Stands Of Mill Research Articles

Structural evaluation of mass concrete damage: a case study of concrete mill stands

Structural evaluation of mass concrete damage: a case study of concrete mill stands

Roll profile and roll shifting strategy for silicon steel edge drop control in cold rolling CVC mill

The cold rolling CVC rolling mill, which is a primary piece of equipment for producing thin-gauge nonoriented silicon steel, lacks suitable edge drop control methods. To construct a theoretical system for high-quality edge drop control of CVC rolling mills, this study focused on a 1780 mm CVC cold continuous rolling mill at a specific factory. Using ABAQUS software, a finite element model was constructed to simulate and validate the production process. Work roll profiles were developed to enhance the mill's edge drop control capability for silicon steel, effectively preventing issues related to excessive edge tensile stress caused by strip misalignment. Additionally, a multistand simulation model was developed to analyse the edge drop and curvature control capabilities of different mill stands. Based on the buckling theory under high tension conditions, an intermediate roll shifting strategy was developed for edge drop control in a cold continuous rolling CVC rolling mill. Field applications have shown that this research effectively reduces edge drop issues, improving the pass rate by 25.1 %, thus confirming the effectiveness of this study.

Study of wear on surface of work rolls barrels of continuous stands of wide strip hot rolling mill

The results of the patterns of wear on the surface of the work roll barrel of the quarto stand of a hot rolling mill are presented. It is established that wear will be mainly determined by the hardness of the work roll barrel surface, the rolling force in the deformation zone, the amount of rolled material produced on the roll, as well as the average diameter of the roll barrel. The greatest effect on wear as the amount of rolled stock increases is the rolling force, as well as the hardness of the barrel surface. The proposed technique makes it possible to predict the uneven wear of the surface of the roll barrel along its length. Taking this unevenness into account can be useful for controlling the profile of the strip and its shape.

Analysis of the roll imprint on the cross-sectional area of hot rolled wire rod by frequency spectroscopy

This work presents an approach for analysing the sensor data of an eddy-current based cross-sectional area measurement for hot rod and wire steel in an innovative manner and for approximating the influence on the forward slip by longitudinal tensile forces between the mill stands. The method is based on frequency spectroscopy of the cross-sectional area of the rolled stock. The measurement data of three sensors already implemented in two hot rolling mills is used in order to obtain information out of the roll imprint on the cross-sectional area. Since measurement data from two measuring sites and from three sensors are evaluated, this allows statements to be made about the reliability and reproducibility of the measurement and shows that the method can be used for different rolling blocks such as 3-roll and 2-roll blocks. In addition, a mathematical model is presented which allows conclusions to be drawn about possible causes for certain characteristics in the measured frequency spectrum of the cross-sectional area.

Synergic Combination of Hardware and Software Innovations for Energy Efficiency and Process Control Improvement: A Steel Industry Application

The present paper proposes a steel industry case study focused on a reheating furnace and a rolling mill. Hardware and software innovations were successfully combined in order to obtain process control and energy efficiency improvement. The reheating furnace at study is pusher type and processes billets. The hardware innovation is related to the installation of an insulated tunnel at the end of the reheating furnace, in order to guarantee a higher heat retention of the billets before their path along the rolling mill stands. The software innovation refers to the design and the installation of an Advanced Process Control system which manipulates the gas flow rate and the stoichiometric ratio of the furnace zones in order to satisfy the control specifications on billets and furnace variables. The control system is based on Model Predictive Control strategy and on a virtual sensor which tracks and estimates the billet features inside/outside the furnace. The designed controller was commissioned on the real plant, providing significant performances in terms of service factor, process control, and energy efficiency.

Rolling stand electric drive model regarding influence of power supply network parameters

<span lang="EN-US">Operation mode of hot rolling mill finishing group stands of ArcelorMittal Temirtau JSC electric drives along with thyristor converter units, intended for the drives supply effect significantly the power network parameters. While being carried out the experimental research on operating modes of power network supplying the rolling mill, some oscillograms were constructed that indicate voltage during the rolling process. Analyzing the oscillograms it appears that there are unacceptable voltage drops throughout the network (more than 10%), that, in its turn, effects negatively the main and auxiliary electric drives functioning. Electric drive simulation model have been constructed with the aim accomplishment to learn more about operating modes features of finishing group stands electric drives as well as power network supplying the hot rolling mill, where the main objective is getting the decreased parameters of their mutual influence. The scientific project purpose is verification of the mathematical model choice correctness, construction of a simulation model of the electric drive control system for the main drives of the hot rolling mill stands, taking into consideration the parameters of the power supply network and checking its adequacy.</span>

Multi-objective optimal edge-drop control in tandem cold rolling of silicon steel strip

In cold rolling of silicon steel strip, edge drop directly affects the side cutting and yield of silicon steel. To improve the edge drop of silicon steel in the cold rolling process, a multi-stand coordinated control strategy and model based on multi-objective optimization are proposed. The first step is to analyze the influence of each control stand work roll shifting (WRS) on edge drop through the finite element model (FEM), then determine the edge drop control effectiveness of each work roll shifting actuator. Meanwhile, a fitting model is proposed to solve the limitation caused by the discrete change of efficiency factors in solving the optimal adjustments of each WRS. On this basis, the target model for silicon steel edge drop control is formulated, and the optimal adjustment model of WRS of each stand is established. To realize the optimal coordinated control among the rolling mill stands, a multi-objective optimal model of edge drop control has been established by the overall modeling method. The improved penalty function algorithm is developed to calculate the optimal adjustment of WRS for each stand. The experiments and application show that the proposed multi-objective optimal control strategy and model can effectively improve the accuracy of edge drop control in silicon steel continuous cold rolling.

Determination of the wear of the surfaces of barrels of work rolls in a continuous finishing group of stands of a wide-strip hot rolling mill

Compensate for elastic and thermal deformations of the work rolls, as well as to ensure the possibility of rolling a flat strip, the surface of the barrel of the work rolls is profiled. During the production of steel strips on a continuous mill, the initial grinding profiles of the barrel surfaces change due to their wear. According to a number of studies, the shape of the worn surface will be determined by a number of factors: by sliding the rolled metal along the roll in the deformation zone, which depends, among other things, on the length of the produced strip; temperature conditions in the deformation zone; the presence of a movable intermediate layer between the roll and the strip, for example, mill scale during hot rolling or cutting fluid during cold rolling; chemical composition of the rolled steel; quality of rolling rolls; applied steel strip reduction modes in the mill stands; uneven heating of the rolled metal over the section, as well as some other parameters. A study was carried out on the basis of experimental data on evaluating the profile of the barrel of work rolls after they were dumped and cooled from the rolling stands. It was found that the main parameter affecting the wear of the surface is the length of the strip rolled in a given stand. It has been confirmed that wear along the length of the roll barrel is uneven. A method for calculating the wear of the surfaces of the barrels of the work rolls of a wide-strip mill along their length, based on the operating mode, is proposed. The results of the study can be used to improve the shape of the grinding profiling curve of the work roll barrels and it can be used in models for controlling the shape of a strip, and calculate technological rolling conditions

Вейвлет-преобразования в задачах контроля и диагностики автоколебаний стана холодной прокатки

Self-excited oscillations remain a frequent problem of cold rolling of thin strips. When self-oscillations occur, the amplitude increases by a jump of more than a hundred times, that is from 2–3 m/s2 to 200–250 m/s2. Oscillation frequencies (from 100 to 500 Hz, i.e. the number of loading cycles) can reach several thousands per a few seconds. Intense self-oscillations normally occur on thin strips with a thickness of less than 1 mm and high rolling speeds. The control of the occurrence of self-oscillations includes special systems, according to the level of vibrations or technological parameters, for example, by fluctuations in the tension of the strip. In control systems, classical methods include the decomposition of the controlled signal into a Fourier series. For stationary processes, Fourier series decomposition provides complete information about the signal structure and is sufficient to diagnose the technical condition of machines and mechanisms. As for a nonstationary non-harmonic signal, the information about the spectral composition of the diagnostic signal is insufficient, since it does not allow for determining the moment of occurrence of an undesirable process. In metallurgy and rolling production, processes are frequently not stationary. The cold rolling process is continuous, but discrete. It takes 5–6 minutes to roll one coil. The process of selfoscillation, even when using control systems, can last no more than 2–3 seconds. A high frequency of vibrations and a high level of stress can lead to the formation of cracks in the elements of the mill stands, for example, CVC plates. A signal conversion wavelet can become an alternative way of monitoring and diagnostics. If the FFT allows you to determine the presence of self-oscillations only in the developed state, the wavelet transform allows you to determine the origin of the selfoscillation process at low oscillation amplitudes. It also allows you to determine it in the absence of fluctuations by changing the signal of the technological parameters.

Performance Analysis of Work-Roll Wear Models on Hot Rolling

The purpose of this work is to evaluate the performance of several wear models, either with different mathematical formulation or different definition of the unknown wear coefficients, on the prediction of the work-roll wear amplitude in Hot Strip Mills (HSM). To achieve this goal, a classical model calibration approach based on inverse optimization has been developed to calibrate these several wear models. A large industrial hot rolling database composed by roll wear amplitude measurements for both later finishing mill stands (F6 and F7) from ArcelorMittal Dofasco HSM was considered and a least-square cost function was applied to minimize the differences between both numerical and experimental results during the optimization process. The averaged roll wear gap between measurements and optimized numerical predictions was then used as a quantitative indicator to compare the performance between the wear models and identify the most suitable one for roll wear prediction. In addition, an Artificial Neural Network (ANN) approach was developed based on the most suitable wear model. Thus, roll wear predictions obtained using the ANN were compared with the ones obtained using Classical calibration to evaluate the performance of both approaches.

Determination of the optimal horizontal boring mill for the repair of the pipe-rolling reduction-stretching mill’s body stands

The article defines the optimal equipment necessary for the repair of the body stands of a pipe-rolling reduction-stretching mill. The body stand of the mill crate, made of 40X structural alloy steel, undergoes wear of the bearing seats during operation. Body stands restoration is carried out by surfacing the worn surfaces of the part with subsequent machining to the dimensions specified in the design documentation. In the process of surfacing medium-carbon steels, carbides are formed, which leads to a sharp increase in hardness in the zone of thermal influence, which affects the durability of carbide plates and processing accuracy.It is necessary to consider the geometric shape, dimensions, weight and material of the part while choosing equipment for repairing the body stand. Using a horizontal boring machine with a horizontal spindle performing rotational and translational movement of the axial feed, it is necessary to take into account the rigidity of the spindle, which affects the accuracy of processing, especially when restoring deep holes after surfacing with hardening surfacing materials. Bending the spindle can cause vibration and beating, which will affect the quality of the work performed. An increase in the rigidity of the machining can be achieved by using a drilling rod or by increasing the diameter of the spindle. Since it is necessary to restore deep blind holes in the repaired housing, it is impossible to use a drilling rod. In the process of work, the optimal diameter of the spindle of the horizontal boring machine was determined, taking into account the design features of the work piece.

Modern materials for cast rolls of hot strip mills

The requirements for the work rolls for the various roll stands of hot strip mills are shown. The modern materials for cast rolls are analyzed and the operational performance of different types of rolls in different stands of the rolling mill is described. The trends in improvement of rolls performance were presented.

Multistep networks for roll force prediction in hot strip rolling mill

Hot rolling processes consist of multiple single rolling stand operating at high temperature and speed to achieve desired steel shapes and superior properties, via exerting roll forces that need to be accurately predicted by a model. The currently used model of the mill of this study shows prediction instability and is unable to accurately accommodate changes in steel grade. In this paper, we propose a machine learning based framework to establish a model that accurately predicts roll forces at each mill stands of the hot strip rolling mill. In contrast to the traditional models, the proposed expert system considers an individual model for each rolling stand and employs rolling history when predicting roll forces. The proposed model includes both steel chemistry and physical process parameters for its predictions. Our experimental results demonstrate that the proposed framework improves both prediction accuracy and stability by 40%–50% over the currently used mill model. The enhanced prediction accuracy will greatly improve dimensional and microstructural control, as well as ensuring the avoidance of mill overloads.

Simulation mathematical model of the pipe reduction process

The paper deals with issues related to longitudinal stresses when rolling pipes on a three-roll reduction-stretching mill. The article presents a simulation model of the pipe reduction process to determine the longitudinal forces arising in the pipe string between the working stands of a continuous tension reduction mill. An algorithm for calculating a simulation model is presented, which makes it possible to calculate the stress from the front and rear longitudinal forces. The algorithm is based on determining the value of the second volume as the product of the crosssectional area of the pipe string coming out of the reduction mill by the average roll speed of the last stand along the groove perimeter. This model was used to calculate the pulling capacity of the rolls in each stand, i.e., what are the maximum possible longitudinal forces they can create in the pipe sections between the stands. The influence of the number of rotation of the rolls in the last group of influence on the longitudinal forces is shown. With the help of a computer, the reliability of the model was assessed.

Study of the friction coefficient during the steady-state process of continuous hot rolling of steel strips in conditions of the 1950 industrial mill

This paper describes a method for determining the value of the friction coefficient in a steady-state hot rolling under industrial conditions of the casting and rolling complex of “Vyksa Steel Works” located in Vyksa. The algorithm implies the forward slip method for determining the friction coefficient using the Ekelund formula. Measurements of hot rolling technological parameters from sensors are used as input parameters. Mathematical formulas are implemented in the ibaAnalyzer software, with the help of calculations are made for several thousand strips and data on the friction coefficient are obtained under various conditions. The data processing results demonstrate a normal distribution of the friction coefficient. The highest value of the friction coefficient is typical for the first finisher stands F1-F2, and the lowest values are found for the thinner gauge products rolled at high speed. The influence of the working layer of the work rolls on the friction value is demonstrated. High-chromium cast iron rolls have lower values of the friction coefficients, in contrast to indefinite cast iron, which is used for the working layer of the last finisher stands of mill 1950. A detailed comparison of the results with the classical methods for determining the friction coefficient in a steady-state process has been carried out. The dependence of the ratio of the friction coefficient during initial entry to the steady-state friction coefficient was refined.

A novel mass flow controller for tandem hot rolling mills

In tandem hot strip rolling mills, the roll speed of the mill stands is synchronized to ensure a uniform mass flow. A uniform mass flow is desirable to keep the strip tension constant and thus avoid large movements of the loopers which are located between the mill stands in order to control the strip tension. This also improves the general thickness quality and prevents the strip from necking in case of too excessive strip tension. In typical state-of-the-art implementations, the roll speed is synchronized in a cascade master–slave control structure where the very last downstream mill stand serves as speed master and the upstream mill stands operate in a slave mode to make sure that the mass flow is kept constant. While the relation between the roll speeds in the classical synchronization control concept is typically constant, a thorough analysis of the mass flow reveals that the slip between the work rolls and the strip is time varying. Therefore, in order to ensure a uniform mass flow, a novel adaptive speed synchronization controller is proposed, which can be easily added to the existing control structure and is computationally undemanding. To this end, a mathematical model of the whole tandem mill including the complete control structure is derived and validated by measurements. Simulation results for this validated model prove that the proposed mass flow controller clearly outperforms the existing solution.

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.

Rolling in Nondriven Rollers of Four-High Mill Stands

Rolling in Nondriven Rollers of Four-High Mill Stands

Experimental Parametrization of the Dual-Mass Electromechanical System of a Rolling Mill

Transients in electromechanical systems need to be modeled adequately if the existing electric drive control algorithms are to be improved, or new ones are to be developed. This fully applies to the electric drives of roll-ing mill stands. When studying such drives, one often needs to find a tradeoff between the complexity of Park-Gorev equation-based mathematical description of processes in variable frequency drives, and the capabilities of simpler models that adequately describe the processes relevant for each specific case. The latter include the known dual-mass model of the electromechanical system of a rolling mill stand featuring a flexible shaft and gaps in transmissions. Research presented herein covers the parameters of this model, which need to be ob-tained experimentally. The most accurate way to find the model parameters is to derive them from the oscillo-grams sampled on the object when running in typical transient. This particular paper addresses the electrome-chanical system of the horizontal stand in Plate Mill 5000 deployed at Magnitogorsk Iron and Steel Works (MMK PJSC). The paper substantiates the methodology behind parametrizing the system and shows how to cal-culate the moments of inertia of rotating masses from oscillograms of unloaded drive acceleration. To showcase the method, the paper presents finding the stiffness factor of an elastic coupling from the transients recorded when halting the electric drive. Focus is made on finding the time constants of the internal torque control cir-cuit as approximated by first-order or second-order filters. By comparing the simulation output against the os-cillograms sampled on the mill itself, the model was proven to adequately compute the parameters of the object. The paper concludes with recommendations on how the developed methods could be used to find the parame-ters of a dual-mass system when modeling the electric drives in rolling mills. The conclusions outline possible further research.

Determination of the reduction coefficients in a continuous finishing group of stands in a hot rolling mill using artificial neural network

There are many problems when creating digital doubles. One of which is the definition of the source data: in this case, the definition of private reductions (coefficient ratios) in a continuous finishing group of stands of the broadband hot rolling mill 2000 of PJSC Magnitogorsk Iron and Steel Work. Algorithms were developed to calculate the thickness of the breakdown bar, the number of stands involved, power required for rolling and coefficient ratios to solve this problem. The algorithms are based on well-known solutions (the Imai method) using neural networks. The training of neural networks was conducted on a sample collected for the period from 01.01.2017 to 01.01.2019 work of the mill in the PyTorch library of the interpreted programming language Python. The average error εME of the calculation of coefficient ratios (according to the developed algorithms with neural networks) does not exceed 8.9% and the standard deviation σ does not exceed 0.074.