Pure zircon brick is mainly composed of zircon, which is called high zirconium brick for short. It is a zirconium containing refractory
One of the important categories of.
1. Production of pure zircon brick
(1) Raw material handling. The raw material of zircon brick is selected zircon ore, which is called zircon sand for short.
The content of zircon is about 90%.
Zircon concentrate sand particle size is very fine and single, generally 0.1-0.2mm, not straight Connect refractory bricks. In order to obtain pure zircon firebricks with coarse particles, it is usually necessary to pre prepare concentrate sand
First calcine or melt at high temperature to make zircon clinker pellets. When calcining clinker, first part of concentrate Sand is ground into fine powder, mixed with another part of concentrate sand, and bonded with temporary organic binder to make materials The ball or blank is calcined into a dense mass at 1500-1700 degrees (lower than the decomposition temperature of zircon)
Block. If there are alkali metal oxides or mineralizers such as MgO and Gao, it can be above 1050 degrees Calcine at a lower temperature. The zircon sand shrinks from 900 ℃ to
The contraction tends to stop at about 1350 degrees, and then it expands slightly, and then it increases sharply after 1700 degrees
Shrink. After calcination, the compactness of zircon concentrate sand pellets is improved, and the bulk density can reach 3.5g/cm3above.
If pure zircon products are produced with fine powder, the concentrate sand can be calcined directly at 1450 ℃
Burn it, loosen it by quenching, and then grind it fine.
(2) Production of high zirconium bricks. Temporary binders should be used to produce pure zircon products, such as sub Sulfate pulp waste liquid, dextrin and lignin, etc. can also be used as ethyl silicate, calcium alkyl acid and phosphorus
Acid and water glass, etc. If plastic fire-resistant clay is used as binder, the product is easy to form and sinter,
However, it often leads to the qualitative reduction of product fire resistance and volume stability. Especially when the ingredients are added When the clay content is high, the impact is particularly significant, as shown in Figure 6-3.
In order to promote the sintering of pure zircon products, a small amount of Cao and Ca (OH) 2 are often added to the ingredients,
MgO or MgF2 and other mineralizers. This additive promotes the separation of ZrO2 • SiO2 at high temperature Solution, form ZrO2 Solid Solution with ZrO2 and enter the glass phase, so as to promote sintering.
When pure zircon is used for batching, in order to ensure that the product has good properties and accurate shape, its particles
The particle size, the amount of binder and admixture must be accurately matched. For coarse particles at all levels Products of. Multi level particle batching is required, and the specific surface area and amount of fine powder should be higher than that of ordinary refractory bricks, so as to It is conducive to making compact green body and sintering. If the green body is completely composed of fine particles, the most The large particle size is usually less than 44 microns, of which several microns should account for the majority. When forming, according to
For the requirements of bulk density of products, ordinary products are generally formed by squeezing method and dry pressing method; DenserMulti use slurry pouring method; Slurry pouring and isostatic pressure method are commonly used for high density. Various components in ingredients It should correspond to the forming method. Pure zircon products must be sintered at a higher temperature and be highly dense Our products need higher temperature. According to the nature and content of fine powder in the green body and the type and
The quantity and maximum sintering temperature are generally about 1700 degrees, which should be controlled so that the sintering surface of the green body does not explode Under the temperature of significant deformation and corresponding to the holding time.
2. Properties and application of high zirconium brick
(1) Properties of high zirconium bricks. The mass fraction of ZrO2 in pure zircon products is about 65%,Almost all of them are composed of zircon crystals, with only a small amount of glass phase and free ZrO2. True densityAbout 4.55g/cm3, up to 4.62g/cm3, and the bulk density of ordinary products is 3.6-3.8g/cm3,The apparent porosity is greater than 13%; The bulk density of dense refractory brick is 3.8-4.0g/cm3; Apparent porosity 5% about; The bulk density of highly dense products is greater than 4G / cm3, and the apparent porosity is less than 1.0%.
Because this product is almost entirely composed of zircon crystals and contains only a small amount of glass phase, in The viscosity is also very high at high temperature, so the fire resistance is very high, more than 1825 degrees. The products have strong pressure resistance at room temperature
The strength is 100-430mpa, and the flexural strength is 17.8-76.3mpa. Load softening temperature is greater than 1650 With the decrease of mineralizer and the increase of firing temperature, the higher one can reach 1750 ℃. thus It is a kind of refractory brick with excellent resistance to thermogravimetric load at high temperature and good wear resistance.
Zircon has low thermal expansion and is fired at high temperature, so the volume stability of the product is high.
From room temperature to 1400 ℃, the thermal expansion rate is only 0.5%. Reburning at 1500 ℃ for 2h, residual shrinkage
The rate is only 0.04% - 0.20%. Some products have no residual shrinkage after reheating at 1650 ℃.
Zircon products with high compactness have poor thermal shock resistance when there are no coarse particles in them. In making
It must be heated or cooled slowly during use. When the product is composed of multi-level particles, the thermal shock resistance will be significant
Improve.
This product is not easy to be wetted and eroded by molten metal and slag, especially aluminum and its Alloy wetting. Therefore, it has good corrosion resistance to molten slag, liquid metal and liquid glass. High density
For example, the degree of corrosion by alkaline slag is only 1% of that of mullite products
／3。
(2) Application of high zirconium bricks.
Zircon products can be used as liners in steel drums for continuous casting and other electrodes eroded by molten slag
Serious parts can also be used as the mouth of copper and aluminum smelting furnace. It can also be used in glass furnaces and glass
Where the glass liquid is in direct contact with the superstructure, and used as a barrier between fused zirconium corundum brick and silicon brick
Leave the brick. For more information, please pay attention to China refractory brick trading website.
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