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Gas forming with integrated heat treatment for high performance steel - a solution approach for press hardened tubes and profiles

: Neugebauer, Reimund; Göschel, A.; Sterzing, A.; Schieck, F.

Oldenburg, M. ; Univ. of Technology, Lulea:
2nd International Conference on Hot Sheet Metal Forming of High-Performance Steel 2009 : June 15th to 17th, 2009, Luleå
Auerbach: Verlag Wissenschaftliche Scripten, 2009
ISBN: 978-3-937524-84-9
International Conference Hot Sheet Metal Forming of High-Performance Steel <2, 2009, Lulea>
Conference Paper
Fraunhofer IWU ()
gas forming; high performance steel; press hardening; tube; closed profile

New lightweight design requirements from the automotive industry call for the realization of structural components with a maximum strength in excess of 1000 MPa. On the other hand, demands as far as component complexity, function integration and component quality are concerned are becoming ever higher.
The press hardening technology involving the use of boron-manganese alloyed steel for blank- based component applications represent the state of the art. Typical applications include reinforcement parts in crash-relevant car body structures. Consistent use of these components will enable the needs of current and future car models as regards crash performance to be met whilst maintaining acceptable structural weights.
In addition to press hardened components, hydro-formed profiles also provide a high level of potential for applications in structural car body elements with high loads. At the same time, hydro-forming tubes and blanks at room temperature is also representative of the state of the art for a number of applications in car body structures or exhaust systems, as well as for special applications outside the car industry. These parts are mainly made from materials such as steel, high-strength steel, stainless steel and aluminium.
Increased demands on hydro-formed parts in terms of maximum strength and complexity mean that the limits of conventional hydro-forming processes have been reached. The use of temperature as a process parameter in hydro-forming offers the opportunity to increase the application field of this innovative technology. The potential of this strategy has been identified; complex car body parts fabricated in aluminium and magnesium have been produced at high temperatures. However, fluids available today can only be used up to 300°C because of the limited thermal resistance of these fluids.
Gaseous media (e. g. nitrogen) offer the chance to make use of the potential of temperature-assisted hydro-forming in steel forming as well. Consequently, temperatures up to 1000 °C can be provided. Parallel to hot stamping processes for blanks, it is also possible to combine the gas forming process with a special heat treatment process and to produce closed structural parts with very high strength in the same way as applications involving hydro-formed car body structures, such as A-pillars (BMW, Volvo, Opel), roof racks (Audi), crossmembers (BMW), crash cans (Volvo) or sill reinforcement parts (Audi, Volvo), in volume production.