真空干燥对熔模铸造用硅溶胶型壳强度的影响

Effects of Vacuum Drying on Strength of Silicon Sol Shell for Investment Casting

硅溶胶是熔模铸造中常用的型壳粘结剂之一,但硅溶胶型壳制备过程中存在的突出问题是干燥慢,制壳周期长。本文采用真空干燥工艺对硅溶胶型壳进行干燥,探索了不同真空度及保压时间下型壳强度的变化规律。研究发现:与自然干燥相比,采用真空干燥工艺下的型壳能在较短时间内达到较高的强度。真空度为-0.07 MPa,保压20 min时型壳抗拉强度可达0.85 MPa。而自然干燥相同时间,型壳抗拉强度仅为0.38 MPa。若只考虑湿强度,真空干燥工艺可用于硅溶胶型壳的硬化,且选用真空度-0.07 MPa,保压30 min左右较为适宜。

The silica sol is a binder,used widely for shell-making for investment casting.However,the prominent problem of this process of the silica sol shell-making is that the rate of drying is low,to result in a long shell-making period.In this work,a vacuum drying process was introduced to dry shells instead of natural drying.A study on the shift in the strength of the silica sol shell at different vacuum and holding time was carried out.It is found that the time of the silica sol shell-making was shortened and the strength of the shell was increased as well in the condition of vacuum,compared with natural drying.As vacuum of-0.07 MPa,holding time for 20 minutes,the tensile strength of the shells reached to 0.85 MPa,while the tensile strength of the shells in condition of natural drying was just 0.38 MPa.Considering the green strength only,vacuum drying process can be applied in silica sol shell-making.The appropriate vacuum drying process of silica sol shell-making is vacuum-0.07 MPa and holding time about 30 minutes.