The Function of Refractory Materials in Enamel Fri
Enamel products need to be fired for many times or at high temperature in the production process. In order to prevent over-burning of enamel products, it is necessary to add refractory raw materials to the grinding admixture. The refractory raw materials are mainly used for the ground coat and primary enamel. During the firing process, they will partially melt and melt with the enamel frit, which increases the firing range of the ground coat and keeps the ground coat layer in the subsequent firing of the cover coat. intact.
The most commonly used refractory raw materials in the enamel industry are quartz, potassium feldspar, zirconium silicate and alumina.
1. Calcined quartz powder: The enamel industry generally adds 325 mesh calcined quartz powder to the ground coat and primary enamel. Protective measures should be taken during the loading and grinding operation. If the human body frequently inhales quartz powder, it will cause "silicosis" disease;
2. Aluminum silicate (ZrSiO4): It can significantly improve the thermal stability and firing range of enamel, and can also improve the alkali resistance and water resistance chemical stability of the porcelain surface, and can be used as an opacifier. The grinding amount of zirconium silicate in the enamel slurry is generally 2%~4%;
3. Alumina (Al2O3); it can improve the anti-focal spot performance of the ground coat, and can be added to the cover coat to obtain a matt enamel surface.
The total amount of the above-mentioned refractory raw materials added to the ground coat or primary enamel accounts for 5% to 30% of the enamel, and the specific grinding amount depends on the type of enamel and the size of the enamel product. The thermal shock resistance of enamel cookware. For kitchen utensils whose firing temperature is 800~830℃, 10%~15% quartz can be added. For products whose firing temperature exceeds 830°C and the thickness of the steel plate is greater than 1.2mm, more than 15% quartz can be added. Of course, as the amount of quartz increases, so does the amount of clay grinding.