Innovative descaling strategies and their influence on heat losses

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en

Hot rolling of long products is composed of several steps: reheating, descaling, roughing, intermediate and finishing rolling, heat treatment, etc. Mills strives to increase the efficiency of these processes as much as possible. Product quality is the top priority, and it is directly connected to descaling quality. High-pressure descaling is typically composed of high-pressure nozzles mounted on a fixed spray bar. Key parameters are water pressure, nozzle configuration, size of nozzles, positioning of nozzles, orientation and overlapping and the arrangement of the descaler header related to descaling performance. These parameters have already been studied and optimized concerning descale ability in [1] – [3]. Innovative trends described in this paper focus on different descaling strategies and systems related to descaling quality and heat loss. Typically, a single row of descaling nozzles is used in a hot rolling process. The first innovative approach was to install a low pressure (20 bar) row of nozzles before the descaling system. The hypothesis was that undercooling of the scale surface could cause microcracks in the oxide layer due to the different thermal expansions of a scale and steel. The next innovative approach was based on placing two descaling rows in opposite directions to improve the descaling process and minimize heat loss caused by reflected water flowing on a workpiece surface. Finally, another two descaling systems were studied. The first one was hydromechanical rotary descaling and shot blasting systems. The above-mentioned strategies and systems were compared with a focus on heat transfer and descaling efficiency, which is a key factor. Heat transfer tests were performed by Heat Transfer and Fluid Flow Laboratory (HeatLab). The descaling trials were done by Centre de Recherches Metallurgiques (CRM) and numerical simulations by VDEh-Betriebsforschungsinstitut (BFI). Hauhinco Maschinenfabrik produced a descaler and mounted it at a blooming line.

descaling efficiency; hydromechanical descaling; heat losses; shot blasting; heat transfer

2025-09-18

Association for Iron and Steel Technology

9780930767402

Sborník z konference

155–166

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