Refractory Bricks

Refractory for top of electric furnace

Jul 23,2019

In order to improve the service life of the top lining brick of electric furnace, after repeated research and experiment, a high-alumina non-fired brick with phenolic resin as a binder was used to add a composite micropowder composed of various chemical components as a matrix part. Electric furnace top.

1 Determination of production process

The raw material used is high-quality sintered bauxite with Al2〇3 content greater than 85%. The main phase is corundum and the bulk density is more than 3.1g/cm3.

The composite micropowder is composed of various chemical components such as Al2o3, SiC, MgO, and has a particle size of 200 mesh. The binder is an organic synthetic resin-phenolic resin, and all raw materials and auxiliary materials are added to the planetary in a certain ratio and feeding order. Fully honed in the mixing machine. Mixing for more than 30 minutes, entering the storage material and standby, the molding equipment adopts 630t friction brick press, and the molding follows the requirements of light weight, heavy pressure, and multiple pressure. Press the brick 15 times or more. It is then placed in a drying kiln for low temperature heat treatment (drying). The heat treatment temperature is 180 to 200 heat treatment for 24 hours or more. After the low-temperature heat treatment, the quality of the product is checked. The items to be inspected are external dimensions such as external dimensions, cracks, and physical properties such as porosity, bulk density, and normal temperature compressive strength. Finally, the high-alumina bricks that pass the inspection will be tested. The variety is stored and stored in a dry, closed warehouse.

2 quality control

Since the high alumina brick is used on a steelmaking electric furnace, it undergoes a high temperature sintering process. In this process, the dense corundum phase reacts to form a lower density mullite to produce volumetric swelling.

3Al2〇3+2Si〇2 →3Al2〇3•2SiO2

The high-alumina refractory material can produce excessive volume expansion during manufacture and use. This will inevitably lead to a decrease in fire resistance and easy deformation at high temperatures, which may cause the top of the electric furnace to be loose. Reduce the service life of the top of the furnace. Therefore, the selection of raw materials should be based on the high content of Al2〇3 and the low content of Sio2. Especially the ratio of Al2o3 and Sio2 is extremely important. The relationship between them is as shown in the right figure. The right figure shows that when the Al2〇3 content is above 65%, the Al2o3, Si〇2 ratio is almost constant; when the Al2o3, SiO2 ratio increases, only the high Al2〇3, Si〇2 ratio of sintered bauxite is in When mullite is produced at a high temperature, the mullite is reduced, and the glass phase content is increased, so that the expansion due to the formation of mullite having a small body enthalpy density is small.

Therefore, using high-quality bauxite clinker with Al2〇3 content greater than 80% and only higher Al2O3/Sio2 ratio, and adding composite powder containing Al2O3, SiC, MgO as matrix part, this not only inhibits bauxite clinker The impurities in the production of low-melting liquid phase reduce the refractoriness of the high-aluminum brick, and also increase the content of Al2O3, reduce the production halo of mullite, thereby reducing the volume expansion of the product when it is fired. The addition of SiC helps to improve the island high temperature volume stability of high alumina refractories and resists high temperature deformation.

The use of phenolic resin as a binder can not only improve the normal temperature strength of high alumina bricks, but also produce about 2% of carbon when fired at a temperature. These carbons can fill the pores generated when high alumina bricks are fired, so that high aluminum Bricks have higher density and lower gas permeability. • Protect bricks from slag intrusion into the internal structure of bricks and improve the high temperature resistance of high alumina bricks.

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