Compared with large complex thin - wall castings, civil products have lower requirements on casting quality. However, for the latter, shorten the production cycle, improve the production efficiency of the problem becomes more prominent. The gelation process of common silica sol mainly depends on the dehydration and drying of silica sol, which takes longer time than the gelation of chemical hardening ethyl silicate. Ethyl silicate shell using ammonia dry each layer can be completed in 2h, and the final hardening of silica sol generally takes more than 12h, for some deep holes and other difficult to dry parts of the need for a longer time. At the same time, because the Investment Casting shell needs to be made in layers, each layer needs to be fully dried, to ensure that the lower shell immersion coating will not cause the problem of remelting off, and immersion coating itself, water will be immersed in the dried shell, resulting in a long overall drying cycle. It is a schematic diagram of the production cycle of silica sol shell investment casting under general conditions. As can be seen from the figure, shell making time accounts for more than 50% of the whole casting production cycle. To shorten the delivery time and shell making cycle is the core of the problem. The key factors to shorten the shell-making period can be divided into two aspects: internal cause and external cause. The main internal cause is the characteristics of the binder, and the external cause is the drying condition.
Silica Sol Casting industry in China is developing rapidly and its application is also very extensive.
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