MIAO Wang, QIAN Sheng, LI Zizheng, ZHANG Ji, WANG Xiaojian, BAI Zhenhua (1.Cold Rolling Plant, Shanghai Meishan Iron and Steel Co., Ltd., Nanjing 210039, China; 2.National Cold Rolling Strip Equipment and Process Engineering Technology Research Center, Yanshan University, Qinhuangdao 066004, China; 3.Huangshan University College of Mechanical and Electrical Engineering, Huangshan 245041,China; 4.Technique Center, Meishan Iron and Steel Co., Central Research Institute of Baosteel Co., Ltd., Nanjing 210008, China; 5.State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China)
In view of the rotational failure issues such as "shaft end seizure" and "strip slippage" in the sink roll system (sink roll, stabilizing roll, and correcting roll) of hot-dip galvanizing units, the mechanism of roll system rotational failure is analyzed based on the characteristics of the unit's equipment and the force conditions of the roll system. Using the strip element method, energy method, and Newton's second law, the critical slip criteria for strip elements is determined, and models for the frictional driving torque of the roll system, external load resultant force, and shaft end frictional resistance torque are established. On this basis, a critical criterion model for roll system rotational failure is constructed, using the rotational dynamic factor as an indicator to measure the rotational capability of the sink roll system. This model is applied to a hot-dip galvanizing unit to analyze the effects of four process parameters, including strip tension, correcting roll insertion amount, radial angle of the scraper blade roll surface, and scraper force, on the rotational failure of the sinkroll system during the production of typical strip specifications. The results show that increasing strip tension moderately enhances the rotational capability of the sink roll but has little impact on the stabilizing and correcting rolls. Increasing the correcting roll insertion amount results in a nearly linear increase of rotational dynamic factor of sink roll, a rapid increase followed by a decrease of the stabilizing roll, and an initial increase followed by a slow increment of the correcting roll,therefore the insertion amount of correcting roll should be smaller than 5 mm. Increasing the radial angle of the scraper blade roll surface enhances the rotational capability of all rolls to varying degrees. Increasing scraper force significantly reduces the rotational dynamic factor of all rolls, but excessive scraper force poses a risk of rotational failure of the stabilizing and correcting rolls. The scraper force of stabilizing roll, correcting roll and sink roll should be smaller than 15、300、800 N in practical production.
