Making vehicles lighter and safer–lightweight automotive construction remains a trend, also in electromobility. With its expertise in developing ultra-high-strength steels, together with its innovative hot forming technologies, voestalpine is excellently equipped for the future of e-mobility.
Cars need to be lighter. This reduces fuel consumption, and consequently CO2 emissions. While combustion engines dominate automotive drives, this is an irrefutable fact. But does it remain the case in the age of electromobility and lightweight construction?
Lightweight construction in the electromobility age
Electric vehicles differ from conventional fossil-fuel driven cars, starting from their construction. They require a subtle balance between net weight and power. One reason for this is recuperation, an effect that electric vehicles and hybrids use to generate electricity from the energy released during braking in order to recharge their batteries. Recuperation is less effective in lighter vehicles. Consequently, using “moderate lightweight construction”, engineers balance considerations of vehicle weight against the overall energy balance. Lighter vehicles generate less power from recuperation; however, they also require less energy to move from the outset than do heavyweight cars under the same conditions.
Markus Borz, Corporate Development at voestalpine AG, who is responsible for strategic electromobility projects, explains:
"Some calculations show that due to recuperation, energy consumption in e-vehicles is no longer so strongly linked to vehicle weight. Although that’s certainly correct, it’s only one aspect, because weight isn’t just a factor in the vehicle drive—it also has a decisive impact on driving behavior, stresses on the chassis, etc. Lightweight construction will continue to be an important issue, also for electric vehicles!"
What is lightweight construction?
But what is lightweight construction? At its focus is the quantity of energy required to generate movement, and the efficiency with which chemical energy (diesel, gasoline, natural gas) or electrical energy is transformed into movement. The goal is to cover longer distances using the same amount of energy, and here weight plays an important role. For that reason, all manufacturers subject their car models to a diet of lightweight materials, processes, and forms.
To date a huge variety of steps have been taken to achieve this end, involving the use of magnesium, aluminum, and CFK (carbon-fiber-reinforced plastics), for example. This has been a huge expense for the automotive industry, since, according to the study “The role of steel in electromobility” carried out by the Handelsblatt Research Institute on behalf of voestalpine (HRI study), the costs of reducing the vehicle weight are five times higher with aluminum and a whopping twelve times higher with carbon than when steel is the mainly used. “Five or ten years ago a lot of money was invested in all forms of lightweight construction,” recalls Enno Arenholz, Head of Preliminary Research/Technology/Innovation at voestalpine Stahl GmbH. Today, the focus is on “affordable lightweight construction”. And while we’re on the subject of costs: By far the most economical and—from the life cycle assessment point of view—most sustainable lightweight construction option is “high-strength and ultra-high-strength steels”.
Lightweight construction in electric cars
The lower vehicle weights realized with lightweight construction mean manufacturers can reduce the size of the batteries required. As the HRI study confirms, the batteries are the main reason for the comparatively high prices of battery-powered electric vehicles—they account for around 30 to 50 percent of the costs. The formula is simple: You need less energy to drive a lighter vehicle the same distance. Lower battery costs means lower overall manufacturing costs.
The HRI study assumes that the proportion of medium- and high-strength steels will rise from the current 18 percent to just under 30 percent compared to conventional steel grades. Lightweight solutions could play a new key role in e-mobility. For example, in housing and securing the batteries of electric cars. Here, steel battery boxes could compete with pure aluminum solutions in terms of crash performance, economy and life cycle assessment (LCA). Battery casings are a new field of activity for European material manufacturers.
voestalpine ready for the future of lightweight construction
Consequently, lightweight construction for electromobility applications requires novel and complex approaches comprising a combination of material, technology, and construction. These are approaches which voestalpine companies have been consistently taking for years. On the one hand in developing ultra-high-strength steels, and on the other with innovative hot forming technologies such as phs-ultraform® and phs-directform®. The Group also already supplies extremely lightweight and secure components for battery casings.
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