真空浸渗水玻璃对粘接剂喷射砂型性能的影响

Binder jetting additive manufacturing process(3DP) has the advantages of high forming efficiency, large forming size, no residual thermal stress, low equipment cost and maintenance cost. It has a wide range of potential applications in sand casting. However, it is difficult to balance the tensile strength and gas evolution of sand mold in 3DP process, which limits its application in high-performance sand casting. A post-treatment method of sodium silicate impregnation is proposed. The effects of process parameters including impregnation time, impregnation solution concentration, post-curing temperature, post-curing time, etc. on the tensile strength and gas evolution of the mold are systematically investigated and the optimized impregnation process is determined. The influence mechanism of vacuum-impregnated sodium silicate on the properties of sand mold is explored through COMSOL software simulation and microstructure as well as morphology analysis. The results show that the tensile strength of the mold is increased to 5.07 MPa, and the gas emission is reduced to 11.425 mL/g after 20 h immersion of 100 wt% sodium silicate and 2.5 h curing at 150 ℃. This is because the sodium silicate can adhere to the resin bonding bridge or the surface of the sand particles and fill the pores between the sand particles to form new bonding bridges, leading the increase of the number of bonding bridges and the improvement of the strength of the sand mold during the impregnating process.