Papers by Keyword: Flatness Control

Abstract: A full Profile Contour and Flatness Control (PCFC) model prototype has been developed for hot finishing mills. This model prototype accounts for several physical based sub-models calculating the different contributions to the roll gap profile and allows for offline predictions in both preset and recalculation modes. To evaluate the PCFC model developed, an exhaustive comparison analysis between its calculations, the ones coming from the plant model and measures at the finishing mill exit has been carried out. An industrial mill database composed of different rolling campaign types was applied for this purpose and both (i) strip crown and flatness indicators as well as (ii) full strip profiles results have been used for the comparisons. Encouraging results were obtained from this performance assessment since the PFCF model developed leads to similar behavior compared to the existing plant’s model (from an industrial supplier). As a result, the PCFC model developed shows high potential for online implementation in hot strip mills.

Abstract: Achenbach supplies worldwide with first-class customized rolling mills and machinery for the manufacturing of flat-rolled products from non-ferrous metals. In order to fulfil the customer-specific production requirements, Achenbach developed a wide variety of options for specific subjects. The control of the strip quality parameters like flatness or thickness in the rolling process is a key performance index.An increase of computation power in the field of industrial computers gave a chance to develop more complex model based control algorithms, which led to a significant improvement of the strip quality. In addition it gave an impulse for the development of a comprehensive mathematical model of the rolling mill.This paper will present the general virtual Achenbach Rolling Mill which is a digital representation of the rolling process in general and the behavior of the major actuators in the rolling process in detail. The behavior of drives, strip-tensions, and roll-gap is simulated in a multi-variable real-time environment. In the same environment the OPTIROLLi3^®- model based controls can interact with the virtual machine. A vast number of challenges of the real rolling situation can be demonstrated by working on this ‘mill simulator’ and improved solutions are developed taking advantages from this platform. As the virtual machine allows all kinds of virtual testing without scrapping ‘real material’ a wide range of applications is possible for this virtual rolling mill. Some results from the SIL (software in loop) simulation will be presented for better clarity.

Abstract: Based on the theory of target curve, a method of improving flatness target curve is proposed. The transverse temperature distributions of strip are measured and described with a biquadratic expression, and the statistics method is used to analyze the temperature distributions. Finally, the additional temperature stress compensation is calculated to improve the strip shape.

Abstract: China Steel Corporation was founded in 1971 being the largest integrate steel mill in Taiwan. After several stages of expansion projects, its crude steel production has reached 16.5 million tons annually. CSC has made consistent efforts on its technology innovation mainly carried out by two R & D departments. One of the major tasks of its R & D activities is to establish the advanced technologies for the manufacturing better steels and aluminum alloys as well as product application technology for downstream users. This presentation will mainly brief the research activities of CSC in the field of metal forming including rolling, sheet metal forming and thermal mechanical simulations carried out at Gleeble 3800. Work rolls with continuously variable crown (CVC) were applied to produce hot-rolled strips having precise profile and flatness. Lubrication rolling technology with high speed steel rolls was developed to diminish the wearing of work rolls at hot strip mills. The campaign life of rolling cycle was greatly prolonged. Computer-aided engineering (CAE) simulation technology of sheet metal forming has been established which proved to be an effective way to deal with the sever spring back and breakage of the cold forming of high strength steel automobile parts. Hot stamping has also been developed to support the technology innovation of CSC’s downstream customers. Flow stress and microstructure evolution during hot rolling for aluminum alloys were investigated using a Gleeble 3800 simulator. Both high strength AA5182 for can end and low earing AA3104 for can body aluminum sheets have been successfully developed.

Abstract: A fuzzy control algorithm of selective roll cooling was developed dependent on a qualitative knowledge possessed by skilled operators. The residual flatness deviation as well as the time and spatial variation in the deviation of flatness were chosen as linguistic sets in the fuzzy control algorithm. Limitation and membership function as well as reasoning rule of the fuzzy sets were determined in accordance with the practical process. Besides, linguistic variables were classed by taking into account the condition of practical rolling process. The fuzzy control algorithm utilizes the Mamdani reasoning method and MAX-MIN composition method to actualize fuzzy reasoning and uses weighted mean method to actualize evaluation of fuzzy output. The applications show that the fuzzy control algorithm of selective roll cooling is capable in flatness control and is significant to obtain better flatness.

Abstract: In cold strip or foil rolling, flatness control is an integral part of modern mill. This paper introduces two typical flatness control systems, pattern recognisation flatness control system and multivariable flatness control. It is found that the latter is effective and has wider application fields. The FEM models of its core parameters, flatness actuator efficiency, are constructed. Influencing factors, such as the rolling force, bending force as well as the tilting force are discussed. Control strategies are proposed for foil rolling. The results demonstrate that the control strategies can reduce flatness error and improve flatness quality.

Abstract: Two new types of six-high cold mills, CVC6 and UCMW, are equally equipped with perfect control systems to meet demands for thinner sheet products with better profile and flatness but diverse from each other in strategy of control. To strike a balance between them is the problem for analysis.

Abstract: In the gaps between cells within continuous groups of rolling mills, as a result of local temperature and mechanical factors, longitudinal elastic stress may arise in the strip; this stress is the sum of uniform and self-balancing components. These components affect metal flow in the deformation source. According to the St Venant principle, the influence of the self-balancing component declines with increasing distance from the point of action. The longitudinal and transversal distribution of the self-balancing elastic stress in the strip was analyzed as well as the maximum distance between the deformation source and the point of elastic stress in the strip at which the self-balancing component still affects the plastic deformation of the metal, i.e., the extent of the influence zone of the self-balancing component. The results of this analysis will be useful for a design of new flatness control methods and devices.

Abstract: In this paper, adaptive learning method of bending force presetting model in a six-high cold rolling mill is introduced. Adaptive learning coefficient of bending force presetting model is calculated by contrast between measured and model calculated actual bending force, then exponential method is used to modify the adaptive learning coefficient to improve the precision of the bending force presetting model. While calculating model calculated actual bending force, Legendre polynomials are used to convert measured flatness data to quadratic and quartic flatness coefficient, then regulating quantity on the quadratic flatness coefficient of intermediate roll bending force and work roll bending force is determined based on their regulate capability. Practical application shows that precision of the bending force presetting model has improved significantly by adaptive learning.

Abstract: In order to improve the flatness of cold rolled strips, the accurate knowledge of actuator performance in flatness control is required. As the basis of flatness control, efficiencies of flatness actuators provide a quantitative description to the law of flatness control. In this paper, a 1250 single stand 6-H reversible UCM cold mill was taken as the object of this study, with efficiency factors of individual actuators analyzed for better flatness control. For the purpose of obtaining accurate efficiency factors matrixes of actuators, a self-learning determination model of actuator efficiency factors was established in accordance with the practical rolling processes. The actuator efficiency factors can be determined and improved continuously by the self-learning model with correlative measurement flatness data input. With this study, performance of actuators in flatness control of UCM cold rolling mill has been obtained, which provides a theoretical basis for better flatness control.