Effect of Complex Alloying Elements on Oxide Scale Formation and Water-Jet Descaling Performance on Continuously Cast Low-Carbon Steels

Abstract The formation and evolution of oxide scale in contact with mold flux during continuous casting, subsequent reheating, and hydraulic descaling are strongly governed by steel chemistry. To elucidate the effect of complex alloying elements (Si, Mn, and Cr), two industrially produced continuously cast low-carbon steel grades for manufacturing stamped parts (a base and alloyed steel grade) were investigated. The objective was to determine how alloying elements influence oxidation behavior, scale morphology, interfacial adhesion, and water-jet descaling efficiency. Continuously cast slab specimens were subjected to controlled thermal and atmospheric oxidation cycles simulating multistage industrial practice. Three initial surface conditions (industrial as-cast, cleaned, and mold flux-contaminated) were reheated in a synthesized natural-gas-fired combustion atmosphere with reduced oxygen potential, followed by high-pressure water-jet descaling using a CNC-controlled setup replicating industrial descaling energetics. Detailed microstructural and compositional analysis (SEM/EDX) revealed significant differences in scale morphology, phase composition, and interface topology in the studied steels. In the alloyed steel, the scale–substrate interface developed complex Si–Mn-enriched oxides within the inner scale layer, which acted as diffusion barriers and reduced oxidation kinetics relative to the base steel. Conversely, mold flux-contaminated as-cast surfaces exhibited partial liquefaction during reheating, leading to local disruption of scale continuity and promoting interfacial fracture and detachment under water-jet impact. Integrated experimental methods were used to identify the mechanisms controlling oxide scale formation under industrial conditions and its removability during high-pressure water-jet descaling. The results demonstrate that alloy chemistry and mold flux contamination jointly control scale evolution, adhesion, descaling efficiency, and final surface quality, highlighting the importance of surface condition control in thin-slab continuous casting.