Effect of Coat Permeability on Temperature Drop of Molten Aluminum Alloy during Mold Filling in Expendable Pattern Casting Process

Abstract

In the expendable pattern casting (EPC) process for the aluminum alloy casting, the thermal decomposition rate of the expendable pattern is smaller than the cast iron, therefore the misrun by the temperature drop at the melt surface occurs easily. This study takes account of the control of the heat release to the mold to investigate numerically and experimentally the effect of the coat permeability on the molten aluminum alloy temperature during mold filling in the EPC process. An aluminum alloy plate was cast by the EPC process, and the temperature change of the melt surface to the melt flow direction was measured. The use of high permeability coat led to a higher melt velocity and a smaller temperature drop at the melt surface than the case of the normal permeability coat. The temperature of molten metal filling into the cavity was numerically simulated, and the obtained temperature drop at the melt surface agreed relatively well with the experimental values.

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

“…Although the thermal conductivity of the coat layer is not mentioned in detail in this paper, the thermal conductivity of the mica based coat (coat A) was approximately one-third that of the silica based coats. Even with different aggregate diameters for silica based coats (coat B-H), the thermal conductivity of the coat layer did not change signi cantly 5) . Figure 3 shows a schematic of the casting apparatus used in the experiments, which was similar to that used in a previous study 5,6) .…”

“…Even with different aggregate diameters for silica based coats (coat B-H), the thermal conductivity of the coat layer did not change signi cantly 5) . Figure 3 shows a schematic of the casting apparatus used in the experiments, which was similar to that used in a previous study 5,6) . The steel molding ask was a cylindrical vessel with an inside diameter of 200 mm and depth of 300 mm.…”

“…In addition, when the pouring temperature and expansion ratio of the EPS pattern change, it seems that the generation rate of the thermal decomposition gas changes and the melt velocity also changes. Especially in the EPC process of aluminum alloys, when the melt velocity is very low, a misrun due to a temperature drop at the melt surface 5,6) can easily occur. On the other hand, when the melt velocity is too high, because non-decomposed parts of the pattern become trapped within the molten metal 1) , internal residue resin defects can easily occur.…”

Effects of Casting Design and Reduced Pressure on Mold Filling of Molten Aluminum Alloy in Expendable Pattern Casting Process

“…Experimental Procedure Figure 1 shows a schematic of the casting apparatus used in experiments, which was similar to that used in a previous study. 5,6) The steel molding flask is a cylindrical vessel with an inside diameter of 200 mm and depth of 300 mm. It has a suction port with an inner diameter of 40 mm to reduce the pressure in the flask.…”

“…Moreover, the mold filling situation is affected by whether the casting design uses bottom pouring or top pouring. 1) Especially when using the EPC process for aluminum alloy, when the melt velocity is very low, a misrun due to a temperature drop at the melt surface 5,6) can easily occur. On the other hand, when the melt velocity is too high, it seems that internal residue resin defects can easily occur because of non-decomposed parts of the pattern trapped within the molten metal.…”