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.

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.

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.

Monitor automatic gauge control strategy with a Smith predictor for steel strip rolling

The simplified transfer function diagram block for a monitor automatic gauge control （Mon-AGC） system of strip steel rolling process was investigated. The new notion of strip sample length was given. In this way, the delay time varying with the rolling speed was evaded. After a Smith predictor was used to monitor the AGC system, the control laws were deduced for both proportional and integral regulators. The control strategies showed that by choosing the controller parameter P=∞ for both control algo- rithms each regulator could compensate the whole strip gage error in the first control step. The result shows that the integral algo- rithm is more controllable for the system regulating process and has a better steady-state precision than the proportional regulator. Compared with the traditional control strategy, the new control laws have a faster response speed and a hieher steadv-state precision.

Research and Application of Non-symmetrical Roll Bending Control of Cold Rolling Mill

The existing research of the flatness control for strip cold rolling mainly focuses on the calculation of the optimum adjustment of individual flatness actuator in accordance with the flatness deviation, which can be used for general flatness control. However, it does not work for some special rolling processes, such as the elimination of ultra single side edge-waves and the prevention of strip break due to tilting roll control overshooting. For the purpose of solving these problems, the influences of non-symmetrical work roll bending and intermediate roll bending on flatness control were analyzed by studying efficiencies of them. Moreover, impacts of two kinds of non-symmetrical roll bending control on the pressure distribution between rolls were studied theoretically. A non-symmetrical work roll bending model was developed by theoretical analysis in accordance with practical conditions. The model was applied to the revamp of a 1250 6-H reversible universal crown mill (UCM) cold mill. Theoretical study and practical applications show that the coordination utilization of the non-symmetrical work roll bending control and tilting roll control was effective in flatness control when there appeared bad strip single side edge waves, especially when the incoming strip was with a wedge shape. In addition, the risk of strip break due to tilting control overshooting could be reduced. Furthermore, the non-symmetrical roll bending control can reduce the extent of uneven distribution of pressure between rolls caused by intermediate roll shifting in flatness control and slow down roll wear. The non-symmetrical roll bending control technology has important theoretical and practical significance to better flatness control.

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.

Industrial shape detecting system of cold rolling strip

A high-precision shape detecting system of cold rolling strip is developed to meet industrial application, which mainly consists of the shape detecting roller, the collecting ring, the digital signal processing （DSP） shape signal processing board and the shape control model. Based on the shape detecting principle, the shape detecting roller is designed with a new integral structure for improving the precision of shape detecting and avoiding scratching strip surface. Based on the DSP technology, the DSP shape signal processing circuit board is designed and embedded in the shape detecting system for the reliability and stability of shape signal processing. The shape detecting system was successfully used in Angang 1 250 mm HC 6-high reversible cold rolling mill. The precision of shape detecting is 0.2 I and the shape deviation is controlled within 6 1 after the close loop shape control is input.

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.

Control Strategies of Asymmetric Strip Shape in Six-High Cold Rolling Mill

It is a complicated problem for cold-rolled strip to improve asymmetric strip shape in strip production. A roll system and strip coupled model of six-high cold rolling mill was established with finite element method to estimate the effect of intermediate roll shifting, tilting, symmetric and asymmetric bending technologies on strip profile. To reduce asymmetric defects of strip shape as much as possible, some control strategies were proposed, including tilting and asymmetric bending of intermediate roll and work roll. The combinations of these three control strategies can effectively eliminate asymmetric strip shape defects. Finally, the closed-loop control model of asymmetric flat- ness at the last stand was given, and the flatness control system with the function of asymmetric strip shape control was also designed for cold tandem mill.

Algorithm design and application of novel GM-AGC based on mill stretch characteristic curve

As the spring equation is limited to the accuracy of mill stiffness and the linearity of the mill spring curve, the traditional gaugemeter automatic gauge control(GM-AGC) system based on spring equation cannot meet the requirements of practical production. In allusion to this problem, a kind of novel GM-AGC system based on mill stretch characteristic curve was proposed. The error existing in calculating strip thickness by spring equation were analyzed first. And then the mill stretch characteristic curve which could effectively eliminate the influence of mill stiffness was described. The novel GM-AGC system has been applied successfully in a hot strip mill, the application results show that the thickness control precision is improved significantly, with the novel GM-AGC system, over 98.6% of the strip thickness deviation of 3.0 mm class can be controlled within the target tolerances of ±20 μm.

Adaptive Coordinated Control for Hot Strip Finishing Mills

To further improve the control accuracy for strip dimension of hot strip mills,an adaptive control scheme is investigated for a hot strip finishing mill based on the decentralization and coordination among the controllers of gauge,tension and looper.Consequently,the adaptive controller designed can regulate simultaneously the strip exit thickness,the strip tension and the looper angle to ensure better performance of the strip quality of finishing mills.Moreover,the control scheme is proposed in consideration of the essential nonlinearity and the unavoidable friction phenomena in the mechanical system,so the controller can be efficient in a wider range of working situations.The simulation results of a model obtained from a real hot strip finishing mill show the effectiveness of the proposed control scheme in comparison with the conventional control method.

冷轧板带卷取间接张力控制

在冷轧钢铁生产线中,板带卷取技术直接影响板带表面质量。相关统计数据显示,因板带卷取技术不过关导致的板带次品率达到10%,严重影响了冷轧钢铁的生产质量和生产效率,成为影响板带整体质量的技术瓶颈。张力大小会对冷轧机组的正常运行和钢铁产量的质量产生直接影响,而确保带钢具有合适的张力则是避免带钢出现热瓢曲、提升板带质量的重要条件。因此,保证钢带在连续退火过程中具有稳定的张力,成为提升板带钢产品表面质量的关键。

Quantitative Evaluation Method of Shape Indicator for Cold-rolled Strip

Quantitative level evaluation of cold-rolled strip was significant for the shape control and the product structure optimization. Based on the probability statistics method and the shape pattern recognition method, the shape evaluation model of cold-rolled strip was established to evaluate real-time shape of the online strip. The model was embedded in the shape control system, and the online strip shape state was real-time observed whether to meet the technical indicators, so the shape level could be identified and evaluated. Based on the shape evaluation indicators, the shape component could be well controlled to improve the shape hit rate and the control stability, so that the rolled strip shape could meet the technical requirements. At a 1050 cold strip mill, the shape data of the scene typical specifications strip were online collected and real-time evaluated, and the hit of macro shape in less than 8 I was 68.44%, indicating that the mill shape control had considerable room for improvement, as well as the evaluation method was feasible and practical for quantitative evaluation of the strip shape. So the new evaluation model has important guiding significance to increase value-added and reduce product quality objection.

冷轧铜带板形控制系统数字孪生研究

本文以冷轧铜带板形控制的物理系统为基础,采用机理分析与数据智能协同建模方法,应用在线传感、互联网、云服务、大数据、虚拟仿真、机器学习等技术,研发了一套冷轧铜带板形控制数字孪生系统,实现了与物理系统的实时互动,形成了面向板形控制的信息物理系统。该系统实现在600 mm四辊轧机和600 mm六辊轧机上的工业应用。结果表明:冷轧铜带板形控制数字孪生系统不仅可以实时监控和优化轧制过程,提高板形控制水平和质量,而且可以预警轧制故障,提高轧机运行的稳定性和安全性。该系统为研发新一代冷轧带材板形智能控制技术,提供新的思路方法和应用场景。

农用收割机滚筒用440MPa冷轧钢带的研发与制备

针对农用收割机滚筒制造用钢提出的母材均质化、高强度、易成型的质量提级需求,采用低碳、低硅、高锰,加铌、钛的微合金化成分设计,配合控轧控冷及罩式退火工艺,成功研制开发了农用收割机滚筒用440MPa冷轧钢带。所得冷轧退火钢带组织以铁素体+点状(部分球状)渗碳体为主,屈服强度≥350MPa,抗拉强度≥450MPa,断后伸长率≥27%,钢带综合性能较好,保证强韧性的基础上,兼顾较好的折弯成型及焊接性,实现了低成本、高性能农用车制造专用钢带的批量制备,满足农用收割机滚筒制造加工要求。

冷连轧机带钢单锥度辊边降控制

针对冷连轧机带钢边降板形控制问题,研究了单锥度工作辊的辊形构成、特点和控制策略,建立有限元模型对比分析了单锥度、常规凸度和SmartCrown工作辊板形控制性能,并结合大型工业轧机调试实验分析了该板形控制新技术在实际生产中的使用情况.结果表明,应用单锥度辊可以有效降低带钢边降,减小带钢总凸度.

冷连轧机动态变规格机架速度控制策略及规律

针对冷连轧机动态变规格特性,提出了以变规格前的带钢张力设定值为控制目标的变规格机架速度控制策略.通过建立张力作用下带钢弹性变形的数学解析模型,推导计算了单步小压下变规格时变规格机架的速度控制规律,并根据流量相等原则对变规格后的冷连轧机前面机架进行速度设定.当变规格前后带钢的几何尺寸或材料特性差异较大时,提出利用楔形段方式完成动态变规格,采用上述张力控制目标策略推导计算了楔形段动态变规格方式每个中间厚度的轧制速度和辊缝设定值控制规律.本策略可将变规格造成的厚度偏差控制在变规格机架之间,同时避免了变规格机架与其他机架轧制因素通过张力的耦合,使轧制过程的动态变规格控制易于实现.

UCM六辊冷轧机中间辊辊形研究

针对1500UCM宽带钢冷轧机轧制薄规格带钢易出现板形缺陷和轧辊剥落等问题,采用有限元软件ANSYS建立六辊轧机辊系弹性变形三维有限元模型,并利用UCM轧机窜辊特性和轧机板形控制性能指标设计中间辊新辊形。有限元仿真研究表明:UCM轧机中间辊新辊形与原辊形相比,轧机板形控制能力明显提高,工作辊弯辊调控功效提高35.21%,辊缝横向刚度增强12.25%,常轧宽度1 280 mm薄板的辊缝凸度调节域面积增大75.26%;且UCM轧机辊间压力分布得到改善,中间辊和工作辊的辊间接触压力峰值和辊间接触压力不均匀度系数分别下降3.16%和2.53%,支持辊和中间辊辊间接触压力峰值和辊间接触压力不均匀度系数分别下降13.29%和17.45%。研究结果为开展UCM轧机中间辊新辊形工业实验提供了理论依据。

热轧带钢精轧过程高精度轧制力预测模型

轧制力模型的计算精度直接影响热轧带钢厚度控制精度,目前大多数轧制力模型都把轧制压力分解成应力状态影响系数和变形抗力的乘积.选用与西姆斯公式吻合较好美坂佳助公式作为应力状态影响系数模型,并考虑残余应变的影响,建立了高精度轧制力预测模型.分析了残余应变对普碳钢和合金钢轧制力的影响,给出了带钢热连轧机组残余应变工程计算方法.现场应用结果表明,该轧制力模型具有较高的预测精度,可以满足在线要求.

SmartCrown四辊冷连轧机工作辊辊形

针对宽带钢冷连轧机首次应用的SmartCrown板形控制新技术,通过对SmartCrown辊形的函数结构和特征参数进行研究,推导出了SmartCrown辊形设计式,分析了辊形特征参数对辊缝形状的影响.该研究可用于SmartCrown工作辊的磨削及板形控制.