Effect and Mechanism Analysis of Post-Treatment on Properties of Dry Phosphate Coated Sand
Based on single-factor and orthogonal tests,the post-treatment process of dry phosphate coated sand was studied to investigate the effects of furnace loading method,heating temperature,holding time and cooling mode on the properties of the samples,a mathematical model between heating temperature,holding time,cooling method and gas revolution was established and validated,and the mechanism was analyzed with the help of characterization techniques such as TG-DSC,SEM-EDS.The results showed that the optimization scheme of the post-treatment process was 120 ℃ ×10 min with furnace heating and air cooling,the gas volume of the sample reduced to 15.9 mL/g by 15.0％,and the tensile strength could be up to 1.91 MPa by 18.6％.The multiple linear regression model matched the experiments results,and the error rate between the experimental value and the predicted value was within 5％.Microscopic analysis showed that appropriate post-treatment could prompt the residual hydrate in the bonding film of the coated sand to further release water,part was formed water vapor and emitted,and the other water molecules wetted the surrounding bonding film,which improved the bonding strength of the coated sand while reducing the gas evolution in the samples.
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