Influence of the remaining water layer on the cooling of moving steel surfaces

Steel is an integral part of today's life. To obtain the desired mechanical properties of hot rolled steel plates or strips, it is necessary to predict and control the cooling process. Cooling of a hot rolled strip on a run-out table or in a continuous annealing line is commonly realized by laminar and spray cooling, and involves a large amount of water, which impinges on the hot surface of the steel. Water is accumulated on the upper surface, which means the jets do not have a direct impact on the steel surface and the cooling intensity is changed. The cooling process is also affected by the remaining water layer that remains on the surface after cooling. This thin layer occurs both on the upper and the bottom surface, and also for light sprays. The remaining water can significantly influence the final temperature of the steel strip if the target temperature is below 500 °C. In this article, the effect of remaining water on cooling is experimentally investigated. A full cone spray nozzle is used for the measurements and the cooling in different areas (under the nozzle, outside the nozzle spray) is studied.