Firing of Enamel Coating
During the firing process, all the finely ground enamel frit, clays, pigments and other grinding and grinding materials are melted into one body. The ground coat is combined with the metal, and all the enamel must be heated and melted to form a uniform and continuous glass layer, which is attached to the surface of the metal body.
The firing temperature and time vary with the type of enamel. Since firing is the last process, it is related to the quality of enamel. If the firing fails, the previous processing and treatment techniques are completely wasted. Successful firing of enamel products must meet the following conditions:
1. Proper firing temperature and time
2. Appropriate burning racks and spreaders
3. Uniform heating and cooling
4. There must be no dust when firing. The content of sulfur and water vapor should be reduced as much as possible.
Some enamel frit require free oxygen when firing, but there is about 1/5 of oxygen in the air, so this condition is easy to meet. The general firing temperature and time of various enamel frits:
Steel ground coat 800~850℃ 3~4 minutes
Steel cover coat 780~830℃ 2~3 minutes
Wet cast iron enamel 720~770℃ 10~15 minutes
Dry cast iron enamel 820~930℃ 3~5 minutes
Aluminum enamel 520~545℃ 5~7 minutes
The firing temperature and time are affected by many factors, such as the thickness and uniformity of the metal body, the thickness and particle size of the enamel layer, the required properties after firing, the ratio of the amount of enamel products in the furnace to the heat, and the atmosphere in the furnace , The size and shape of the enamel product, and the position of the blank placed in the furnace, etc.