Study on the Effect and Mechanism of Mold Temperature and Ceramic Particle Alumina on the Strength and Water Solubility of NaCl–Na2CO3 and NaCl–Na2SO4 Composite Cores

In the process of pouring salt cores, it is crucial to select the appropriate mold temperature, which is essential for the shaping and strength of the salt cores. Additionally, salt cores need to undergo water-soluble cleaning after casting, which has certain requirements for their water solubility. In order to obtain composite water-soluble salt cores with a certain strength suitable for high-pressure die casting processes, sodium chloride, sodium sulfate, and sodium carbonate are used as salt core materials, with ceramic alumina particles as reinforcement materials. The influence of alumina on the performance of NaCl–Na₂CO₃ and NaCl–Na₂SO₄ composite salt cores was studied. Through molecular dynamics simulation calculations, the change curve of the adhesion work of salt cores at different mold temperatures was analyzed. Combining XRD detection results and comparative analysis of actual salt core flexural strength, it was found that sodium aluminate generated at high temperatures has a strong interface binding ability with other components in the salt core, which is a key factor affecting the strength of the salt core. Through experimental research combined with simulated calculations of water molecule adsorption at different salt core interfaces, it was found that with increasing water temperature, the water adsorption capacity of NaCl–Na₂CO₃ and NaCl–Na₂SO₄ salt cores gradually increases, leading to an accelerated water solubility rate. The addition of Al₂O₃ reduces the water solubility rate of NaCl–Na₂CO₃ and NaCl–Na₂SO₄ salt cores, but significantly improves their strength. The addition of Al₂O₃ enhances the NaCl–Na₂CO₃ salt core due to the formation of highly water-soluble sodium aluminate, resulting in a certain improvement in water solubility rate.