Optimizing Continuous Casting Through Protective Slag Functions
1. Barrier Protection (Liquid Slag Layer)
The liquid slag layer acts as a protective barrier, preventing direct contact between air and molten steel. This effectively reduces secondary oxidation and minimizes carburization on the slab surface, particularly crucial for low-carbon and ultra-low-carbon steels, where surface carburization can lead to brittle billets. By isolating the carbon-rich layer from molten steel, it enhances slab surface quality and reduces steel loss.
2. Thermal Insulation (Solid Slag Layer)
A sufficiently thick solid slag layer improves thermal insulation, maintaining a stable casting environment by reducing heat radiation. This helps prevent cold steel and floating steel from solidifying at the mold’s meniscus, minimizing defects such as surface cracks and porosity. Proper temperature control in the meniscus area also reduces operational risks and enhances casting stability.
3. Impurity Absorption & Purification (Liquid Slag Layer)
The liquid slag layer efficiently absorbs and dissolves impurities, including refractory materials, deoxidation byproducts, and metallic inclusions. This assimilation process helps maintain slag performance while purifying molten steel, leading to higher slab surface purity. Optimizing slag viscosity and composition enhances impurity absorption, ensuring smoother casting operations.
4. Lubrication Performance
High-quality protective slag significantly reduces friction between the billet and the copper mold wall, ensuring smooth billet movement and improved speed control. The ability to regulate casting speed depends not only on process adjustments but also on the slag’s lubrication properties, which directly influence operational efficiency.
5. Heat Transfer Regulation
Uniform slag film distribution between the mold wall and billet shell is essential for consistent heat transfer. Uneven heat flow can lead to crack formation. For peritectic steels, controlling the heat transfer rate is critical—excessive heat transfer intensifies the peritectic reaction, increasing the risk of severe surface cracking. Proper slag film management ensures stable thermal conditions, reducing defect formation.
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