Carbon-containing refractories are widely used in off-furnace refining equipment, ladles and continuous casting functional materials due to their excellent slag resistance and thermal shock resistance. At present, the commonly used shaped carbon-containing refractories mainly include magnesium carbon (MgO-C) bricks, aluminum magnesium carbon (Al2O3-MgO-C) bricks and aluminum carbon (Al2O3-C) bricks. Among them: MgO-C bricks are mainly used in severely eroded areas such as slag lines, with a graphite content of 10%~15% (w); Al2O3-MgO-C bricks are used in areas such as ladle walls and ladle bottoms, with a graphite content of 8%~10% (w); Al2O3-C materials are mainly used for flow control functional elements in the continuous casting process, and the graphite content is usually greater than 20% (w).
In recent years, with the increasing demand for clean steel/special steel such as automotive thin plate steel, high-end bearing steel, and nuclear power special steel, on the one hand, in order to reduce the impact of carbonization of molten steel caused by graphite dissolution on the quality of clean steel, the graphite content in carbon-containing refractory materials must be reduced, but this further deteriorates the service performance of carbon-containing refractory materials.
On the other hand, the progress of refining technology outside the furnace and the development of continuous casting technology have put forward higher requirements on the service performance of carbon-containing refractory materials. Therefore, it is an inevitable trend to develop low-carbon carbon-containing refractory materials while maintaining their good service performance. To this end, the coordinated regulation method of low carbonization of carbon-containing refractory materials and their performance enhancement is reviewed, and the development trend of low-carbon refractory materials is pointed out.
Optimization of carbon source
Carbon raw materials in carbon-containing refractory materials are mainly introduced in two forms: one is flake graphite as matrix raw material, and the other is phenolic resin as binder. Therefore, the optimization of carbon source usually has the following ways:
(1) Select different carbon sources: graphite (flake graphite, expanded graphite, microcrystalline graphite), two-dimensional nanocarbon materials (graphene, graphite oxide sheets), zero-dimensional or one-dimensional nanocarbon (zero-dimensional nanocarbon black, one-dimensional carbon nanotubes or carbon fibers);
(2) Modification catalysis of binders: for example, using nickel nitrate to pyrolyze phenolic resin into carbon nanotubes.
Use of additives
Additives can not only introduce a variety of strengthening mechanisms through the generation of their own or in-situ ceramic phases, effectively improving the mechanical properties, thermal shock resistance, and erosion resistance of carbon-containing refractory materials, but also play an antioxidant role by consuming oxygen.
In addition, many studies have shown that the combined use of multiple additives can more efficiently improve the comprehensive service performance of carbon-containing refractory materials due to the synergistic effect of multiple components and different morphological characteristics.
Introduction of pre-synthesized composite powders
Composite powder combines the advantages of single components. Compared with most pure powders, the preparation cost of composite powder is lower. A large number of studies have shown that composite powder modification of refractory matrix is also an effective way to improve the performance of refractory materials. Therefore, the preparation of composite powder with good performance by simple, economical and effective methods has also been a hot topic in recent years.
The current development of low-carbon refractory materials is mainly reflected in two aspects.
First, the service performance of refractory materials is continuously improved to achieve “longevity”;
Second, it is to ensure that carbon-containing refractory materials can meet the requirements of the continuously improved smelting process, especially the stringent requirements of the current clean steel.
Among them, “nano-ization” is an important research direction to achieve the long life of carbon-containing refractory materials; “low carbonization” is a simple and efficient way to meet the requirements of clean steel process, and the deterioration of thermal shock resistance and slag resistance of carbon-containing refractory materials caused by “low carbonization” also needs “nano-ization” to improve.
Therefore, the coordinated development of “longevity”, “low carbonization” and “nano-ization” has important practical significance for the development and application of carbon-containing refractory materials.
The introduction of nanocarbon and nanoceramic phases can optimize the microstructure of low-carbon refractory materials and effectively improve the key service performance of low-carbon refractory materials, such as thermal shock resistance and erosion resistance.
Compared with single micro-nano components, additives of composite components have more advantages in improving the performance of refractory materials. Pre-synthesized composite powders can more efficiently exert the strengthening effect on low-carbon refractory materials by solving the agglomeration problem of nano components.
Studying the strengthening mechanism of micro-nano additives to improve the performance of refractory materials can provide a theoretical basis for improving the performance of low-carbon refractory materials, and can better regulate the service performance of refractory materials through micro-nano additives.
Using finite element simulation to simulate the temperature field and stress field distribution of carbon-containing refractory materials in the service process, obtain the micromechanical parameters of refractory materials under different service conditions, analyze the interaction mechanism between micromechanical parameters and thermal shock resistance, and form a thermal shock resistance prediction model based on micromechanical parameters, which is of great significance to the development of low-carbon carbon-containing refractory materials with long service life and high service stability.
