Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Reducing Weight through Laser-assisted Material Processing in Automobile Construction

13.10.2016

Lightweight construction concepts have become an indispensable part of today's production technology. The automobile industry, for example, uses press-hardened and ultra-high strength steels with a tensile strength of up to 2,000 MPa in car body construction to reduce weight. Compared to steels with lower strength, these high-performance steels allow smaller sheet thicknesses leading to lighter components, which in addition exhibit equally good or even improved crash behavior. To process these demanding high-performance materials, laser material processing is the method of choice.

Together with project partners from science and industry, scientists from the Fraunhofer Institute for Laser Technology ILT have advanced the development in separation and joining as well as heat treatment technologies. They will present selected results at the EuroBLECH from October 25 to 29 in Hanover, Germany (Hall 11, joint Fraunhofer Stand B135).


Laser combi-head for cutting and joining as well as additive manufacturing by means of laser metal deposition.

Fraunhofer ILT, Aachen.


Laser cutting with subsequent laser for heat treatment.

Fraunhofer ILT, Aachen.

Laser Processing of Ultra-high Strength Steels

Sheets made of ultra-high strength steels are commonly used for B-pillars or side door sills of passenger cars, where an extremely high absorption of kinetic energy is a key issue in the event of an impact. However, the high strength of these materials makes it necessary to adjust the processing methods, such as cutting and joining. Conventional mechanical cutting and joining processes, such as stamping, clinching or riveting, cannot be used at a reasonable expense.

As an alternative, the tool “light” has proven its value as a processing method in industrial applications. Laser cutting has already proven itself many times as a separation process, while joining is essentially achieved by spot welding. Both methods, however, lead to metallurgical effects that can adversely affect the component properties. During cutting, hardening occurs in the edge zone of the cut edge; in the case of spot welding, a heat-affected zone forms with a distinct hardening reduction around the welding spot.

These two effects lead, in the worst case, to the failure of the joint and thus, in the case of damage, to a reduced absorption of the kinetic energy in the component. By means of local laser heat treatment in the cutting edge region and in the joining zones, this weakening can be counteracted. The hardness and ductility of the material can thus be adjusted locally to tensile elongations of 10 to 15 %.

Joining ultra-high strength materials requires a low energy per unit length. This can be achieved with laser welding at 20 to 80 kJ/m. For thin plates of chromium steels with martensitic microstructure and tempering steels, suitable fusion welding parameters have been developed at Fraunhofer ILT. TWIP steels containing high content of manganese have also been successfully joined by laser welding in joints with the same as well as with dissimilar materials. A loss of the strength was countered here by a suitable load control.

Laser Combi-heads for the Processing of Car Body Components

Last but not least, it makes sense to combine individual process steps in one tool for economic reasons. This is the starting point of the collaborative project KLASSE, sponsored by the German Federal Ministry of Education and Research (BMBF); the project is being carried out by the Fraunhofer Institute for Laser Technology ILT along with partners from the automotive industry and laser plant construction. The work in "KLASSE" has resulted in a combined processing head with a hybrid laser beam source consisting of a diode laser for heat treatment and a fiber laser for cutting.

For several years now, a laser processing head developed by Fraunhofer ILT and marketed by Laserfact GmbH has been successfully used in the industry, combining different work steps. The head incorporates the two process steps "cutting" and "welding" into one machine without a need for retooling. In the spring of 2016, a powder nozzle was integrated into the combi-head, enabling it to carry out additive manufacturing steps by means of laser metal deposition.

Thanks to this integration, set-up times can be minimized and highly flexible production made even more efficient. In addition, the combi-head can also be used to cut composite materials, e.g. carbon-fiber reinforced components, which are becoming increasingly popular in car body manufacturing due to their low weight and excellent mechanical properties.

Local Softening of Cold-rolled Steels

After cold-rolling, cold-strengthened steels are generally subjected to overall recrystallization annealing. In the cold-strengthened state, the thickness of the steel sheets can be reduced, but the material can only be deformed to a lesser degree, and its ability to absorb energy – in the event of a crash – is reduced significantly. A local heat treatment can improve the crash properties of the components (e.g. controlled folding of a crash box) by introducing soft zones into it. In sheet-metal plates made of low-alloy steels, a combination of cold rolling and local laser heat treatment prevents cracks from occurring in the subsequent forming process at particularly stressed areas, typically at the edges of shaped components.

The project "Local Laser Heat Treatment of Cold Strengthened Steels for Improvement of Forming and Functional Characteristics" (LAKS) is being funded by the German Federation of Industrial Research Associations (AiF) and carried out at Fraunhofer ILT and the Metal Forming Institute (IBF) at RWTH Aachen University. Based on parameter studies, the institutes are first determining correlations between the temperature-time profiles and the resulting properties and mechanical properties. Subsequently, deformation tests and crash tests shall be carried out. The latter will be validated in forming tests under quasi-static as well as under sudden loads. In future development steps, the institutes shall investigate corrosion properties, simulate the deformation in production and operation as well as arrange the process into the production process optimally.

Contact

Dr. Andreas Weisheit
Head of Group Cladding and Heat Treatment
Phone +49 241 8906-403
andreas.weisheit@ilt.fraunhofer.de

Dr. Dirk Petring
Head of Group Macro Joining and Cutting
Phone +49 241 8906-210
dirk.petring@ilt.fraunhofer.de

Fraunhofer Institute for Laser Technology ILT
Steinbachstraße 15
52074 Aachen, Germany

Weitere Informationen:

http://www.ilt.fraunhofer.de

Petra Nolis | Fraunhofer-Institut für Lasertechnik ILT

Further reports about: ILT Laser Lasertechnik heat treatment kinetic energy mechanical properties

More articles from Trade Fair News:

nachricht COMPAMED 2016 connected medical devices and people
23.11.2016 | IVAM Fachverband für Mikrotechnik

nachricht Successfully transferring Industrie 4.0 into reality
21.11.2016 | Deutsches Forschungszentrum für Künstliche Intelligenz GmbH, DFKI

All articles from Trade Fair News >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>