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 and high strength, it is necessary to select high purity magnesia (MgO content as high as possible, CaO / 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 or flake graphite brick with high carbon content (C ≥ 95-96%) is selected to ensure the corrosion resistance, spalling resistance, high temperature strength and oxidation resistance of the magnesia carbon brick for electric furnace.

At present, the most 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. Refractories for blast furnace ironmaking; 5. By adding carbon, a variety of refractory bricks can be produced, especially high-grade magnesia carbon basic refractories.

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 aggregate, binder and additive with water to make slurry with certain consistency, and then spray the slurry onto 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 the compressed air is sprayed onto the gunning surface. The amount of water can be adjusted at any time 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 that uses compressed oxygen to transport refractory aggregate, flux or heating agent mixture to the nozzle, and then burns it with high calorific value fuel, and instantly heats the surface of magnesia alumina carbon brick fire aggregate particles to molten or semi molten state, and then spray adheres to the furnace lining. The gunning layer obtained by this construction method has compact structure, high strength, corrosion resistance and erosion resistance Strong ability, solid and durable.

The formed magnesia carbon brick can only be used after hardening treatment. The epidemic disease 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 ensuring the bulk density and reducing the porosity of the 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.