In the last article, we explained that the enamel frit of cast iron enamel products can be divided into dry cast iron enamel and wet cast iron enamel according to the different coating methods. Enamel way and firing.

1. Enameling

Wet enamel generally uses spray enamel. The best way is to first burn the white enamel with the ground coat. Many enamel manufacturers choose to spray the cover coat directly on the workpiece. The workpiece should be inspected before enameling, and all the holes need to be filled with dry enamel to avoid enamel defects caused by air escaping during firing. The wet spray enamel of cast iron enamel is similar to the spray enamel of steel plate enamel, and attention should be paid to spraying into a uniform coating.

The dry powder coating of cast iron enamel is to first coat the workpiece with a thin layer of ground coat slurry by dipping or spraying, and then enter the box-type firing furnace for firing after drying. If it is a large object, when it is inconvenient to dip the enamel, you can let the enamel frit flow through the workpiece, or use the method of spraying to enamel. When the enamel is applied by spraying, part of iron oxide can be added to the enamel frit to facilitate observation. After the enamel is painted and dried, it still needs to be checked, and the holes and gaps need to be filled. Dry powder coating of enamel cover coat requires skills and experience. After taking out the hot body from the firing furnace, immediately apply the sieved enamel cover coat powder, and use the residual heat of the body to burn the enamel on the surface. , and then put it back into the furnace for firing.

2. Firing

For the firing of wet cast iron enamel glaze, if the workpiece is large, the firing time needs to be extended, but in order to prevent the enamel from overboiling, the firing temperature must be lowered. Wet enamels will boil in the initial stage of firing, but gradually stop boiling and form a smooth film in the later stage. The gas that promotes the boiling may come from the decomposition of clay, the gas contained in the cast iron metal, or the gas produced by the reaction between the enamel and the iron.

The body of dry cast iron enamel is larger, and the firing temperature should rise slowly, which can usually be divided into two stages. The object is heated only to bright red during the preheating stage, and then moved to the firing furnace (840~925°C). When the workpiece reaches the temperature of the firing furnace, it is quickly removed and sprinkled with enamel powder, and then returned to the furnace until the enamel melts to a smooth surface.