Aluminum Hot Rolling Research Articles

Mechanisms and kinetics of pore closure in thick aluminum plate

Interrupted in situ tests at high temperature characterized with X-ray microtomography were employed to study porosity evolution under loading conditions representative of aluminum hot rolling. Coupling digital volume correlation and simulations, it is possible to access, for each pore, its morphological evolution, and the mechanical fields it experienced. The closure kinetics of hundreds of pores were studied, which is described as the pore volume as a function of the hydrostatic integration. Closure kinetics are a function of the shape of the pore. Focus is put on pores with a complex shape which are more detrimental to mechanical properties. Their closure kinetics are exponential due to the pore fragmentation during closure. The closure of complex pores is fostered by an initial orientation perpendicular to the loading direction and a low initial fragmentation. Based on the closure kinetics of 243 complex pores, a new pore closure model is proposed.

Thermal Camber and Temperature Evolution on Work Roll during Aluminum Hot Rolling

Flatness is an important quality characteristic for rolled products. Modern hot rolling mills are equipped with actuators that can modify the uneven thickness distribution across the width of the strip (crown), taking into account online measurements of various process parameters such as temperature, force and exit strip profile, either automatically or manually by the operator. However, the crown is also influenced by many parameters that cannot easily be measured during production, such as work roll temperature evolution through thickness and roll geometric variation due to thermal expansion (thermal camber). These have an impact on the strip flatness. In this paper, a thermo-mechanical finite element model on LS-DYNA™ software was utilized to predict the influence of process parameters, and more specifically strip temperature, cooling strategy (application of cooling on the entry or entry and exit side simultaneously) and roll core temperature, on the evolution of roll temperature and thermal camber. The model was initially validated with industrial data. The results indicate that the application of both entry and exit cooling is ~30% more efficient compared to the entry cooling only, thus the thermal camber will be reduced by 2 μm. A hotter roll (380 K) is more stable compared to the cold roll (340 K), showing also an improvement of 2 μm. The hotter roll will also reach a thermal steady state on the surface faster compared to the colder one, without making a significant difference on the steady state temperature. Strip temperature plays a roll in the thermal camber evolution, but it is a less important parameter compared to cooling strategy and roll temperature.

Prediction of Plate Crown during Aluminum Hot Flat Rolling by Finite Element Modeling

The roll deflection during hot rolling can result in uneven thickness distribution across the width of a plate (crown). A conventional rolling mill is equipped with bending systems that can control this convex shape of the plate. However, the determination of the proper bending load is very complicated as the plate crown is influenced by the rolling conditions. In this paper, a thermo-mechanical Finite Element Model on LS-DYNA™ software was utilized to predict crown evolution based on the rolling conditions in order to determine the setting values for achieving the target crown. The simulation results were compared and verified with actual industrial data for rolling force, plate temperature and plate crown. This approach is essential for pass schedule design and process parameter optimization in order to achieve the desired product quality.

Multi-objective optimization of rolling schedules on aluminum hot tandem rolling

In hot strip rolling process, rolling schedule is a key technology which directly influences strip product qual- ity. Rolling schedule optimization is actually a problem of load distribution. To make a better rule of the load dis- tribution of aluminum hot tandem rolling, multi-objective optimization algorithm is used to optimize rolling schedule. Preventing slipping, power margin and minimum energy consumption are selected as the optimization objectives. To make a precision calculation of rolling schedule, an adap- tive neural network which is based on classification system is applied to improve the prediction ability for the rolling force, and its on-line training system reduces the prediction errors caused by different rolling conditions. The improved differential evolution algorithm is used to search the Pareto front, and it obtains a good approximation of the Pareto- front and decreases computation time. Load distribution strategies focused on different objectives are generated from the Pareto front to meet the requirements of industrial spots. The experiment result shows the algorithm covers the front quickly and distributes well. Comparing with the original schedule, the proposed method reduces the probability of slippage and energy consumption.

Study on Forward Slip Model for Aluminum Hot Tandem Rolling

Forward slip is an important parameter in the schedule of aluminum hot finish mill. Its precision directly affects the mass flow of the strip through the stands, the pre-set roll speed and the adjustment time of the tension. In this paper, a practical forward slip model is established based on the analysis of reduction, output thickness, work roll radius, friction coefficient and strip temperature. The result is obtained by the least-squares regression. All these are based on a large number of field data which come from 1+4 aluminum hot rolling mill in Henan.

Tension Control Study in the Finishing Mill of Aluminum Hot Rolling Mills Based on PSO+CMAC

Aimed at decreasing the tension variation during transforming process of 1+4 aluminum hot rolling mills unit in one factory of Henan, we analyzed the factors affecting tension variation and improved the tension formula of hot rolling mills process considering the influence of tension on forward slip value. The tension forming process of hot rolling mills from stand 1 to stand 4 is simulated, and the tension structure diagrams of the four-stands are constructed. Due to non-linear characteristics of the aluminum hot rolling mills tension system, conventional PID controller could not meet the requirement of the system. So we proposed the mixed control of Cerebellar Model Articulation Controller (CMAC) coupled with PID to solve the problem of online parameters control and we used Particle Swarm Optimization (PSO) algorithm to optimize PID controller parameters. By simulation, it could be found that the using of PSO+CMAC significantly reduced surplus adjustment and transition time, and strip tension coupling degree among stands was also reduced.

Effects of Strip Thickness Difference on Deviation in Aluminum Hot Rolling

In aluminum hot rolling process, strip thickness difference plays a more important role in deviation. An FE model was presented to simulate the rolling process in which strip thickness difference was taken as a horizontal asymmetry factor of disturbance. Parameters information of nodes is processed, with the characteristic quantity of deviation and the asymmetrical thickness difference rate calculated. The result of simulation illustrates the deviation result under the disturbance of thickness difference, and the relationship among deviation function, characteristic quantity of deviation and the asymmetrical thickness difference rate. Deviation tracks under these circumstances are figured out. The effect of thickness difference on deviation in aluminum tandem hot rolling is revealed.

Prediction on Transverse Thickness of Hot Rolling Aluminum Strip Based on BP Neural Network

For aluminum hot rolling process with multi-variables, strongly coupling, nonlinear, it is difficult to establish accurate mathematical model to solve transverse thickness distribution. A method based on BP neural network with hot rolling aluminum transverse thickness prediction was proposed; According to multi-channel measurement characteristics of IMS transverse thickness collection system, the BP neural network prediction model for single channel was established; predicting every channel thickness by BP neural network, transverse thickness distribution of aluminum strip was obtained. Simulation results compared with the measured datas, the relative error is less than 2.5%. The results indicate that the BP neural network is suitable for transverse thickness prediction of hot rolling aluminum strip.

FATIGUE ANALYSIS ON THE END COUPLING OF THE ALUMINUM HOT ROLLING EQUIPMENT

The End Coupling is the main component of the aluminum hot rolling equipment. The End Coupling is used for transmission of rotational power with heavy-duty load. Fracture of the End Coupling causes serious economic losses because an End Coupling is a very expensive component and it takes a long time to repair it. Therefore, preventing the destruction of the End Coupling is essential for ensuring a long mechanical life cycle. In this paper, a parameter study on the End Coupling was performed in order to minimize maximum stress of the End Coupling under static loads. As a result of an optimum design for life extension on the End Coupling, the maximum stress of the modified End Coupling was lower than that of the initial model by 29%. The fatigue analysis for fatigue life prediction of the modified End Coupling was performed using the commercial finite element method. In the results of the fatigue life analysis, the safety factor of the modified End Coupling was 1.123. Therefore, it was demonstrated that the modified End Coupling has infinite life.

Aluminum Hot Finishing Rolling Process Parameters on the Effect of Temperature Field Distribution

According to actual structure parameters and the technological parameters in an aluminum hot rolling production line, consider the rolling of metal plastic deformation heat, the contact surface heat conductivity, friction heat effect on the rolled piece and the roller heat transfer, use finite element analysis software MSC.Marc to build thermo-mechanical coupled finite element simulation model about aluminum hot rolling frame F2. Analyzing different rolling process parameters on the influence of the temperature field distribution regularity, and by adjusting the rolled-piece technology parameters to control temperature distribution, so as to achieve the purpose of improving product quality, and to provide theoretical basis for production of aluminum strip.

Optimum Design for Life Extension on the End Coupling of Aluminum Hot Rolling Process

The end coupling is the main component of the aluminum hot rolling process. The end coupling used for transmission of rotational power with heavy-duty load. Fracture of the end coupling causes serious economic injury because an end coupling is a very expensive component and takes a long time to repair. To prevent the destruction of the end coupling it is essential for mechanical life cycle to be known. In this paper, a parameter study on end coupling was performed in order to minimize maximum stress of an end coupling under static loads. To verify the interference of spindle assembly with modified end coupling, kinematic simulation was performed by applying the various combination type and dynamic boundary condition of the spindle assembly. The interference of an optimized model did not occur during combination process and driving process. As a result of an optimum design for life extension on end coupling, the maximum stress of end coupling was reduced about 26% compared with original model.

Transfer Model of Transverse Asymmetry Characteristic in Standers during the Steady Hot Rolling Stage

During the hot rolling process, the perturbation of transverse asymmetry factor will generate strip steering, strip delivery wedge and other failure state. During the steady rolling stage, the constraint action of tension and so on can restrain strip steering. Transverse asymmetry characteristic mainly passes in the form of strip delivery wedge between the standers. Firstly this paper researches correlation of transverse asymmetry characteristic parameter toward single stander, establishes a function model to reflect transverse asymmetry result status, for instance strip delivery wedge, strip entry wedge, strip eccentric, gap wedge and other transverse asymmetry disturbance factor. Then the paper establishes transfer model of transverse asymmetry characteristic between standers, gets result status of strip delivery wedge between each ensuing standers under strip entry wedge, strip eccentric, gap wedge and other combination of disturbance. At last the paper takes working condition of actual aluminum hot rolling production line as an example, computes transfer coefficient of strip delivery wedge under several perturbation and discuss transfer discipline of transverse asymmetry characteristic between standers.

알루미늄 열간 압연공정의 동력전달용 슬리퍼 메탈에 대한 형상 최적설계

슬리퍼 메탈은 열간 압연 공정의 동력전달 부품이다. 슬리퍼 메탈은 스핀들과 커플링을 연결한다. 그러므로 슬리퍼 메탈이 심각하게 손상되면 스핀들과 커플링은 서로 충돌할 것이다. 슬리퍼 메탈의 파손을 방지하는 것은 기계적 수명을 연장하는 필수적인 요소이다. 본 연구에서는 슬리퍼 메탈의 수명 연장을 위하여 유한요소법을 사용하여 구조해석 및 형상 설계를 수행하였다. 수정된 슬리퍼 메탈과 스핀들 조립의 간섭을 검증하기 위해 다양한 체결 타입과 동적 경계 조건을 적용하여 동적 시뮬레이션을 수행하였다. 슬리퍼 메탈의 구조 해석과 형상 설계의 결과로써 수정된 슬리퍼 메탈의 최대응력은 초기 모델과 비교하여 22 % 감소하였다.

2511 アルミニウム熱延工程におけるスケジューリングシステム(S78-1 生産システムの新展開-産業応用(1),S78 生産システムの新展開(産業応用を中心に))

This paper describes a development of scheduling system for an aluminum hot rolling process. A scheduling of hot rolling process is consist of three elements that a decision of rolling sequence, a selection of furnace and an arrangement of slabs in a furnace, and it requires special knowledge because there are many constraint for the decision of above scheduling process. Consequently, we have developed a scheduling system which uses local search method and heuristic approach, and it makes possible to plan a hot rolling scheduling without skilled processing staff.

Modeling the microstructural changes during hot tandem rolling of AA5XXX aluminum alloys: Part II. Textural evolution

A comprehensive mathematical model of the hot tandem rolling process for aluminum alloys has been developed. Reflecting the complex thermomechanical and microstructural changes effected in the alloys during rolling, the model incorporated heat flow, plastic deformation, kinetics of static recrystallization, final recrystallized grain size, and texture evolution. The results of this microstructural engineering study, combining computer modeling, laboratory tests, and industrial measurements, are presented in three parts. In this Part I, laboratory measurements of static recrystallization kinetics and final recrystallized grain size are described for AA5182 and AA5052 aluminum alloys and expressed quantitatively by semiempirical equations. In Part II, laboratory measurements of the texture evolution during static recrystallization are described for each of the alloys and expressed mathematically using a modified form of the Avrami equation. Finally, Part III of this article describes the development of an overall mathematical model for an industrial aluminum hot tandem rolling process which incorporates the microstructure and texture equations developed and the model validation using industrial data. The laboratory measurements for the microstructural evolution were carried out using industrially rolled material and a state-of-the-art plane strain compression tester at Alcan International. Each sample was given a single deformation and heat treated in a salt bath at 400 °C for various lengths of time to effect different levels of recrystallization in the samples. The range of hot-working conditions used for the laboratory study was chosen to represent conditions typically seen in industrial aluminum hot tandem rolling processes, i.e., deformation temperatures of 350 °C to 500 °C, strain rates of 0.5 to 100 seconds and total strains of 0.5 to 2.0. The semiempirical equations developed indicated that both the recrystallization kinetics and the final recrystallized grain size were dependent on the deformation history of the material i.e., total strain and Zener-Hollomon parameter (Z), where \(Z = \dot \varepsilon exp \left( {\frac{{Q_{def} }}{{RT_{def} }}} \right)\) and time at the recrystallization temperature.

状態フィードバックを用いたアルミニウム熱間圧延機の蛇行制御

A new steering control system of aluminum hot rolling mills has been developed. The features of the new system are as follows:(1) The steering process is stabilized by the state feedback control which adjusts bending force using the signal of rolling load difference.(2) After stabilization of the steering process, an integrate feedback controller which adjusts roll gap difference using the signal of the steering sensor, is designed to reduce the steady-state steering deviation.The effectiveness of the new system has been demonstrated by the application for a real plant.