This paper presents the latest advancements in the production of SFLH (Steel Foil Lacerable by Hand,SFLH) and BMF (Blown Metal Foil,BMF) using rolling techniques. It defines the thickness ranges for various thin strips, super-thin strips, ultra-thin strips and foils. The process characteristics of rolling SFLH and BMF under conditions approaching the theoretical MRG (Minimum Rolling Gauge,MRG) are discussed. Several formulas for calculating MRG are introduced and compared, including the Stone formula, the LTAR formula which accounts for speed ratio differences, and the Xiao-Hong formula based on Fleck′s ultra-thin strip rolling theory. Approximate estimation formulas and curves illustrating the relationship between work roll diameter and MRG under both synchronous and asynchronous rolling conditions are provided, along with roll diameter, thickness, and speed ratio diagrams. Related theoretical issues such as the suitable rolling thickness of sheet and strip materials,and the mechanical model of negative-gap rolling are also discussed. Typical applications of SFLH and BMF in copper foil, aluminum foil, stainless steel foil, as well as in the electronics and semiconductor industries, new energy sectors, and precision structural component micro-manufacturing are introduced. Finally, future development directions for rolled BMF are outlined.

Driven by the burgeoning demand for ultra-thin, high-strength, and difficult-to-deform metal materials in high-end manufacturing sectors such as aerospace, new energy, and electronic information, multi-high mills have garnered increasing attention due to their unique advantages. This paper systematically reviews the historical evolution, fundamental principles, and current research status of multi-high mills. It specifically analyzes the characteristics and distinctions between the two mainstream configurations of the 18-high mill and 20-high mill in terms of roll system structure, adjustment mechanisms, and engineering applications. Furthermore, this study summarizes the latest research advancements concerning high-precision physical modeling, the mechanisms and control strategies for strip shape and rolling instability, and intelligent prediction and control models. This work aims to enhance the understanding of multi-high mills and serve as a valuable reference for future research and engineering applications.

Stable production of high-strength, ultra-thin cold-rolled strips places extremely high demands on rolling mill performance.Addressing the challenge of frequent and unpredictable strip warpage defects in S6-high cold rolling mill during the production of such products, this paper proposes a strip warpage prediction model that integrates physics-based simulation with data-driven approaches.First, the kinematic mechanism of self-excited crossing and misalignment of work rolls, induced by complex contact-friction coupling within the unique floating work roll configuration of the S6-high cold rolling mill, is thoroughly analyzed.Second, a roll-strip coupled finite element model is constructed, incorporating roll system elastic deformation, strip elastoplastic flow, and contact nonlinearity.The reliability of the model is rigorously validated by comparing simulated results with industrial measurements of post-rolling strip profiles and thickness reduction.To alleviate the scarcity of onsite samples for abnormal instability conditions, the Latin Hypercube Sampling (LHS) method is employed to design experiments for key disturbance variables, such as work roll misalignment and crossing angles, thereby constructing a high-fidelity warpage behavior database covering non-self-stabilizing conditions.Subsequently, a nonlinear warpage prediction model is established using the CatBoost ensemble learning algorithm with an ordered boosting mechanism.The results demonstrate that the model achieves a coefficient of determination R² of 0.921 and a root mean square error (RMSE) of 3.81×10^-5 mm on the test set, significantly outperforming traditional algorithms such as XGBoost and SVR.Finally, an interpretability analysis based on SHAP values is conducted to quantitatively identify the key sensitive features leading to warpage in high-strength thin strips.This study provides a novel approach to controlling warpage behavior under non-self-stabilizing states in S6-high cold rolling mill.

18-high mill has a small diameter of work roll, and the side backup rolls on both sides of the work roll greatly increase the rigidity of the rolling mill and avoid the elastic deformation of the rolls, so it is an ideal equipment for producing thin-gauge strip. In order to investigate the deformation behavior of roll and strip in cold rolling process and to control strip shape with high precision and improve strip quality, a three-dimensional finite element model with equal proportion and high precision was established by using finite element simulation software ANSYS/LS-DYNA and LS-PrePost, taking a 1 250 mm 18-high tandem cold rolling production line of a factory as the research object. Based on the established finite element model, the influence of the position of side backup roll on the stiffness of rolling mill and the shape of each regulating mechanism is systematically studied. The experimental results show that the longitudinal stiffness of the roll system decreases with the increase of the included angle of the roll system, the horizontal displacement of the side backup roll and the transverse displacement of the middle roll; The influence of intermediate roll transverse movement and intermediate roll bending on transverse stiffness is far greater than the other two; The rolling stiffness of work roll is most affected by the horizontal displacement of side backup roll. With the decrease of roll angle, the increase of middle roll transverse movement and the increase of middle roll bending, the strip crown and edge thinning decrease, the strip thickness distribution along the width direction is more uniform, and the control effect of roll angle and middle roll transverse movement on the secondary wave pattern of strip is more obvious.

Edge drop and flatness, as important indicators of cold-rolled silicon steel, directly affect the product′s dimensional accuracy and yield rate.For a steel mill where the shape quality ofsilicon steel ultra-thin strip produced by the Sendzimir mill does not meet production needs, field process parameters were used to establish an explicit dynamic three-dimensional finite element model of the integrated roll system-strip steel via ANSYS/LS-DYNA software, with field measurement data employed to verify the model′s accuracy.Strip edge drop and flatness were used as evaluation indices of strip shape to determine the influence of rolling parameter variations on the metal flow of strip under stable rolling conditions.The results indicate that both increasing the strip width and reducing the reduction can alleviate edge thinning; however, the ability of tension adjustments to affect edge thinning is limited,and changes in roll speed exhibit no significant effect on edge thinning, while increased tension markedly improves flatness.The comprehensive flatness decreased from 27.09 IU to 6.77 IU.The results provide process guidance for the effective shape control of thin-gauge silicon steel strips during production.

Inconel718 alloy strip serves as a critical material for manufacturing fuel assembly grid springs in pressurized water reactors. However, the strip frequently encounters shape defects during 20-high mill rolling processes due to the material's high work-hardening rate and deformation resistance. To investigate the influence of key rolling parameters on the strip shape and develop optimization strategies, this study established a rolling simulation model integrating a 20-high mill roll system with Inconel718 alloy strips using ABAQUS finite element software. The effects of friction factor, rolling tension, and axial shifting amount of the first intermediate roll were analyzed, and the ranges of critical rolling parameters were determined. The results show that as the friction factor or rolling tension increases, the variance of transverse thickness displacement decreases, the residual stress distribution becomes more uniform, while edge drop and crown remain nearly unchanged. When the friction factor is controlled at 0.14, the variance of transverse thickness distribution is reduced to 0.000 9. With a rolling tension of 200 kN, the variance decreases to 0.001 1. Increasing the axial shifting amount of the first intermediate roll effectively reduces edge drop and crown. At a shifting value of 65 mm, edge drop and crown decrease to about 3.68 μm and 14.37 μm, respectively. The recommended parameter ranges for improving flatness are as follows:friction factor of 0.14, rolling tension of 180-200 kN, and axial shifting amount of 40-65 mm.

The L-warping issue caused by the uneven stress distribution on the upper and lower surfaces of the strip is a key factor restricting the improvement of strip shape quality in high-strength steel rolling using precision rolling mills. Since strip production involves numerous interrelated factors, traditional numerical simulations and on-site experiments are not effective in analyzing the causes and mechanisms of L-warping defects, making it difficult to meet the strip shape control requirements of high-precision rolling mills. To enhance the ability to regulate strip shape warping defects, this study established an integrated elastic-plastic coupling finite element model of the eighteen-roll stand and the strip. By analyzing the causes of uneven stress distribution on the upper and lower surfaces of the strip, key factors including work roll offset, slab thickness before rolling, and reduction rate were selected for quantitative analysis. The effects of these factors on L-warping deformation of the strip and the plastic deformation behavior of the strip were studied. The analysis results of multi-parameter varying working conditions indicate that the offset of the work rolls has the greatest impact on the post-rolling warping. A change in the offset within the range of ±3.0 mm can induce a warping deformation of ±11 mm. Under the same work roll offset, the warping behavior caused by the asymmetric offset mode of the rolls shows regular differences. Increasing the entry plate thickness reduces the post-rolling warping and improves the warping behavior. Increasing the reduction results in the warping initially increasing and then decreasing, ultimately stabilizing. Therefore, this study suggests strengthening the control accuracy of the work roll position, enhancing its self-maintenance, reasonably configuring the rolling process parameters, and planning the process parameter windows to weaken the warping deformation influenced by the base material and process parameters.

Taking the 20-high Sendzimir mill as the research object, this paper establishes an integrated finite element model of roll system and rolled stock. Through multivariate simulation, the effects of shape control mechanisms including radial adjustment of backup rolls (As-U-Roll), taper and axial shifting of first intermediate rolls, as well as rolling process parameters on the flatness of grain-oriented silicon steel are investigated. The results show that the adjustment of As-U-Roll for the end back-up bearings can effectively restrain edge drop, while the adjustment of other back-up bearings significantly improves the central flatness. The influence of As-U-Roll adjustment becomes greater closer to the central area of backup rolls. The collaborative adjustment of taper and shifting stroke of first intermediate rolls can effectively mitigate edge thinning of strip steel. In addition, process parameters such as strip width, thickness, tension and rolling speed exert non-linear effects on strip flatness. For grain-oriented silicon steel, cold rolling flatness control and material properties shall be comprehensively considered to inhibit the initiation and propagation of edge cracks and realize stable rolling.

At a certain steel plant, the S6-high mill frequently encountered strip shape problems when producing wide ultra-thin strips. The strip shape acceptance rate was only 73.3%, leading to a significant drop in the product acceptance rate and severely restricting product quality and production efficiency. Analysis revealed that this issue is closely related to the setting of key parameters of the roll system. To address this problem, the whale optimization algorithm was adopted and optimized based on practical scenarios to search within a multi-dimensional parameter space. While considering equipment and process constraints, the optimal combination of key roll system parameters that minimizes strip shape deviation was identified. The resulting optimal roll system parameters were then applied to the actual production line for industrial verification. On-site verification results showed that the optimized parameters significantly improved the strip shape. Taking the shape target value of 5 IU as the criterion, the shape deviation along the entire length of the strip remained strictly stable within the target range after optimization. No defects exceeding the tolerance were detected during the production process, effectively solving the problem of low qualification rate of wide ultra-thin strips.

To address the issues of uncontrollable rib waviness and higher-order strip shape defects when rolling ultra-high-strength steel with wide widths on an 18-high single-stand mill, this paper establishes finite element models for both the 18-high single-stand mill and CVC cold mill and systematically compares their strip shape control characteristics. The study finds that while the transverse stiffness of the roll gap in the 18-high single-stand mill is smaller than that of the CVC cold mill, its bending roll control capability and roll shifting regulation effectiveness are superior. Based on these findings, the paper proposes three core optimization measures:first, designing a segmented adaptive tapered intermediate roll with a 250 mm shifting stroke to achieve precise edge pressure control for multi-width strip; second, optimizing the large fillet transition zone of the tapered section and adopting a sine curve grinding process to effectively mitigate stress concentration and improve strip shape quality; third, innovatively proposing a "bending roll dominance-shifting roll compensation" primary-secondary collaborative control strategy, where 76% of the symmetric quadratic strip shape deviation is regulated by the faster-responsive bending rolls, while only 24% is compensated by roll shifting, fundamentally suppressing rib waviness defects caused by excessive roll shifting. This research provides an effective theoretical foundation and engineering solution for addressing the "bottleneck" plate shape challenges in producing ultra-high-strength steel with 18-high mill.

To address the challenges of strong nonlinearity, parameter time-variation, and insufficient adaptive capability of traditional methods in hydraulic servo roll gap control during thin strip and ultra-thin strip rolling processes with multi-high mill, this paper proposes an intelligent control method integrating Bayesian estimation with deep reinforcement learning. A control-oriented mechanistic model of the hydraulic servo system for multi-high mills is established. Bayesian estimation is employed to identify key system parameters, achieving a mean square error of 1.788×10^-7 mm². On this basis, a deep reinforcement learning controller based on a multi-head attention mechanism and the TD3 algorithm is designed. The roll gap control problem is formulated as a Markov decision process through incremental action definition and state space construction incorporating historical deviations and process parameters. Simulation results demonstrate that the proposed method converges faster than the standard DDPG algorithm, reduces the tracking error fluctuation range to -3.4×10^-3~1.2×10^-3 mm, and significantly improves control accuracy. This provides intelligent control technical support for high-precision thin strip and ultra-thin strip rolling in multi-high mills.

Significant differences in thermal crown of work rolls occur in a 20-high mill of a steel plant due to different configurations of the cooling system for upper and lower roll assemblies, resulting in poor flatness of the rolled strip. To solve this problem, this paper first establishes a flatness prediction model considering the asymmetric thermal roll profile of the upper and lower roll systems of the 20-high mill, and systematically analyzes the influence of the original roll profiles of the work rolls and first intermediate rolls on the strip flatness. On this basis, a multi-objective control function is constructed, which takes the coincidence degree between the actual strip flatness and the target flatness as the core objective, and simultaneously considers the stress concentration of inter-roll pressure and the suppression of edge thinning. An optimization design method for the original crown of the work rolls and the end taper of the first intermediate rolls of the 20-high mill is formed. After applying this method to on-site production practice, the flatness control ability of the rolling mill is improved, and the flatness problem caused by the asymmetry of the thermal roll profiles of the upper and lower roll systems is solved. The on-site application shows that the average flatness of the finished strip is reduced from 15.3 IU to 8.5 IU, and the flatness improvement effect is significant.

Due to the size effect, the mechanical properties of ultra-thin stainless steel strips differ from those of conventional strips, and their tensile leveler and processes have unique characteristics. However,the domestic theoretical foundation in this field is weak, and such equipment and process models primarily rely on imports, which severely impacting the production of new varieties and high-quality ultra-thin strips. In this paper, the metallographic structure, mechanical properties, and Bauschinger effect of ultra-thin strip were analyzed. By integrating tensile bending theory with practical applications, a shearing-folding experimental device was developed that simulates repeated loading deformation with small bending radius, created a tension leveller with a minimum thickness of 0.01 mm, width of 200 mm, maximum yield strength of 1 000 MPa and elongation 3%,and a tension leveling model was eatablised. The research methods and outcomes can provide reference for the independent development of a tension leveller for ultra-thin strips.

Focusing on CoCrNi medium-entropy alloy (MEA) and addressing challenges in fabricating and regulating the performance of its ultra-thin strips, this study employed the accumulative roll bonding (ARB) process to overcome conventional rolling limits, successfully producing ultra-thin strips with thicknesses of 0.1-0.27 mm. It was found that with decreasing thickness, grains elongated significantly along the rolling direction, accompanied by synchronous increases in dislocation density and substructure fraction, leading to enhanced strength but reduced plasticity. Specifically, the 0.1 mm strip exhibited a tensile strength of 1 295 MPa and an elongation of merely 2.5%. To optimize comprehensive performance, 750 ℃ annealing treament was further conducted:short-time annealing (5-15 min) is dominated by recrystallization as the primary mechanism, resulting in balanced properties with a tensile strength of approximately 950 MPa and an elongation rate of about 35%. Prolonged holding time to 30 min enhanced internal recovery, increasing the fraction of subgrains and deformed grains to 48.6%; although grain coarsening slightly raised strength to 1 001 MPa, plasticity significantly decreased to 22.2%. This study revealed the correlation between microstructural evolution and mechanical properties of CoCrNi MEA ultra-thin strips, providing important theoretical basis and technical support for their application as ultra-thin metallic materials in high-performance micro/nano devices.

Invar 36 alloy ultra-thin strips, as a key material for fine metal masks (FMM), directly determine the pixel precision and display performance of orgarlic light-emitting diode,(OLED) screens through the quality of the micro-hole structures. This paper systematically studies the influence of different processing techniques on the surface morphology, microstructure and mechanical properties of the base plate, solid plate and hole plate of invar 36 alloy ultra-thin strips. The research results show that annealing treatment will change the rolling texture and surface roughness of the invar 36 alloy ultra-thin strip surface, and these features will be inherited and highlighted in the subsequent corrosion thinning process, playing a decisive role in the final hole formation. Compared with high-temperature annealing, low-temperature stress relief annealing can effectively reduce the roughness of the base plate and achieve the best surface quality. Low-temperature stress is an ideal process for achieving uniform hole formation. Microscopically, increasing the proportion of recrystallized structure, enhancing the preferred orientation of (111) and (220) crystal planes, and increasing the content of A texture components are conducive to promoting the uniform formation of hole structures. Annealing treatment maintains the tensile strength basically unchanged while significantly reducing the yield strength and increasing the strain rate, especially low-temperature annealing performs better in improving the plasticity of the material. This paper reveals the influence mechanism of FMM hole formation quality from the perspectives of surface characteristics and microstructure, providing a theoretical basis and process optimization path for controlling material properties from the process source, suppressing etching anomalies, and improving the qualification rate of FMM products.

Carbon-based films are widely used in fuel cell bipolar plates due to their excellent corrosion resistance and chemical stability. In this paper, amorphous carbon (a-C) films were deposited on SS316L stainless steel ultra-thin strips by magnetron sputtering technology to enhance the corrosion resistance of proton exchange membrane fuel cell (PEMFC) bipolar plates. A Taguchi orthogonal design combined with SEM and electrochemical analyses was employed to evaluate the effects of working pressure, sputtering power, substrate bias, and deposition time. The optimal process parameters were determined using the TOPSIS multi-criteria decision-making method as 1.5 Pa working pressure, 150 W sputtering power,-250 V bias voltage, and 60 min deposition time. Under these conditions, the corrosion current density decreased to 1.61×10^-6 A/cm², corresponding to a corrosion rate of 0.018 mm/a. The results confirm that optimized magnetron sputtering significantly improves the corrosion resistance of stainless steel ultra-thin bipolar plates.

Aiming at the strip-like gray-white color difference defects appearing on SUS430 J1L ultra-pure ferritic stainless steel strip used in luxury automotive trim after finishing rolling, experimental measurements confirmed that the primary cause of these color defects is the higher surface roughness of the affected strip areas compared to normal regions. Surface observations further revealed a higher density of scratches in the defect regions. By comparing the distribution of roll surface discoloration with the positions of color-difference defects on the strip, and by analyzing the formation mechanism of roll surface discoloration, it was clarified that the surface roughness variation of the strip was closely related to the lubrication state in the roll bite during cold rolling. The difference in lubrication state was further attributed to the non-uniform distribution of Cr oxide films with different compactness on the strip surface after bright annealing. To effectively eliminate this type of color-difference defect, the uniformity of the Cr oxide film was improved by strictly controlling the annealing dew point temperature below-60 ℃ and maintaining a cooling rate not lower than 35 ℃/s. Meanwhile, the oil film uniformity during rolling was enhanced by reducing the rolling speed, increasing the rolling force, and selecting a low-viscosity rolling oil with sufficient extreme-pressure additives. These measures effectively mitigated the color-difference defects on the surface of ultra-pure ferritic stainless steel and improved the surface quality of the stainless steel strip.

Aiming at the problems of poor flatness, excessive transverse thickness deviation and within-strip thickness variation, as well as the resulting strip breakage during the production of cold-rolled silicon steel, this paper takes a Sendzimir twenty-high rolling mill of Henan Iron and Steel Group as the research object, and systematically analyzes the influences of raw materials, processes, equipment and control measures on strip flatness accuracy. By establishing raw material inspection and preheating systems, optimizing rolling process parameters including pass reduction rate, tension and rolling speed, improving roll management and grinding accuracy, and adopting a coordinated control strategy for intermediate roll shifting and back-up roll crown, the strip flatness quality is greatly improved and the risk of strip breakage is effectively reduced. Industrial practice shows that the finished product rate, first-grade product rate and equipment operation rate of the mill are significantly increased after optimization, which verifies the engineering effectiveness and practicability of the proposed flatness control technology.

Ultra-thin stainless steel precision strip serves as a key foundational material for applications in flexible displays, flexible photovoltaics, highend electronic components, aerospace, and related fields. However, its production has long been hindered by challenges such as unstable thickness control, poor strip shape, susceptibility to surface ridging, and skidding caused by residual rolling oil. Based on the industrial production practice of the precision 20-high rolling mill at Ningbo Baoxin, this study systematically addresses these core technical difficulties through research on rolling schedule optimization, improved thickness control strategies, roll system configuration development, design of strip shape target curves, and control of surface residual oil. An integrated technical solution has been established, encompassing high precision thickness control, shape regulation, ridging suppression, and skidding prevention. This approach has enabled the stable mass production of 0.03-0.05 mm wide ultra-thin strips and pushed the minimum achievable thickness down to 0.02 mm. The results break through the technical barriers in producing wide ultra-thin stainless steel strips and offer practical guidance for process optimization and product upgrading on similar production lines.

The main domestic manufacturers of ultra-thin strip, together with the configuration, technical characteristics and key performance indicators of cold rolling equipment are summarized. The production technologies for thin and ultra-thin strips of Shougang Group are emphatically elaborated, involving high-precision flatness control, surface quality control, tension and threading control, as well as equipment accuracy guarantee technology.Shougang has established a complete full-chain innovation system integrating basic research, process development, equipment integration and industrial application for cold rolling of thin and ultra-thin strips, and possesses remarkable differentiated advantages in product portfolio. Following the development strategy of ultra-thinning, high-end positioning, differentiation, green low-carbon and high added value, Shougang will continuously achieve breakthroughs in limit specification rolling, intelligent manufacturing, green low-carbon production, emerging application fields and international layout.

Ultra-thin silicon steel is a core soft magnetic material for high-efficiency motors and transformers, and also serves as an important indicator of a country's iron and steel industrial capability. This paper reviews the global development status of the ultra-thin silicon steel industry and introduces the self-bonding coating production line of Shougang Zhixin. It discusses the characteristics of ultra-thin silicon steel coated products, key processes and equipment, as well as measures for stable production and product quality control. As the world's largest producer and consumer of silicon steel, China still relies on imports for high-end products, and core manufacturing technologies including precision rolling and surface coating are confronted with technological bottlenecks. Focusing on the current situation of the ultra-thin silicon steel industry, this paper analyzes its technical hurdles and market challenges, and explores approaches for technological breakthrough and industrial upgrading, aiming to provide references for the independent development and high-end transformation of China's ultra-thin silicon steel sector.

Aiming at the problems of poor operation flexibility, easy wear and high maintenance cost caused by the copper strip limit adopted in the existing roll saddle of Sendzimir rolling mill, a structural optimization scheme based on roller assembly is proposed. By arranging evenly distributed cylindrical holes on the side wall of the eccentric disc, the optimized roll saddle is internally equipped with a roller assembly composed of pin shafts, deep groove ball bearings and springs, which realizes the replacement of traditional sliding friction with rolling friction between the eccentric disc and the support ring. Structural design, parameter optimization and performance tests show that the rotational friction torque of the eccentric disc of the optimized roll saddle is reduced by more than 60%, the axial positioning accuracy is improved to the 0.01 mm level, the maintenance cycle is extended by 3 times, and the processing qualification rate is increased from the original 75% to 98%. The optimization scheme effectively solves the core defects of the traditional structure, and provides a feasible way for the design and upgrading of roll system supporting parts of high-precision rolling mills.