Inclusion Absorbers

Inclusion absorbers are specialized components of continuous casting mold flux formulations that actively attract, absorb, and chemically bind non-metallic inclusions (such as alumina, silica, and other oxides) present in molten steel during the continuous casting process. They function within the flux layer to improve steel cleanliness by preventing these inclusions from becoming trapped in the solidifying steel strand, thereby enhancing final product quality and reducing defects. These absorbers are typically composed of calcium-aluminate based compounds, fluoride-containing compounds, and reactive oxide blends. Their performance is characterized by parameters such as melting point (1050–1250 °C), density (2.5–3.5 g/cm³ per ASTM D792), particle size (0.1–1.0 mm per GB/T 6003.1), Al2O3 content (30–50% per GB/T 6609), CaO/Al2O3 ratio (0.8–1.2), moisture content (≤0.5% per GB/T 6283), ignition loss (≤1.0% per GB/T 6730), bulk density (1.2–1.8 g/cm³ per ASTM D7481), melting rate (15–30 s at 1500°C), viscosity at 1300°C (0.5–1.5 Pa·s per ISO 7884-2), sulfur content (≤0.05% per GB/T 214), and phosphorus content (≤0.05% per GB/T 223). These values serve as reference ranges for procurement and verification; actual model-specific values must be confirmed with the legal manufacturer or supplier. The absorbers are designed to be compatible with the mold flux melting range and to optimize dispersion and absorption efficiency. Proper selection depends on the steel grade, casting conditions, and desired cleanliness levels. Verification questions should address the specific inclusion types targeted, the flux system compatibility, and the required performance under actual operating conditions. Maintenance signals include changes in melting behavior, reduced absorption capacity, or increased inclusion counts in the cast product. Failure boundaries are defined by the absorbers' inability to maintain effective inclusion removal, which may lead to defects in the final steel product.

Inclusion absorbers operate through chemical affinity and physical absorption mechanisms. When molten steel passes through the mold, non-metallic inclusions migrate into the liquid flux layer. The absorbers, typically composed of reactive oxides or compounds with high solubility for common inclusions, chemically react with or dissolve these particles, incorporating them into the flux matrix and preventing their re-entry into the steel. The process is influenced by the flux's viscosity, melting rate, and the absorbers' particle size and composition. Effective absorption requires proper dispersion and sufficient residence time in the flux layer. The CaO/Al2O3 ratio and Al2O3 content are critical for absorption capacity, while moisture and impurity levels must be controlled to avoid steel contamination. The absorbers' performance is validated through parameters such as melting point, density, and viscosity, which affect mass transfer and settling behavior. Regular monitoring of these parameters helps ensure consistent inclusion removal and steel cleanliness.