Requirements For The Development Of Silica Sol To Improve The Efficiency Of Investment Casting

Compared with large and complex thin-walled castings, civil products have low requirements for casting quality. However, for the latter, the problem of shortening the production cycle and improving production efficiency has become more prominent. The gelation process of ordinary silica sol mainly relies on the dehydration and drying of silica sol, which takes longer than the gelation of chemically hardened ethyl silicate. The ethyl silicate shell can be hardened in about 2 hours per layer by ammonia drying, while the final hardening of silica sol generally takes more than 12 hours, and it takes longer for some deep holes and other difficult-to-dry parts. At the same time, since the investment casting shell needs to be manufactured in layers, each layer needs to be dried fully to ensure that the lower layer of the shell will not cause the problem of back dissolution and shedding when the coating is dipped. The water in the dip coating itself will penetrate into the dried shell, resulting in a long overall drying cycle. This is a schematic diagram of the production cycle of silica sol shell investment castings under normal circumstances. As can be seen from the figure, the shell making time accounts for more than 50% of the entire casting production cycle. To shorten the delivery time of the product, shortening the shell making cycle is the core link of the problem. The key factors for shortening the shell making cycle can be divided into two aspects: internal factors and external factors. The internal factors are mainly the properties of the binder, and the external factors are the drying conditions.