The effects of antioxidants on the oxidation resistance of magnesia carbon refractory bricks are mainly reflected in the following aspects:
1. Slowing down the oxidation rate of carbon
During the use of magnesium carbon bricks, the oxidation of carbon is a major problem. The addition of antioxidants can effectively slow down the oxidation rate of carbon, thereby extending the service life of magnesium carbon bricks. This is because antioxidants can react with oxygen to generate corresponding oxides or carbides, which can block pores and reduce the permeability of products, thereby inhibiting or slowing down the oxidation of carbon.
2. Improving high temperature performance
Antioxidants can not only slow down the oxidation of carbon, but also improve the high temperature performance of magnesia carbon bricks. For example, after adding antioxidants such as metal Al, Si, B4C, these elements will react with oxygen to generate corresponding oxides or carbides, and form new mineral phases at high temperatures. These new mineral phases can enhance the density of bricks, improve their high temperature strength and resistance to slag erosion.
3. Forming an antioxidant protective layer
After adding antioxidants to magnesia carbon bricks, these additives will react with oxygen at high temperatures to form a dense antioxidant protective layer on the surface of the brick. This protective layer can effectively prevent further penetration of oxygen, thereby protecting the carbon inside the brick from oxidation. For example, magnesia carbon refractory bricks with B4C added will generate low melting point phases such as magnesium borate at high temperatures. These low melting point phases form a liquid layer on the surface, further enhancing the effect of the antioxidant protective layer.
4. Improving corrosion resistance
The addition of antioxidants can also improve the corrosion resistance of magnesia carbon bricks. This is because antioxidants can improve the microstructure of the brick body, making it more dense and uniform. This dense and uniform microstructure can reduce the penetration and erosion of slag and molten steel on the brick body, thereby improving the corrosion resistance of the brick body.
5. The role of specific antioxidants
Metal Al: Metal Al powder has good thermal conductivity and a low melting point (659°C). It reacts in the brick to generate compounds such as Al4C3, AlN, and Al2O3. These compounds can form a dense protective layer at high temperatures, inhibit carbon oxidation, and enhance the high-temperature performance of bricks.
Metallic Si: Si has a low standard formation free energy, strong affinity with oxygen, and is easy to combine with oxygen to form the corresponding oxide SiO2, thereby inhibiting carbon oxidation.
B4C: B4C can generate low-melting-point phases such as magnesium borate at high temperatures. These phases form a liquid layer on the surface, preventing oxygen penetration and improving oxidation resistance.
Other additives: such as Al-Mg, SiC, CaB6, etc. are also often used as antioxidants for magnesia carbon bricks. They improve the oxidation resistance and high-temperature performance of bricks through different mechanisms.
VI. Application Examples
In actual applications, many manufacturers add an appropriate amount of antioxidants to improve the oxidation resistance of magnesia carbon bricks when producing them. For example, magnesia carbon bricks widely used in high-temperature metallurgical equipment such as converters, electric arc furnaces and ladles often add antioxidants such as Al, Si, and B4C. The addition of these additives significantly improves the service life and performance stability of magnesia carbon bricks.
In summary, antioxidants have a significant effect on the oxidation resistance of magnesia carbon refractory bricks. By selecting suitable antioxidants and controlling their addition amount, the high temperature performance, corrosion resistance and service life of magnesia carbon bricks can be effectively improved.
