Research Group Flat & Long Products
The group for flat and long products deals with all questions concerning the production of semi-finished products. An emphasis lies on rolling processes such as flat rolling, roll bonding and caliber rolling. For those processes fast online models, new tool concepts and modelling approaches are developed. Thus, new process controls and geometries of the semi-finished products as well as deeper process knowledge become accessible.
High Precision Rolling with Roughness Control
In a joined project with the Institute of Automatic Control of the RWTH Aachen University, new approaches to extend the flexibility and process window of the imprinted roughness of a skin-pass rolling process are investigated. Based on the previous research project of the high precision rolling with piezoelectric actuators, a fast rolling model and its online identification, the strip tension is used as an additional actuator to control the imprinted roughness during skin-pass rolling. A model-based control is realized from the results of FE simulations. To identify the deviation and defects during the process, an optical roughness sensor has been integrated in the high precision rolling mill des IBF integriert. Ziel ist es die Lackierbarkeit sowie die tribologischen Eigenschaften der Produkte durch einen Softsensor mit Eigenschaftsmodellen vorherzusagen.
For further information, please contact Xinyang Li.
Damage Controlled Forming - Caliber Rolling
Based on the increasing demand on light-weighted metal parts with long service time, innovative methods to predict and control damage evolution in metal forming processes need to be developed. With this goal, caliber rolling process is studied on the case-hardening steel 16MnCrS5. Caliber rolling is a hot rolling process to produce semi-finished product and undergoes damage evolution, which can be characterized as nucleation, growth and coalescence of voids. In caliber rolling, several process parameters such as caliber geometry and roll diameter are identified to influence factors the damage evolution and will be investigated in FE simulation. For damage prediction, some existing damage models as well as a further developed damage model will be implemented. Furthermore, rod-shaped metal parts with the same geometry but various damage will be produced by caliber rolling on a universal rolling mill during the research period, which will be subject to further manufacturing processes, e.g. cold extrusion.
For further information, please contact Dorothea Czempas.
Damage Controlled Forming - Flat Rolling
Flat rolling is a forming process for the production of semi-finished sheet metal products. These products are commonly used in the automotive sector for instance to further process them into structural components. The two main goals of flat rolling are the thickness reduction in order to reach the desired geometry and the improvement of the mechanical properties compared to the raw material, usually cast slabs. The cast slab usually contains voids and pores, which are formed during solidification. The pores can be eliminated by mechanical closure and hot pressure bonding of the voids through favorable process conditions. One of the major factors in this regard is considered to be the so-called load path. It describes the sequence of different states of stress and strain throughout the forming history of the part. The main focus of this project is the determination of the spectrum of accessible load paths and their influence on the pore evolution in simulation and experiments on a universal rolling mill and a cold rolling mill.
For further information, please contact Dorothea Czempas.
Roller Leveling
Research in field of roller leveling aims on developing a process control for an automatic setting of the leveler according to the characteristics of the strip to be leveled. The process control shall identify variations in the strip characteristics, e.g. material properties, and compensate them. Therefore, the force in the first load triangle is measured. This measurement is used as a reference value to correlate strip characteristics and the optimum setting of the leveler. In order to generate the necessary data, a wide variety of parameters is calculated within an FE model of the leveling process. Based on the results the control concept is transferred to an actual leveling machine. According to the results the process control is able to detect changes of the strip characteristics and to compensate those successfully. In addition to the flatness of the strip the possibility to set defined residual stress distributions within the strip is investigated.
For further information, please contact Pavlo Pavliuchenko.
Form Closure by Rolling
Lightweight-design is an ongoing trend in the automotive industry. New materials and processes reveal new opportunities to reduce the weight of car bodies. One option to produce these optimized components is a combination of a steel sheet with a reinforcing aluminium rib structure. By the use of specific surface structures a clamping of the components should be achieved resulting in a high stiffness of the components.
New processes to create the desired structures are developed on a strip profile rolling machine and optimized at the Institute of Metal Forming. The focus here lies on channel-like structures and undercuts. Therefore, experiments and numerical simulations are used. As a result, new tool geometries, suited for different structures, have been designed in numerical simulations and proven in experiments. Depending on the process, the geometry of the structure and the used material, different sized undercuts can be realized.
For further information, please contact Aron Ringel.
Roll Bonding Technology
Roll Bonding is a process to join at least two metals permanently using rolling and possibly higher temperature.
Therewith it is possible to combine different material properties in an economical and reproductive way.
In an especially for this purpose designed basic experiment it is possible to characterize the bond strength between the joining partners under different loads. The generated data is put into a subroutine. Based on this subroutine, numerical simulations are carried out to investigate the development of the bond strength during rolling. Using these results, experiments are performed on the different available mill stands.
Aims are the optimization of existing processes and the development of those for new material combinations. The current research deals with both hot and cold Roll Bonding with different dimensions and material combinations.
For further information, please contact Aron Ringel.
Bistable Sheets
Bistable sheets have two stable states due to the residual stresses introduced via forming processes: In the transport state, they can be transported in a space-saving manner before being unfolded into an elongated shape at the place of use. The elongated shape has greater stability when it is completely closed, i.e. tubular.
To create the bistable properties, the sheet is bent along two orthogonal axes in two opposite directions. In the previous investigations, thin sheet with high yield strength was formed in an incremental process. There are two possible production processes: “Incremental bending in two steps” (Trumpf Trumabend V 50) and “Incremental bending and roll forming” (Roll Forming Machine - Dreistern P3).
For further information, please contact Pavlo Pavliuchenko.
Flexible Rolling
Flexible Rolling enables the production of metal strips with a variable thickness in longitudinal direction. Employing such semi-finished products enables the development of load-aligned structural components. Compared to conventional components light-weight design becomes possible and resources can be saved. During the process, the roll gap is adjusted according to pre-calculated trajectories resulting in the desired thickness distribution. Based on research on the layout of a suitable process control Flexible Rolling has made the step to an industrial-scale application at the company Mubea. A wide variety of thickness profiles and materials is produced for various applications such as automotive parts.
For further information, please contact Dorothea Czempas.
Strip Profile Rolling
Strip Profile Rolling is a modified rolling process allowing for a thickness variation transversal to the rolling direction. Such semi-finished products offer a potential for light-weight design and enhanced use of material. In order to achieve a thickness distribution in transversal direction it is necessary to use narrow rolls. Narrow rolls guide the material flow into the transverse direction and thereby prevent buckling even though there is an inhomogeneous thickness reduction in transversal direction. A multi-pass process on a strip profile rolling machine can achieve a distinct width of the area with reduced thickness. Besides the investigation of process boundaries, a combination of Strip Profile Rolling and Flexible Rolling has been investigated. A combination of these processes can lead to semi-finished products in both longitudinal and transversal direction.
For further information, please contact Pavlo Pavliuchenko.