Category: Zircon Brick

Zirconium Refractory Material for the Slag Part of the Steel Drum

KilnRefractory

Zircon-based and ZrO2-based refractories made from zirconium-based refractory raw materials have excellent resistance to chemical attack and high-temperature performance. For example, zircon bricks are used for the slag part of the steel drum, ZrO2 brick linings are used for the nozzle holes of the sliding nozzles, and ZrO2 quality sizing nozzles are used for horizontal continuous casting. At the same time, zirconium-based raw materials are introduced into other refractory materials, and the performance of the original materials, especially the thermal shock stability, is greatly improved by using the phase transition of ZrO2.

Zircon Sand
Zircon Sand

The Effect of Adding Zirconium-Based Raw Material to the the Slag Part Refractories of the Steel Drum

Adding ZrO2 substances to refractory materials has the following two functions:

①The main crystalline phase or the secondary crystalline phase is generated so that the material has special properties.

For example, the most well-known fused corundum bricks. It is a mass-produced 33# fused cast zirconium corundum brick. Its composition is near the eutectic point of the Al2O3-SiO2-ZrO2 ternary system, and its molecular formula is equivalent to 2Al2O3-SiO2-ZrO2, abbreviated as AZS fused cast brick. Its main crystal phase is the eutectoid of baddeleyite and corundum (Z+C), or baddeleyite, corundum and mullite (Z+C+M). The presence of (Z+C) eutectoid makes AZS bricks 15 times more resistant to chemical attack by glass solution than high alumina materials made by sintering. The (Z+C) eutectoid of independent components is an important structural unit to maintain the structural stability of the AZS brick body in the middle and later stages of the erosion of the glass molten pool.

In the iron and steel industry, the use of stable ZrO2 has the ability of oxygen ions to move between two phases with an oxygen potential difference, that is, the deoxidation ability and the use of stable ZrO2 bushings suppresses the precipitation of oxides. The clogging degree caused by Al2O3 deposition in the immersion nozzle for continuous casting is reduced by half.

② Modification of the original material.

High alumina and basic refractory products have good chemical stability and high-temperature performance, but poor thermal shock stability. Adding ZrO2 to corundum bricks, high alumina bricks, and magnesia bricks can significantly improve the thermal shock stability of these refractory products by using the toughening effect of ZrO2. Anti-spalling high-alumina bricks for cement kilns are made by adding zircon powder to the ingredients of high-alumina bricks. After firing, many microcracks are formed around the ZrO2 particles, so that the thermal shock stability (1100℃-water cooling) of this brick can reach more than 40 times. Good results have been achieved in the upper transition zone of the cement rotary kiln and the side wall of the grate cooler. As early as the early 1930s, some people developed magnesium-zirconium products, whose thermal shock stability and resistance to iron furnace slag and open-hearth slag are better than those of magnesia bricks. After adding ZrO2, the strength of magnesia zirconium brick is also higher than that of ordinary magnesia brick. This product is expected to be used in cement rotary kilns, which can partially replace magnesia-chrome bricks to reduce chromium pollution and protect the environment.

For free samples and quotations of refractory zircon bricks for ladle slag, please contact us.

Preparation of 65% Zircon Brick

KilnRefractory

Zircon (ZrSiO4) belongs to the tetragonal system. The theoretical composition is 67.2% of Zr02 and 32.8% of SiO2, which is the only compound in the binary system of Zr02-Si02. 65% Zircon Brick. The thermal expansion coefficient is small, the load softening temperature is high, the thermal shock stability is good, and the thermal conductivity decreases with increasing temperature. Therefore, As the refractory materials manufacturer said, the zircon refractory brick is an indispensable material for industrial kilns such as building materials, light industry, electronics, metallurgy, and so on.

In recent years, with the advancement of glass industry technology and the application and promotion of kiln insulation technology, the amount of machined 65% Zircon Brick has been increasing. Mainly used in the gap, upper partition wall, fire observation hole, temperature measurement hole, and other parts of the glass kiln. The temperature of this part is high and it is eroded by flying materials and eroded by hot airflow, so the environment is very engraved.

RS Zircon Refractory Bricks Manufacturer
RS Zircon Refractory Bricks Manufacturer

Preparation of 65% Zircon Brick

To produce zircon bricks with a Zr2O3 content greater than 65%, the content of the raw material Zr2O3 used must be greater than 66%. The decomposition temperature of the zircon is 1676℃. As the content of impurities increases, the decomposition temperature decreases. The high purity of the raw materials is the primary condition for the production of zircon refractory bricks with 65% zirconium with excellent properties.

The raw material of zircon is granulated and cannot be directly used for making bricks, but must be ground into a fine powder. Because zirconite has a large wearability index, the fine powder is obtained by vibrating mill and air-jet mill.

Due to the use of 65% zircon brick containing ZrO2. The material should have good high-temperature physical properties, and the aggregate is closely related to it. The zircon sand is ground first, then made into a green body, which is crushed into different particle sizes after high-temperature calcination. Because the zircon material is brittle, the broken particles are in the form of flakes. The normal temperature compressive strength of sheet materials is about 50% higher than that of granular materials. On the contrary, under the same conditions, the bulk density of granular granules is 0.12g/cm³ higher than that of flakes on average. Taking into account the compressive strength and density performance, the crushed material must be properly treated before it can be used.

The batch materials are mixed on a wheel mill mixer, and the materials are trapped for 16 hours, and then formed on a large-tonnage friction brick press. The forming pressure is 700~1000Kg/cm³. Applying large pressure can cause the average distance between adjacent particles to decrease and the contact area to increase, which is beneficial to sintering. But after increasing to a certain level, the effect is extremely insignificant. Appropriate pressure and pressurization methods are the keys to solving the formation of barren materials.

The sintering of zircon is more difficult, and its speed is slow due to solid-phase diffusion at high temperatures. Adding MgO, CaO, Y2O3, TiO2, ZnO2 can reduce the sintering temperature and promote its sintering. In this sintering, 1.5% to 2.75% of Y2O3 and TiO2 were added as sintering accelerator, sintered in a shuttle kiln, and the firing temperature was 1580 to 1650℃.

RS High Quality Zircon Bricks
RS High-Quality Zircon Bricks

Use Performance of Zircon Brick in Steel Ladle

The use performance of zircon bricks in steel Ladles is also called zircon bricks in steel Ladles. It is made of zircon as the main raw material and participates in the combination of a certain amount of fused alumina, high-silica content of clay soil, clay, and chromium oxide. This kind of steel barrel lining bricks has been developed abroad for a long time. In order to improve the uneven erosion of semi-silicon brick steel lining bricks, it gradually expanded from strengthening local lining to all lining bricks. As a result, the service life of large steel Ladles is increased by 2 to 3 times. In order to meet the use of the first phase of Baosteel in China, this brick has been developed and used.

The defects of zircon bricks are slag, steel, and spalling. The main reason is that it is not easy to reduce the porosity due to the zircon brick, and it is affected by the infiltration and the glass property generated in the matrix part. The advantage is that the service life can reach more than 100 times, which is conducive to the turnover of the steel drum. The high cost of this kind of brick is also limited by the source of domestic raw materials, which restricts its development.