The automobile manufacturer has been using hot-formed steels since 2004; these materials’ extreme strength also makes them eminently suitable for use in lightweight construction and even for the most complex component geometries, depending on the process. Hot-formed steels made a significant contribution to breaking from the trend of increasing weight in vehicle construction. “Above all, they are still indispensable for the structural components that are key to vehicle safety,” says Ilda Hujdur. She is a production engineer in hot forming at Volkswagen and responsible for quality and tools.
Lightweight and stable
Lighter vehicles consume less fuel and release a lower level of CO2 emissions. The best example is the VW Golf 7; its chassis alone is 23 kilograms lighter than its predecessor’s. Components made of hot-formed steel from thyssenkrupp played an important part in weight reductions of this nature. “MBW® 1500 is standard for these applications today; it was one of the decisive developments in the area of cost-effective lightweight steel construction,” says Dr. Jürgen Schramm, Product Manager for Coated and High-Strength Steels at thyssenkrupp Steel in Duisburg. And development continues, with steels of even higher strengths being created: Because thyssenkrupp Steel’s precise goal is to provide products with exactly the properties needed to meet the specific requirements of customers’ intended applications. “Lighter weights and optimized costs and processes are the key considerations here,” Schramm says.
In order to fully tap the potential for lightweight construction, the material must be suitable for martensitic microstructural transformation. That is the only way to achieve the high level of strength required to reduce materials and weight while maintaining the same level of stability. And naturally, the steel needs to be highly formable. “This is made possible by the high temperatures in the process; MBW® allows for the manufacturing of highly complex components,” Schramm says. “If we consider the growing prevalence of hybrid and electric vehicles, we can expect demand in this area to rise.” Thanks to their very high resistance to deformation, hot-formed components are ideal for the stringent safety requirements surrounding batteries.
Speed and precision: Ilda Hujdur (VW Kassel) and Dr. Jürgen Schramm (thyssenkrupp Steel) know why stable processes for hot forming are so important.
Ideal for electric cars
In terms of electric vehicles, Volkswagen already has a platform for mass production with its Modular Electrification Toolkit (MEB). Hot forming also has a role to play here: Starting from the end of the year, a whole series of structural components for the MEB will be produced in Kassel. “We want to expand on that, because the MEB will contain twice as many hot-formed components as standard toolkits,” Hujdur says. That’s good news for Duisburg, because when it comes to electric vehicles, thyssenkrupp is well-positioned. “Steel is in high demand not just as a lightweight material for chassis, but also as electrical steel, an indispensable basic material for electric motors,” Schramm says.
Mass-produced lightweight construction
The VW plant in Kassel developed hot forming for mass production at a very early stage. Currently, there are 11 hot forming lines in operation, with two more planned, making it the group’s largest hot forming site. Approximately 64,000 components are produced here every day, some using just one tool, while others require three tools at the same time. Currently, Ilda Hujdur doesn’t see an alternative to hot forming: “At least not if we want to work cost-effectively.”
In the expansive Hall 2, growing numbers of work units have relocated around this technology. “In terms of workflows, this all makes sense,” Hujdur says as we tour the facility. “First, we cut the blanks, then we form them and use a laser to finish the contouring.” The pressed components roll out of hot forming and into laser automation constantly and are then packed up. A driverless transportation system picks up the package from there and drives it to the shipping facility. As of recently, parts can also be welded on site and shipped out as complete components, such as finished side members.
Efficient production processes and intelligent use of resources make all the difference. For thyssenkrupp Steel, this means getting customers involved in the development process for new products and technologies as early as possible and understanding their production processes. “As a manufacturer, we would like to have the largest possible process window in the future,” says Hujdur, referring to more durable materials, efficient processes, and an optimum use of materials. Corrosion protection also plays a major role, particularly in battery housings. thyssenkrupp Steel is already working on new solutions. “We are constantly refining our portfolio,” says Schramm. “Steel is the dominant material in automotive manufacturing, and it will stay that way.”