Magnesia carbon bricks are very suitable for the requirements of iron and steel smelting due to their superior high temperature resistance, slag erosion resistance, and good thermal shock stability. Taking advantage of the properties of carbon materials that are difficult to be wetted by slag and molten steel and magnesia, high slag resistance and solvent resistance, and low high temperature creep, magnesia carbon bricks are used in severely corroded slag lines and outlets. Steel mouth and other parts. So far, due to the extensive use of magnesia carbon bricks in the steelmaking process and the improvement of the steel smelting process, huge economic benefits have been created.
LMM GROUP uesd for MgO-C bricks instead of high alumina bricks to increase high using performance for Egypt customer Previously service life of high Al brick is 50 heats. But now, after designed and changed by LMM engi-neer, MgO-C brick finally achieved 86 heats operation. They are satisfied to our quality.
The use of magnesia carbon bricks on ladles
When MgO-C bricks are used in refining ladle furnaces and ladles, they are mainly used in headroom and slag lines. According to the operating conditions, the refractory materials used in these parts must have high temperature resistance, thermal shock resistance, and mechanical corrosion resistance caused by slag erosion.
Because the magnesia-carbon bricks in the new ladle will be seriously damaged during the preheating process, the loose and decarburized layer can reach 30-60mm. This layer is washed away during the injection of molten steel and brings the magnesia grains into the slag. Obviously, preventing the carbon in the magnesia carbon brick from being burned during preheating becomes one of the important steps to improve the service life of the magnesia carbon brick at the ladle clearance and slag line. Its technical measures, in addition to adding composite antioxidants to 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 of the ladle.
The use of magnesia carbon bricks on electric furnace
At present, almost all the furnace walls of electric furnaces are built with magnesia-carbon bricks, so the 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 magnesia as the source of MgO, the type of impurities, the bonding state and grain size of periclase grains; the purity, degree of crystallization and scale size of flaky graphite as the source of carbon introduction; Usually thermosetting phenolic resin is used as the binder, and the main influencing factors are the amount of addition and the amount of residual carbon. It has been proved that adding 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 a necessary raw material for magnesia carbon bricks. And only for electric arc furnaces with high FeOn slag, 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 in the slag line shows the formation of obvious reaction dense layer and decarburized loose layer. The reaction compact zone also becomes the slag erosion zone, which is the erosion area where the high temperature liquid phase slag penetrates into the interior of the brick body after the decarburization of the magnesia carbon brick forms a large number of pores. In this region, FeOn in the slag is reduced to metallic iron, and even the presolvated phase and intergranular Fe2O3 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 the graphite remains. Under normal circumstances, the decarburization layer in magnesia carbon bricks is relatively thin due to the presence of graphite.
The tapping port of the electric furnace has two methods: the tapping of the tapping chute and the tapping of the bottom of the furnace. The tapping hole at the bottom of the furnace adopts magnesia-carbon brick tube bricks, and the aperture size of the tube bricks is determined according to factors such as furnace capacity and tapping time. Generally, the internal diameter is 140-260mm.
The electric furnace of a steel factory used medium and low-grade magnesia-carbon bricks in the steel outlet, and the two sides of the copper outlet replaced the original sintered magnesia bricks and achieved good results. The furnace life was increased from about 60 furnaces to more than doubled. . After use, the magnesia carbon brick at the slag line remains relatively intact and does not stick to slag. There is no need to repair the furnace at the slag line, which not only reduces labor intensity but also improves the purity and productivity of molten steel.
The use of magnesia carbon bricks on the converter lining
Since the working conditions of each part of the working lining of the converter are different, the effect of using magnesia carbon bricks is also different.
The mouth of the furnace lining is constantly impacted by the cold and hot liquid steel, so the refractory materials used for the furnace mouth must be resistant to high-temperature slag and high-temperature exhaust gas, and it is not easy to hang steel and easy to clean in time. The furnace cap is not only subjected to severe slag erosion, but also undergoes rapid cooling and rapid heating temperature changes, as well as the comprehensive action of scouring by high-temperature airflow due to carbon oxidation and high-temperature exhaust gas from dust. Therefore, magnesia carbon bricks with strong resistance to slag erosion and spalling are used.
The charging side requires magnesia-carbon bricks to have high resistance to slag erosion, high temperature strength and good spalling resistance, so high-strength magnesia-carbon bricks with metal antioxidants are usually used. Studies have shown , the high-temperature strength of magnesia-carbon bricks added with metal aluminum at lower temperatures is lower than that of samples with composite metal aluminum and metal silicon added, but at high temperatures, its high-temperature strength increases instead. The slag line is the three-phase junction of the furnace lining refractory material, high-temperature slag and furnace gas, and is the most severely slag-eroded part. Therefore, it is necessary to build magnesia-carbon bricks with excellent slag erosion resistance, and magnesia-carbon bricks with higher carbon content are required at the slag line.