Alumina Tabular Sand Blasting Material with Low SiO2 Content White and Versatile

The performance of tabular alumina and its main application areas in refractories
Introduction: For 40 years, tabular alumina has been widely used in high-performance refractories for steel, foundry, petrochemical and ceramics. The Tabular alumina is the leading synthetic high-purity alumina aggregate due to its high refractoriness, excellent thermal shock resistance, creep resistance and wear resistance. Although the overall consumption of refractory materials has fallen sharply, especially in steel manufacturing, the use of tabular aluminahas not only increased relatively, but has definitely increased. The steady increase in the proportion of continuous casting into the amorphous refractory and the violent trend of high-quality steel are the driving force for the development oftabular alumina -based refractories. The purpose of this paper is to describe the typical properties of tabular alumina , how it compares with other synthetic high alumina aggregates, and its typical application. The latest developments in the use of Tabular alumina with spinel and calcium-free binders will also be introduced.

First, performance of Tabular alumina
The Tabular alumina is dense, fully contracted, and the sintered α-Al 2 O 3 is composed of 50-400 μm crystal grains. Plate-shaped corundum is named for its grain shape like a board. The plate-shaped corundum was prepared by rapidly calcining the ultrafine α-Al 2 O 3 pellet at a temperature slightly lower than the melting temperature. After heat treatment, the 18-20 mm ball was crushed or milled to obtain Tabular alumina of various sizes.
For excellent high temperature performance, the low content of silicon oxide, iron oxide and titanium oxide in sorghum corundum is very important. The ultra low content of ferric acid is typically less than 0.002% and is very important for phosphate bonded refractories. Comparing sintered tabular aluminaand other synthetic high alumina aggregates, such as fused white corundum, the biggest difference was found to have a finer size of impurities. This can cause huge performance differences, especially at high temperatures. The introduction of higher impurity levels in finer sizes greatly reduces high temperature volume stability and creep resistance. Comparing the porosity of fused white corundum andtabular alumina , we can see a huge difference. Although the total porosity of the two aggregates is the same, there is a significant difference in grain porosity.
The open porosity of the electrofused grains is 2-3 times that of the sintered grains. Most of the pores of fused alumina are composed of large open pores, and more than half of the pores of tabular aluminaare closed pores. A high proportion of closed pores is necessary for high thermal shock resistance, which is typical oftabular alumina .
The Tabular alumina exhibits high thermal shock resistance and high strength. Scanning electron micrographs show that the surface of the tabular alumina grains is not as smooth as the surface of the fused corundum grains, and is relatively rough and shallow. This surface structure promotes its reaction with the matrix and mechanical interlocking to increase the strength of the refractory.
The main properties of the Tabular alumina industry are as follows:

1. High-purity Al2O3 concentration: 99.4%;

2. High crystal hardness;

3. Low open porosity and 2-3 times high closed porosity;

4. High particle bulk density 3.55-3.6g/cm3

5, high melting point: 2000 °C

6, chemically inert;

7, good thermal shock resistance;

8, excellent volume stability;

9, the presence of microcracks;

10, high single grain strength.

Second, the main application areas of tabular alumina
The properties of tabular aluminahave many applications in the field of refractory materials. The main application area of tabular aluminais tabular alumina suitable for ceramic, chemical and water-binding substrates. The Tabular alumina can be used alone or in combination with the calcined and/or activated alumina. Because Tabular alumina exhibits extremely high purity even in fine powder, it can be used to improve the performance of lower alumina aggregates. For example, bauxite and fused brown corundum use coarse particles of these aggregates and medium particles and fine powder of tabular alumina . It has been mentioned earlier that the increase in the consumption of tabular aluminais mainly due to the continuous casting of steel. In particular, the use of tabular aluminafor skateboards, dip tubes and nozzles is an industry standard.
Third, the new development of tabular alumina/ spinel
Japan has found that the addition of 20-30% of aluminum-rich spinel to cement-bonded tabular aluminarefractories can significantly improve slag corrosion resistance. Because the concept of aluminum-rich spinel is very common around the world, it has caused more new applications oftabular alumina . In particular, the amorphous lining of the ladle promotes the use of tabular aluminain the future. The spinel can increase the thermal flexural strength of the cement-bonded cement tabular aluminacastable at 1500 ° C to 22 N/mm 2 . It is important to note that even 15% cement does not degrade high temperature performance. Considering that the high-temperature flexural strength of castables with lower cement content is reduced by an order of magnitude, it cannot be seen that these findings will have a significant impact on future refractory technology. It is possible to use some castables which have a higher cement content and higher thermal performance than ultra low cement castables and have no known repeatability limitations of ULCC. Interestingly, the addition of 2% silicon micropowder to the spinel tabular aluminacastable can reduce the thermal flexural strength at 1500 °C to below 1 N/mm2.
Fourth,tabular alumina
Because of the limitations of cement-bonded alumina systems in silica-rich slag environments, Alphabond systems with pure alumina-based binders were developed. The main chemical component is that alumina contains impurities CaO; 0.1%, SiO2; 0.2%. Na2O; 0.5% and water ≤ 9%. It can be treated like ordinary calcium aluminate cement. This system can be used alone or in combination with silicon micropowder.
Conclusion: The new water-binding system enables the refractory industry to use alumina castables where cement-bonded systems do not exhibit optimal performance. It once again proves that tabular aluminacan be flexibly applied to many different fields.

Packing of Tabular alumina

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