Numerical simulation of slab deformation process with different reduction values in vertical rolls of mill 2000 roughing stands

Perfection of rolled stock production processes at continuous wide-strip hot rolling mill (CWHRM) aimed at minimization of metal consumption, is an effective mean to decrease its cost. In the process of slabs rolling at CWHRM, the metal consumption is stipulated first of all by complicated workpiece forming in roughing stands during consecutive reduction by vertical and horizontal rolls. Results of the numerical study of slab deformation with different values of reduction in vertical rolls of roughing stands of mill 2000 are presented. The implementation of rolling process model based on application of DEFORM-3D program of finiteelement analysis described for evaluation of metal shifting from the edges of slab in the direction of the middle of the width. The convergence of the simulation results with the measurements data of workpiece forming during roughing rolling at Severstal mill 2000 was experimentally confirmed. It was found that an increase of reduction in vertical rolls has no significant effect on the metal shifting from a narrow edge to a wide one. Increase the total reduction in vertical rolls leads to an unfavorable stress-strain state of the edge region and the Cockcroft–Latham criterion rises by 20–30%. It was proposed to reduce the total reduction in the vertical rolls of the roughing stands of mill 2000 down to 40–50 mm. It was shown that increase of time of slab moving from the heating furnace to the scale breaker causes growth the Cockcroft-Latham criterion and does not affect the amount of metal shifting from a narrow face to a wide one. The proposed method of simulation the process of slab deformation in the roughing group of the mill 2000 proved by results of industrial rolling can to be used for further study of the effect of rolls profiling and forming of surface defects with the provision of minimal metal shifting onto a wide face.

Vibration Characteristics of Hot Rolling Mill Rolls Based on Elastoplastic Hysteretic Deformation

Based on the analysis of the influence of roll vibration on the elastoplastic deformation state of a workpiece in a rolling process, a dynamic rolling force model with the hysteresis effect is established. Taking the rolling parameters of a 1780 mm hot rolling mill as an example, we analyzed the hysteresis between the dynamic rolling force and the roll vibration displacement by varying the rolling speed, roll radius, entry thickness, front tension, back tension, and strip width. Under the effect of the dynamic rolling force and considering the nonlinear effect between the backup and work rolls as well as the structural constraints on the rolling mill, a hysteretic nonlinear vertical vibration model of a four-high hot rolling mill was established. The amplitude-frequency equations corresponding to 1/2 subharmonic resonance and 1:1 internal resonance of the rolling mill rolls were obtained using a multi-scale approximation method. The amplitude-frequency characteristics of the rolling mill vibration system with different parameters were studied through a numerical simulation. The parametric stiffness and nonlinear stiffness corresponding to the dynamic rolling force were found to have a significant influence on the amplitude of the subharmonic resonance system, the bending degree of the vibration curve, and the size of the resonance region. Moreover, with the change in the parametric stiffness, the internal resonance exhibited an evident jump phenomenon. Finally, the chaotic characteristics of the rolling mill vibration system were studied, and the dynamic behavior of the vibration system was analyzed and verified using a bifurcation diagram, maximum Lyapunov exponent, phase trajectory, and Poincare section. Our research provides a theoretical reference for eliminating and suppressing the chatter in rolling mills subjected to an elastoplastic hysteresis deformation.

Vertical–Horizontal Coupling Vibration of Hot Rolling Mill Rolls under Multi-Piecewise Nonlinear Constraints

This study establishes a vertical–horizontal coupling vibration model of hot rolling mill rolls under multi-piecewise nonlinear constraints considering the piecewise nonlinear spring force and piecewise nonlinear friction force constraints of the hydraulic cylinder in the vertical direction of the rolls, the piecewise stiffness constraints in the horizontal direction, and the influence of the nonlinear dynamic rolling force in the rolling process. Using the average method to solve the amplitude–frequency response equation of the coupled vibration system and taking the actual parameters of a 1780 mm hot rolling mill (Chengde Steel Co., Ltd., Chengde, China) as an example, we study the amplitude–frequency characteristics of the mill rolls under different parameter settings. The results show that the amplitude and resonance region can be reduced by appropriately reducing the external disturbance force and the nonlinear spring force of the hydraulic cylinder, appropriately increasing the nonlinear friction force, and eliminating the gap between the bearing seat and the mill housing, to avoid the amplitude jump phenomenon due to piecewise variation. Furthermore, using the singularity theory to study the static bifurcation characteristics of the coupled vibration system, we establish a relationship between the vibration parameters and the topological bifurcation solution of the coupled system. The transition sets and their corresponding bifurcation topological structure in three cases are given, and the steady and unsteady process parameter regions of the rolls are obtained. The dynamic behavior of the coupled vibration system can be controlled by varying the bifurcation parameter. This study provides a theoretical basis for restraining the vibration of hot rolling mill rolls and optimizing the process parameters.

Conceptual Directions of Creating Digital Twins for Electrotechnical Systems of Rolling Mill Facilities

This article considers the development of digital twins (DT) for the mechatronic facilities of the coiling machine group in a wide-strip hot rolling mill. The analysis of Russian and foreign sources confirmed that a lot of attention is paid to the economy digitalization. All of the leading metal plant equipment and electrical engineering system manufacturers are working on creating DTs. The analysis of the literature showed that the authors lack a uniform understanding of the conceptual directions in the creation of DTs and there are many definitions of this term. Therefore, the first part of the article deals with the analysis of the digital twin concepts according to their application at industrial companies. The authors substantiate the feasibility of the DT de-velopment for the electromechanical and mechatronic systems of the most complex metal production components, i.e., rolling mills. This initiative development is relevant due to the reconstruction of the 2500 wide-strip hot rolling mill at Magnitogorsk Iron and Steel Works PJSC (MMK PJSC) that involves the installation of unique equipment. Due to this, the development of DTs to implement the virtual commissioning of the equipment becomes a priority. The virtual adjustment of automation and process control systems is also required. This problem can be solved through the example of three coiling machines, each of which has electric and hydraulic auxiliary equipment. These coiling machines are used for rolling the heavy hot-rolled bar and they feature a unique design. Therefore, the development of DTs for mechatronic facilities is a novel scientific problem. The authors propose the methods for the development of DTs used in the virtual commissioning of process control systems. They present the structure of the coiling section automation system and the structure of the DT imple-mented on the basis of programmable logic controllers (PLC). The authors provide the specifications for the Siemens PLCs installed at each of the coiling machines and the coiling machine master controller. To develop the control systems for electric and hydraulic drives, it is recommended to use the Matlab Simulink software package. The authors provide temporal dependencies obtained using DTs and other similar oscillograph charts produced during the operation of the coiling machine that can help model the operation of the mechanisms in question. The results of their comparison show that the processes correspond to each other. Thus, the use of the developed DT to adjust the electrotechnical systems of rolling mills is reasoned. The accepted concept of making digital twins for the electrotechnical systems of rolling mill components is relevant and technically feasible