Magnesia carbon bricks are very suitable for the requirements of steel smelting due to their superior high temperature resistance, slag erosion resistance and good thermal shock stability. The use of carbon materials that are difficult to be wetted by furnace slag, molten steel, and the high refractory properties of magnesia, high slag resistance and solubility, and low high temperature creep. It is used in severely corroded slag lines and taps, etc. Location. So far, due to the extensive use in the steelmaking process and the improvement of the steel smelting process, huge economic benefits have been created.
1. Usage on the lining of the converter
Because the working conditions of each part of the converter working lining are different, the use effect is also different.
The furnace mouth part of the furnace lining is constantly impacted by cold and hot molten steel, so the refractory materials used in the furnace mouth must be resistant to the erosion of high temperature slag and high temperature exhaust gas, and it is not easy to hang steel and is easy to clean in time. The furnace cap is not only subject to severe slag corrosion, but also undergoes rapid cold and hot temperature changes, as well as the combined effects of high-temperature airflow due to carbon oxidation and dust and high-temperature exhaust gas. Therefore, the use of slag-resistant and peel-resistant . The loading side requires that it not only has high resistance to slag erosion, but also has high high temperature strength and good peeling resistance. Therefore, high strength with metal anti-oxidant is usually used. Research shows that adding metal aluminum The high-temperature strength at lower temperatures is lower than that of the sample with composite addition of metal aluminum and metal silicon, while at high temperatures, its high-temperature strength increases instead. The slag line is the junction of the lining refractories, high-temperature molten slag, and furnace gas. It is the most severe part of slag corrosion. Therefore, the masonry needs to have excellent slag corrosion resistance, and the slag line needs to have a higher carbon content.
2. Use on electric stove
At present, the walls of electric furnaces are almost entirely built with magnesia carbon bricks. Therefore, the life of bricks determines the service life of electric furnaces. The main factors that determine the quality of electric furnace bricks include the purity of MgO source magnesia, impurity types, and periclase grain bonding state And the grain size; the purity, degree of crystallinity and scale size of the flake graphite as the source of carbon introduction; thermosetting phenolic resin is usually used as the binder, and the main influencing factors are the amount of addition and the amount of residual carbon. It has now been proven that adding antioxidants can change and improve its matrix structure. However, when used under normal operating conditions of electric furnaces, antioxidants are not essential raw materials, and only electric arc furnaces used for high FeOn slag, such as direct use Reduced iron or irregularly oxidized parts and hot spots of electric furnaces, adding various metal antioxidants can become an important part of it.
The corrosion behavior of magnesia-carbon bricks used in the slag line is manifested by the formation of an obvious reaction dense layer and a decarburized loose layer. The dense reaction zone also becomes the slag invasion zone, which is the erosion area where the high temperature liquid phase molten slag penetrates into the brick body after the decarburization of the magnesia-carbon bricks forms a large number of pores. In this area, FeOn in the slag is reduced to metallic iron, and even the desolvent phase and intergranular Fe2O3 solid dissolved in MgO are also reduced to metallic iron. The depth of slag penetration into the brick is mainly determined by the thickness of the decarburized loose layer, which usually ends at the place where graphite remains. Under normal circumstances, the decarburized layer is relatively thin due to the presence of graphite.
There are two methods for the tapping of the electric furnace: the tapping trough tilting tapping and the bottom tapping. When the tapping channel is used for tilting tapping, magnesia-carbon bricks are basically not used, but Al2O3 or ZrO2 is selected, and non-oxygens such as C, SiC and Si3N4 are added. When the bottom of the furnace is used for tapping, the tapping opening is composed of outer sleeve bricks and inner tube bricks. The tapping port of the furnace bottom adopts magnesia-carbon brick pipe bricks, and the hole size of the pipe bricks is determined according to factors such as furnace capacity and tapping time. Generally, the inner diameter is 140~260mm.
A steel mill’s electric furnace used medium- and low-speed magnesia-carbon bricks at the tapping port. The two sides of the copper tapping port replaced the original sintered magnesia bricks and achieved good results. The furnace age was increased from about 60 furnaces to more than doubled. . After use, the magnesia-carbon bricks at the slag line are kept relatively intact and do not stick to the slag. There is no need to repair the furnace at the slag line, which reduces labor intensity and improves the purity and productivity of molten steel.
3. The use of aluminum-magnesium-carbon bricks on ladle
When MgO-C bricks are used for refining ladle furnaces and ladles, they are mainly used in clearance and slag lines. According to the operating conditions, the refractory materials used in these parts must have high temperature resistance, heat shock resistance, and resistance to mechanical corrosion caused by slag erosion. So in the past, magnesia-chromium refractories were used for these parts, but considering that chromium pollutes the environment, its consumption has been reduced, and now magnesia-carbon bricks are used.
As the magnesia-carbon bricks in the new ladle will be severely damaged during the preheating process, the loose decarburized layer can reach 30-60mm thick. This layer is washed away during the injection of molten steel, bringing the magnesia grains into the molten slag. Obviously, preventing the carbon in it from being burned off during preheating becomes one of the important steps to improve the service life of the magnesia carbon bricks at the ladle clearance and slag line. Its technical measures, in addition to compounding a composite antioxidant, the key is to cover its surface with an alkali-containing low-melting glass phase liquid after lining, so as to protect the carbon from being lost during the preheating process of the ladle. Burned.
