Parametric optimization of modifiers for ester-hardened sodium silicate bonded sand

Abstract

ABSTRACTIn this paper, the parameters of composite modifiers composed of polyvinylpyrrolidone (PVP), lithium tetraborate and disodium hydrogen phosphate for ester-hardened sodium silicate bonded sand (SSBS) were optimized by orthogonal experiment. The results of orthogonal experiment showed the optimal parameters of PVP, lithium tetraborate and disodium hydrogen phosphate were 8%, 0.15% and 0.2% of sodium silicate binder, and the1 h tensile strength (σ1 h) and the 24 tensile strength (σ24 h) of modified sand samples increased by 44% and 66% and the residual strength (σ950°C) decreased by 49%. The experimental results indicated that the modifiers promoted the bonding bridges of sand sample smoother and tighter at room temperature, which improved the 1 h and 24 tensile strength, and facilitated the formation of Na2Si2O5, Na3PO4, Na4B2O5 and Li2B8O13 and the volatilization of PVP in the process of heating and cooling at 950°C, resulting in the formation of cracks and blow holes on bonding bridges, thereby improving the collapsibility of SSBS.