Performance of water-soluble composite sulfate sand core for magnesium alloy castings

A novel water-soluble sand core hardened by twice microwave heating was fabricated using composite solution of magnesium sulfate and sodium sulfate as a binder. The tensile strength, water absorption rate, gas evolution and water-soluble rate of the water-soluble composite sulfate sand core (WCSSC) were studied. The micro-morphology of WCSSC was observed by scanning electron microscope (SEM). The results show that tensile strength of WCSSC is 1.2 MPa, and the 4 h storage tensile strength exceeds 1 MPa, and also the water-soluble rate is about 42.65 kg/(min m2), which indicates that WCSSC possesses good moisture resistance and water-soluble collapsibility. The microscopic analysis demonstrates that there are some micro-cracks or holes in the bonding bridge that decreases the strength of WCSSC after being put in humidistat for several hours.