The effect of scale structure on pickling of steel strip

Abstract

During hot rolling and subsequent cooling, scaling always occurs on the steel strip. It is necessary to be completely removed before further processing (such as cold rolling). Usually continuous pickling is a more economic and convenient process to be used to remove the scale. However, the pickling rate is affected by many variables such as the type of acid, acid solution condition, steel composition, scale structure and different inhibitors at various concentrations as reported in the literature. In the mill, except machine breakdown, the troubles in the pickling line are often caused by the presence of acid‐resisted scale of nonuniform scale structure. Although a lot of information has been accumulated on the relationship between the microstructure of scales on steel strip and their response to pickling, most of them concerned the pickling in sulphuric acid. In the present work, the scale composition and thickness are examined after isothermal oxidation and simulated different mill cooling processes. Furthermore, their effects on pickling rate in hydrochloric acid solution is also studied and discussed.