Complex steel for a stable crumple zone
March 03, 2026 | Reading time: 7 minutes
Salzgitter AG has launched a new grade of complex phase steel, paving the way for safe and sustainable automotive design.
In 2025, 545,142 newly registered electric vehicles (EVs) hit the road in Germany – the highest figure in any year to date, according to statistics from the German Federal Motor Transport Authority (KBA). Yet, despite their growing popularity, EVs present new challenges for manufacturers. In a collision, for example, the bodywork needs to keep the EV’s occupants safe while also providing the battery with reliable protection and preventing fires. Consequently, many components are now subject to much stricter requirements. The latest standards published by the German Association of the Automotive Industry (VDA) demand improvements in areas including crash safety and fire prevention.
To meet these evolving requirements, the industry has turned to innovative materials. In this context, complex phase (CP) steel presents a means of optimizing both crash performance and lightweight design. Although CP steels have been developed for conventional vehicles with internal combustion engines (ICEs) since the 2000s, these materials are now revealing their full potential the context of e-mobility. The increased weight of EVs increases the need for energy-absorbing structures, such as rocker rails and B-pillars. Unlike other steel grades, complex phase steel is exceptionally stable but still offers workable, controlled formability. This makes it ideally suited to components designed to save lives in an emergency – from the crumple zone to the passenger compartment to the battery housing. Complex phase steel allows manufacturers to create structures that precisely absorb energy and adapt to wide-ranging requirements.
“This steel grade has long been a niche product in the European automotive industry, and used more heavily in Asia, because European manufacturers achieved similar results using established materials. However, rising requirements – especially in the context of e-mobility – are making complex phase steel an increasingly sought-after material for safety-related components,” says Frank Klose, Head of Technical Customer Service at Salzgitter Flachstahl GmbH.
New steel grade integrated into portfolio
Salzgitter AG has now expanded its range of complex phase steels with an additional strength grade. “All steel producers face the challenge of ensuring their portfolio is optimally aligned with their production facilities,” says Klose. “We have purposefully expanded our portfolio – and can now serve our customers in the automotive industry even more effectively.”
In developing this new steel grade, Salzgitter AG has collaborated closely with automotive manufacturers. “We defined the steel’s properties in our joint standardization work. We then tested and adjusted different alloys and process variants in our research laboratories until we achieved the ideal outcome for the product characteristics and our production processes,” explains Klose. The result is a steel that fulfils the industry’s expectations and sets new standards in hole expansion testing.
Crack-free punched holes
The hole expansion value describes the extent to which a punched hole in the sheet expands during the forming process without cracks forming along the edges. This is a key criterion for automotive manufacturers. Many safety-related components – such as crumple zones, side impact bars and battery housings – feature notches, apertures and attachment points, which are subject to significant stresses during the manufacturing process. A high expansion value indicates that components remain stable even following forming processes and reliably absorb energy in the event of a crash. “This makes it possible to realize challenging geometries and attachment solutions without compromising on safety,” explains Timo Geddert, Product Manager at Salzgitter Flachstahl. For high-strength steels used in automotive construction, the required hole expansion figure is usually in the region of 30% to 60% – while the new steel grade from Salzgitter AG achieves a notable figure of 70%.
Saving material and conserving resources
The new complex phase steel from Salzgitter AG also delivers impressive performance in terms of sustainability. “Thanks to its high strength, thinner sheet thicknesses can be realized – without any negative impact on component performance. That lowers the average component weight by around 7% and reduces material consumption per vehicle,” explains Geddert. But that’s not all: “At the same time, we’re helping our customers to implement modern safety and lightweight design concepts in an efficient manner. With this new steel grade, we’re actively shaping the transformation of automotive development.”
And, revealing a little secret, Klose adds: “We’ll soon be able to offer our customers the next strength class – CP1200.”
Related topics
Sourcing raw materials from rusty car bodies
A climate-friendly cycle: Engaging in the Car2Car funding project, industry and science worked together on new solutions geared to achieving a genuine circular economy in automotive engineering – under the auspices of the BMW Group. Salzgitter Mannesmann Forschung was also involved and researched how to return steel to the cycle even more efficiently – thereby reducing CO₂ emissions in the process.
Read post
"You can always do just a little bit better"
Optimizing in-house processes, scaling solutions and listening as closely as possible to customers: How the new "Operational Excellence" unit at subsidiary Salzgitter Flachstahl GmbH is driving Salzgitter AG's performance forward.
Read post
Salzgitter Flachstahl GmbH
Salzgitter Flachstahl is part of the Salzgitter Group and produces hot-rolled wide strip, strip steel, strip sheet, cold-rolled thin sheet, and surface-finished products.
The address of this article has been copied to your clipboard.