Research On Plate Shape Control During Straightening Process In 3450mm Production Line In SGIS

Recent years, with the increasing user demand for plate quality, the flatness requirement in international market reaches to 5 mm/m, even to 2 mm/m, the flatness problem becomes more and more critical due to the wide application of TMCP technology. The flatness has been the bottleneck of plate production quality upgrading in steel mills. The research of plate shape control in straightening process which eventually decides the shape quality is significant to the plate quality improvement. In this paper, plate shape laws in straightening process were studied based on the nine-roller hot straightening machine in 3450 mm production line in SGIS by using the coupled means including the theoretical analysis,analytic calculation, finite element simulation, and field experiments. The main works and results in this paper are as follows:(1) The straightening process was analytical calculated. Based on concentrated load hypothesis, the analytical calculation model of straightening force of each roller was established. In consideration of contact position between plate and rollers, the analytical relationship between reduction and bending moment was established.(2) Based on the finite element software Marc, a three-dimensional mathematical model of straightening process was established, and the stress state of plate during the straightening process was simulated, It is seen that plate straightened is formed by the recycle tensile and compressive stress of plate. Moreover, based on the analysis on the stress field and temperature field for the straightened plate, the laws of stress and temperature field distribution were revealed. The straightening force was calculated, the results of straightening force for each roller obtained form the model were verified with the analytical results and filed data. The results shown that the straightening force of the sixth roller was the biggest among all rollers. In addition, the changing process of straightening force during straightening process was analyzed from the perspective of straightening element.(3) Based on two-dimensional model of straightening process simulated by Marc, theinfluence of initial curvature and thickness of plate on shape quality of straightened plate were investigated, the adjustment laws of exit reduction, tilting and exit edge roller position parameter as well.(4) According to the analysis results, the corresponding improvement measures for three process parameters were put forward. It is shown that plate defects rate range is decreased from 6%~7% to 2%~3% after the application, the plate quality was improved and controlled steadily.