Tailored Preforms

  Bended Forging Component IBF

Examples for tailored preforms are sheets with weight-optimized thickness distribution, near net shape forming, semi-finished products made of a combination of different metals as well as high-performance materials. They can be used for lightweight design, cost reduction and functional integration.

The research topics embedded in this cross-sectional area are assigned to different research groups and are presented below.

 
 

Flexible Rolling

Walzgerüst für das flexible Walzen

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.


Image: Roll stand for Flexible Rolling, Copyright: IBF
 

Strip Profile Rolling

Anlage zum Bandprofilwalzen und hergestelltes Band

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.


Image: Machine for Strip Profile Rolling and rolled strip, Copyright: IBF
 

Strip Casting of Strips With Tailored Cross Sections

Schematische Darstellung des Profilgießens

Load optimized parts are indispensable in modern light-weight constructions. But their production is still extensive and non-trivial.
Following the idea of process shortening, twin-roll strip casting is used to produce hot strips with tailored cross-sections directly from melt.
Combining contoured casting rolls and a complementary contoured hot roll pass, which exploits the process heat, it is possible to produce hot strips with continuous transitions, which possess a slope up to 45 °, and thickness differences up to 60 % energy-efficiently. These strips are well suited as semi-finished products for various parts with tailored cross-sections.

 

For further information, please contact Dennis Münster.


Image: Schematic depiction of the strip casting process, Copyright: IBF
 

High Precision Rolling

Spaltband läuft in ein Quarto-Walzgerüst

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.


Image: Slit strip runs into a 4-high stand, Copyright: IBF
 

Profile Ring Rolling

Axialwalzspalt während des Axialprofilierprozesses

Profiling of ring rolled components is an important step for the near net shape production, which leads to material savings as well as time saving regarding the machining. Based on the area of application, all four sides of the cross section can be profiled. Dependent on the type of the profile and the geometry of the ring different challenges during the process occur. Examples for these challenges are the reaching of the desired profile filling and conicity in the cross section.
At the Institute of Metal forming strategies for a stable process, which leads to the desired final geometry are developed and investigated numerically as well as experimentally. Therefore, tool and preform design as well as modifications of the actual process strategy are subject of the research.

For further information, please contact Gideon Schwich.


Image: Axial roll gap during the axial profiling process, Copyright: IBF
  Ring rolling of a profiled cross section
 
 

Increasing the Range of Geometries in Open-Die Forging

Biegeschmieden durch Überlagerung von Pressen- und Manipulatorbewegung

Open-die forging is an incremental bulk metal forming process, which is mainly used for the production of long and straight workpieces with a simple geometry as round or square. The production of complex geometries by open-die forging usually requires additional manufacturing steps or can only be realized by a high amount of machining. A new manufacturing approach is based on the idea to realize the production of complex workpieces through superimposed manipulator displacements during a forging stroke. Due to the plastic state of stress, already small superimposed stresses are sufficient to control the material flow towards the intended final geometry. This new forging method was successfully realized for the production of curved and twisted workpieces from steel and aluminium. The general approach significantly increases the range of producible geometries in open-die forging.

For further information, please contact Martin Wolfgarten.


Image: Production of curved workpiece by superimposed manipulator displacements, Copyright: IBF
  Forging and bending
 

Roll Bonding Technology

Plattierpaket im Walzspalt

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.


Image: Roll stock in roll gap, Copyright: IBF
 
 

Clad Strip Produced by Vertical Strip Casting

Plattiertes Rohrsegment aus dem Gießplattierprozess

Clad metals are found in various applications, since they allow for cost-efficient combination of properties of different metals and alloys. Their wide-spread application means several production methods already exists, albeit each with their own limitations. Their production via vertical strip casting poses an alternative, which exploits the short process route of twin-roll strip casting to address these limitations. The Institute of Metal Forming operates its own twin-roll caster. On this caster a prefabricated strip is inserted into the process and, exploiting the process heat, a bond between prefabricated and cast strip is created in the roll gap. Clad strips with thickness ratios between cast and inserted strip of 6:1 to 10:1 have been realized for various steel alloy pairings. The strips have been subsequently examined to describe and understand the underlying bonding mechanism. As the next step cladding of steel strips with non-ferrous metals via this route is to be researched.

For further information, please contact Dennis Münster.


Image: Clad pipe segment produced by twin-roll strip casting, Copyright: IBF
 
Cladding with Strip Casting
Cladding with Strip Casting
 

Form Closure by Rolling

Formschlüssiger Verbund aus Aluminium und Stahl

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.


Image: Form closure connection of aluminium and steel, Copyright: IBF
 

Twin-Roll Strip Casting of High Manganese Steels

Coil eines bandgegossenen Hochmanganstahls

Within the collaborative research project SFB 761 “Steel – ab initio“, the entire process chain for the production of high and medium manganese steels, including strip casting, hot and cold rolling is investigated. The investigated steel alloys require comprehensive adaptions regarding casting additives, refractory material, and casting, hot and cold rolling parameters. In addition, potential opportunities for influencing the mechanical properties of the strip by varying the casting and rolling parameters will be examined. Thus, taking advantage of the outstanding strain hardening behavior of these manganese steels enables the production of tailor-made semi-finished products in a drastically shortened process chain.

For further information, please contact Marco Haupt.


Image: Strip cast high manganese steel coil, Copyright: IBF
 
Strip Casting of a High Manganese Steel
Strip Casting of a high manganese steel