Stage

Main Response

Changes and Phenomenon

Stage Termination Characteristics

The first stage

removes the adsorbed water in the porcelain powder, and the temperature of the powder body rises from room temperature to 150 ℃.

The adsorbed water of the porcelain powder turns into steam and evaporates in large quantities, and some electrolytes begin to decompose.

The second stage

the organic matter is oxidized, the structural water begins to be excluded, the eutectic appears between the interface of the ground coat and the cover coat, and a small amount of point-like solid-phase reaction occurs. The temperature is 150~400℃.

The gas generated by the reaction is removed, and tiny cracks and pores (gas channels) appear in the dust. Ground coat - a solid phase reaction occurs between the cover coat interface, and point-like fusion, so that the cover coat is not easy to fall off from the ground coat layer

The interfacial cover coat particles are sintered with the ground coat, but the entire cover coat has not yet been fired.

The third stage

the powder layer is sintered, and mutual infiltration occurs between the interfaces. The temperature is 400~600℃.

Continue to remove the structural water, the cover coat is completely sintered, partially softened, and the gas channel begins to be closed, a large amount of gas is contained in the sintering, and the structure is loose.

The phenomenon of "mutual infiltration" between the ground coat and the cover coat interface tends to be intense, so that the two phases are mixed, and the middle layer begins to form, but the entire cover coat layer is only fired.

The fourth stage

a smooth porcelain surface is formed, the intermediate layer between the interfaces is further formed, and the temperature rises from 600 °C to the firing temperature, generally 820~880 °C. Low temperature enamel is 700~760℃, and opalescence begins to form.

The cover coat melts, the ground coat continues to melt, the interfacial interpenetration phenomenon intensifies, the intermediate layer grows, the adhesion is further improved, the porcelain surface tends to be smooth, opacity and coloring, and begin to form. The surface of the porcelain is smooth and clean, and the porcelain layer still has small holes, initially showing opacity and coloration.

The fifth stage

The gas in the porcelain layer basically escapes, the middle layer has formed a solid structure, and the opacity and coloration are in a good state. The firing temperature is 820~880℃, and the low temperature enamel is 700~760℃.

The enamel melt has good fluidity, reduced surface tension, which is conducive to gas removal, smooth porcelain surface, good opalescent color, and the product must be discharged from the kiln at this time.

The iron blank - the ground coat - the cover coat has formed a composite body, the porcelain surface is smooth and smooth, and the opaque color is good. If it is still out of the kiln at this time, an over-burning defect is formed.

The sixth stage

cooling

After the product leaves the kiln, the temperature gradually decreases, and the residual stress varies with the cooling speed.