The Evolution of the Surface Morphologies and Microstructures of an Unleveled Hot-Rolled Steel Strip During Cold Rolling
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CURRENTLY, pickling is the main method that is used to remove oxide scales on the surface of a steel strip prior to cold rolling. However, the disadvantages of the method are obvious. Regel-Rosocka noted that steelwork plants in the European Union (EU) produced 300,000 m3/year of spent pickling solutions (SPS). The composition of SPS depended on the composition and thickness of the surface oxide scales and consisted of hydrochloric acid, iro zinc ions for mild steel pickling, and hydrofluoric acid, sulfuric acid, nitric acid or hydrogen peroxide, iron or other metal ions (mainly: Cr, Ni) for stainless steel treatment.[1] If the SPS were discharged directly into sewage system, it would be hazardous to the environment. Therefore, new acid-free YU-AN JING, QIUYUE SHANG, XIAOMING ZANG, and LEI ZHANG, Masters, XINGDONG PENG, Vice Professor, and PINFENG JIA, Doctoral Student, are with the School of Materials Science and Engineering, University of Science and Technology Liaoning, 185 Qianshan Zhong Road, Anshan 114051, Liaoning, P.R. China. Contact e-mail: [email protected] Manuscript submitted May 7, 2015. Article published online October 29, 2015 424—VOLUME 47A, JANUARY 2016
descaling processes, instead of pickling descaling, have long been desired by steel companies throughout the world to reduce or eliminate environmental pollution. Fainshteinv reported that a shot-blasting technology utilizes high-speed iron sand jet strip surface to remove the oxide scale on the strip surface.[2] The disadvantages of this technique are inefficient descaling, large noise, dust pollution, and a rough steel surface after simultaneous treatment. Ning and Jun studied the tight scale technology, which controls the morphology and the thickness of oxide scale on the strip surface by controlling the hot-rolling process parameters and then directly taking the hot-rolling strip into cold rolling or cold forming before coating.[3] This technology prevents the use of the pickling process. However, it is difficult to control the oxide scale structure and its thickness by controlling the hot-rolling process parameters. In addition, the technology is limited to low carbon steel series products. Another method is the gaseous reduction of oxide scale in the atmosphere to obtain a descaling effect. As early as 1985, Hudson first measured the thickness and distribution of the oxide scale of a hot-rolling steel strip.[4,5] The method of strapping reduction (pack and box samples) in an airtight METALLURGICAL AND MATERIALS TRANSACTIONS A
container is used to study oxide scale reduction under a hydrogen atmosphere with the presence of carbon. The reduced weight of each sample from the reduction was studied in detail, but the paper only discussed the surface morphological evolution of the samples after reduction, cold rolling, and hot dip coating. Samways reported that Danieli Wean United developed a hydrogenreduction method to remove the oxide scale from the surface of a hot-rolled strip steel.[6] This technology can be used to produce steel bands with
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