In the steelmaking industry, Basic Oxygen Furnaces (BOF) are critical for producing high-quality steel. However, the harsh operating conditions within BOFs, including high temperatures and corrosive slags, can lead to significant wear and tear on refractory linings. Understanding the common causes of corrosion in BOF refractories is essential for improving their durability and efficiency.
1. Chemical Reactions and Dissolution
One of the primary causes of corrosion in BOF refractories is the chemical reaction and dissolution of magnesium oxide (MgO) in the refractory lining. The interaction between MgO and the slag leads to the formation of low-melting-point compounds, which can penetrate the refractory material and cause degradation. This process is exacerbated by the presence of iron (Fe) and other elements in the slag, which can form eutectic compounds with MgO, further weakening the refractory structure.
2. Slag Penetration
Slag penetration is another significant factor contributing to the corrosion of BOF refractories. Slag can infiltrate the pores and grain boundaries of the refractory material, leading to mechanical degradation and the formation of a decarburized layer. This decarburized layer is more susceptible to further corrosion and can result in the formation of cracks and spalling. The depth of slag penetration depends on various factors, including the temperature and the chemical composition of the slag.
3. Thermal Shock and Mechanical Stress
The rapid temperature changes and mechanical stress experienced by BOF refractories during the steelmaking process can also lead to corrosion. Thermal shock causes the refractory material to expand and contract, leading to the formation of microcracks. These microcracks can then serve as pathways for slag penetration and further corrosion. Additionally, mechanical impacts from molten metal and slag can cause physical wear and tear on the refractory lining.
] 4. Oxidation of Carbon
In MgO-C refractories, the oxidation of carbon is a significant contributor to wear. Oxidation increases the porosity of the refractory material, reducing its strength and resistance to further exposure to oxidizing agents. This process is particularly pronounced at temperatures above 1400°C, where indirect oxidation becomes the dominant mechanism.
5. Three-Phase Interactions
The interaction between the refractory material, slag, and molten metal can lead to localized corrosion. The formation of CO bubbles at the interface between these phases can either inhibit or enhance the corrosion process, depending on their location. Additionally, the movement of slag films and the formation of low-melting-point compounds at the refractory-slag interface can accelerate the corrosion rate.
The common causes of corrosion in BOF refractories include chemical reactions and dissolution of MgO, slag penetration, thermal shock, mechanical stress, oxidation of carbon, and three-phase interactions. Addressing these issues requires a comprehensive approach that includes selecting high-quality refractory materials, optimizing the chemical composition of the slag, and implementing advanced furnace design and operating practices. By understanding and mitigating these causes of corrosion, steel producers can enhance the durability and efficiency of their BOF refractory linings, leading to cost savings and improved operational performance.
