How important is light construction for future mobility?
What are the best ways to inexpensively extend the range of electric vehicles? This was discussed at the 2019 Light Construction Summit in Würzburg, Germany and one surprising takeaway message was that in some situations this may be achieved by optimizing the electrical (and electronics) systems rather than by lightweighting their structure. Many summit participants, nevertheless, expressed concern that the high investments in electromobility were draining financial and human resources from lightweighting projects.
Other summit takeaways:
- Electromobility (EVs) designs continue to have a profound influence on lightweighting designs for all vehicles: electric, hybrid, and traditional.
- In the ongoing battle between weight reduction vs. cost efficiency, designs using lightweight steels are experiencing a renaissance, noted several speakers. New high-strength and ultra-high-strength steels can enable cost-saving weight reductions while maintaining required properties.
- The growing realization that the intelligent allocation of lightweight materials under the maxim “The right material in the right place” is more pragmatic than the wholesale substitution of aluminum (previous Audi A8) or carbon fiber (BMW i3).
Furthering that maxim, an increasing number of farsighted carmakers are experimenting with natural-fiber reinforced biomaterials — which lighten both the vehicle and its ecological footprint. And experts are also predicting that carbon-fiber reinforced materials will eventually reach mass production levels, providing more mature and rational manufacturing methods for the once exotic material.
New techniques in hybrid material construction
Car components made from hybrid materials are becoming more important for areas of the vehicle vulnerable to powerful, localized stresses. At the summit, for example, Volkswagen presented its E-Golf model with a sill/B-pillar area that is fiberglass-reinforced plastic glued to high-strength steel sections. The resulting structurally reinforced area reduced intrusion by 50% in crash tests. With this hybrid approach, Volkswagen is able to meet the 2015 changes to the New Car Assessment Program (NCAP) pillar impact test, while adding less than 200 grams of weight, and without having to change their mass-produced bodywork or associated manufacturing processes.
Using foamed material is another approach. However, it is more expensive and requires careful consideration from the very beginning of a development process. Nevertheless, in combination with other materials (e.g., advanced high-strength steels or AHSS’s), foamed materials have good properties at low weight.
Fully leveraging computer simulations when lightweighting car components
Advances in computer modeling — with dynamic simulations of component designs using specific lightweight materials — are becoming more important than ever. For example, the consequences of making materials thinner can be calculated with greater and greater accuracy. Several summit speakers presented designs, some of which result in considerable material savings (and cost reductions).
A second important advance, alongside computer simulation, is additive manufacturing (aka, 3D printing), which not only permits extreme component geometries but also allows the high integration of functions within a car component.
It was notable that many of the presentations took a holistic view of lightweight construction. For example, the focus on production costs has been joined with ecological footprint analysis: What is the holistic environmental impact over the component’s entire life cycle, from raw material to recycling?
Another holistic example: automotive lightweighting has grown to be much more than just looking at individual component construction. True, the process still starts with extensive component computer simulations. But it goes on to include total vehicle simulations, then vehicle crash calculations, then vehicle manufacturing and assembly simulations, before reaching the estimation of the ecological footprint.
Can the steel industry match future need for lightweight and CO2 efficiency?
"The 2019 Lightweight Construction Summit in Würzburg has confirmed that SSAB, with its innovative materials and extensive services, is accurately anticipating many of the trends in lightweight construction," says Thomas Müller, Head of Business Development Automotive at SSAB, and one of the speakers at the event. With its portfolio of automotive steels under the Docol® name, SSAB is an important "enabler" of automotive lightweight construction, as their AHSS steels prove their functional worth through their high strength, excellent ductility, and good fatigue performance. As SSAB assigns each AHSS steel to a fixed production line, these steels also exhibit highly consistent material properties. And in addition to the standardized Docol® AHSS steel portfolio, customer can also request special AHSS grades.
SSAB’s commitment to the global environment is both heartfelt and highly pragmatic: further regulations on CO2, including “embedded carbon” in car materials, seem virtually inevitable. Currently, SSAB emits only 2 kg of CO2 for each kilogram of steel produced — making it one of the world’s most carbon-efficient steel manufacturer. Steelmakers in the EU, on average, produce 7% more CO2, the USA 11% more, China 26% more, and India 42% more.
"Nevertheless, even two kilos of CO2 per kilo of steel is not the end of the story for us," Müller says. “Our goal is to make steel with virtually no CO2 emissions. In Luleå, Sweden, we are constructing an experimental HYBRIT plant that will use hydrogen, instead of carbon, in the blast furnace. The hydrogen will be produced using new and existing sources of hydro and wind power.
SSAB’s plan is to have commercially available fossil-free Docol® AHSS steel by 2045. In the meantime, SSAB is experimenting with biocarbon and will convert part of one of their plants to all-electric, eliminating all coal/coke use.
Lightweight construction for EV as a process
As an example of “lightweight construction as a comprehensive process,” SSAB presented a design concept for the crash protection of batteries in electric vehicles. Using selected Docol® AHSS steels, the protective battery enclosure is:
- Thoroughly robust
- Lightweight and efficient
"And this battery housing is attracting great interest," Müller notes, “not just among German OEMs, but more particularly among Chinese carmakers."
“This battery enclosure for EVs is an example of what SSAB can do if it is involved early in the car development process,” says Müller. “For optimum automobile lightweighting and component performance, that early involvement is critical. Depending on the application, our Knowledge Service Center has helped car makers reduce component weights by up to 50%.”
The Docol® Knowledge Service Center helps car designers in their everyday tasks, answering their full range of questions about advanced high-strength steels. This could be with concept and construction studies, calculation and computer simulation services (for example, digitally modeling the forming processes and crash performance), or with suggestions for tool design, tooling solutions, or the welding of AHSS steels.
The Docol® Knowledge Service Center team includes highly trained computer simulation engineers, designers, welding experts, and forming specialists. The team has access to the latest forming machinery and computer modeling programs. To allow potential customers to experience the benefits of SSAB steels for themselves at an early stage, SSAB operates a test material store which is one of a kind in the world. The store’s stock inventory includes sheets and coils of many of the Docol® AHSS steel grades, which SSAB can cut to size and ship within two weeks — often within two business days. This comprehensive, highly specialized, and fast-response sampling service is probably unmatched by any other AHSS steel manufacturer.
Thomas Müller, Head of Automotive Business Development at SSAB