Magnesia carbon bricks are widely used as lining materials in various steelmaking furnaces due to their excellent corrosion resistance and thermal shock resistance.In recent years,the development of low-carbon magnesia carbon bricks with low carbon content and excellent performance for refining ladle has been paid attention to by domestic and foreign industry,the research and development work in this area has achieved certain results and shows good development prospects
The main problems caused by the reduction of carbon content in magnesia carbon bricks are thermal shock stability and slag permeability resistance.it is well known that after the carbon content of the magnesia carbon brick is lowered,the thermal conductivity of the brick is lowered and the elastic modulus is increased,so that the thermal shock resistance stability of the brick is deteriorated.after the carbon content is lowered,the wettability of the slag and the molten steel and the material is enhanced,and the permeability of the material against slag and molten steel is deteriorated.the traditional magnesia carbon bricks w=10%-20%,with the new requirements of smelting technology for refractory materials,the traditional magnesia carbon bricks have found the following problems in the long-term application practice:
- Due to the high thermal conductivity,the heat loss is increased,the tapping temperature is increased,the energy consumption is increased and a series of problems such as erosion of the refractory material are increased;
- As a lining material for special refining furnaces,such as smelting high-quality clean steel and ultra-low carbon steel in VOD refined ladle,it will cause carbonation problems
- Consumes a lot of valuable graphite resources
At present,the understanding of solving these problems mainly includes the following three aspects:
Improve the thermal shock stability of magnesia carbon bricks by improving the carbon structure combined with carbon:
The binder of the traditional magnesia carbon brick is mostly phenolic resin,the carbon structure of the binder after carbonization is in an isotropic glass state,so the magnesia carbon brick is brittle and has high elastic modulus,which is unfavorable for the thermal stability of the product .and the high temperature strenght of the product is also low,after the graphitizable carbon precursor is introduced into the phenolic resin,the composite binder can be carbonized into a secondary carbon having a fluid or mosaic structure in the environment of the magnesia carbon brick,or the nano carbon fiber can be formed in situ,improvement of carbon structure and enhancement of nano carbon fiber formation to improve thermal shock stability and high temperature strength of low carbon magnesia carbon bricks;
Optimize the matrix structure of magnesia carbon bricks:
the thermal shock stability and slag permeability of magnesia carbon bricks mainly depend on the composition and structure of the matrix,How to increase the contact frequency of aggregate particles with carbon particles,ie reduce the scale of carbon particles,in the case of a significant reduction in carbon content,and to ensure its high dispersion,it is one of the important measures to improve the thermal shock stability and slag permeability of low carbon magnesia carbon bricks,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.
Use high-efficiency antioxidants:
With the reduction of carbon content in magnesia carbon bricks,the oxidation protection of carbon is particularly important,so it is necessary to use suitable high-efficiency antioxidants.