Effects of Process Parameters on Internal Quality of Castings during Novel Casting

Abstract

In this study, the A356 aluminum alloy castings were obtained using the expendable pattern shell casting process with vacuum and low pressure (EPSC-VL). The effects of process parameters including gas flow rate, vacuum level, and gas pressure on the internal quality of the castings were investigated through measuring the density and section porosity of castings experimentally as well as computing the porosity defects of the castings by simulation. The results showed that the density of castings increased and the porosity defects of castings decreased with the increase of gas flow rate, vacuum level, and gas pressure, respectively. As a result, the internal quality of castings was greatly improved. The simulation results were in accordance with the experimental results and showed that the trend of splash and turbulence of the molten metal during the filling process increased under the excessively high gas flow rate, which may lead to porosity and oxide inclusion defects. In addition, EPSC-VL process had significant advantages in internal quality, microstructure, and mechanical properties compared to expendable pattern shell casting process under gravity casting (EPSC-G) and lost foam casting (LFC). A complicated and thin-walled aluminum alloy part with high quality has been successfully manufactured using this technology.

Keywords:

• A356 aluminum alloy
• Density
• Expendable pattern shell casting
• Internal quality
• Process parameters

ACKNOWLEDGMENTS

The authors gratefully acknowledge the contribution of the financial support of the National High Technology Research and Development Program of China (No. 2007AA03Z113) and Analytical & Testing Center of Huazhong University of Science and Technology (HUST) as well as Center of Analysis and Test of Wuhan Institute of Technology.