Rapid recycling of waste salt core materials in foundry industry using fractional crystallization

The water-soluble composite salt core materials have attracted increasing interest in the manufacture of hollow castings with complex structures due to their high strength and excellent water solubility, while the treatment of waste brine generated from the salt core represents a major pain point for its large-scale application. To change the above situation, the recycling technology of the waste brine from composite salt core materials was developed using cooling crystallization combined with solvent-driven crystallization. The influences of dissolution temperature and solvent content on the recovery rate of the composite salt core materials, including inorganic salt and fortifier, were investigated. In addition, the mechanical properties and microstructures of the composite salt core with multiple cycles were compared and analyzed. The results show that the fortifier material of corundum powder exhibits excellent chemical and thermal stability with a 100% recovery rate, and the recovery rate of inorganic salt material can reach 79.31% with a 40 °C dissolution temperature and a 1.0 mass ratio of methanol to brine. The microstructures, phase compositions and mechanical properties of the multi-recycled composite salt core have not changed, demonstrating that the recycling of the water-soluble composite salt core is feasible, and favoring the green development of the foundry industry.