Abstract: Aiming at frequent sudden strip shape variation and rolling instability occurring during speed-up single-pass rolling of high-silicon non-oriented silicon steel on a 20-high reversible cold rolling mill, field comparative tests and single-variable experimental investigations were carried out with fixed process parameters including roll surface roughness, reduction ratio and emulsion temperature to systematically clarify the formation mechanism of the above defects. The results reveal that offset of spray header position deteriorates the spreading uniformity of emulsion, resulting in mismatching between lubrication/cooling conditions at rolling interface and rolling speed, as well as abnormal fluctuation of roll thermal crown, which serves as the dominant trigger for abrupt strip shape defects. Based on the revealed mechanism, the optimal opening rate of 20% for roll cooling pipeline valves was determined via optimization, and a standardized adjustment specification of 10-15 mm for spray header clearance was formulated. Practical industrial application verifies that the proposed optimization completely eliminates strip shape defects during acceleration, raises the stable single-pass rolling speed by 25% and improves I-Unit flatness control precision by 74.7%, substantially enhancing rolling stability and production efficiency. This study fills the adaptability gap of existing theories under on-site special rolling conditions and develops a practically implementable flatness control process, which provides valuable engineering references for stable cold rolling production of high-silicon non-oriented silicon steel and troubleshooting of analogous rolling defects.

Key words: non-oriented electrical steel; sudden strip shape change; emulsion; twenty-high cold rolling mill; rolling stability