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Coating preparation method for investment casting
2022-12-21
Physicochemical parameters of silica sol mainly include SIO2 content, density, Na2O content, PH value, kinematic viscosity, colloidal particle diameter, etc. These physical and chemical parameters mainly affect shell strength, coating stability and powder liquid ratio of coating.
As it is difficult for investment casting enterprises to detect these physical and chemical parameters, on the one hand, it is necessary to strengthen the selection, evaluation and confirmation of suppliers; on the other hand, different specifications of silica sol should be selected for the surface layer and back layer, S-830 silica sol should be selected for the surface layer, and S-1430 silica sol should be selected for the back layer. The preparation method of coating will directly affect the quality of castings in investment casting. Let's first understand the preparation of coating.
Generally, silica sol is added first, then wetting agent is added for mixing, refractory powder is added during mixing, and finally defoamer is added. To ensure the coating quality, when all the surface coatings are new materials, the mixing time should be more than 24h before use. If some are new ingredients, the mixing time can be shortened to 12h. The mixing time of the transition layer and back layer coatings can be less than that of the surface coatings. If all the coatings are new, the mixing time is more than 10h. If some are new ingredients, the mixing time can be shortened by half. If the prepared paint is not used, it shall be covered and sealed to prevent moisture evaporation.
It is better not to prepare coating in shell making operation, but to set up special coating preparation equipment.
As it is difficult for investment casting enterprises to detect these physical and chemical parameters, on the one hand, it is necessary to strengthen the selection, evaluation and confirmation of suppliers; on the other hand, different specifications of silica sol should be selected for the surface layer and back layer, S-830 silica sol should be selected for the surface layer, and S-1430 silica sol should be selected for the back layer. The preparation method of coating will directly affect the quality of castings in investment casting. Let's first understand the preparation of coating.
Generally, silica sol is added first, then wetting agent is added for mixing, refractory powder is added during mixing, and finally defoamer is added. To ensure the coating quality, when all the surface coatings are new materials, the mixing time should be more than 24h before use. If some are new ingredients, the mixing time can be shortened to 12h. The mixing time of the transition layer and back layer coatings can be less than that of the surface coatings. If all the coatings are new, the mixing time is more than 10h. If some are new ingredients, the mixing time can be shortened by half. If the prepared paint is not used, it shall be covered and sealed to prevent moisture evaporation.
It is better not to prepare coating in shell making operation, but to set up special coating preparation equipment.
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