Effect of Coat Permeability on Melt Velocity of Molten Aluminum Alloy in Expendable Pattern Casting Process

Abstract

  The effect of the coat permeability on the melt velocity of molten aluminum alloy in the expendable pattern casting (EPC) process was investigated experimentally. For eight kinds of coats, the linear relationship between the inter-coat differential pressure and the airflow rate was obtained. Coat permeabilities conforming to JIS were determined from the gradient of the linear relationship. Using the eight kinds of coats, aluminum alloy plates were cast by the EPC process for three kinds of expansion ratios of expendable polystyrene (EPS) pattern, in the case of bottom pouring and without reduced pressure. The arrival time of the molten metal was measured and the melt velocity was obtained. The use of high expansion ratios of EPS pattern or high permeability coats led to higher melt velocities. In the high coat permeability region, the melt velocity did not increase so much, even when the coat permeability increased. The effects of the pouring temperature and casting thickness on the melt velocity were also examined. The application of high pouring temperature or large casting thickness, led to higher melt velocity. The experimental values of the melt velocity were compared with the calculated values based on the mold filling model used in the previous study. The experimental values were in relatively good agreement with the calculated values, except for when the coat permeability was high and the casting thickness was small.