How is stainless steel driving innovation in automotive design?
Stefan Lindner and Markus Buckner explore how stainless steel is continuing to drive the future of automotive design.
In the race to build safer and more efficient vehicles, material selection could give designers the edge. The International Energy Agency (IEA) expects the global EV fleet to reach 250 million by 2030, and there is more interest in alternative fuels like bioethanol and hydrogen than ever. But even for petrol and diesel vehicles, sustainability is front of mind for a growing number of customers and manufacturers alike. To create new designs and components that satisfy both customers’ expectations and the physical requirements of future transportation, we must go beyond aluminium.
As part of this shift, we’re looking to redefine the role of stainless steel. It’s currently viewed as a specialist material solely for exhaust systems, but it’s underappreciated as a versatile option for many other areas of automotive design. In this article, we explore the advantages of stainless steel in the factory and on the road, with a focus on its formability, durability, safety, and recyclability.
FLEXIBLE FORMABILITY
Flexibility is the cornerstone of modern vehicle design. Whether for visual appeal or mechanical necessity, stainless steel allows for intricate and complex geometries without compromising structural integrity. Its diverse grades have adjustable ductility and hardness, often eliminating the need for multiple materials in a single project.
By optimising mechanical properties through temper rolling and strain hardening, a single stainless steel grade can achieve specific outcomes suitable for different automotive applications. For instance, crash boxes, door-side impact beams, and EV motor components benefit from the material’s combination of rigidity and elongation. Folding techniques enable engineers to form origami-like structures that minimise material usage and simplify assembly.
With over 320 grade-surface combinations available, stainless steel surfaces can be aesthetically appealing without requiring additional coatings or treatments — as seen in vehicles like the Tesla Cybertruck and the iconic DeLorean, which incorporate them into both exterior and interior design.
DON’T UNDERESTIMATE DURABILITY
Stainless steel has incredible longevity, even in the most demanding environments. Unlike carbon steel, which typically requires protective coatings, stainless steel is inherently corrosion-resistant and can self-heal via chromium oxidation, which reduces maintenance needs.
This resilience is particularly crucial for safety-critical components such as EV battery enclosures. EV battery trays made of stainless steel not only withstand the test of time, but also heat. Some stainless steels can endure temperatures of up to 1250°C for over 10 minutes with minimal deflection, significantly exceeding aluminium’s threshold of 660°C. This could provide crucial time for rescue teams to respond in cases of battery fires.
The high strength of stainless steel also enables the use of thinner sheets, reducing weight while maintaining performance. In one simulation involving buses, the use of high-strength stainless steel reduced total weight by nearly a ton.
SAFETY IS KEY
High elongation properties combined with strain-hardening techniques allow stainless steel to absorb high crash energy, reducing the risk of injury to occupants during collisions. Whether it’s a race car, a bus, or a tractor, the material’s behaviour under impact can be precisely tuned to align with specific design needs. While its advantages in exhaust systems are well noted, stainless steel’s corrosion resistance extends to use in fuel tanks. With the increasing diversity of synthetic and biochemical fuels available, it ensures performance without the risk of leaks or failures caused by material degradation.
For a completely different perspective on safety, the anti-bacterial properties of stainless steel are of particular interest in a post-pandemic world. As car-sharing and automated taxiing services become more prevalent, materials that are inherently hygienic make a strong case.
A SUSTAINABLE OPTION
Materials that promote sustainability across both the production and lifecycle of a vehicle are needed to make a deep impact on emissions. Aluminium is light and easy to transport, so its on-road emissions appear low. But it has faced criticism due to the carbon intensity of mining and refining bauxite, as well as the lower availability of recyclable aluminium scrap.
Stainless steels boast much higher recyclability, with European stainless steel stock having a staggering 85% average recycled content. With a production volume of around 1.9 million tons, Outokumpu achieved a recycled content of 95% in 2023. Outokumpu’s Circle Green goes even further, being made of up to 100% low-emission raw materials such as scrap and produced entirely with renewable energy sources. This creates an unparalleled sustainability profile. With transparency on emissions across scopes 1, 2, and 3, vehicle manufacturers utilising Outokumpu’s materials can confidently communicate their reduced environmental impact
to customers.
DRIVING THE FUTURE
New types of vehicles — consumer cars, agricultural machines, public transport, and the new ways to power them — will require new ways of thinking. Stainless steel has the potential to change the game with its unmatched sustainability and sheer performance. A future of sleek vehicles that are not only aesthetically unbounded, but safer, stronger, and made with 100% recycled content and renewable energy, is within reach. If there ever was a time to shake up the traditions of the automotive industry, it’s now.
Stefan Lindner and Markus Buckner are at Outokumpu.
