| 摘要 |
PURPOSE:To prevent pickup by removal of scale without deteriorating its appearance in a continuous annealing stage for a steel strip by subjecting the steel strip to a pretreatment including specified pickling prior to annealing in said stage. CONSTITUTION:A steel strip prior to continuous annealing is subjected to pickling with hydrochloric acid of 5-15wt% acid concn. kept at 20-60 deg.C or with sulfuric acid of 5-10wt% acid concn. kept at 20-40 deg.C. Pickup is prevented by the removal of scale, etc. from the surface of the steel strip and the pickling in a specified range wherein roughening of the base iron surface is averted. The influence of the difference in pickling condition on the cleaning performance and appearance of the steel strip is expressed by the ordinate (the content of oxygen in the total oxide in the surface of the steel strip) shown in the figure. The figure reveals that as the value at the ordinate is smaller the oxide such as scale or the like is correspondingly removed. The content of oxygen, 70-80ppm, prior to the pickling is decreased by the pickling to 10-30ppm. |
