Aluminium Oxide or alumina (Al2O3) is one of the most versatile of refracto ry ceramic oxides and finds use in a wide range of applications. Alumina re fractories are the part of alumina- silica group of refractories. Different from fire clay refractories, high Alumina refractories normally have Al2O3 content of more than 45 %.
The raw material base for these refractories are different than the fire cl ay bricks. For the production of high Al2O3 refractories, both natural raw materials (such as kyanite, sillimanite, andalusite, and bauxite etc.) as w ell as synthetic materials (sintered mullite, fused mullite, calcined alumi na, sintered corundum, and fused corundum etc,) are used.
Alumina (Al2O3) has the physical stability such as melting temperature, har dness, resistance to abrasion, and high mechanical strength. The material h as the same chemical composition but have a different crystal structure whi ch is ?- Al2O3, ?-Al2O3 and ?- Al2O3. The melting point, ref ractoriness, corrosion resistance and strength of alumina refractories incr ease with the increase in the Al2O3 content.
Based on the content of alumina, high alumina refractory is classified into 50%, 60%, 70%, 80%, 85%, 90% and 99%.
Refractories with 90 % and 99 % Al2O3 are among the highest strength and er osion resistant refractories. They can be used for temperatures greater tha n 1800??The most widely used alumina refractory with more t han 90% Al2O3 content used in glass furnaces is Fused cast Alumina Block an d Alumina Bubble block. There are three types of Fused cast Alumina Block: ? Alumina, ? Alumina and ?-? Alumina. Fused cast Alumin a Block ? Alumina is an ideal product for the lower temperature zones of the glass melting furnaces due to its high density, superior corrosion r esistance and low blister potential. ? Alumina is the best material fo r molter crown, port crown, and feeder channel due to its high resistance t o alkali vapor and excellent thermal shock resistance. ?-? Alumin a is widely used in working tank, feeder channels, superstructures and lips tone due to its excellent corrosion resistance against molten glass and no contamination to molten glass under 1350 ?. Alumina Bubble block ha s low bulk density, excellent insulating properties and high hot strengths. These features make it an excellent insulating material that can withstand exceptionally high temperatures. It is always used as back-up insulation b ehind other refractories.
High alumina refractory with about 70% Al2O3 contains mullite as a major ph ase. It is made of bauxite. It can be used for temperatures greater than 17
50?. Mullite brick and high alumina brick belong to this group. Mul lite brick is characterized by good high temperature resistance and good th ermal shock resistance, which comes into being mullite through calcine with clay, high alumina materials and ceramics. It is mainly used in fibrous gl ass furnace. High alumina brick is made of high-quality bauxite clicker. It features high chemical corrosion resistance and high refractoriness. It is usually used in hot areas in glass melting tanks without glass contact.Refractories containing 50 % and 60 % Al2O3 exhibit improved refractoriness over fireclay products. High alumina insulating brick is a new type of lig htweight insulating material which contains approximately 48% alumina,mulli te and glass phase or corundum. It has advantages such as high porosity, sm all volume density, good insulation effect, high mechanical intensity, smal l thermal conductivity and long service life. It is widely used in insulati ng layers of glass furnaces. Sillimanite brick is a kind of refractoriness which made by sillimanite and other minerals. And silimanite can be transfo rmed to be mullite under more 1500? high temperature. It is mainly used in rider arches, forehearth and bushing for fiber glass furnaces.
Sunrise supplies all kinds of alumina refractories including fused cast alu mina block, Alumina Bubble block, Mullite brick, High alumina brick, High a lumina insulating brick, sillimanite brick, etc..