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Introduction of chrome corundum brick[04/09/2018]
In the reheating furnace, using push-pull skid bricks and platform blocks to replace the water-cooled pipe system can generally save about 20% energy, it can also eliminate the “black mark” of the billet and improve heating quality. Normally, the maximum temperature in reheating furnace is about 1200℃ to 1300℃,during use, metal rails are gradually oxidized, abraded, cracked and damaged; and due to the effect of high temperature, deformation will occur, which will affect the straightness of the entire track, and it will need to be replaced, then product costs will increase accordingly, affected the smooth progress of production and reduced the efficiency of the furnace and wasted energy. Therefore, a high-performance refractory is developed based on this to replace heat-resisting rails.
To be applied on reheating furnace, skid bricks are required to withstand the slag erosion such as scales of iron oxide and the constant wear and impact of the movable billet at high temperatures. So these bricks must be with good erosion resistant wear and impact resistance and thermal shock resistance. In the meantime, it should keep high strength during using.
Most of the skid bricks are made of fired or fused mullite and corundum refractory products, having poor wear resistance due to the oxidation of the pores when being fired. While, the fused cast products are compact and with good wear-resistant, however, it has the problem of internal shrinkage and poor uniformity. With the wear of the surface dense layer, the performance and service life will drop sharply.
By using α-Al2O3 as refractory raw material, adding appropriate amount of chromium oxide powder and chrome corundum clinker fine powder, the chrome corundum bricks are shaped at 1700℃, having a lower chromium oxide content than cast fused corundum bricks.
The high-performance chrome corundum brick technology uses α-Al2O3 and chromium oxide powder to fill the sintered pores, which greatly improves the compactness of the material. The composite binder is combined with highly active AL2O3 and Cr2O3 to form mullite and aluminum, to make it has high strength, good thermal shock resistance and low porosity. So the chrome corundum brick has better wear resistance and impact resistance compared with fused alumina quality. According to ASTM-704 standard, the wear index of the chrome corundum slide brick is 1.5 cm?, while the fused alumina is 2.0 cm?.
Conclusion: The practical application in recent years shows that the high wear-resistant chrome corundum brick has the following characteristics:
(1) High density, uniform surface and uniform inner layer organization, low porosity, high strength, high temperature wear resistance.
(2) Good resistance to sudden cooling and heating. In the areas near the exit gate and the door opening at the end side, there has frequent changes of temperature at the furnace door, cracks seldom happen in the tap channel refractory brick.
(3) Good slag resistance. The iron oxide scale does not bond with the tapping brick, and part of the slag is carried out with the billet out of the furnace, this can reduce the number of times to remove slag in the production process and reduce the labor intensity when cleaning the slag.
(4)The price of such chrome corundum bricks is not only lower than high-alloy heat-resistant and wear-resistant rail steels, but also lower than fused zirconium corundum bricks, which is undoubtedly a favorable factor for reducing production costs.