FRAUNHOFER INSTITUT E FOR LASER TECHNOLOGY ILT
PRESS RELEASE
PRESS RELEASE
October 1, 2014 || Page 1 | 3
Joining ultra-high-strength chromium steels reliably with laser
technology
Incredibly light and holds up in collisions – but often impossible to weld: this characterizes ultrahigh-strength chromium steels that, thanks to their high carbon content, could not be reliably
bonded together by laser until now. At this year’s EuroBLECH, the International Sheet Metal
Working Technology Exhibition, the Fraunhofer Institute for Laser Technology ILT will use a B-pillar
to show how laser welding can be reliably used on press-hardened, martensitic chromium steels.
Within the scope of the research project SECOMAL, the Fraunhofer Institute for Laser
Technology ILT in Aachen has determined process parameters and process windows for
the laser welding of three ultra-high-strength chromium steels: pure ferritic, ferriticmartensitic, and pure martensitic with carbon content ranging from 0.02 to 0.46 mass
percent. Hardened, they achieve a tensile strength of up to two gigapascals with fracture
strain of 10 percent. Their inherent resistance to corrosion makes these steels ideal for
vehicle manufacturing.
The materials with the lowest and the highest carbon content – ferritic and martensitic
chromium steels, respectively – can now be easily joined, even when the materials are
hardened. “Only the martensitic stainless grade 1.4021, with an average carbon content of
0.21 percent poses dfficulties,” says Dipl.-Ing. Martin Dahmen, a researcher of the
Fraunhofer ILT.
According to the textbook, preheating martensitic steel is recommended before joining
and then tempering it – that is, heating the welding zone locally – to improve the
toughness in the heat-affected zone. Hardened sheets can be tempered up to 450°C
without causing any loss of quality. In principle, all types of laser beams are suitable for
welding materials, but since the laser should produce parallel seam edges, Dahmen
recommends using only the so-called brilliant beam sources and CO2 lasers.
But how does the laser compare to metal active gas (MAG) welding? “With judicious heat
treatment, the hardened chromium steel can be joined without difficulty, with the
exception of 1.4021,” says the ILT researcher. “On the other hand, MAG welding is
problematic because of the resulting high-energy input in the joining areas, even with
appropriate heat treatment.”
What successful laser welding looks like in practice will be showcased by the Fraunhofer
ILT on its test specimen of a B-pillar of ultra-high-strength steel welded to a vehicle rocker
panel. “This proves that welding ultra-high-strength materials by laser offers a viable
alternative to manganese-boron steels,” says Dahmen. Visitors to EuroBLECH 2014 can
Editorial Notes
Dipl.-Phys. Axel Bauer | Head of Marketing and Communications | Phone +49 241 8906-194 | axel.bauer@ilt.fraunhofer.de
Petra Nolis M.A. | Leader Communications Group | Phone +49 241 8906-662 | petra.nolis@ilt.fraunhofer.de
Fraunhofer Institute for Laser Technology ILT | Steinbachstraße 15 | 52074 Aachen, Germany | www.ilt.fraunhofer.de
Steinbachstraße 15 | 52074 Aachen, Germany | www.ilt.fraunhofer.de
FRAUNHOFER INSTITUT E FOR LASER TECHNOLOGY ILT
visit the demonstrator exhibit and learn more about laser welding chromium steels and
other Fraunhofer ILT projects at the Fraunhofer Joint Stand in Hall 11, Booth C05.
SECOMAL joint research project
The focus of this research project is investigating how laser and MAG welding can be used
for fusion welding ultra-high-strength stainless steels with a martensitic structure.
SECOMAL is a collaborative research project of the Fraunhofer ILT and the Paderborn
University Laboratory of Materials and Joining Technology (LWF), the Fraunhofer Institute
for Structural Durability and System Reliability LBF, and the steelmaker Outokumpu
Nirosta. It is funded by the German Federal Ministry for Economic Affairs and Energy
(BMWi), the German Federation of Industrial Research Associations Otto von Guericke e.V.
(AiF), and the Research Association for Steel Application (FOSTA).
Picture 1:
Microstructure of weld in 1.4034.
Picture Source: Fraunhofer ILT,
Aachen, Germany.
PRESS RELEASE
October 1, 2014 || Page 2 | 3
FRAUNHOFER INSTITUT E FOR LASER TECHNOLOGY ILT
Picture 2:
At EuroBLECH 2014, Fraunhofer ILT
will use a test specimen for Bpillars to demonstrate that laser
welding can be used reliably on
press-hardened, martensitic
chromium steels. Picture Source:
Fraunhofer ILT, Aachen, Germany.
PRESS RELEASE
October 1, 2014 || Page 3 | 3
The Fraunhofer-Gesellschaft is the largest organization for applied research in Europe. Its research activities are conducted by 67 Fraunhofer Institutes at
numerous locations throughout Germany. The Fraunhofer-Gesellschaft employs a staff of more than 23,000, who work with an annual research budget
totaling 2 billion euros. Of this sum, 1.7 billion euros is generated through contract research. More than 70 percent of the Fraunhofer-Gesellschaft’s
contract research revenue is derived from contracts with industry and from publicly financed research projects. Affiliated research centers and
representative offices around the world provide contact with regions of greatest importance to present and future scientific progress and economic
development.
Contact
Dipl.-Ing. Martin Dahmen | Macro Joining and Cutting Group | Telephone +49 241 8906-307 | martin.dahmen@ilt.fraunhofer.de
Dr. Dirk Petring | Leader Macro Joining and Cutting Group | Telephone +49 241 8906-210 | dirk.petring@ilt.fraunhofer.de
Fraunhofer Institute for Laser Technology ILT, Aachen, Germany | www.ilt.fraunhofer.de
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