Strip Rolling Research Articles

Research and design of the process of asymmetric cold rolling of steel strips. Message 1

Research and design of the process of asymmetric cold rolling of steel strips. Message 1

Intelligent Analysis and Optimization of Lubrication Status Factor Based on Dynamically Loaded Roll Gap in Cold Strip Rolling

Lubrication is a critical process in cold strip rolling, and the accurate characterization of lubrication characteristics is an essential factor affecting the strip quality. The roll bending and tilting roll in the flatness actuators change the loaded roll gap profile and affect the lubrication characteristics by flatness dynamic correction, thus the mismatch between the actual and setting values of the lubrication status factor. Firstly, the flatness deviation correction model of roll bending and tilting roll based on the key information of the rolling process is established according to the high-order flatness target. Secondly, the characterization of the instantaneous oil film thickness in the work zone based on the loaded roll gap profile is derived from Reynolds’ equation. Finally, the explicit characterization method of the lubrication status factor in the rolling force model of the final stand is established with the work roll bending, tilting roll, and instantaneous oil film thickness of the work zone as variables, relying on the UCM five-stand, six-roll tandem cold rolling mill. The statistical evaluation and application results show that the mentioned optimization method can improve the setting accuracy of the rolling force by about 60% and the after-rolling gauge accuracy by about 50%.

EMC-YOLO: a feature enhancement and fusion based surface defect detection for hot rolled strip steel

EMC-YOLO: a feature enhancement and fusion based surface defect detection for hot rolled strip steel

Digital twin-based methodology for schedule execution in hot strip rolling

Hot strip rolling (HSR) is a critical process in the iron and steel industry, significantly impacting manufacturing efficiency. While schedule optimisation for HSR has received considerable attention in industry and academia, there is a lack of research focusing on schedule execution, which directly affects the makespan, despite its significance. During schedule execution, various factors such as uncertain events, information asymmetry and abnormal disturbances can lead to deviations from the planned schedule, impacting both productivity and stability. However, traditional methods are inadequate in effectively addressing these challenges. To tackle this issue, the concept of a digital twin (DT) is introduced to facilitate the integration of the physical and information spaces, leading to a novel method for HSR schedule execution. This paper presents the development of a mathematical model for HSR schedule execution. Subsequently, a focused five-dimensional DT model is established, emphasising the key influencing factors of the model. Moreover, this research explores DT-based methods for start time prediction, deviation detection and rescheduling, resulting in the development of a comprehensive methodology for HSR schedule execution. Finally, the proposed approach is validated by implementing the DT system in a HSR production line at a company.

Modeling of thermal processes during wide hot strip rolling

Modeling of thermal processes during wide hot strip rolling

Possibilities for improvement of technology and equipment for continuous hot rolling of steel strips

Possibilities for improvement of technology and equipment for continuous hot rolling of steel strips

Исследование распределения нормальных контактных напряжений в очагах деформации при горячей прокатке полос из конструкционных низколегированных сталей для повышения стойкости рабочих валков

Introduction. During the operation of the working rolls of the finishing groups of continuous wide-strip hot rolling mills, normal contact stresses have a decisive influence on its resistance and strength, especially when rolling a range of low-alloy structural steels with a minimum thickness range of 5.5–2.0 mm, which does not correspond to the passport characteristics of such mills. The subject of the study. Previously performed studies of the stress-strain state of the rolled strip in the deformation zones make it possible to estimate the level of normal contact stresses acting on the working rolls during hot rolling of strips of low-carbon steels. The paper discusses the results of the study of the stressed state of strips of low-alloy structural steels in contact with rolls, taking into account the features of the chemical composition of the metal and changes in its elastic properties during deformation at hot rolling temperatures. The results obtained are applicable to the evaluation of the contact strength of the finishing rolls of the rolling mill. The purpose of the work is to investigate the distribution of normal contact stresses in the deformation zones during hot rolling of strips of low-alloy structural steels to ensure high resistance of the working rolls. Material and methods. The study is based on the elastic-plastic model and equations for calculating normal contact stresses for each section of the deformation zone. The specificity of variation of Young's modulus (modulus of elasticity) of low-alloyed structural steels in accordance with certain hot rolling temperatures is studied in detail, and the contact strength of high-chromium cast iron work rolls is evaluated. Results and discussion. A reliable regression equation is obtained for determining the values of the Young’s modulus of the rolled strip as a function of changing hot rolling temperatures. The results of a numerical experiment are presented in the form of calculating the maximum normal contact stresses using the elastic-plastic model of the deformation zone and assessing the contact strength of the work rolls based on actual rolling conditions on an operating mill. New improved technological modes of hot rolling of low-alloy structural steels (0.1 C-Cr-Si-Ni-Cu, 0.18 C-Cr-Mn-Ti and 0.14 C-2 Mn-N-V) are proposed, which make it possible to reduce the maximum contact stresses and increase the resistance of the working rolls.

Influence of temperature regime of the combined process of casting and rolling of strips from high-alloy aluminium alloys

Influence of temperature regime of the combined process of casting and rolling of strips from high-alloy aluminium alloys

Research on roll profile thermal-force driving characteristics and joint control strategy in the multi-zone roll profile electromagnetic control technology

Roll profile electromagnetic control technology (RPECT) is a new roll gap shape control technology that can flexibly control the roll profile to meet the flatness control requirements of cold rolling mill. As basic control elements, electromagnetic sticks (ES) can drive the local zone bulging of electromagnetic control roll (ECR) to generate thermal-force contribution roll profiles. Due to the high order profile defects in the thin-gauge strip rolling process, the requirement of roll gap shape control in cold rolling mills is usually characterized by multi-zone and micro-scale. Therefore, a multi-zone roll profile electromagnetic control technology is proposed in this paper, which includes a multi-zone joint control strategy and a parameter preset method for basic control elements targeting roll profile. To conduct the parameterized impact analysis of stick distance and multi-stick control modes, a multi-zone joint control simulation model is established. Through the simulation analysis, the results show that it is feasible to use multiple basic control elements to adjust the multi-zone roll profile in the mechanism of action, and the total roll profile curve can be equivalent to the superposition of the individual bulging curve of different basic control elements with different space-time parameters. Meanwhile, the reasonable distance setting can effectively avoid the instability of thermal contribution roll profile control caused by too small distance between sticks and too strong thermal bulging driving. For the double-stick control mode or the three-stick control mode, using different temperature control method can assist ECR to realize the roll profile control goal that the low-order roll profile of the basic control element is superimposed to construct the high-order roll profile curve. According to strip flatness electromagnetic control experiment, the multi-zone joint control of RPECT can adjust the flatness defects above 100 IU to flat state, and can flexibly regulate local shape problems and control local buckling.

Evaluating the process operating state taking into consideration operator interventions with application to a hot rolling mill process

In complex industrial processes, process operators often intervene in automatic control systems based on their assessment of the operating state. Traditional operating state evaluation methods do not take into consideration or cannot effectively use this intervention information, and thus may incorrectly evaluate the operating state. In this paper, a convolutional-neural network-conditional variational auto-encoder (CNN-CVAE)-based method for evaluating the operating state is proposed to address this problem. First, the operating-state labels are constructed considering the operator-intervention information. Next, the features of operator-intervention variables (OIVs) are extracted based on CNN, and the obtained probabilities of belonging to different operating states are used as conditional probabilities of CVAE to supervise the feature extraction from the ordinary process data. Finally, both features are fused in a fully connected layer to obtain the predicted operating state. Compared with traditional methods, CNN-CVAE can capture features from both OIVs and process data for evaluating the operating state. The proposed method is validated in a real, hot strip rolling mill process. The results show that the proposed method improves the evaluation accuracy by 54.72% compared with five methods that do not fully use the OIVs.

Functional properties of plastic deformation resistance of 12Kh18N10T steel

The resistance of metals and alloys to plastic deformation has functional properties, since it depends on the history of the development of deformation over time. This is especially true for hot deformation processes. At the same time, complexity of the mathematical description and lack of the necessary experimental equipment for a long time did not allow us to design functionals of this type. Currently, due to the emergence of multifunctional research complexes like Gleeble, such an opportunity has appeared. Accordingly, a methodology was developed to study the functional properties of the resistance of metals and alloys of plastic deformation, which was applied to the study of 12Kh18N10T steel. The choice of steel grade is due to the fact that the behavior of austenitic stainless steel during plastic deformation differs significantly from carbon steels. On the other hand, at present, more and more attention is being paid to the production of metal products from stainless steels. This is due, on the one hand, to the tighte­ning of the operating conditions of metal products, the development of new areas of their application and, on the other hand, a fairly high share of imports in the market of products made of austenitic stainless steels. Therefore, the study of the technological properties of such metals and alloys is relevant. At the same time, it should be noted that the most significant functional properties of the metal resistance to plastic deformation are manifested during hot deformation under continuous rolling conditions. Therefore, in this paper, the temperature range of hot plastic deformation is investigated. The results obtained can be used to determine the energy-power parameters in such processes as continuous rolling of strips in the finishing groups of strands and continuous rolling of sleeves in the lines of modern pipe rolling units.

Iterative Convergence for Solving the Exit Plastic Zone and Friction Coefficient Model of Ultra-thin Strip Rolling Force

Iterative Convergence for Solving the Exit Plastic Zone and Friction Coefficient Model of Ultra-thin Strip Rolling Force

Research on nonlocal contact stress at deformation zone in lubricated cold strip rolling

Research on nonlocal contact stress at deformation zone in lubricated cold strip rolling

Prediction of steel strip flatness based on the difference in drawing coefficients along its width during steel strip rolling

The paper presents a brief overview of approaches to calculating flat strip shape defects. It is shown that the most important technological factors in forming a flat sheet are the difference in draw bars across the strip width and the inter-roll gap profile, which depends mainly on elastic deformations that are uneven along the barrel length. The elastic deformations of the working roll surface were simulated, which, together with its thermal profile and wear, made it possible to estimate the transverse profile of the rolled product. The process of deformation of a set of rolls in a quarto stand was studied in the ANSYS Mechanic program using the Static Structure module. The results of calculating the elastic deformations of the roll surface in contact with the deformed strip with varying parameters over a wide range of values made it possible to obtain a statistically reliable equation for estimating the roll barrel profile in the deformation zone and the transverse profile of the rolled product. The obtained roll profile was used to study the formation of the flatness defect “waviness” using the DEFORM-3D program. It was carried out by simulating the rolling of a steel strip with a given transverse profile in profiled roll barrels. On the finished strip, the amplitude of the flat shape defect was estimated by comparing the vertical displacements of the strip section at its edge and in its middle at the exit from the rolls. Using a well-known technique, the amplitude of the “wave” and “box” was also calculated. The assessment was carried out on the basis of the difference in the elongation coefficients across the strip width. The results of the assessment and modeling of the rolling process showed very close results, which confirms the possibility of calculating the flatness parameters by the difference in the strip elongations across its width using a well-known formula.

Generalisation of the hydrodynamics model method for hot and cold strip rolling application

The present work constitutes a generalization of the hydrodynamic model used to predict the pressures and the rolling speeds during the hot rolling of aluminum and copper strips. The hydrodynamic model with a linear behavior (Newton viscous) of the materials shows good predictions in the literature but its applicability is questionable in non-linear cases, when the materials exhibit viscoplastic or plastic behavior. This work extends the model to accommodate non-linear cases commonly encountered in rolling models (viscoplastic and plastic behaviors). The obtained results are in good agreement with experimental data from the literature. The validated model can, therefore, be considered an enhanced hydrodynamic model for predicting pressures and velocities during both hot and cold rolling of thin strips.

Impact of boron and titanium on the mechanical properties and recrystallization behaviour of low carbon cold rolled and batch annealed HSLA steels

This study investigates the impact of boron (B) on the mechanical properties and recrystallization behaviour of cold rolled and batch-annealed titanium (Ti) microalloyed high-strength low-alloy (HSLA) steels. HSLA steels are essential in industries such as automotive and construction due to their superior mechanical properties and cost-effectiveness. The addition of microalloying elements, particularly Ti, has shown significant promise in enhancing these properties through mechanisms like precipitation strengthening and controlled recrystallization. However, the role of B in this context remains underexplored. Here, three alloy compositions were systematically examined: a reference low carbon steel base alloy with no Ti or B (Ref), the base alloy with added Ti (Ref + Ti), and the base alloy with both Ti and B additions (Ref + Ti + B). The findings showed that microalloying with Ti + B can provide excellent strength improvements in the hot rolled strip, mainly due to increased hardenability that promotes the formation of finer ferrite grains with a high dislocation density. However, the recovery and recrystallization behaviour is such that it is not possible to reproduce these benefits after cold rolling and batch annealing, highlighting the complexity of optimizing microalloying strategies for cold-rolled and batch annealed products. The insights gained from this study provide a deeper understanding of the mechanisms governing the recrystallization of Ti and B microalloyed HSLA steels, paving the way for the development of advanced materials with tailored properties for critical applications.

Integrated AGC Approach for Balancing the Thickness Dynamic Response and Shape Condition of a Hot Strip Rolling Control System

Thickness and shape are two significant indices in the tandem hot strip rolling process. Excessive thickness correction can cause rolling force imbalance, leading to deteriorated shape conditions. Aiming at this problem, we propose a new monitor automatic gauge control (M-AGC) with consideration of the rolling force distribution to not only keep the shape condition but also improve the robustness of the rolling process. First, the M-AGC with the Smith predictor control structure was studied. Second, based on the rolling force and thickness correction redistribution algorithm, shape balance automatic gauge control (SB-AGC), the phenomenon of rolling force imbalance was improved. Third, the transient response was improved by adding a command prefilter to the upstream stands, which is asynchronous shape balance automatic gauge control (ASB-AGC). The proposed algorithms can be applied to all steel grades and are easy to implement. Finally, cross-validation was conducted through numerical simulations and application results, confirming the alignment between the theoretical derivation and practical implementation. The simulation results show improvements in both the rolling force balance and the thickness response. The practical application results also confirm that better flatness conditions and thickness response can be achieved, significantly reducing the amount of head-end cutoff losses.

Relationship between tension and vertical vibration of roll system of twenty-high rolling mill

Abnormal vibration of the roll system seriously affects the quality of the rolled product and even the occurrence of strip breakage. There are many reasons for roll system vibration, such as roll damage, roll bearing failure, and fluctuations in rolling parameters. Especially for 20-roll high-precision ultra-thin strip mills, a key condition for strip rolling is to apply substantial inlet and outlet tension, with the impact of tension fluctuation increasing as the strip becomes thinner. In this paper, firstly, a dynamic rolling force model that accounts for tension fluctuations and vertical vibrations is established. Subsequently, a vertical vibration dynamics equation for the roll system of the twenty-high rolling mill was established. Then the rolling force model was substituted into the dynamics equation to investigate the relationship between tension fluctuations and roll system vibrations. The results indicate that: (1) Tension fluctuations can cause vibrations in the roll system. With the same fluctuation amplitude, the amplitude of the roller system vibration caused by the inlet tension can reach 10 times the amplitude of the roller system vibration caused by the outlet tension; (2) The vibration amplitude is affected by both the tension magnitude and the fluctuations amplitude and it is mainly influenced by the tension fluctuation when the tension magnitude changes are not significant; (3) Fluctuations in inlet and outlet tension will reduce the damping term and stiffness term, respectively, which increases the main resonance amplitude. Finally, the effectiveness of the model is verified by the experiment. The average inaccuracy between the simulated and measured vibration amplitudes is 13 %.

Analysis and Prospects of Lubrication and Friction Characteristics in Cold Strip Rolling: A Review

Lubrication and friction are the core processes in cold strip rolling, which are the key links to realizing the stable production of high‐quality strips, reflecting country advanced level in rolling technology. This review investigates the crucial properties of lubrication and friction in cold strip rolling by analyzing the mechanism, characterization methods, and influencing factors. The lubricant forms an oil film on the surface of rolls and strips based on the lubrication dynamics and tribology theory, changing the asperity contact state in the loaded roll gap, leading to changes in friction characteristics. Oil film thickness and coefficient of friction (COF) are crucial parameters for characterizing and judging the characteristics of lubrication and friction, theoretical calculations have become the core analytical method, and the study of the measurement method is still a great challenge. Parameters like rolling speed and oil viscosity affect the lubricant distribution and asperity contact in the loaded roll gap, changing the lubrication and friction state. The influence of parameters is strongly linked to the experimental or rolling environment. Prospective research trends on lubrication and friction in cold strip rolling are presented based on the status of research on lubrication and friction characterization.

Vertical vibration analysis of rolling interface based on dynamic rolling force with variable friction characteristics

This study investigates the impact of variable friction characteristics at the rolling interface on the vertical vibration of plate and strip rolling mills. Based on the optimized Karman equilibrium theory, a dynamic rolling force model considering the front and back tension, elastic stretching, and rolling speed was established. The amplitude-frequency response equation of rolling mill system is solved by multi-scale method, and the influence of main parameters on vertical vibration of rolling mill system is analyzed. The results show that the increase of the first stiffness coefficient of dynamic rolling force leads to the decrease of the principal common amplitude of the system. On the contrary, when the third stiffness coefficient increases, the system exhibits a jump phenomenon. When the third stiffness coefficient of dynamic rolling force is reduced within a certain range, a stable and unique solution is obtained without jumping phenomenon. Moreover, the smaller the damping coefficient of the upper and lower roller system is, the larger the vibration amplitude is and the jump phenomenon occurs. Decreasing the external disturbance force can effectively reduce the system’s vertical vibration amplitude and suppress the resonance. In addition, with the change of external disturbance force, the roll system of the rolling mill shows a variety of complex motion states, such as periodic motion, double-periodic motion, and chaotic motion. The research results provide an effective theoretical reference for the suppression of vertical vibration of rolling mill.