parts to be modeled by the Fractional Area/Volume Obstacle Representation (FAVOR) method. The grey iron automotive components including a brake disc and a flywheel were cast using an automatic sand casting production line. For simulation analysis, the solid models of the casting, the gating system and the ceramic filter were spatially discretised in a multi-block pattern. The surface roughness and the contact angle of the mould were taken into account in the model, based on the properties of the sand mould used. The turbulent flow was simulated using the k-e turbulence model. The Darcy's law was used to analyse the fluid flow throughout the ceramic filter designed in the gating system. Proper boundary conditions were assigned for the model so that both the simulated filling time and the solidification time were achieved in the range of real experimental measurements. The predicted hot spot of the castings were in agreement with experiments. The verified simulation model showed that the four-cavity mould used for the flywheel part is more suitable than the three-cavity one of the brake disc, in getting a more uniform fluid flow and heat transfer conditions which causes similar cast parts in each mould. The simulated flow pattern during the mould filling of the castings showed that the first gate of the gating system was not working properly as it remains partially-filled (not pressurised) throughout the half of the filling stage, causing a possible air absorption by the melt. A smaller cross sectional area for the first gate was suggested. The present simulation model is able to analyse different casting parameters of the automatic multi-cavity sand casting process.