Thermophysical Properties of Green Sands

The work presented in this paper investigated the thermophysical properties of green sands. Three experimental sands with different sodium bentonite clay levels were examined, as well as two green sands from industrial production. The industrial sands had a much more complex composition than the experimental sands. Density, as a function of temperature, was determined by dilatometry while specific heat, as a function of temperature, was measured by differential scanning calorimetry. To find the thermal conductivity verses temperature, a series of ingot casting experiments were conducted. Thermocouples were inserted into the ingot mold, and the temperature verses time was recorded. An inverse heat transfer optimization using a commercial solidification simulation package was then performed using the thermocouple, density, and specific heat data to calculate the thermal conductivity. For all the experiments, the sands were tested at the production moisture levels. The thermophysical properties of the molding sands demonstrated complex behavior. The specific heat of the molding sands was dominated by the evolution of water while being heated. This behavior had not been completely realized in previous work. Additionally, there was an indication that phase reactions, such as the α to β quartz reaction, could take place at a temperature lower than previously reported. It is certain that continuing to improve simulation accuracy will require foundries to determine their own sand’s thermophysical properties. ---- 8 Seiten