Quality Control Of Cold-rolled Electrical Steel Products

In the trial and production of cold rolling and continuous annealing of non-oriented electrical steel based on thin slab casting and rolling (TSCR) process, including compact strip process (CSP) and flexibility thin slab rolling (FTSR) process, some problems such as strip cracking and breakage during cold rolling, defective shape and flatness and edge cracking of cold rolled strip, several kinds of surface defects and corrugated defects, etc., have been appearance. In this paper, through the analysis to the cold rolling and continuous annealing practice in Shougang Tonggang Group (Tong Steel) FTSC process based and HBIS Handan Iron and Steel Group Co. Ltd. (Han Steel) CSP process based non-oriented electrical steel production, the process for cold rolling and annealing of cold rolled non oriented electrical steel based on the thin slab casting and rolling technology, as well as the production quality control of the cold rolled non oriented electrical steel are investigated.Optical metallographic observation, SEM analysis, spectrum analysis, hardness analysis are implemented to. Such as non-oriented electrical steel cold cracking analysis, non-oriented electrical steel cold rolling edge wave, edge grand and edge crack analysis, non-oriented electrical steel wire surface defect analysis, non-oriented electrical steel corrugated defect analysis test, based on the non oriented electrical steel surface defect analysis, draw the following conclusions:1) The reason of non-oriented electrical steel strip crack in the first cold rolling is the tissue near the crack is non-recrystallized fibers, in the process of rolling, strip steel internal uneven deformation, and then cracking.2) The reason of non-oriented electrical steel cold rolling edge wave edge grand and edge crack was the correspond hot rolled strip edge existence" hard band".3) The surface "dark line" defects found in the after coated strip might be caused by the foreign substances from the bottom rolls of the continuous annealing furnace, which were embedded under the surface scratches at elevated temperature after the strip surface had been scuffed by the nodules on the graphite bottom rolls in the soaking furnace (SF) segments, and then were covered by the coating in the coating process.4) The surface longitudinal hair crack defects found in both the cold rolled strip and after coated strip was caused by the complex aluminate inclusions, which were broken and edged out from the inside layer after the slab were hot rolled and cold rolled successively.5) The corrugated defects in non-oriented electrical steel may have a relationship with not uniform deformation in the local position of cold rolling process, The fundamental reason is that the hot rolled strip of tissue is not uniform, that is the hot rolled strip have larger size of not fully recrystallization of fibrous tissue. Analysis shows that it has a relationship with the inclusions in the grain boundary hampered grain recrystallization.