Blog - September 2019

As clean air regulations are more stringent than ever, the electrification of vehicles plays a critical role in the reduction of carbon dioxide emissions.
However, the batteries and their necessary protection can add approximately 1,500 pounds of weight to a vehicle. With more OEMs making the shift from internal combustion engines (ICE)to electric, car manufacturers are also relying on advanced high-strength steels (AHSS) to meet their strength, cost and lightweighting requirements.

Steel and strength go hand-in-hand

One limitation of BEVs is the need for greater reinforcement to protect the battery and the passengers in the event of a crash. A BEV requires greater energy absorption to handle the larger kinetic energies of a heavier vehicle and a stronger roof structure to manage greater roof crush loads. AHSS grades offer greater strength per unit density than competing materials, providing an advantage to BEVs. The unmatched strength of steel not only enhances intrusion resistance, but the thinner, stronger steel allows for more space to accommodate larger batteries, increasing driving range.

Controlling costs without compromising safety

Controlling electric vehicle costs is a motivator for manufacturers in order to compete with ICE alternatives. Optimizing the driving range may be done by weight saving or by additional batteries; the plunging costs of batteries makes expensive weight saving solutions less and less relevant.

This opened the door for auto manufacturers to pivot back to steel – at a much lower material cost than aluminum – to keep the overall vehicle costs down.

After building its first two luxury models with aluminum, Tesla recently shifted to a blend of steel and aluminum for the body and chassis of its mass-market Tesla Model 3. The shift is even also occurring among premium ICE vehicles, including the Audi A8. The vehicle is abandoning its heavy use of aluminum in favor of a mixed material approach, while Audi considers a fully electric version for the next generation of the model.

“If you compare the stiffness weight ratio, press hardenable steel is currently ahead of aluminum,” said Dr. Bernd Mlekusch, head of Audi’s Leichtbauzentrum (Lightweight Construction Center).

Throughout time, steel has remained the most cost-effective lightweight material. Its continued use in the BEV demonstrates this. We have always pushed the boundaries of what steel can do, inventing new smarter steels and steelmaking processes that help our customers to succeed in their transformation to e-mobility. For example: today we produce steels with strengths up to 2000 MPa to allow lighter, safer, and more affordable cars. In the 1990s, the maximum strength of our steel was only 340 MPa, a spectacular increase.

Lighweighting to create a more sustainable future

Electric vehicles were designed to make a more sustainable world, driven by both changing consumer demands and increasingly stringent global regulations. Stricter policies are being introduced throughout Europe, China, India and North America designed to reduce CO2 emissions and improve fuel efficiency while minimizing or even eliminating the production of ICE vehicles altogether.

While some regulations only consider the tailpipe emissions during the “drive” phase of a vehicle, the total environmental impact of the car’s production must be considered. For ICE vehicles, the “production” phase represents around 20 percent of the total greenhouse gas (GHG) emissions over the total course of its life. For a BEV, 47 percent of the car’s lifetime GHGs occurs during production, more than doubling that of an ICE vehicle. As greater emphasis shifts to the production of these vehicles, manufacturers must consider that the production of aluminum requires seven times more energy than steel and emits as much as five times more GHGs.

Electric vehicles are a fast-growing segment of the auto industry and will soon
represent most of the new vehicles on the road. Offering the optimal balance of strength, performance and mass weight reduction with the least impact on the environment, steel is the material of choice for today’s vehicles and will be the OEM’s choice for the BEVs of tomorrow.

Bala Krishnan
Director, Automotive Product Applications
ArcelorMittal

Sources:

• Bloomberg NEF Electric Vehicle Outlook
• Audi considering electric A8
• Tesla switch, aluminum/steel price difference 

Original publication: Wards Auto