Performance of a Water-Soluble Ceramic Core and Its Application in Aluminum Casting

When an aluminum investment casting with a complex internal cavity or deep pore is fabricated, a core that can be dissolved and collapsed in water is needed. In this paper, a water-soluble ceramic core with fused corundum powder as refractory material and K₂SO₄ as binder was prepared. The results show that as the content of K₂SO₄ increases, the bending strength, porosity, and shrinkage of the core decreases, but the solubility of the core improves. The K₂SO₄ will decompose and react with Al₂O₃, resulting in the low-soluble KAlO₂ produced. The solubility of ceramic cores is affected by the porosity, the reacting product, and the residual salt. When the amount of binder is 30 wt.%, the core possesses the best comprehensive properties. In three conditions: hot water at 80 °C, ultrasonic vibration, and mechanical stirring assistance processes, the core has the fastest dissolution rate with ultrasonic assistance. An S-shaped core embedded in aluminum casting was fabricated, and the core was removed completely in water with ultrasonic assistance. The pore surface of the casting was bright and clean, which means that the water-soluble ceramic core prepared in this paper was expected to be used to produce the aluminum alloy casting with complex inner cavities.