Novel Macro-Tensile Approach for Quantifying Oxide Scale Adhesion Energy on Recycled Hot-Rolled Steel: Interplay of Steam and Silicon

The surface quality of hot-rolled steel products derived from recycled materials is critically impacted by oxide scale formation and adhesion, a behavior significantly influenced by residual silicon (Si) and the processing atmosphere. This study addresses a key research gap by thoroughly investigating the combined effect of water vapor content (10% to 30%) and residual Si content (across various slab types) on scale formation and adhesion, with a direct focus on process optimization to minimize surface defects. Crucially, this research introduces a novel quantitative assessment utilizing a macro-tensile test. This innovative method provides accurate mechanical scale adhesion energy data (measured in J/m2) directly applicable to hot-rolled recycled steel, a technique previously underexplored for this challenging material system. Results reveal that increasing water vapor concentrations significantly accelerate the formation of thicker and more defective oxide scales, thereby directly diminishing scale adhesion strength substantially across tested conditions. Conversely, steel with higher residual Si consistently maintained significantly higher scale adhesion energy than low-Si steel under similar steam conditions. Based on these quantitative findings, this study proposes a specific two-factor strategy for industrial application, strictly minimizing residual Si content while maintaining the furnace water vapor concentration at an intermediate level (approximately 20%). This strategy is shown to optimize scale formation conditions, facilitating efficient scale removal. Such results are crucial for optimizing hot-rolling parameters in recycled steel production, enabling enhanced surface quality and promoting sustainable manufacturing practices by providing a reliable quantitative metric (adhesion energy) for industrial quality control.