Aluminum brake discs: casting quality assurance by computer simulation

Abstract

"As a result of the increasing demand to minimize the weight of automotive vehicles as well as reducing particle emissions, Al-matrix composite (Al-MC) is gaining interest as a potential material for manufacturing automobile brake discs because of its good corrosion property, high thermal conductivity and higher wear resistance when compared to the traditional grey cast-iron brake disc material. However, to mass-produce Al-MC brake discs, an efficient and robust manufacturing process is required. The squeeze casting technique is considered as one of the economical casting processes by which Al-MC material can be shaped into readily usable components. This process is attractive because squeezed cast products exhibit better mechanical properties due to the presence of fewer common defects such as porosity and shrinkage cavities, and the segregation of the reinforcing material is eliminated. To efficiently use squeeze casting industrially, its processing parameters such as squeeze pressure, pouring temperature, mould die temperature and melt flow speed must be optimized to ensure sound castings. When a newly designed component is to be produced by squeeze casting, the casting parameters must be optimized for such a component. This optimization is conventionally performed through experimental trials which consume a lot of material resources and time. Nowadays, the application of computer simulation to model casting processes has enabled foundry engineers to shorten casting development time, maximize material usage, establish a robust process window by optimizing casting process parameters, reduce quality costs by preventing metal casting defects resulting from turbulence and other inclusions, predict and prevent defects in castings, and hence ensures quality castings and reduces product manufacturing costs. This paper discusses how a casting simulation program could help to ensure a high-quality casting of Al-MC brake discs by investigating the influence of squeeze casting parameters on the possibility to minimize casting defects through parameters optimization. The 3D mechanical CAD software (Inventor LT) program was used to construct the 3D model of the brake disc and the forming tool, and the step files were imported into the NOVACAST software to simulate the casting and solidification processes. Further, two-parameter settings from the simulation results were implemented experimentally to produce squeeze cast Al-MC brake discs. The cast discs were examined and compared with the simulation results to check the adequacy of the simulation in predicting the quality of the brake disc. "