The effects of surface roughness on the heat transfer at the metal-mold interface

Heat transfer coefficient values at the metal-mold interface are an important parameter in the production of sound quality castings. This investigation focused primarily on the effect of surface roughness on heat transfer coefficient values. The paper will describe the development of a versatile apparatus. This apparatus was instrumented with thermocouples, displacement sensors-LVDT (Linear Variable Differential Transformer) and an electrical contact detection circuit. The equipment facilitated the recording of the temperature profile in chill and casting, as well as the detection and measurement of movement at the metal-mold interface including mold expansion and air-gap detection and measurement. Experiments were carried out by casting various aluminum alloys against different chill materials, each of various surface roughness. Inverse heat transfer analysis was used to estimate the heat transfer coefficient at the metal mold interface. This estimation revealed how the heat transfer coefficient changes during the metal solidification. Generally, an increase in surface roughness results in a decrease in the heat transfer coefficient at the metal mold interface. (author)