Process and operation points of manufacturing fused zirconia mullite products

1,Key points of the process for manufacturing fused zirconium mullite products

The raw materials for manufacturing fused zirconium mullite products are bauxite, soft clay, and zircon, and the mineralizer is magnesium oxide. The above-mentioned raw materials are added into water in a certain particle ratio to make mud, which is pressed, dried, and fired into blanks. The raw material ratio is: raw bauxite 64.5%, soft clay 23%, zircon 12.5%, water 4.5~5.5%. The fired blanks are crushed to about 40mm and placed in a three-phase electric arc furnace to melt. The working voltage is 110~140V, the working current is 1100~1500A, and the melting time is 2h. When melting, first spread the 2~5mm coke on the bottom of the electric furnace to start the arc, add the broken blanks, and then add the MgO mineralizer and powder to adjust the chemical composition of the material. The material can be cast after being melted at 1780~1800°C. In order to ensure that the bulk density of the product is greater than 2.85g/cm3, supplementary pouring can be carried out.
The cast product should be slowly cooled and cooled strictly according to the cooling rate. The physical and chemical properties of fused zirconium mullite products are as follows: Al2O360%, SiO224%, ZrO27-9%, flux 7.5%; volume density 2.85g/cm3, normal temperature compressive strength 200MPa.
 

Main points of operation for manufacturing fused cast AZS bricks

The raw materials for making baked AZS bricks are alumina light burnt material, zircon and waste clinker.
The alumina powder is lightly burned at 1100°C, and the fine powder smaller than 0.088mm is controlled to account for 50 to 70% and not more than 2%. The waste clinker of the same material is crushed to the required particle size for later use. The ingredients are as follows: light burnt alumina powder 50.3%, zircon concentrate 46.1%, sodium carbonate 2.2%, borax 1.4%, and 20-30% clinker. The powder is melted in a three-phase electric arc furnace, the working current is 2200A, the working voltage is 180V, and the melt temperature is 1800~1840°C. Pour the melt into the mold to make AZS fused cast brick with a bulk density of 3.4g/cm3 and a ZrO2 content of >33%.

The main points of operation for making AZS fired bricks

The raw materials for making AZS fired bricks are zircon, industrial alumina (or super high-bauxite). The zircon and industrial alumina powder are prepared according to 6:4, and 2% MgO is added. Grind the batch material to less than 0.04mm with vibration mill for use. After mixing the prepared batch materials, the blocks are pressed on a 300t friction brick press, and the mature materials are calcined at 1400~1500°C. The clinker is sintered at about 1600℃ after being crushed, crushed, shaped and dried.

Why does cast AZS brick crack? How to prevent cracking?

When the A12O3 in the raw material exceeds 30%, the material is difficult to melt, which can increase the cracking rate of the casting. Therefore, the A12O3 content of the raw materials must be measured before entering the furnace so that it does not exceed 30%.
The input method of the ingredients during melting directly affects the melting. It is difficult to melt through one feeding, and the product is easy to crack; a small amount of multiple feeding is better.
If the melting temperature is too high or too low, the product will have a high rate of cracking during solidification. In actual production, the second smelting is carried out, that is, the material is melted at the melting temperature, after which the power is increased, the refining temperature is increased, and the cracking of the product can be reduced when the product is solidified.

When the casting temperature is too high during casting, the shrinkage rate increases during solidification, the temperature difference between the inside and outside of the product increases, and the product is easy to crack. Therefore, before casting, stop the arc for 3~5min to lower the refining temperature to the casting temperature (about 1760°C) and then proceed with casting, which can reduce product cracking. In addition, the products should be placed in an incubator for cooling. The temperature in the box should not be too low. For example, the temperature of 33# fused zirconium corundum in the box is 1200°C, and the cooling rate should be slow, and the temperature out of the box should not be higher than 300°C. This is good for reducing product cracking.