5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

In Low Pressure casting (LPC), the filling stage is led by gradually increasing the gas pressure above the liquid metal, which is pushed through the pipe and into the mould cavity. In opposite to gravity casting, the LPC filling stage however does not only depend on the filling system and part geometries. By smartly choosing the pressure casting ramp, one could control the filling flow and thus avoid the filling induced defects. To avoid defects when considering the filling stage, it is necessary to simultaneously fill the mould cavity fast enough to avoid misrun and sufficient slowly to avoid oxides defects in the part. Indeed, when filling too fast, the oxides forming at the metal front are more susceptible to entrapment into the bulk [1], leading to poorer final mechanical properties. The relationship between the imposed gas pressure ramp, the system geometry and the induced metal filling dynamics needs to be investigated. Moreover, several oxides entrapment risk criteria were proposed in the literature [2][3][4] without reaching consensus. Filling flow criteria adapted to LPC should be defined. In this work, the filling dynamics induced by the geometry and LPC process parameters is investigated. An experimental setup developed at the semi-industrial scale permits to track the metal front during filling using electrical contacts. The experimental results are compared to commercial software fluid flow simulations and to a new proposed analytical model. Combining those three techniques, the link between process parameters, geometry and filling dynamics is quantitatively determined. Moreover, experiments with different process conditions are analysed in order to link the filling flow to the final mechanical properties of the parts. Eventually, new design rules adapted to LP can be proposed.