Due to the development of clean steel and ultra-low carbon steel and the requirements for energy saving and consumption reduction,the development of low carbon refractories has become an inevitable trend.at present,the main development trend of carbon containing refractories used in various parts of electric arc furnaces,such as magnesia carbon bricks,aluminum carbonaceous materials,Al2O3-MgO-C materials or other carbon-containing amorphous materials,is low carbonization and longevity,in recent years,with the development of preparation processes,the development of new binders,and the development of application technologies of nanocarbons in refractories,it has become possible to develop carbon-containing refractories in the direction of low carbonization or even no carbonization.
It is well known that the main problem caused by the decrease in carbon content in carbon-containing refractories is the reduction in thermal shock resistance and slag resistance,the current solutions to this problem mainly include:
- Improve the thermal shock resistance of materials by improving the carbon structure combined with carbon:
Most of the binders of tradtional carbonaceous materials are coal tar pitch or phenolic resin,the carbon structure of there binders after carbonization is in an isotropic glass state,sot the material is brittle and has high modulus of elasticity,which is unfavorable to the thermal stability of the materials is also low,after introducing a graphitizable carbon precursor or a catalytic oxide into a coal tar pitch or a phenolic resin,the modified binder can be carbonized into graphitized carbon or in situ to form nano carbon fibers in a product use environment,the thermal shock resistance and high temperature strength of the material are improved by improvement of the carbon structure and the enhancement of the formation of the nano carbon fiber.
- Optimize the matrix structure of the material:in the case of significant decrease in carbon content,how to increase the contact ration of aggregate particles to carbon particles,that is ,to reduce the size of carbon particles and ensure their high dispersion,is important for improving the thermal shock resistance and slag penetration resistance of low carbon materials,one of the measures,controlling the size,shape and distribution of the pores by adjusting the particle size composition of the matrix ingredients also has a significant effect on the thermal conductivity of the material.
- Using high-efficiency antioxidants:As the carbon content of the material decrease,the protection against oxidation of carbon is particularly important,so the use of suitable high-efficiency antioxidants is also necessary.
The conductive refractory material used in the bottom anode of ABB type DV arc furnace determines the life of the bottom electrode of the electric arc furnace.it requires good electrical conductivity and insulation from the furnace shell,and it is absolutely safe.the most common refractory material is MgO-C brick.the MgO-C refractory material is required to have the following characteristics:low resistivity,uniformity and small influence by temperature,small thermal conductivity,high temperature corrosion resistance,high temperature mechanical properties and wear resistance,in order to meet the performance requirements,Japan first used high-carbon MgO-C bricks in this part,with a carbon content of up to 25%.Conductive MgO-C bricks with a content of 18% carbon are used in China,in recent years,Japanese researchers have analyzed the residual bricks for electrodes and found that the erosion and damage of MgO-C bricks is mainly caused by the cracking of brick joints during heating or cooling,it is thus proposed that reducing the shrinkage seam of the brick by suitable residual expansion can effectively improve the durability of the electrode MgO-C brick,based on this ,a new type of electrode MgO-C brick has been developed which maintains low electrical resistance at both low and high temperatures,with low thermal expansion and high residual expansion,the performance of this new type of brick makes the operation very stable and greatly increase the service life of the ABB type bottom electrode.
In addition,in view of the fact that castables have been widely used in ladle linings,but they are difficult to apply when used in electric furnace linings,Japanese researchers have developed the same non-burning Al2O3-MgO bricks as Al2O3-MgO castables,its basic performance can replace traditional MgO-C bricks for electric furnace sidewalls,compared with MgO-C bricks,this new non-burning brick has high room temperature strength and low thermal conductivity,and has good energy saving effect.