At ArcelorMittal’s recent media day in Paris, Philippe Aubron, CMO of Automotive Europe, discussed the company’s global automotive business and what the move to electric vehicles means for steel and ArcelorMittal. While the share of electric vehicles will dramatically increase in the next years, one constant that will remain is the critical role that steel plays in vehicle design.
2017 is likely to mark the first year that global sales of battery electric vehicles (BEVs) exceed one million units globally. Although sales of EVs are still a long way behind conventional internal combustion engine (ICE) vehicles, there are expectations that they will make up a quarter of all new car sales by 2025. While the EVs of 2025 are likely to be very different to the models available today, steel will still play a critical role in vehicle design.
In early November 2017, the EU announced its emissions targets for the period from 2025 to 2030. This will see average fleet emissions down by 30 percent compared with 2021. Many European countries and cities have also decided to ban sales of ICE-powered vehicles. Other governments around the world are also expected to tighten their regulations while targeting fast growth in electrification at the same time. These factors are increasing the sales of EVs. As they emit no carbon dioxide or nitrogen oxides, EVs can reduce overall fleet emissions significantly.
In many established markets, the most popular EVs are typically ‘hybrids’. They combine an ICE with an electric engine to maximize range. In other regions, such as China, where personal mobility options have traditionally been limited, fully electric vehicles (known as battery electric vehicles or BEV) dominate the market.
One of the limitations of EVs has been the weight of the battery and extra reinforcement needed to protect it during a crash. Total weight of the battery and protection can be up to 700 kg. Positioning this mass in the vehicle has been a major challenge for carmakers. The most common approach is to keep the battery low in the vehicle.
“Advanced high strength steels (AHSS) are enabling OEMs to provide the protection required, but without adding significantly to the weight of the vehicle,” notes Jean-Luc Thirion, head of ArcelorMittal's Global R&D for Automotive. “Our offer includes Usibor®, a press hardenable steel (PHS) with strengths up to 2000 megapascals (MPa), and Fortiform® for cold stamping. Fortiform® is currently available in strengths up to 1180 MPa, but this is set to increase in 2018 with the release of Fortiform® 1470.”
Stiffness is another consideration for OEMs. To mimic the handling performance of an ICE, the stiffness of the chassis and wheels in an EV must be increased. AHSS solutions ensure stiffness performance is maintained without additional weight.
AHSS is also the preferred material to house and protect the battery in the event of a crash. The unmatched strength of the steel used in this application absorbs more energy during a crash. Thanks to their very high strength it is possible to reduce the thickness of the protection and housing systems. Intrusion resistance is still enhanced, but the space dedicated to batteries can be increased. This allows OEMs to use larger batteries and increase range – one of the biggest limitations of EVs.
“Reducing the weight of an EV by 100 kg only improves range by around 6 to 11 km depending on the size of the vehicle,” explains Jean-Luc Thirion. “The same range increase can be obtained by increasing battery capacity by 1.1 to 1.2 kilowatt hours (kWh).”
Increasing battery capacity by one kWh typically costs around €100. OEMs must assess the cost of weight savings against the cost of a positive increase in battery capacity. Today, AHSS steels are still a more cost-effective solution to increase range.
Carmakers are recognizing this, leading to a major usage of steel in EVs. The body and chassis of Tesla’s new Model 3 mass-market vehicle is a blend of steel and aluminum, unlike the Tesla Model S which has an aluminum body (source: Tesla website: https://www.tesla.com/compare). The body-in-white of the Chevrolet Bolt is composed of 86-percent steel, including 44-percent AHSS. These OEMs are using the advanced lightweighting potential of steel to achieve their range goals.
One of the megatrends ArcelorMittal is watching closely is the battery technology itself. While existing lithium-ion (Li-ion) technology is likely to dominate for the near future, solid-state and graphene batteries are under development. These technologies have the potential to make batteries smaller while extending vehicle range. However, they come at a higher cost than Li-ion technology.
The improvements in battery performance will have an impact on lightweighting: a small increase in battery efficiency is likely to be a more cost-effective way of increasing range than lightweighting with alternative materials. “With less emphasis on lightweighting due to battery technology improvements, alternative materials to steel become much less interesting for automakers,” notes Jean-Luc Thirion. “Steel will be the most cost-effective material for vehicles and will remain the material of choice.”
Another way to increase range is to improve the efficiency of electric motors and generators. ArcelorMittal has developed the iCARe® range of electrical steels specifically to address this issue. Three grade families have been developed:
It’s important to note that there are many motors in modern vehicles. They drive functions such as electric windows, seat adjustors, and the motor itself. They all must be light and compact to maximize vehicle performance and range.
During 2017, ArcelorMittal released the second generation of iCARe® steels which are lighter and offer improved performance – following customer demand. We are already working with customers around the world to develop the third generation of iCARe®.
By 2030, when new regulations come into effect around the world, autonomous vehicles and automated car sharing services are likely to be more common. In turn, this will increase the number of EVs on the road significantly.
However, this is unlikely to result in a fall in the amount of steel used in their construction. Vehicle autonomy will not prevent all accidents. Weather and human drivers on the road are just two of the challenges that need to be addressed through passive safety solutions. At the same time, steelmakers such as ArcelorMittal will continue to improve the strength of their offer, ensuring that steel will maintain its dominant position in mobility.
Steel offers the optimal balance of strength, performance, mass reduction and cost with the least impact on the environment. Steel is the material of choice for today’s vehicles and will remain the material of choice for vehicles of tomorrow.