Humidity-resistant inorganic binder for sand core making in foundry practice

摘要

The performance of sand core was improved by using the modified water glass as a binder andadding powder additives in the sand hardening process. The optimal proportion of the compound additives wasdetermined by an orthogonal test, with a ratio of microsilica: polyvinyl alcohol solution: borax: B agent = 25: 20:2: 1. The binder accounted for 2% of the sand by weight, and the compound additives accounted for 0.96%. Thecore box was heated to 175 °C, and the compressed hot air of 120 °C kept blowing for 40 s. Tensile strength wasused as the main indicator to evaluate the humidity-resistance of the sand core. For the sand core, the instanttensile strength reached 0.73 MPa, the tensile strength at room temperature was 1.81 MPa, and that of sand coreholding at the condition of 35 °C and 90% RH for 2 h and for 4 h reached 1.61 MPa and 1.19 MPa, respectively.The gas evolution was 7.5 mL·g-1 at 850 °C for 3 min. The residual tensile strength was 0 MPa at 750 °C for5 min. Fourier-transform infrared spectroscopy analysis showed that the humidity-resistance of the core wasgreatly improved by the powder additives.