Sol physicochemical parameters mainly by: SIO2 content, density, Na2o content, PH value, kinematic viscosity, colloidal particle diameter, these physical and chemical parameters affecting the powder-liquid ratio main shell strength, stability and paint coatings. Because precision casting business is difficult to detect these physicochemical parameters, so that on the one hand to strengthen the supply side of the selection, evaluation and confirmation. On the other hand, the surface layer and the backing layer should choose to use different sizes of silica, the surface layer of silica select S-830, S-1430 Select the backing layer of silica sol. Coatings formulated in precision casting method will directly affect the quality of the casting, that we first understand the preparation of the coating. Usually before adding silica coating formulation, coupled with a wetting agent mix of refractory powder is added with stirring, and finally add defoamers. In order to ensure quality when coating, surface coating all of the new material, mixing time should be greater than 24h can be used, as part of new ingredients, mixing time can be shortened to 12h. Transition layer and a backing layer coating stirring time may be less than the surface-layer coating, with all new paint is stirred for longer than 10h, part of the new feature, the stirring time can be shortened by half. With a good paint if not used, it should be capped to prevent evaporation. Best not with paint in Shell operations, and set up a special coating formulation equipment.
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