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This study presents new experimental results showing how strongly the surface quality of steel plates influences their cooling rate during continuous production. The investigated phenomena are directly relevant to industrial water-based cooling technologies applied to steel plates on the Run Out Table, during accelerated cooling, and in interstand cooling sections of hot rolling mills. The work focuses on solid jet nozzles operating in a low pressure system, which are commonly used in industrial cooling lines. Three types of surfaces were tested: a slightly oxidized stainless-steel surface, and once oxidized and twice oxidized surfaces on standard low carbon steel. The stainless-steel surface remained homogeneous both after heating and after cooling, forming only a thin and continuous oxide layer. In contrast, the carbon-steel surfaces sometimes developed blister-like defects during heating. When these blisters peeled off during cooling, they left behind a very rough oxide layer that completely changed the cooling behavior of the material. Our results show that this rough and uneven oxide layer can significantly slow down or accelerate cooling, depending on how water flows and breaks on the surface. This behavior is particularly important for controlling cooling uniformity and reproducibility under real operating conditions of continuous rolling and cooling lines. The contribution demonstrates the importance of controlled experimental testing for understanding real cooling behavior in production conditions. These findings are relevant for manufacturers and research organizations seeking to improve product quality, optimize cooling strategies, and increase the efficiency of continuous steel processing lines.
Keywords: Surface roughness; Oxide layer; Steel plate cooling; Water jet cooling; Continuous steel processing; Heat transfer coefficient; Surface oxidation© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.