The performance of sand core was improved by using the modified water glass as a binder and adding powder additives in the sand hardening process. The optimal proportion of the compound additives was determined 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%. The core box was heated to 175 °C, and the compressed hot air of 120 °C kept blowing for 40 s. Tensile strength was used as the main indicator to evaluate the humidity-resistance of the sand core. For the sand core, the instant tensile strength reached 0.73 MPa, the tensile strength at room temperature was 1.81 MPa, and that of sand core holding 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 for 5 min. Fourier-transform infrared spectroscopy analysis showed that the humidity-resistance of the core was greatly improved by the powder additives.

No abstract

No abstract

No abstract

I n the process of casting, it is inevitable that t h e t r a d i t i o n a l o rg a n i c b i n d e r w i l l p o l l u t e the environment [1]. With the increasingly strict requirements of environmental protection, the inorganic binder has attracted more attention [2, 3]. Water glass binder, a kind of inorganic binder, which is usually used in aluminum alloy casting, has some advantages in environmental protection because of its non-toxic nature and low gas evolution in casting [3, 4]. However, due to the low bond strength, the amount of unmodified water glass accounts for as much as 6.0%-8.0% of the weight of molding sand [5]. At the same time, the molding sand using unmodified water glass has poor collapsibility [6, 7]. These disadvantages limit the