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 Functional films and efficient coating processes
14.02.2017 | Fraunhofer-Gesellschaft

nachricht Nanotechnology for life sciences and smart products: international innovations with IVAM in Tokyo
07.02.2017 | IVAM Fachverband für Mikrotechnik

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Switched-on DNA

20.02.2017 | Materials Sciences

Second cause of hidden hearing loss identified

20.02.2017 | Health and Medicine

Prospect for more effective treatment of nerve pain

20.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>