Raw material of magnesia carbon brick for electric furnace

The raw materials for making magnesia carbon brick for electric furnace are high quality sintered magnesia, fused magnesia, graphite, binder and antioxidant. Periclase particles in magnesia act as aggregate in refractory brick. In order to produce high quality, it is necessary to select high purity magnesia (MgO content as high as possible, / SiO2 ≥ 2, bulk density ≥ 3.34g/cm3, good crystal development and porosity ≤ 3%).

Graphite is also the main raw material of electric furnace magnesia carbon brick. Its fixed carbon content, ash composition, oxidation resistance, particle size, shape, volatile matter and moisture directly affect the performance and application effect of electric furnace magnesia carbon brick. High purity flake graphite or flake graphite brick with high carbon content (C ≥ 95-96%) is selected to obtain the corrosion resistance, spalling resistance, high temperature strength and oxidation resistance of electric furnace magnesia carbon brick.

At present, the important application fields of carbon containing refractories are: 1. Electric furnace and ladle work; 2. Crucible for metal smelting; 3. Key components for continuous casting; 4. Refractory materials for blast furnace ironmaking; 5. Various refractory bricks can be produced by adding carbon, which is a high-grade basic magnesia carbon refractory.

thumb_ 20201029171605_ 449.jpg

Manufacturer of magnesia carbon brick for electric furnace

There are many ways to add carbon to refractories

The open porosity of sintered oxide refractories is about 12%, most of which can be filled with tar pitch or resin. Due to the relatively low volatilization and density of volatiles, the residual carbon rate of these products is about 2% ~ 3%. The alumina magnesia carbon brick was developed by using special bauxite clinker, fused magnesia, phenolic resin and high-purity graphite as main raw materials and various additives. It was applied to 80 ton EAF ladle of Xuanhua Iron and Steel Co., Ltd. and good results were obtained and production requirements were met. Wet gunning is a method of mixing refractory aggregates, binders, additives and water into a dense slurry, and then the slurry is put on the gunning surface with compressed air magnesia alumina carbon brick by gunning machine. It is characterized by simple operation, high adhesion and rapid sintering. However, due to the large water content and fine grain size, the shrinkage is also large. At the same time, due to the thin gunning layer, durability.

Semi dry gunning is a method of mixing refractory aggregates, binders, additives, etc. with water through the water ring hole at the atomizing end of the spray gun, and then the compressed air is sent to the gunning surface. The amount of water can be adjusted according to the gunning condition, and generally fluctuates between 10-20%, which is much lower than that of wet gunning. Therefore, the gunning layer has large bulk density and small shrinkage, and can obtain thick gunning layer with good durability, but the rebound is slightly higher than that of wet method, so this gunning method is widely used.

Flame gunning is a repair method in which the mixture of refractory aggregate, flux or heating agent is transported to the nozzle by compressed oxygen, mixed with high calorific value fuel, and the surface of magnesia alumina carbon brick fire aggregate particles is instantly heated to molten or semi molten state, and then adhered to the furnace lining. The gunning layer obtained by this construction method has compact structure, high strength, corrosion resistance and erosion resistance Strong, solid and durable.

The formed magnesia carbon brick can only be used after hardening treatment. The plague of hardening treatment has a great influence on the properties of refractory brick. It has been proved that the hardening treatment at 200-250 ℃ is more suitable for the volume density and reduction of porosity of brick. When the temperature is higher than 250 ℃ and lower than 200 ℃, the hardening treatment will bring adverse effects. It is necessary to strictly improve and control the air. Generally, when the temperature is 50-60 ℃, due to the softening of the resin, it should be kept warm; when it is 100-110 ℃, because there is a large amount of solvent discharged, it should be kept warm; if the temperature is 200-250 ℃, it should also be kept properly to make the reaction complete.