Composition Optimization and Strengthening Mechanism of High-Strength Composite Water-Soluble Salt Core for Foundry

This paper aims to improve difficult cleaning and high core requirements in castings with complex internal cavities. The mixed salt was composed of NaCl, Na2SO4, BaCl2, and ceramic reinforced powder Al2O3 was added as core material. A high strength water-soluble salt core was prepared by melting gravity casting. Besides, the performance characteristics of NaCl salt core, Na2SO4 salt core, binary NaCl+Na2SO4 salt core, ternary NaCl+Na2SO4+BaCl2, and composite salt core after the addition of Al2O3 powder are compared and analyzed. The results demonstrated that the ratio of ternary salt cores was NaCl: Na2SO4: BaCl2=6:4:1; with the addition of Al2O3 powder, the bending strength of salt cores reached 27.9 MPa, and the bending strength of salt cores increased to 38.5 MPa. The composite salt core has a better water solubility than the unit NaCl salt core. Moreover, the water solubility time of the salt core can be shortened from 15 to 2 min when the water temperature was 85 degrees C. Scanning electron microscopy and X-ray powder diffractometer were used to analyze the microstructure and phase composition of salt cores. The composite salt core's energy during crack propagation is weakened by the deflection and passing through the composite phase, increasing the bending strength of the salt core.