Cooling Effect of Remaining Water Layer on Various Steel Surfaces

Abstrakt

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Accurate prediction and control of the cooling process during hot rolling are crucial for producing high-quality steel with the desired mechanical properties. In many steel companies, hot-rolled steel plates or strips are commonly cooled on a run-out table or in a continuous annealing line using laminar jets or spray cooling, which involves a large amount of water impinging on the steel surface. This process forms a water layer on the top surface, which changes the cooling intensity significantly. The water layer is often removed by water wipers or using air knives; however, thin water layer remains on the surface in most cases. Due to surface tension, this thin water layer forms on both the top and bottom surfaces. The remaining water layer is also formed when using light sprays and can significantly affect the final temperature of the steel strip, especially if the target temperature is below 500 °C, as confirmed by steel producers. This study experimentally investigates the influence of the remaining water layer on heat transfer during cooling after hot rolling. Cooling experiments were conducted using a full-cone spray nozzle and moving steel samples with two different surface finishes: a grinded surface (Ra = 0.9 µm) and an oxidized surface (Ra = 3.1 µm, oxide thickness 27 µm). The cooling effect of the remaining water on both surfaces was compared to determine the impact of surface quality.

2025-09-18

ISBN 978-84-09-73131

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