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.

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.

Effect of Deformation between Stands on the Strip Shape in Hot Rolling

A theoretical model about the secondary deformation is developed by the combination of analytical and experimental approaches. A system simulation based on the model is completed to predict the strip profile after the interstand deformation. On the other hand, comprehensive experiments and quantitative comparisons are made to calibrate the model for a wide variety of products. As a result, the correction of the model has been verified by the actual rolling data from production mill and it is helpful to improve the strip shape control.

Strip shape control capability of hot wide strip rolling mills

The elasticity deformation of rolls was analyzed by means of two-dimensional finite element method （FEM） with variable thickness. Three typical mills were used as objects for analysis. A thorough study was done on the control capabilities of these mills on the strip shape. Then the strip shape control capabilities of the three mills was compared synthetically. 2008 University of Science and Technology Beijing. All rights reserved.

Shape Setup System for 1700 Hot Strip Mill

Shape setup （SSU） system is the core technology for hot strip mill （HSM）. A precise SSU system was used to improve the strip quality for HSM. The function of SSU, setup, and feedback was introduced. The main mathematical models of roll gap profile and longitudinal strain difference are set up. Strip profile allocation strategy was researched according to the SSU system of a domestic 1 700 mm HSM. The SSU system was put into practical use and the measurement results showed that strip flatness variation and strip profile variation could be controlled in target scope.

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.

Optimization of pass schedule to improve the strip shape in hot strip rolling

In this study,the authors proposed a new algorism which can simultaneously meets the strip shape control criterion and the strip crown control criterion.Based on the new algorism,the pass schedule is optimized to maximize the allowable PC angle range.To calculate the objective value for optimization of pass schedule,a slab method has been integrated with the roll stack deformation to simulate the strip profile.

Novel Impact Absorption Device Using NiTi Shape Memory Alloy Strips

The aim is to propose and design a kind of novel impact absorption devices using constant-force elements made from Ni Ti shape memory alloy( SMA) strips for safety protection.The availability evaluation results indicate that the constant-force elements can absorb over one half of the impact energy for its martensite transformation and thus the maximum impact force is reduced by nearly 80%.Compared with the ordinary cylindrical compression spring,the device's maximum impact force is reduced by nearly 50%,otherwise it has a very compact structure and insensitivity to the varying impact,and thus it is especially suitable for narrow space and safety purpose.

TORSIONAL IMPACT RESPONSE OF A PENNY-SHAPED CRACK IN A FUNCTIONAL GRADED STRIP

The torsional impact response of a penny-shaped crack in a nonhomogeneous strip is considered. The shear modulus is assumed to be functionally graded such that the mathematics is tractable. Laplace and Hankel transforms were used to reduce the problem to solving a Fredholm integral equation. The crack tip stress field is obtained by considering the asymptotic behavior of Bessel function. Explicit expressions of both the dynamic stress intensity factor and the energy density factor were derived.And it is shown that, as crack driving force, they are equivalent for the present crack problem. Investigated are the effects of material nonhomogeneity and (strip's) highness on the dynamic fracture behavior. Numerical results reveal that the peak of the dynamic stress intensity factor can be suppressed by increasing the nonhomogeneity parameter of the shear modulus, and that the dynamic behavior varies little with the adjusting of the strip's highness.

Comprehensive contour prediction model of work rolls in hot wide strip mill

The predictive calculation of comprehensive contour of work rolls in the on-line strip shape control model during hot rolling consists of two important parts of wear contour calculation and thermal contour calculation, which have a direct influence on the ac- curacy of shape control. A statistical wear model and a finite difference thermal contour model of work rolls were described. The comprehensive contour is the equivalence treatment of the sum of grinding, wear, and thermal contours. This comprehensive contour calculation model has been applied successfully in the real on-line strip shape control model. Its high precision has been proved through the large amounts of actual roll profile measurements and theoretical analyses. The hit rates （percent of shape index satisfying re- quirement） of crown and head flatness of the strips rolled, by using the shape control model, which includes the comprehensive contour calculation model, have about 16% and 10% increase respectively, compared to those of strips rolled by using manual operation.

Off-line Simulation of PFC for Hot Rolling Strip

In order to improve the quality of the strip for the hot continuous rolling, the high accuracy set-up control must be applied to production. In the paper, we analyze the RFC (profile and flatness control) system and simulate the set-up process. Calculation results are in agreement to the actual measurements. It is the basis on the developing model.

Research on Single-Side Long Edge of Hot Rolled Strip Caused by Asymmetrical Stiffness of Mill Stand

To analyze and solve the problem of single-side long edge of hot rolled strip in certain domestic factory, the asymmetrical deformation of rolls and strip in asymmetrical stiffness mill stand based on slit beam model, the strip profile and rolling force distribution at the exit of asymmetric stiffness stand mill were calculated using influence function method. Considering the character of in-site equipment and technology, a scheme of adjusting load distribution in finishing mill was made and the experiment was applied. Comparison of strip profile between new load distribution and the old one shows that the method can solve single-side long edge problem well.

Establishment Method of Shape Standard Curve Based on Stepwise Optimization and Its Compensation Models

There are very few researches on the shape standard curve currently,and they merely remain on the level of description of the general concept and production experiences,lacking of the in-depth theoretical analysis,and the concrete principle,method and steps for determining the shape standard curve are not put forward,therefore,they are not applicable in industrial production.This is the weakest spot in the research on the basic shape theory.In this paper,the basic shape standard curve and the transverse distribution curve of the exit thickness are attained with stepwise optimization,which is based on the theoretical calculation method of the shape standard curve of strip mills proposed by authors.By calculating the shape discrimination model and the shape forecast model separately,the simultaneous iterative calculation by the previous method is avoided,and the speed and stability of calculation are improved.The compensation models of the transverse temperature difference of the strip,the shape detection roller deflection and the shape of the strip coil are established,respectively,meantime,the basic shape standard curves are compensated,and the relatively perfect theoretical establishment method of the shape standard curve is formed.The simulation and calculation are done on a 1 220 mm five-stand cold strip tandem mill.The simulation and calculation result shows that the principle,method and steps for determining the shape standard curve are correct and feasible,and the correctness of theoretical analysis and calculation is verified.This paper proposes an idea and a method for the establishment of the shape standard curve in the rolling processes of cold strip mills,which develop the theory and model of the shape standard curve and improve the quality and efficiency of the shape control in the rolling processes of cold strip mills.

Shape Control Simulation on 4-High CVC Mill

The computation model of shape and crown on 4-high CVC mill was established by combining the stream surface strip element method for analyzing three-dimensional plastic deformation of strip and the influence coefficient method for elastic deformation of rolls, and the simulation of the shape and crown control on 4-high CVC hot strip mill was conducted. The simulated results indicate that the influence of the shifting of CVC work roll on shape and crown is very large, and the shifting of work roll can be used to preset shape and crown. The influence of the bending force of work roll on shape and crown is smaller, and it is suitable to use the bending force of work roll for shape and crown adjustment on line. With the increase of strip width, the exit crown of strip increases firstly and decreases then, and the roll gap becomes smoother increasingly. Meanwhile, the transverse difference of front tension stress decreases firstly and increases then.

Complete Mill Simulation of the Rolling Process of 1660 mm Hot Strip Continuous Mills

The three-dimensional plastic deformations of strip are analyzed using the stream surface strip element method, the elastic deformations of rolls are analyzed using the influence coefficient method, the analyzing and computing model of shape and crown of 4-high mill was established by combining them, and the rolling process of 1660 mm hot strip continuous mills was simulated. The simulated results tally well with the experimental results. The modei and the method for simulation of shape analysis and control of hot strip mills were provided.

Study and application of crown feedback control in hot strip rolling

Crown feedback control is one part of the automatic shape control （ASC） system. On the basis of large simulation researches conducted, a linear crown feedback control model was put forward and applied in actual strip rolling. According to its successful op- eration in the ASP 1700 hot strip mill of Angang Group for one year and also from the statistical results of several crown measurements, it can be definitely said that this control model is highly effective and shows stable performance. The control effectiveness of different gauges of strips with the feedback control is found to increase by 10%-30% compared with that without feedback control.

Lab experiments on the innovative rapid thick strip casting process

Rapid thick strip casting （RTSC） by Anton Hulek, Inventmetall, is an innovative concept for the production of hot strips with a final as-cast thickness of about 25 mm before rolling. The innovation of the mechanism consists in a vertical mould performing a caterpillar motion. This moving mould has an unconventional parallelogram-shaped cross-section. The conventional rectangular shape is formed in the shaping machine, which is placed straight below the mould. Further elements of the technology are state-of-the-art. For the investigation of this new casting system theoretical calculations were complemented with practical experiments. The investigation focused mainly on two key aspects： the characteristics of the mould and the shaping process. For the practical analysis a static mould with three pairs of elements in laboratory scale was developed and commissioned by the Dept. of Ferrous Metallurgy @ RWTH Aachen University. The shaping experiments were carried out in model scale with two different materials and in variable boundary conditions. The results of these experiments delivered important mechanical as well as thermal informations about the casting system.

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.

柳钢1450热轧线粗轧板形控制方法探究

柳钢1450热连轧生产线精轧工序头尾穿带稳定性极大程度受到粗轧中间坯板形影响,偶尔发生因来料板形差引发的楔形大、轧破、甩尾等现象。特此结合粗轧区域设备特性探索粗轧板形控制方法,对关键设备采取针对性改进措施,如设备对中精度、压下系统精度、装备配合间隙等,并开发投用板形调整功能适配工艺参数优化,应用于实际生产并取得明显效果。

C形翘曲热轧钛带退火酸洗生产过程控制研究

热轧钛带在热轧生产过程中产生C形翘曲,在后续退火酸洗生产过程中如果不采取有效措施进行治理,将导致更严重的表面划伤,甚至因钛带过度跑偏与生产设备发生机械擦刮引发严重的生产停止、设备事故和产生废品,导致重大的经济损失。通过在退火酸洗线生产过程中采用有效控制工艺及措施,如增加压辊、托辊、保护板,辊凸度,套量控制,加热冷却工艺控制,张力-速度控制等措施进行生产过程综合治理,从而保证C形翘曲的热轧钛带在退火酸洗线安全稳定高质高效生产。