METHOD AND DEVICE FOR PRODUCING SI-CONTAINING COLD ROLLED STEEL SHEET

摘要

This invention provides methods and apparatuses which can manufacture Si-containing cold rolled steel sheets exhibiting excellent chemical conversion properties even if a chemical conversion treatment solution is used at a lower temperature while minimally suppressing the generation of sludge as well as reducing running costs. The method includes steps of cold rolling a steel containing 0.5 to 3.0 mass% Si, continuously annealing the cold rolled steel sheet, pickling the surface of the continuously annealed cold rolled steel sheet, and repickling the surface of the pickled steel sheet with a non-oxidative acid. The repickling is performed such that a repickling solution is sampled continuously or periodically, an acid concentration in the sampled solution is measured, and the acid concentration in the repickling solution is regularly controlled within a prescribed concentration range.