Development of modes for straightening of hot-rolled strip in order to obtain rolled products for high-tech processing

Abstract

Modern requirements for the quality indicators of hot rolled sheet steel are associated with maintaining high flatness of sheet metal during further processing by high-tech methods, for example, by laser or plasma cutting. When laser cutting a sheet it may bend due to the release of residual stresses that are unevenly distributed over the volume. The final stage in the production of hot rolled steel is straightening on roller straightening machines under cyclic alternating deformation. The solution to the problem is the optimal control of residual stresses at the main final stage of hot rolled sheet production when straightening strips on roller levelers under cyclic alternating deformation. The existing numerous approaches of calculating the parameters of the straightening on roller straightening machines do not allow determining the optimal modes that eliminate the initial inhomogeneous stress state of the hot rolled strip and ensure the minimum level of residual stresses in the rolled product. The paper substantiates the relevance of developing a methodology for selecting a strip straightening mode, which provides an expansion of the possibilities of the straightening process on roller straightening machines and obtaining hot rolled sheets with a minimum level of residual stresses and potential energy, suitable for plasma and laser cutting. The article describes the implementation of the method for selecting the mode of hot rolled strip straightening process based on the results of finite element modeling, confi rmed by experimental data obtained during leveling and subsequent cutting of sheets. The modes of straightening of strips with a thickness of 4 mm, 8 mm and 10 mm of steel grade S355MC have been calculated on 13-, 15- and 17-roller straightening machines of Severstal, providing minimum residual stresses, potential energy in sheets after straightening and deviations from the flatness of sheets during high-tech cutting. Based on industrial tests, the method for calculating straightening modes was introduced into production, the developed modes were accepted for use at Severstal. The proposed improvements of technology of the production of hot rolled sheet metal in the conditions of Severstal made it possible to obtain products suitable for laser cutting.