Glaze Classification And Properties

Enamel glaze according to metal substrate can be divided into cast iron glaze, steel plate glaze, stainless steel glaze, aluminum enamel glaze and so on.

Stainless steel enamel glaze: stainless steel substrate 304 is appropriate, but also useful 316. Stainless steel needs sand treatment, degreasing treatment without dense. Stainless steel enamel divided into bottom glaze, surface glaze, a enamel. Stainless steel glaze can also be varied ten colors.

Steel enamel glaze: steel enamel bottom glaze according to the different adhesive, can be divided into cobalt bottom glaze (cobalt oxide), nickel bottom glaze (nickel oxide), cobalt nickel bottom glaze, antimony bottom glaze (antimony oxide), antimony molybdenum bottom glaze (antimony oxide and molybdenum oxide), the main requirement is that the enamel bottom glaze can be well close with the steel plate. The glaze of the steel plate is the enamel coated on the bottom glaze, which can be divided according to the emulsion agent, antimony glaze, titanium glaze, tin glaze, zirconium glaze, etc., which requires the enamel products to achieve good whiteness and gloss effect after firing, and can adapt to the needs of acid and oxidation resistance to a certain degree. However, the enamel surface glaze cannot be directly coated on the metal substrate, and the enamel production factory also takes into account the adaptation of the bottom glaze when selecting the surface glaze, the firing temperature of the surface glaze is lower than the bottom glaze, and the coefficient of expansion of the surface glaze is also very important.

Cast iron glaze: cast iron bottom glaze, cast iron surface glaze, colored glaze, matte glaze, etc.

The cast iron body is generally sanded, sandblasted, polished surface residue; Some sand after annealing and tempering; Some do not anneal, directly after sand enamel. The quality of the enamel made after annealing is stable only, and the defects such as pinhole, foaming, exploding porcelain, and poor porcelain surface are easy to produce without annealing. Matte cast iron enamels are generally not annealed, but directly sanded. Because the matte porcelain layer is thinner, generally 80-120um gas permeability is better than the bright glaze, the porcelain surface does not need to be smooth, and the quality is passable.

Aluminum enamel: aluminum embryo body can not be degreased, generally burning oil method. Remove oil at 550 degrees, and remove surface impurities quickly with 5-10% nitric acid solution. Clean and dry with water. Aluminum enamel grinding without clay, using sodium silicate solution as suspension agent. The firing temperature is between 550 and 600 degrees. Aluminum enamel can also be printed after a titanium white glaze is made, and then burned. The bottom plate of the high-end electric iron is aluminum enamel.

Titanium glaze and antimony glaze are more popular glaze on the market, especially titanium glaze, emulsion turbidity ability is very strong, coated once can get a good emulsion effect, chemical stability and thermal stability are very prominent. Antimony glaze has good impact resistance, but its emulsion ability is slightly worse than titanium glaze, generally need to be coated 2 times, the amount of enamel is larger, and can not be used as a container for contact with food. Tin glaze because of less resources, so the cost is high, zirconium glaze melting temperature is higher than ordinary enamel glaze, and acid resistance is relatively poor, so these two enamel glaze rarely used.

In addition to meeting the following basic requirements in the selection of ordinary daily enamel surface glaze, enamel production factories also need to combine their own needs according to the characteristics of different surface glaze to make choices:

1. Good lactation and gloss;

2. The expansion coefficient of enamel surface glaze (slightly smaller) should be adapted to the bottom glaze;

3. The firing temperature is slightly lower than the bottom glaze (excluding the 2 boring 1 firing process surface glaze);

4. Good acid, water and heat resistance;

5. Good elasticity (not easy to produce defects and defects) and wear resistance and pressure;

6. If it is a color glaze, it also needs stable color and beautiful appearance.

Titanium glaze: The surface glaze made of titanium oxide as a milky raw material is called "titanium glaze".

The enamel products made by using it to coat the metal billet are called "titanium enamel". Since the titanium glaze is very acid resistant and has no toxicity, titanium enamel has been widely used in China since the 1960s. In the purchase of enamel products, how to distinguish antimony enamel and titanium enamel? Just look at the label colors on the back of the product: sky-blue is antimony enamel; Blue green or light blue is titanium enamel.

Antimony glaze has strong impact resistance. Antimony glaze emulsion turbidity ability is poor, generally need to be coated twice, the coating is thicker, the amount of porcelain glaze is larger. Antimony in enamel may be present in a toxic trivalent state of antimony, so it should not be used in products that come into contact with food.

Chemical composition range of ordinary daily steel enamel surface glaze:

Antimony overglaze

SiO2:35~45%

B2O3:5~8%

Al2O3:6~8%

K2O+Na2O: 12~18%

CaF2+Na2SiF6:5~15%

Sb2O3:10~15%

Titanium glaze

SiO2:38~50%

B2O3:15~20%

Al2O3:0~3%

K2O+Na2O: 10~15%

Na2SiF6:5~10%

TiO2:15~20%

Under normal circumstances, the ratio of SiO2 and K2O+Na2O in the formula determines the burning temperature of the surface glaze, the antimony bottom glaze ratio is 2.0~2.5, the antimony smooth glaze is 3.5~4.0, the titanium surface glaze is 3.5~4.0, and the titanium color glaze is 2.5~3.0.

The chemical stability, thermal stability and gloss of the enamel can be improved by increasing the content of SiO2 in the enamel. If the dosage is too high, the burning temperature and surface tension of the glaze will increase, and the defects such as burning shrinkage and line pattern will easily occur on the porcelain surface. The increase of B2O3 content can improve the thermal stability, gloss and elasticity of the topglaze, but it is unfavorable to the opacidity of the antimony glaze. The high content of K2O+Na2O easily reduces the chemical stability and gloss of the surface glaze, and promotes the formation of rutile crystal form during the firing of titanium surface glaze, which makes the porcelain complexion turn yellow. High CaF2 makes antimony glaze surface rough and poor luster.