The Finnish company Outokumpu, working in partnership with the German Fraunhofer Institute for Laser Technology (ILT), has developed a new lightweight, stainless steel electric vehicle battery pack, according to recent reports.
The two organizations have been working together on a number of different lightweight, stainless steel solutions for electric vehicles (EVs) that make use of the Finland-based company’s stainless steel expertise and Fraunhofer’s engineering know-how.
Outokumpu’s Forta H1000 fully-austenitic, ultra-high-strength stainless steel (an alloy of manganese-chromium) opens up a number of interesting opportunities with regard to lightweighting efforts.
Green Car Congress provides more details:
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.
…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.
The Senior Technical Manager for Automotive segment at Outokumpu, Stefan Lindner, commented: “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.”
The Head of the FSEM II Project at the Aachen-based Fraunhofer Institute for Laser Technology ILT, Paul Heinen, commented as well: “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%.”