Interfacial heat transfer coefficients (HTCs) were measured during pressure casting JIS-AD12.1 aluminum alloy (A383) against dies coated with a power lubricant. The effect of the power lubricant amount on the HTC was examined. It was found that the HTC value decreased as the powder lubricant amount increased. Cross-sectional thicknesses of the powder lubricant layer at the interface between the casting and steel mold after casting were evaluated. As the powder lubricant amount increased, the mean thickness of the powder lubricant layer and the casting surface area covered by the powder lubricant increased. The microscopic state of contact at the interface suggested that, the heat transfer path from the casting to the steel mold is equivalent to parallel circuit with a route through the powder lubricant layer and a route without it. The apparent thermal conductivity of the powder lubricant was determined from the relationship between the thickness and the thermal resistance of the lubricant to be 0.10~0.13 W/mK. The wax contained in the powder lubricant may have gasified during casting, causing the gas to remain in the layer, resulting in lower thermal conductivity.
