Introduction of chrome corundum brick

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 refractory fire 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 cm3, while the fused alumina is 2.0 cm3.

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.

Article Source：Introduction of chrome corundum brick
Company name: Henan Xinmi Changxing Refractory Materials Co.,Ltd
Email: sales1@chinafirebrick.com
Website:http://www.chinafirebrick.com/

The clssification of corundum brick

According to the refractory raw materials, corundum brick can be divided into sintered, rebond sintered, fused and rebond fused corundum bricks.
The first is made from sintered corundum clinker, while the third is made from light burning corundum powder particles and fine corundum powder.
The second is fused corundum refractories, including fused cast corundum refractories. Fused cast corundum refractory or fused cast alumina refractory is made by casting molten glass into a mold and then cooling it into a solid. The refractory raw materials are always melted in an electric arc furnace.
Rebond fused corundum brick is made of fused corundum clinker and fine fused corundum powder or sintered corundum powder as the matrix. The key to its production is the processing of fused corundum materials. when fused gray or white corundum used as the main refractory raw materials, the frits should be smashed first and then seleted to remove silicon iron alloy. Silicon iron alloy may cause the burst of refractory products.
Article Source: refractory fire brick
Company name: Henan Xinmi Changxing Refractory Materials Co.,Ltd
Email: sales1@chinafirebrick.com
Website:http://www.chinafirebrick.com/

Tabular Alumina for High Purity Corundum Brick

High purity corundum brick with Al2O3 content above 99% is studied based on tabular alumina and white fused alumina (WFA) as single aggregate and the combination of both. In comparison with Tabular alumina, WFA aggregate has relatively higher SiO2 content of above 0.10% and shows fluctuation on soda content. WFA also has a high open porosity of 8.8%, which very often exists in the form of single large pore or in the form of agglomeration of pores rather than the small closed and evenly distributed pores in tabular alumina. Refractory brick china with different ratio of tabular alumina and WFA have been tested for firing shrinkage, bulk density and apparent porosity, cold and hot strength, thermal shock resistance, and abrasion resistance. Also slag tests with a coal gasifier slag and an oil cracking slag have been conducted. The results from this evaluation conclude that high alumina brick outperforms WFA bricks and importantly gives more balanced performance.

Introduction
High purity corundum brick is widely used as refractory lining for oil cracking unit, coal gasifier, carbon black furnaces, black liquor gasification and other industrial furnaces. This is attributable to the outstanding performance of corundum brickon chemical corrosion resistance, mechanical abrasion resistance and thermomechanical properties like high temperature strength, refractoriness under load and creep resistance, even in environments with corrosive gas or liquid and with high pressure.
Synthetic alumina based aggregates like white fused alumina and tabular alumina are the two main aggregates available for high purity corundum brick. They are selected due to low impurity content (e.g. SiO2), high bulk density and thermomechanical properties, which enables corundum bricks that meet the requirements on thermal, chemical and structural attacks [1] which gasifiers and other furnaces apply in operation.

The different processes for WFA and tabular alumina production (fusion vs. sinter) certainly create differences between the aggregate, which also have an impact on the properties and performance of the corundum brick. Tabular alumina is well received and extensively used in the refractories for steelmaking such as slide gate plate, Al2O3-MgOC brick, castables and pre-cast shapes.

However, for a long period of time, WFA is very commonly used as the aggregate for high purity corundum brick to non-steel applications like gasifier and other industrial furnaces. It is often claimed that WFA aggregate has higher bulk density which consequently increases the density of fire brick China and the corrosion resistance which could enhance the overall performance. However these perceptions should be investigated by an extensive evaluation. This work is designed to evaluate in a comprehensive way the differences on performance of tabular alumina and white fused alumina in respect to aggregate itself and brick properties in order to understand these differences and provide appropriate application guideline for high purity corundum brick.

1. Refractory raw material Almatis global tabular alumina product T60/64 and a common commercial Chinese WFA grade are selected as the aggregate and fine. In the matrix, Almatis’ calcined alumina CT800FG is also used. Sulphite pulp liquor is used as temporary binder for corundum brick making.

2. China refractory brick formulation Five recipes are used in this evaluation. As per the tabular alumina content in aggregate, the formula is named as T100, T75, T50, T25 and T0 and the numbers stand for tabular alumina content in respective brick. Table 1 gives the details with bold highlighted for tabular alumina.

Article Source: refractory fire brick
Company name: Henan Xinmi Changxing Refractory Materials Co.,Ltd
Email: sales1@chinafirebrick.com
Website:http://www.chinafirebrick.com/