Research Group Flat & Long Products

Contact

Name

Markus Grüber

Group Manager

Phone

work
+49 241 80 95920

Email

E-Mail
 

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 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

Slit strip runs into a 4-high stand IBF Slit strip runs into a 4-high stand

In a joined project with the Institute of Automatic Control of the RWTH Aachen University financed by the Deutsche Forschungsgesellschaft, new approaches for further enhancing the thickness tolerances of cold rolled metal strips are investigated. Particularly in new rolling mills with high rolling speeds, the dynamics of electromechanical or hydraulic actuators for roll gap adjustment are too slow to compensate high-frequency interferences in the strip. In comparison to electromechanical or hydraulic actuators, piezoelectric actuators show significantly better dynamics. In order to investigate the suitability of such actuators for a high dynamic roll gap adjustment, two piezoelectric stack actuators are installed in a test rolling mill of industrial scale. The piezoelectric actuators are embedded into a model predictive controller, which finds the optimal, high-dynamic trajectory of the actuators stroke.

For further information, please contact Sven Stockert.

 
 

Damage Controlled Forming - Caliber Rolling

FE model of caliber rolling IBF FE model of 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 during the research period, which will be subject to further manufacturing processes, e.g. cold extrusion.

For further information, please contact Shuhan Wang.

 
 

Damage Controlled Forming - Flat Rolling

Roll gap during hot flat rolling IBF Roll gap during hot 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 are the determination of the spectrum of accessible load paths and their influence on the pore evolution.

For further information, please contact Conrad Liebsch.

 
 

Roller Leveling

Roller leveling machine at the Institute of Metal Forming IBF Roller leveling machine at the Institute of Metal Forming

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 Markus Grüber.

 
Process control for roller leveling
Process control for roller leveling
 
 

Testing Under Bending Load

Test stand for bending loads IBF Test stand for bending loads

Various forming processes apply an alternating bending load to the workpiece. Such changes in the load direction make the consideration of the material behavior under low cyclic loading necessary. In order to test materials under alternating loads, a test rig has been designed at the Institute of Metal Forming. The test rig offers the possibility to apply unidirectional bending as well as cyclic bending. A flexible tool enables a fast variation of bending radii and distance of the bending dies. The material data can be derived from an inverse simulation using the measured machine data of bending force and displacement.

For further information, please contact Markus Grüber.

 
 

Form Closure by Rolling

Form closure connection of aluminium and steel IBF Form closure connection of aluminium and steel

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 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 Stefan Senge.

 
 

Roll Bonding Technology

Roll stock in roll gap IBF Roll stock in roll gap

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 Paul Simon.

 
 

Flexible Rolling

Roll stand for Flexible Rolling IBF Roll stand for 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 Markus Grüber.

 
 

Strip Profile Rolling

Machine for Strip Profile Rolling and rolled strip IBF Machine for Strip Profile Rolling and rolled strip

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 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 Stefan Senge.

 
 

Riblet Rolling

Aluminium sheet with riblet structure IBF Aluminium sheet with riblet structure

Riblet rolling is an innovative and newly developed rolling process to manufacture so-called riblet surfaces from ductile metallic materials. A riblet surface consists of small microscopic grooves in the range of 50 µm in rolling direction and is inspired by the skin of sharks. When positioned in flow direction a riblet surface can reduce the frictional drag by approx. 5 %. In addition, a riblet surface has an enlarged surface area, which compared to a normal flat surface, can have certain advantages in terms of thermodynamic or tribological use. The aim of the riblet rolling process is to produce large quantities of durable metallic riblet surfaces in a cost-efficient manner and on a large scale.
To manufacture a riblet surface a work roll is structured using the “MicroWind” process. This creates a negative imprint on the work roll, which is transferred into the rolling stock during rolling. In one single pass the structure is imprinted into the rolling stock.

For further information, please contact Markus Grüber.

 
 

Efficient Machine Elements

Structured shaft with magnified structure feature IBF Structured shaft with magnified structure feature

Specially designed surfaces can reduce the coefficient of friction and shift hydrodynamic lubrication to lower rotational speeds and thus increase the efficiency of bearings. In this regard hemispherical surface structures with a depth and a diameter of 50 µm act as pockets for the lubricant and can store abrasive particles. Additionally, channel-like structures can guide lubricant to the tribological contact zone. The IBF has developed forming operations to manufacture such structures in collaboration with the Chair of Functional Materials, Universität des Saarlandes. The application of these structures on slide and roller bearings showed the beneficial tribological properties successfully.

For further information, please contact Markus Grüber.