Joining MaterialsCopyright: IBF
The joining of different materials, in order to achieve tailored product properties, requires profound process and material knowledge.
The research topics embedded in this cross-sectional area are assigned to different research groups and are presented below.
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.
For further information, please contact Stefan Senge.
Image: Form closure connection of aluminium and steel, Copyright: IBF
Roll Bonding Technology
Roll Bonding is a process to join at least two metals permanently using rolling and possibly higher temperature.
For further information, please contact Paul Simon.
Image: Roll stock in roll gap, Copyright: IBF
Investigation of Bond Formation and Failure of Metallic Alloys
Roll bonding enables the targeted combination of different materials and thus their mechanical and thermal properties in a single material composite. However, the connection created under pressure load can tear up again due to shear stress at the end of the roll gap. Thus, industrial production requires very long process chains, which are often determined by trial and error. In order to allow for a knowledge based design of such process chains, a basic experiment, using the torsion plastometer TA STD 812, was developed at the Institute of Metal Forming to characterize bond formation and failure. In this test, the connecting partners are heated inductively and joined under combined pressure and shear stress. After bond formation, the strength can be tested at deformation temperature under a combination of tensile, compressive and shear stress. The procedure thus enables testing under near-process conditions.
For further information, please contact Jürgen Nietsch.
Image: Hot glowing steel specimens during bond investigation, Copyright: IBF
Finite-Element Based Process Design for Fabrication of Metal Composites by Roll Bonding
Roll Bonding enables the production of composites with customized combinations of properties. In roll bonding, the bonding partners are permanently joined together by plastic deformation. The bond formation is a complex process influenced by material properties and process parameters. At IBF an Abaqus subroutine has been developed for computing the formation and failure of the bonds. In a DFG transfer project, this subroutine will be further improved to develop efficient process routes for new material combinations. With this subroutine and the Abaqus process model, Roll Bonding can now be mapped. The bond strength is calculated depending on the surface enlargement. The established bond can also loosen again due to unfavorable load condition after roll gap. The influences of parameters such as temperature and height reduction on the bond strength and the bonding status can now be simulated.
For further information, please contact Zhao Liu.
Image: FE model for simulating bond strength evolution during Roll Bonding, Copyright: IBF, Hydro
Composite Ring Rolling
Composites offer the opportunity to satisfy locally different requirements of parts by combining materials depending on local loads. Contradicting mechanical, thermal or chemical demands can be fulfilled or by combining high-grade and cheap materials, part costs can be reduced.
For further information, please contact Stefan Günther.
Image: Joined ring after cutting. Outside: X5CrNiMo17-12-2, inside: 13CrMo4-5, Copyright: IBF
Clad Strip Produced by Vertical Strip Casting
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