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 for refining ladles has gained attention. Both domestic and foreign industries have achieved certain results, showing good development prospects.
Problems with low carbon magnesia carbon bricks
The main problems caused by the reduction of carbon content in magnesia carbon bricks are thermal shock stability and slag permeability resistance.
Reducing the carbon content in magnesia carbon bricks lowers thermal conductivity and increases the elastic modulus, which deteriorates thermal shock resistance.
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 in traditional magnesia carbon bricks is usually phenolic resin. After carbonization, the binder’s carbon structure becomes isotropic glass, making the bricks brittle with high elastic modulus. This brittleness affects thermal stability. The product’s high-temperature strength is also low.
Introducing a graphitizable carbon precursor into the phenolic resin can help. The composite binder can carbonize into secondary carbon with a fluid or mosaic structure. This process occurs in the magnesia carbon brick environment. Alternatively, in-situ formation of nano carbon fibers is possible. Improving the carbon structure and enhancing nano carbon fiber formation boosts 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 depend on the matrix composition and structure. Increasing the contact frequency of aggregate particles with carbon particles is crucial. Reducing the scale of carbon particles while ensuring high dispersion is essential. This improves the thermal shock stability and slag permeability of low-carbon magnesia carbon bricks.
Controlling the size, shape, and distribution of pores is also important. Adjusting the particle size composition of matrix ingredients affects the material’s thermal conductivity. These measures ensure the material’s performance under thermal shock and slag conditions.
- 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.
