Circle Green stainless steel achieved 95% recycled material content.
Stainless steel has been the old faithful of the automotive industry for decades. Continuous reinvention has kept the material relevant during the rise of electric and hydrogen fuel cell vehicles, offering crucial light-weighting and sustainability advantages.
From the 1936 Ford Deluxe Tudor sedan to the 1967 Lincoln Continental, stainless steel has long been the material of choice for iconic car models the world over. Since the material’s birth in 1912 with the patent V2A, stainless steels have progressed to meet the evolving demands of the automotive sector, from corrosion and thermal resistance in the 1900s, to the formability of complex geometries at the turn of the millennium. Now, in 2024, the material is being optimised to improve crash safety, lightweighting and environmental sustainability within today’s vehicles.
Desirable properties
Gone are the days when stainless steel was pigeon-holed as being too heavy and cost-intensive for automotive manufacturing. Diverse grades and advanced production techniques have enabled the material to evolve to suit the requirements of current vehicle applications, from car bodies and structural components to intricate design elements.
As part of its sustainability mission, Outokumpu has unveiled its concept for the sustainable luxury car of the future, an innovative platform for automotive suppliers. The company’s stainless steel enables the design of next generation vehicles using lightweight yet strong materials
Thanks to its unique durability, low maintenance and resistance to corrosion, stainless steel is a strong and economically sustainable material for a wide range of demanding applications, whether for electric, hydrogen or combustion engine vehicles. This has been made possible by redefined stainless steels from the likes of Outokumpu, which offer automotive manufacturers high crash energy absorption, thermal and corrosion resistance and formability, alongside a combination of strength and reduced weight.
“We are producing stainless steels with a chromium content of at least 10.5%, which delivers a chromium oxidised layer on the surface to provide added durability and corrosion resistance. We are offering a material that can really last forever in terms of material supply, as stainless steel is 100% recyclable, but also in terms of significantly extending component and overall vehicle lifetime,” said Stefan Lindner, technical sales manager mobility and transport at Outokumpu.
Lightening up
Although stainless steel is denser than aluminium, its adjustable strength allows for thinner components, which can offset the weight difference. Outokumpu has developed a new generation of nickel-free austenitic manganese-chromium materials for structural vehicle components, with a particular focus on crash-relevant and safety-critical parts. The company’s Forta H-Series – available as Forta H500, Forta H800 and Forta H1000 – offers a yield strength Rp0.2 ≥ 1000 MPa in combination with high elongations at fracture in order to open up new opportunities in lightweight engineering and design with steel.
The sustainable luxury car of the future concept
The Forta H-Series’ unique alloy system, microstructure and hardening characteristics combination gives the material great potential for lightweight engineering. When combined with special manufacturing processes like hydroforming or roll-forming, the stainless steel grades enable new designs for lightweight parts. Where mild steels are still used, weight savings of as much as 40% are possible, while functional integration helps to reduce the number of parts within a component or vehicle.
Safety improvements go hand in hand with the Forta H-Series’ light-weighting benefits, as material thickness can be reduced while crash performance is improved. The stainless steel’s hardening properties means it can absorb the impact energy without failing and transmit this energy to surrounding parts, even in welded areas.
Cost-efficient industrial processes are critical to component manufacturing, with high processability an essential factor. Outokumpu’s Forta H-Series is notable for its excellent processing characteristics and reproducibility, enabling it to fulfil the very highest quality standards.
Sustainability at the forefront
“As well as the sustainability advantages delivered to vehicles by lightweight stainless steel component design, it’s important to ensure the material’s supply chain is ticking the green credential box, too,” said Lindner.
“We want to create real change in terms of sustainability,” he explains. “We consider our own scope one and two emissions – the direct emissions from our facilities, indirect emissions from the purchase of electricity, mining, transportation and distribution – alongside the scope three emissions of our total supply chain. It’s really important that we as a material manufacturer start the process of collecting that data to inform and improve our operations, considering raw materials, manufacturing processes, joining processes and corrosion protection. We have already integrated a circular economy for our stainless steel Circle Green, achieving our highest recycled material content ever of 95% in 2023 and reducing 12 million tonnes of CO2 emissions.”
As part of its sustainability mission, Outokumpu has unveiled its concept for the sustainable luxury car of the future, an innovative platform for automotive suppliers. The concept car will be made out of more than 95% recycled stainless steel, combining sustainability with high-strength and crash-safe materials. With a chassis constructed from folded stainless steel, an extremely lightweight construction would become possible via an easy and cost-efficient manufacturing method. The concept is naturally electric, with batteries integrated into a stainless steel platform. Stainless steel materials would also be used in the vehicle’s other drive technology, such as the bi-polar plates of fuel cell systems or the bio-fuel drives like tanks and engines. Overall, the concept is presented as a holistic approach to vehicle safety and sustainability. Whether we will actually see one in the flesh – or steel – in the future though, remains to be seen.