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

ABSTRACT

In 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 (σ_1 h) and the 24 tensile strength (σ_24 h) of modified sand samples increased by 44% and 66% and the residual strength (σ_950°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.

KEYWORDS:

• Casting
• silicate
• sodium
• sand
• modifiers
• optimization
• bonding
• bridges
• strength
• collapsibility

Highlights

• The polyvinylpyrrolidone was the most dominant parameter for the properties of SSBS.

• The 1 h and 24 h tensile strength of modified sand samples increased by 44% and 66% and the residual strength decreased by 49%.

• The composite modifiers promoted the bonding bridges of sand samples smoother and tighter at room temperature.

• Cracks and blow holes emerged on the bonding bridges of modified sand samples in the process of heating and cooling at 950°C.

Additional information

Funding

This work was supported by the The Science and Technology Research Project of Henan Province of China [172102210009].