铝(镁)合金消失模-型壳复合铸造型壳制备

Ceramic shells for expendable pattern-shell compound casting of aluminum and magnesium alloys

采用基于发泡塑料模样、薄壁型壳和干砂真空造型技术制造铝(镁)合金复杂精密铸件,研究了粉液比对不同粉料配制的硅溶胶涂料性能及其型壳强度的影响,并进行了复合型壳制备优化工艺研究.结果表明:随着粉液比增大,涂料粘度、密度、涂片质量不断增大,型壳强度不断提高;锆英粉和铝矾土型壳焙烧后,型壳强度有较大提高,石英型壳强度出现下降现象系多晶转变所致.采用锆英粉-硅溶胶为表面层,背层为铝矾土-水玻璃2～3层复合型壳,具有较好表面质量和较高强度,且制壳周期短、成本低、脱壳方便.经浇注实验证实,该复合型壳完全能满足铝(镁)合金的浇注成形要求.

Complicated aluminum and magnesium alloy precise castings were produced by thin-wall ceramic shell based on expendable foam pattern and dry sand as well as vacuum technology.Coatings performance of different refractory and silica sol was studied,and the effects of powder solution ratio on the coatings performance and shell strength were discussed,and optimizing process of compound shell was processed.The results indicate that with increasing the powder solution ratio,the viscosity,density and smear weight of the coatings would increase gradually,meanwhile the shell strength is also increased incessantly.The zircon and alumino-silicate shell after roasting,shell strength is increased largely.However,the shell strength of quartz shell is reduced due to polymorphi transformation.The 2～3 layers compound ceramic shell of silica sol-sodium silicate using zircon and silica sol as surface coat,and the powder lot of back-up coat making use of alumino-silicate has better surface quality,high strength and short preparation time as well as low cost and exuviating easily.After casting experience,compound shell can wholly meet casting of aluminum and magnesium alloy.