Preparation and properties of a binary composite water-soluble salt core for zinc alloy by die casting

For realizing complicated shapes of the inner cavity of zinc alloy castings by pressure die casting, the problem of poor leachability has to be solved and the high-strength requirement of the water-soluble salt core should be met. High-melting potassium chloride salt and low-melting potassium nitrate salt were used as the core materials. High-strength binary composite water-soluble salt core (WSSC) was formed by the process of melting and gravity pouring. The performance characteristics of the potassium chloride core, potassium nitrate core, and binary composite WSSC (20% KCl-80% KNO₃) were investigated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies were performed to examine the micro-morphology and phase composition of WSSC. The results indicate the following:the binary composite WSSC has excellent comprehensive performance, its bending strength can exceed 21.2 MPa, the 24 h hydroscopicity rate is 0.568%, the water-soluble rate can exceed 208.63 kg·min^-1·m^-3 in water at 80℃ and its surface has no cracks and folds unlike the pure salt core. Crack growth in the binary composite salt core occurs by deflection, which is the main reason for the improvement in bending strength.