Outokumpu and Fraunhofer Institute develop lightweight stainless steel battery pack for EVs; up to 20% weight reduction
19 April 2016
Finland-based stainless steel expert Outokumpu is working on lightweight stainless steel solutions for electric vehicles in cooperation with Fraunhofer Institute for Laser Technology ILT, in Germany. Their latest innovation is a new battery pack that combines several lightweight engineering technologies as well as new types of cooling and structural strategies.
The Forta H1000 fully-austenitic, ultra-high-strength stainless steel (an advanced manganese-chromium alloy) from Outokumpu enables the implementation of structural lightweight engineering initiatives, while providing a high level of safety.
A high capacity for energy absorption and increased stiffness with thinner wall thicknesses are crucial characteristics for the development of future lightweight designs in automotive engineering. The Forta H-series fulfills these requirements.
—Stefan Lindner, Senior Technical Manager for Automotive segment at Outokumpu
Because the batteries for electric vehicles are mainly installed in the underfloor area, their casings have very high requirements in terms of hardness and crash safety. At the same time, the structures have to be as lightweight and compact as possible, which is where conventional materials such as aluminum and carbon steels reach their limits.
With Forta H1000, we were able to engineer a safer casing despite its leaner structure and thus save a considerable amount of weight. Using 1.2 mm thick sheets instead of 1.5 mm wall thickness allows a weight reduction of about 20 percent.
—Dipl.-Ing. Paul Heinen, Head of the FSEM II Project at the Aachen-based Fraunhofer Institute for Laser Technology ILT
Forta H-Series. Outokumpu has been developing a new generation of Ni-free austenitic manganese-chromium materials for structural vehicle components since 2012.
With a yield strength of Rp0.2 ≥ 1000 MPa and high elongations at fracture, the material is targeting new opportunities in lightweight engineering and design with steel. The material also has very high energy absorption in the event of an impact.
The well-balanced alloy composition obtains a fully austenitic structure. The result is a non-magnetic microstructure which forms no martensite and is not prone to delayed fracture.
The austenitic structure is characterized by the TWIP (Twinning Induced Plasticity) strengthening mechanism: when formed or crashed the material structure transforms creating deformation twins and therefore hardens continuously.
Outokumpu has commercialized the new Forta H-Series as Forta H500, Forta H800 and Forta H1000; the designations refer to yield strength. Due to the natural CrxOy passivation layer, Forta H-Series can be used without a zinc coating.
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