The coating used in precision casting consists mainly of silica sol. Silica sol consists mainly of silica, high-density materials, sodium dioxide, pH-adjusting substances, moving adhesives, colloidal particles, etc. The physical and chemical parameters of these materials mainly affect the strength and coating of precision casting shells. Stability.
Since it is difficult for precision foundry manufacturers to detect these physical and chemical parameters, it is necessary to strengthen supplier selection, evaluation and confirmation. On the other hand, different sizes of silica sol should be used for the surface layer and the back surface, s-830 type silica sol is used for the surface layer, and s-1430 type silica sol is used for the back surface. In precision casting production, the preparation of the coating directly affects the quality of the casting.
The coating is usually prepared by first adding a silica sol, then adding a wetting agent, adding a refractory powder to the mixture, and finally adding an antifoaming agent. In order to ensure the quality of the coating, the surface coating is a new material, the mixing time should be more than 24 hours to use, such as some new ingredients, the mixing time can be shortened to 12 hours. The mixing time of the transition layer and the back layer can be less than that of the surface coating, all of which are new paints, the mixing time can exceed 12 hours, and when the new coating is used, the mixing time can be shortened by more than half. If the coating is not used, it should be capped to prevent evaporation of water.