Research On Profile Control In2250mm Hot Strip Mill

Width of2250mm HSM is the present domestic biggest "ultra-wide" hot rolled strip production line. With1450mm and1700mm wide strip mill, roller diameter of the2250mm HSM is basically the same, but roller length increased by30%-50%, and lead to lateral stiffness significantly lower, mill mechanical behavior more complex. And the specifications of the production also more complicated than the general wide HSM. As a result, the asymmetry and local characteristics with strip shape on mill stiffness, roll force, roll wear and thermal aspects are more prominent in2250mm mill, Which lead to strip plate profile asymmetry and local high points in the actual ultra wide strip production, seriously affected the product quality of strip shape.This paper is based on an enterprise scientific research project, with a2250mm HSM as the research object. Combination of theoretical analysis, numerical calculation and experimental study, the formation and genetic regularity of asymmetric and local high point defects were studied. Combined with the characteristics of the2250mm production line and the strip profile control methods, the control of the strip profile defects were discussed and researched. In this paper, the main work and achievements are as follows.(1) Based on strip profile measurement and analysis, it is found that the existence of asymmetry and local high point defects in the ultra wide strip profile will make traditional crown and wedge can not be accurately described with strip profile shape, thereby reducing the precision of the strip shape quality control and evaluation. In this paper, the profile defects and its influence on the profile control was analyzed, and the local high parameter identification method, asymmetric contour description method, and strip profile estimation method based on the local profile weights are proposed pointedly.(2) Measuring and analyzing the asysmmetric state of mill and rolled pieces in2250mm HSM. Then using the asymmetric roll deformation model based on influence function method and hereditation method, the formation mechanism of the asymmetric profile is analyzed, and the influence and hereditation of asysmmetric disturbance factors are also confirmed.(3) In allusion to work roll uneven wear due to the rolling plan complex, the shifting characteristics of CVC roll and the strip surface transverse temperature distribution, and its hereditation to strip cross-section contour, the work roll uneven wear calculating model is put forward and realized, providing a new way for roll wear online calculation.(4) Uilizing the strip local deformation model, the local high point formation and evolution was researched. It is found that the work rolls uneven wear is the main cause of strip local high point, and the work roll wear in downstream stands is the decisive factor. Based on this conclusion, the high-speed steel work roll was used in downstream stands for experimental study. Experiment results showed that it is useful for improving strip quanlity.(5) According to the analysis of production and theoretical data, the control methods, including the regulatory standards about rolling mill stiffness, rolled piece wandering, horizontal temperature distribution, the use specification of HSS roll and rolling plan adjustment, are proposed and implemented. The profile defects of2250mm hot strip mill have been eliminated by and large. The profile defect rate decreased from1.2%in2012to0.02%in2014.