Stainless steel offers surprising flexibility for automotive manufacturing 

Gone are the days when stainless steel was faced with prejudices of being too heavy and too cost-intensive for automotive manufacturing. Due to diverse grades and advanced production techniques, stainless steel has become ideal for various applications, from car bodies to structural components and intricate design elements.

Whether for electric, hydrogen, or combustion-engine vehicles, stainless steel opens doors for new possibilities.

"With modern stainless steel, it's possible to achieve multiple benefits simultaneously. It all depends on the customer needs and balancing between different aspects,"

says Stefan Lindner, Technical Sales Manager of Mobility and Transport at Outokumpu.

Towards safer, lighter and cleaner vehicles

The redefined stainless steel of Outokumpu offers automotive manufacturers high crash energy absorption, thermal and corrosion resistance, formability and a combination of strength and reduced weight. Stainless steel is also compatible with complex forming operations and is fully recyclable. Although stainless steel is denser than aluminum, its adjustable strength allows for thinner components, which can offset the weight difference.

"We've seen simulations where the total weight of a bus was reduced by a ton simply by using high-strength stainless steel," Lindner explains. Concurrently, Outokumpu is developing new stainless steel grades to decrease material costs and further improve properties such as non-ferromagnetism, energy absorption, and durability.

Stainless steel enables structural optimization and creativity in design

“We can optimize the mechanical properties of an established grade by temper rolling and strain hardening. In addition, we can support our customers in their component manufacturing to achieve the desired outcomes. Instead of using multiple grades or alloys, a single grade can often be applied. This simplifies design work and decreases production costs, for example, by applying the same grade used in SOCF fuel cell solutions also on other parts of the vehicle," Lindner explains.

In addition, stainless steel enables the creation of visually appealing surfaces that reduce CO₂ emissions. "Why cover coated steel with plastic? Let's make the structures visible, just like in Tesla Cybertruck or DeLorean—not just for looks, but also for reduced maintenance and increased durability,” Lindner encourages.

“The choices are plentiful, as we have more than 320 different combinations of material grades and surface finishes available. Also, a mixed-constructed car body made of stainless steel becomes more corrosion-resistant in point of contact corrosion behavior by replacing nickel with less-noble manganese," he continues.

Versatile applications for modern stainless steel

Stainless steel is a proven solution for next-generation automotive manufacturing in many terms: 

• In the Body-In-White (BIW) stage, where all the body components are joined, strength, stiffness, and impact resistance can be increased. Other adaptable structural components include cross members, crash boxes, door-side impact beams, pillars, and further reinforcing elements. 

• EV traction motors benefit from non-magnetic properties — ideal for electric motor components like shafts and shrouds, while up to 300°C heat resistance enhances performance. 

• EV battery compartments can be designed to be safe and lightweight, withstanding temperatures up to 1300°C for over 10 minutes with minimal deflection (unlike aluminum).

• PEM fuel cells for hydrogen-accelerated vehicles benefit from the ideal combination of electrical conductivity, high corrosion resistance, and strength needed to manufacture bipolar plates. Additionally, stainless steel offers excellent formability and lower costs compared to graphite.

• Internal combustion engines and GDI systems' strength, corrosion resistance, and high-temperature properties can be improved. Concurrently, fuel efficiency, torque, and horsepower can be enhanced, and emissions for components like exhaust valves, gaskets, and fuel pumps decreased.

• In exhaust systems, stainless steel guarantees corrosion resistance. This is especially crucial around the catalytic converter area and in components including the manifold, downpipe, catalytic converter, resonator, intermediate pipe, and silencer.

• Fuel tanks can be designed to be lighter, safer, more durable, and resistant against internal pressure. Outokumpu’s large stainless steel portfolio can meet a range of different requirements independent of the type of fuel, be it conventional, synthetic or upcoming biofuel.

• The exterior surface layer of vehicles can be made without the need for additional coatings or treatments. In addition to being inherently corrosion-resistant, stainless steel offers a stylistic choice. 

• Visual parts, such as exterior and interior trims, can be manufactured in a timelessly classy manner with the added benefit of hygienic and easy-to-clean touch surfaces.

  
  
  

Rethinking the use of stainless steel: why total costs matter the most 

Ultimately, automotive manufacturers should choose materials with total lifecycle costs in mind. Outokumpu's experts are happy to help select suitable grades and find optimal solutions by considering all the production steps throughout the supply chain and the vehicle’s lifecycle.

"For example, when selecting material for battery housing, aluminum is lighter than stainless steel and would, thus, decrease CO₂ emissions. However, considering the overall sustainability score of both materials, including production stages, recycled content and recyclability at the end of the vehicle’s lifespan, stainless steel stands out as the winner," Lindner notes.