Ductility Variation of а Raw Sand-Clay Mold under Influence of Geometric and Thermophysical Properties of the Casting

One of the ways to increase economic efficiency of the foundry is to reduce the production cost by reducing scrap, a significant proportion of which is formed due to the formation of hot and cold cracks during solidification and cooling in the casting-mold system. The formation of cracks occurs due to the force interaction of casting with mold. Currently, a number of approaches are used to determine the value of stress state in the casting material and, accordingly, to determine the value of force interaction. The paper considers the developed estimation of stress-strain state of a casting-mold system, which is determined by deformation resistance of the molding mixture. Change in deformation resistance of the molding mixture is complex due to the multi-factor nature of resulting stresses interaction with thermal and component composition of the layer of a sand-clay mixture. We have studied the influence of geometric parameters and thermophysical properties of the casting on deformation resistance of the molding mixture. A mathematical model was developed that considers the following: heat transfer between casting and mold, increase in mold dry layer, and moisture migration in layer of the sand-clay mixture. On the basis of mathematical modeling, we have performed a quantitative analysis of the influence of thermophysical properties of casting (thermal conductivity, volumetric heat capacity, heat of crystallization, geometric parameters) on ductility of raw sand-clay mold with a moisture of 5% expressed in terms of the average resistance to deformation under an obstruction element 100 mm long. It has been established that an increase in the above-mentioned factors at a fixed instant of time increases the average value of deformation resistance. The quantitative relationship is found between the released heat and the growth of the dry layer of the molding mixture. It has been noted that dynamics of changes in the average temperature does not always coincide with the increase in deformation resistance of a molding mixture.