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. Utilizing carbon materials that are difficult to be wetted by slag, molten steel, and magnesia's high fire resistance, high slag resistance and solubility resistance, and low high temperature creep properties, magnesia carbon bricks are used in severely corroded slag lines and output Steel mouth and other parts. So far, due to the extensive use of magnesia-carbon bricks in the steelmaking process and improved steel smelting processes, huge economic benefits have been created.
The Use of Magnesia Carbon Brick on the Converter lining
Because the working conditions of each part of the converter lining are different, the effect of the use of magnesia-carbon bricks 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 subject to 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 Magnesia carbon brick. The loading side requires magnesia carbon bricks to have high resistance to slag erosion, but also to have high high temperature strength and good peeling resistance. Therefore, high strength magnesia carbon bricks with metal antioxidants are usually used. Research shows , The high temperature strength of the magnesia-carbon bricks with metal aluminum at lower temperature is lower than that of the samples with metal aluminum and metal silicon, but at high temperatures, its high temperature strength increases instead. The slag line is the junction of the three phases of lining refractories, high-temperature slag and furnace gas. It is the most severely corroded part. Therefore, it is necessary to build magnesia carbon bricks with excellent slag corrosion resistance. The slag line needs to have a higher carbon content Magnesia carbon bricks.
The Use of Magnesia Carbon Brick on Electric Furnaces
At present, the walls of electric furnaces are almost entirely built with magnesia carbon bricks. Therefore, the service life of magnesia carbon bricks determines the service life of electric furnaces. The main factors that determine the quality of magnesia carbon bricks for electric furnaces include the purity of MgO source magnesia, impurity types, and periclase Grain bonding state and grain size; the purity, crystallinity and scale size of flake graphite as the source of carbon introduction; thermosetting phenolic resin is usually used as the binder, and the main influencing factors are the addition amount and the amount of residual carbon. It has now been proved that the addition of antioxidants to magnesia carbon bricks can change and improve its matrix structure, but when used under normal operating conditions of electric furnaces, antioxidants are not an essential raw material for magnesia carbon bricks, but only arcs used for high FeOn slag Furnace, such as using direct reduced iron or irregularly oxidized parts and hot spots of electric furnaces, adding various metal antioxidants can become an important part of magnesia carbon bricks.
The corrosion behavior of magnesia-carbon bricks used at the slag line is manifested by the formation of an obvious reaction dense layer and a decarburized loose layer. The reaction dense 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 brick 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 where graphite remains. Under normal circumstances, the decarburized layer of magnesia carbon bricks is relatively thin due to the presence of graphite.
There are two methods for the tapping of the electric furnace: tapping trough tilting tapping and bottom tapping. When the tapping channel is used for tilting steel, magnesia-carbon bricks are basically not used, but Al2O3 or ZrO2 are selected, and non-oxygens such as C, SiC and Si3N4 are added. When the bottom of the furnace is used for tapping, the tapping port is composed of outer sleeve bricks and inner tube bricks. The tapping hole 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 remain relatively complete and do not stick to slag. The slag line does not need to be repaired, which reduces labor intensity and improves the purity and productivity of molten steel.
The Use of Alumina Magnesia Carbon On the Steel 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, thermal shock resistance, and resistance to mechanical corrosion caused by slag erosion. Therefore, 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.
Since 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 slag. Obviously, preventing the carbon in the magnesia carbon bricks from being burned out during preheating is 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 composite antioxidants into the magnesia carbon bricks, the key is to cover the surface of the magnesia carbon bricks with an alkali-containing low-melting glass phase liquid after lining to protect the magnesia carbon bricks Carbon is not burned off during the preheating process of the ladle.
