The role of steel in electromobility

In electric motors, steel literally “moves”, because an electricity-powered motor relies on modern electrical steel to propel a vehicle forwards. Between 40 and 100 kilos of non-grain oriented electrical steel is used in the construction of a purely electric vehicle. That could increase demand for this product to over a million tons a year in Europe alone, depending on the growth in demand for electric vehicles. Steel manufacturers are focusing on making electrical steel, i.e. magnetically-soft material, tougher and thinner, without impacting its magnetization. This simultaneously reduces the overall weight of the motor. As the physical limits in this field have almost been reached, in future steel manufacturers will only be able to differentiate themselves through their expertise in bonding, joining, and forming technologies: the potential for efficiency gains lies in more careful processing methods with fewer cutting and punching steps which raise output efficiency. In addition, special alloys with a higher silicon and aluminum content reduce heat loss in the motor during magnetic reversal by up to 30 percent. Manufacturers able to demonstrate know-how in this segment will be well placed to compete in the “e-market”.

Lightweight construction as a means of reducing vehicle weight is not just an issue in the construction of vehicles with conventional drives. In electric vehicles, too, the trend towards lightweight construction plays an important role as a means of compensating for the still huge weight of the batteries, and to lower the overall weight of the vehicle. Developments focus on the conflicting demands of

• vehicle weight;
• cost efficiency gains made via material costs, and
• the requirements for their processing, as well as
• sustainability in terms of the extent to which the materials used can be recycled.

And here steel as a material continues to score well. High-strength steel brands are an important basis for modern and sustainable lightweight construction, winning out against aluminum and carbon. They reduce vehicle weight by around 25 to 39 percent. This helps save up to 4.5 tons of greenhouse gas emissions over a vehicle’s life cycle.
This is something major manufacturers are also taking into account. BMW, for example, will be constructing its model i5 in steel and light alloys from 2021, rather than using carbon as in the i3. Tesla has also converted, with the aluminum and titanium content in its Model 3 recently delivered to foreign markets being reduced in favor of steel, the Handelsblatt study notes.
Furthermore, using steel is also more economic because it is significantly less expensive than other materials.

A new and core element of the automotive future–at least in terms of the drive–is the battery. Its size demands that new construction solutions be found and new safety challenges overcome. This opens up a completely new field of operation for material manufacturers, namely the production of battery cases as housing for the battery, i.e., enclosing the battery packages which weigh several hundred kilograms. It is one aspect of automotive construction without decades of previous experience to draw on.
As battery development continues apace, manufacturers of battery casings must be able to react flexibly to innovations. The casings need to be general in design, perhaps modular, to ensure compatibility with a wide variety of car models. The materials used must be chemical and temperature resistant, as well as offering fire protection. A battery casing naturally needs to protect its contents in the event of crashes and prevent leaking, as well as reliably dissipating heat. The capacity to reconcile this spectrum of requirements with the demand for reduced weight and lower manufacturing costs underscores the advantages of high-strength and ultra-high strength steels over single material solutions in aluminum, titanium, and fiber composites.

Passenger safety remains a key consideration when it comes to vehicle construction, whether in an e-vehicle or a conventionally-driven car. According to the Handelsblatt study, here new steel types are increasingly important because they have 3 to 4-times the tensile strength, and can be specifically produced to be deformable. That makes them ideal for use in integral subframes and B pillars. In addition, compared to conventional brazed joints, modern joining technologies such as laser welding reduce the tension in bonded metal parts, in turn enhancing safety in the event of a crash.

Life cycle assessment is an important factor in all development and production steps: climate protection is the driver of electromobility. Even the so-called “ecological baggage” of energy intensive battery production doesn’t change this. Here, too, according to the Handelsblatt study, future improvements in manufacturing technologies will change this balance. Other ecological advantages include the increasing use of materials whose life cycle assessment alter the overall balance, for example, by using steel in place of aluminum or carbon. Recycling with no loss of quality–that gives steel a huge advantage in life cycle assessments.
The more energy generated from renewable sources that is used in production, and in charging electric vehicle batteries, the more positive the impact on the ecological balance of tomorrow’s electromobility.

In short, future electro-mobility will feature an intelligent mix of materials, with steel playing a decisive role in terms of its contribution to cost effectiveness, sustainability, and safety.

For the authors of the Handelsblatt study it is clear that steel is an indispensable element in the growing electromobility sector. The associated developments require steel manufacturers to continue to specialize further in high quality products which simultaneously provides them with new opportunities.
The following are the opinions of the experts interviewed by the Handelsblatt study:

• “Producing such steels is incredibly complicated; it’s not something many manufacturers can do.”Dierk Raabe, Director of the Max-Planck-Institut für Eisenforschung, Düsseldorf, on manufacturing specially alloyed electrical steel.
• “It is assumed that whoever supplies the battery casing will also be asked to provide the material for the chassis–an important economic aspect.”Wolfgang Wieland, CEO of the Research Association for Steel Application (Fosta)
• “The ultra-lightweight construction trend is now over. Steel is the winner of this development.” Franz W. Rother, Editor-in-Chief of Edison magazine, summarizing developments in the materials mix.
• “The overall life cycle assessments are becoming increasingly important in the material mix.”Stefan Bratzel from the Center of Automotive Management, Bergisch-Gladbach, highlighting the growing significance of the life cycle assessment.