Flatness Control Based on Dynamic Effective Matrix for Cold Strip Mills

Steel strips are the main of steel products and flatness is an important quality indicator of steel strips. Flatness control is the key and highly difficult technique of strip mills. The bottle-neck restricting the improvement of flatness control techniques is that the research on flatness theories and control mathematic models is not in accordance with the requirement of technique developments. To build a simple, rapid and accurate explicit formulation control model has become an urgent need for the development of flatness control technique. This paper puts forward the conception of dynamic effective matrix based on the effective matrix method for flatness control proposed by the authors under the consideration of the influence of the change of parameters in roiling processes on the effective matrix, and the concept is validated by industrial productions. Three methods of the effective matrix generation are induced： the calculation method based on the flatness prediction model; the calculation method based on the data excavation in rolling processes and the direct calculation method based on the network model. A fuzzy neural network effective matrix model is built based on the clusters, and then the network structure is optimized and the high-speed-calculation problem of the dynamic effective matrix is solved. The flatness control scheme for cold strip mills is proposed based on the dynamic effective matrix. On stand 5 of the 1 220 mm five-stand 4-high cold strip tandem mill, the industrial experiment with the control methods of tilting roll and bending roll is done by the control scheme of the static effective matrix and the dynamic effective matrix, respectively. The experiment result proves that the control effect of the dynamic effective matrix is much better than that of the static effective matrix. This paper proposes a new idea and method for the dynamic flatness control in the rolling processes of cold strip mills and develops the theory and model of the flatness control effective matrix method.

MENDED GENETIC BP NETWORK AND APPLICATION TO ROLLING FORCE PREDICTION OF 4-STAND TANDEM COLD STRIP MILL

In order to make good use of the ability to approach any function of BP (backpropagation) network and overcome its local astringency, and also make good use of the overallsearch ability of GA (genetic algorithms), a proposal to regulate the network's weights using bothGA and BP algorithms is suggested. An integrated network system of MGA (mended genetic algorithms)and BP algorithms has been established. The MGA-BP network's functions consist of optimizing GAperformance parameters, the network's structural parameters, performance parameters, and regulatingthe network's weights using both GA and BP algorithms. Rolling forces of 4-stand tandem cold stripmill are predicted by the MGA-BP network, and good results are obtained.

Compound control for speed and tension multivariable coupling system of reversible cold strip mill

To weaken the nonlinear coupling influence among the variables in the speed and tension system of reversible cold strip mill, a compound control(CC) strategy based on invariance principle was proposed. Firstly, invariance principle was used to realize static decoupling between the speed and tension of reversible cold strip mill. Then, considering the influence caused by the time variation of steel coil radius and rotational inertia of the left and right coilers, as well as the uncertainties, a CC strategy that is composed of extended state observer(ESO) and global sliding mode control(GSMC) with backstepping adaptive was proposed,which further realized dynamic decoupling and coordination control for the speed and tension system. Theoretical analysis shows that the resulting closed-loop system is global bounded stable. Finally, the simulation was carried out on the speed and tension system of a 1422 mm reversible cold strip mill by using the actual data, and through the comparison of the other control strategies, validity of the proposed CC strategy was shown by the results.

Improvement on strip flatness of cold temper mills by modifying roll contour shape

A study on roll gap profile (strip profile) control was accomplished in a1700 mm single-stand temper mill. Some critical problems such as the deviation of work roll contourcaused by grinding and wear, the effectiveness of work roll bending were discussed. Using a finiteelement model, the effects of roll contours (ground and wear) on strip profile were investigated.The roll bending effect on strip thickness was also analyzed. It is pointed out that there are somespecial features of flatness control in the temper mill: during temper rolling, roll deformation isslight due to small rolling load, and the loaded roll gap profile mainly depends on work rollcontour, while the backup roll has a little effect on gap crown; the effect of bending force ongauge can not be ignored due to the coupling between flatness control and gauge control. A new rollcontour arrangement adaptable to the mill was presented and has been put into practical production.The application of the new set of rolls showed some good results: larger crown control range of workroll bender, higher rolling stability, better strip profile and flatness quality.

STUDY ON STRIP AND ROLL DEFORMATION COUPLING OF COLD STRIP ROLLING ON 4-H MILL

The cold strip rolling process on a 4 h mill is studied by coupling the 3 dimensional plasticity deformation of the strip with the elastic deformation of the rolls. On the conditions of that the width to thickness ratio of the strip is 660 and the exit strip shapes are respectively edge wave, centre wave and good, the computed results of the transverse distributions of the roll gap, the rolling pressure, the inter roll pressure, and the front and back tension agree with the experimental results well. The studing methods and the studied results are of great importance to forming shape theory and guiding the development of shape control technology.

Research and Development Trend of Shape Control for Cold Rolling Strip

Shape is an important quality index of cold rolling strip. Up to now, many problems in the shape control domain have not been solved satisfactorily, and a review on the research progress in the shape control domain can help to seek new breakthrough directions. In the past 10 years, researches and applications of shape control models, shape control means, shape detection technology, and shape con- trol system have achieved significant progress. In the aspect of shape control models, the researches in the past improve the accuracy, speed and robustness of the models. The intelligentization of shape control models should be strengthened in the future. In the aspect of the shape control means, the researches in the past focus on the roll opti- mization, mill type selection, process optimization, local strip shape control, edge drop control, and so on. In the future, more attention should be paid to the coordination control of both strip shape and other quality indexes, and the refinement of control objective should be strengthened. In the aspects of shape detection technology and shape control system, some new types of shape detection meters and shape control systems are developed and have successfully indus- trial applications. In the future, the standardization of shape detection technology and shape control system should be promoted to solve the problem of compatibility. In general,the four expected development trends of shape control for cold roiling strip in the future are intelligentization, coordi- nation, refinement, and standardization. The proposed research provides new breakthrough directions for improv- ing shape quality.

Transverse Distributions of Front and Back Tension Stresses in Cold Strip Rolling

In this paper,such a new lateral displacement function is proposed that the lateral flow velocity is con- tinuous at the entry and the exit of deformation zone.A new kind of finite strip method—the third power B-spline finite strip method—is put forward to simulate strip rolling process.Front and back tension stresses are formulated.The computed results of the transverse distributions of the front and back tension stresses are close to the experimental results.The paper lays a foundation for further analysing the three-dimensional stresses and deformations of strip rolling.

Application of a new feature extraction and optimization method to surface defect recognition of cold rolled strips

Considering that the surface defects of cold rolled strips are hard to be recognized by human eyes under high-speed circumstances, an automatic recognition technique was discussed. Spectrum images of defects can be got by fast Fourier transform （FFF） and sum of valid pixels （SVP）, and its optimized center region, which concentrates nearly all energies, are extracted as an original feature set. Using genetic algorithm to optimize the feature set, an optimized feature set with 51 features can be achieved. Using the optimized feature set as an input vector of neural networks, the recognition effects of LVQ neural networks have been studied. Experiment results show that the new method can get a higher classification rate and can settle the automatic recognition problem of surface defects on cold rolled strips ideally.

Online application of automatic surface quality inspection system to finishing line of cold rolled strips

An automatic surface quality inspection system installed on a finishing lineof cold rolled strips is introduced. The system is able to detect surface defects on cold rolledstrips, such as scratches, coil breaks, rusts, roll imprints, and so on. Multiple CCD area scancameras were equipped to capture images of strip surface simultaneously. Defects were detectedthrough 'Dark-field illumination' which is generated by LED illuminators. Parallel computationtechnique and fast processing algorithms were developed for real-time data processing. Theapplication to the production line shows that the system is able to detect defects effectively.

Surface Inspection System for Cold Rolled Strips Based on Image ProcessingTechnique

A new surface inspection system for cold rolled strips based on image processing is introduced. The system is equipped withtwo different illumination structures and CCD matrix cameras. The structure and image processing of the inspection system are described. Some efficient algorithms for image processing and classification are presented. The system is tested with strip samples fromcold rolling plants. The results show that the system can detect and recognize six common defects of cold rolled strips successfully.

Preset model of bending force for 6-high reversing cold rolling mill based on genetic algorithm

The hydraulic roll-bending device was studied,which was widely used in modern cold rolling mills to regulate the strip flatness.The loaded roll gap crown mathematic model and the strip crown mathematic model of the reversing cold rolling process were established,and the deformation model of roll stack system of the 6-high 1 250 mm high crown (HC) reversing cold rolling mill was built by slit beam method.The simulation results show that,the quadratic component of strip crown decreases nearly linearly with the increase of the work roll bending force,when the shifting value of intermediate roll is determined by the rolling process.From the first pass to the fifth pass of reversing rolling process,the crown controllability of bending force is gradually weakened.Base on analyzing the relationship among the main factors associated with roll-bending force in reversing multi-pass rolling,such as strip width and rolling force,a preset mathematic model of bending force is developed by genetic algorithm.The simulation data demonstrate that the relative deviation of flatness criterions in each rolling pass is improved significantly and the mean relative deviation of all five passes is decreased from 25.1% to 1.7%.The model can keep good shape in multi-pass reversing cold rolling process with the high prediction accuracy and can be used to guide the production process.

Analysis of the cause of crack in cold rolling of QSn6.5-0.1 strip

In order to know the cause of cracks in cold rolling of QSn6.5 0.1 copper alloy strip, a lot of experiments and analysis were done. The microstructure changes of QSn6.5 0.1 were investigated by means of metallurgical microscope. The morphology of cracks and surface defects were examined using scanning electron microscope. Macroscopic residual stresses produced in every process during manufacturing in the QSn6.5 0.1 strip were measured by X ray diffraction method and hole drilling method. The results show that the cracks in the QSn6.5 0.1 cold rolling strip were caused due to the derivation of metallurgical defects, such as SnO 2, S, fine looses,the inverse segregation unable to clear up when milling, and the accumulation of all kinds of resi dual stresses. When the accumulation of the residual stress reaches the material′s breaking strength, the cracks will be generated. Several measures to avoid the development of these kinds of cracks were put forward, such as: controlling the casting technology, improving homogenization annealing procedure (680 ℃/7 h) and milling quality(using the second milling when necessary), working out a more reasonable rolling technology to ensure intermediate annealing in time.

Application of automatic surface inspection system in cold-rolled strip production

The detection and classification of real-time surface defects play an important role in automotive sheet inspection and production. In this paper, an automatic surface inspection system （ASIS） based on signal processing in Baosteel NO. 4 cold-rolled plant is briefly presented. We demonstrate that the strip surface defect properties such as image, type, pitch, and position can be accurately calculated and classified by the automatic surface inspection system. In the manufacturing of the high-quality cold-rolled strips, it is necessary that the real-time surface defects can be detected and transferred by the automatic surface inspection system combined with annealing lines and recoiling lines.

Backup roll contour of a SmartCrown tandem cold rolling mill

SmartCrown was a new system developed by VAI for improving the strip profile and flatness control first applied in 1700 mm tandem cold rolling mills at Wuhan Iron ＆ Steel （Group） Corporation （WISCO）. After tracing and testing, the application of the conventional crown backup roll matching the SmartCrown work roll of the production mill led to heavy and nonuniform wear, and the edge spalling of the backup roll often occurred. A 3-dimension finite element model of roll stacks was established, which was used to analyze the above-mentioned problems, and it was found that the main reason was the highly nonuniform contact pressure distribution between the work roll and the backup roll. A new FSR （flexible shape backup roll） was developed and applied in 1700 mm tandem cold rolling mills. A lot of good actual effects of FSR, such as evident improvement in profile and flatness of strips, non-occurring edge spalling, wear uniform, and remarkable decrease in roll consumption were validated by long-term industrial applications.

Development of the entire roller inlayed block intelligence cold strip shape meter and its industrial application

The entire roller inlayed block intelligence cold strip shape meter is developed successfully in this paper,which can stably work chronically in the cold rolling workshop,the independent innovation of the key technology of cold strip shape measuring,the foreign technical monopoly and blockade are broken through.The structural form which is different from the international popular segmented detection roller is put forward,the entire detection roller inlayed block is developed,a group of elastic blocks in that the sense organs are installed are inlayed in the radial symmetry rectangular grooves of the detection roller body,the entire roller structure is composed of elastic pieces and the roller body,the scratch of the strip surface due to different thermal expansion of the traditional detection roller measuring unit is avoided effectively.The signal transmission form which is different form the international popular dry slip ring is put forward,the spray wet slip ring is developed,slip ring and detection roller can be taken down and installed as possibly as fast,so the maintain is convenient,while through the section auto-spray cleaning,lubrication and cooling, the service life is remarkable improved and the outside interference signal is reduced.The signal processing form which is different form the international popular gathering card is put forward,the embedded DSP shape signal processing hardware system is developed,the electromagnet,temperature,humidity and vibration's interference of industry practice to shape transmission signal can be effectively avoided,which can guarantee the instantaneity and measured precision of shape measured signal.The shape signal processing software system whose function contains error compensation,pattern recognition,establishment of the target shape and the closed-loop control calculation is built,the shape meter' computer human interaction is friendly,and function of shape meter is strong,at the same time the intellectualized level of the shape meter is improved.Now,this shape meter has been successfully applied on the 1 250 mm cold strip mill of Angang Steel Company Limited,the long-term operating testing is done,every guide line achieves the anticipative effect,the measuring precision is high and the measuring signal is stable and reliable,the shape meter is tested on high speed,big tension,changed wrap angle and big depressed complicated working conditions,any scratch of the detection roller surface and the strip surface is not appearing,it can completely adapt well to the industrial production environment,reaching the international advanced level.

Applied principle of minimum potential energy in analyzing buckle phenomenon of cold rolled strip

When solving buckling type based on minimum potential energy, it is first to make hypothesis for strip buckling type. Under the simple strain condition, buckling type and strain distribution have a certain similarity, so the hypothesis is reasonable comparatively. However, under the complicated strain condition, it is difficult to give more reasonable buckling type. Moreover, the existing algorithms usually ignore the effect which the transverse stress and the shear stress have on the buckling type. After assuming strip was only affected by shear stress for the edge wave and affected by both transverse stress and the shear stress for the center wave in the paper, the buckling form of strip under simple strain situation was calculated. It was seen from the calculating result that wave height and half wavelength were smaller than those of the existing algorithms, and the wave height and half wavelength of edge wave were all bigger than those of center wave in the same stress distribution. Secondly, a more reasonable hypothesis method of buckling type for the complicated stress distribution was put forward. After analyzing, the result showed that it was more reasonable by using the optimizing algorithm.

STUDY OF THE 3-DIMENSIONAL STRESSES OF COLD STRIP ROLLING UNDER CENTRE WAVE

On the conditions ofthe width to thickness ratio 625 and the centre wave the 3-dimensional stresses distributions of cold strip rolling are studied by using the third power spline function finite strip method. The computed results of the rolling pressure, the 2-directional friction stresses and the front and back tension stresses agree with the experimental results well. In this paper, the frictional stresses of stagnation zone are computed by using preliminary displacement principle and the computing precision is improved.

铝带冷轧机组结构技术改进与优化

我国每年铝制品的消耗总量突破1400万吨,在市场需求不断增长的同时,提高铝制品产量成为许多企业追求的目标。铝带冷轧机作为一种重要的铝制品生产设备,如何优化冷轧机的设计,提高生产效率,是从业人员需要深入研究的问题。本文通过对铝带冷轧机设备情况和生产工艺进行研究,提出了改进优化建议,旨在帮助相关生产企业提升生产效率,创造更多的经济价值。

Intelligent representation method of image flatness for cold rolled strip

Real flatness images are the bases for flatness detection based on machine vision of cold rolled strip.The characteristics of a real flatness image are analyzed,and a lightweight strip location detection(SLD)model with deep semantic segmentation networks is established.The interference areas in the real flatness image can be eliminated by the SLD model,and valid information can be retained.On this basis,the concept of image flatness is proposed for the first time.An image flatness representation(IFAR)model is established on the basis of an autoencoder with a new structure.The optimal structure of the bottleneck layer is 16×16×4,and the IFAR model exhibits a good representation effect.Moreover,interpretability analysis of the representation factors is carried out,and the difference and physical meaning of the representation factors for image flatness with different categories are analyzed.Image flatness with new defect morphologies(bilateral quarter waves and large middle waves)that are not present in the original dataset are generated by modifying the representation factors of the no wave image.Lastly,the SLD and IFAR models are used to detect and represent all the real flatness images on the test set.The average processing time for a single image is 11.42 ms,which is suitable for industrial applications.The research results provide effective methods and ideas for intelligent flatness detection technology based on machine vision.

一种液驱冷轧机辊热凸度动态SVR预测模型

辊热凸度是当轧件发生变形或因摩擦作用生成热量而引起轧辊温度上升并由此产生轧辊外形尺寸改变的现象。为了降低液驱冷带轧机辊随温度的变化影响,综合分析了辊热凸度因素引起的变形效果差异性。选择液驱轧机作为测试对象,从热凸度作用原理方面考虑,同时根据实际获得的监测参数探讨了辊热凸度情况受到外部因素的影响程度。建立基于支持向量机的液驱冷带轧机辊热凸度动态预测模型,该模型结构较简单,并且可以获得优异的性能。对于辊热凸度的预测表现出了明显的优势。利用SVR模型以及交叉验证的方式确定参数,结果形成了一致的变化趋势与周期性特征。拟合优度与均方根误差分别为0.84与0.0153,获得了较理想的预测性能。该研究对提高板材的控制精度以及轧机节能具有较好的实际指导意义。