Experimental Study on Modification of Phosphate Binder No-bake Sand Excipients Based on Orthogonal Design

The effects of ultrafine fused magnesia powder, citric acid aqueous solution and aluminum sulfate octadecahydrate solution on the properties of phosphate no-bake sand were investigated by orthogonal test. The influence mechanism was preliminarily analyzed by SEM and FTIR. The results show that the properties of no-bake sand are better when 12% ultra-fine fused magnesia powder, 4% citric acid aqueous solution and 10% aluminum sulfate octadecahydrate aqueous solution are added to the mixed sand. The demoulding time of the sample is about 38 min, and the dry strength of the hardened 24 h is 0.96 MPa. After 72 h of storage（in this period, the laboratory humidity was between 40%RH and 60%RH）,the tensile strength still increases. The highest strength is 1.16 MPa when stored for 24 h, and then maintained at about 1 MPa.Reducing the amount of fused magnesia powder and adding an appropriate amount of aluminum sulfate octadecahydrate can reduce and refine the cracks at the bonding film and the bonding bridge. There are superimposed absorption peaks HPO₄^2-and SO₄^2-at 1100 cm^-1in the bonding system, which can improve the bonding strength and storage performance of the sample.