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Thinking about tomorrow today

engineering. tomorrow. together – that’s how thyssenkrupp makes its brand promise a reality. For us, ‘tomorrow’ means constantly researching new raw materials and production processes in order to meet the future needs of the market and our customers.

(Text: Judy Born, Photos: Dominik Asbach)

Mobility is and will remain one of the megatrends of the future. It is an expression of freedom, independence, self-determination. Today, the desire for mobility is primarily satisfied by the automobile. And that is not likely to change in the foreseeable future, because any time enthusiasm for mobility decreases, it is balanced out by an increase somewhere else. This is true in part because of another megatrend: population growth.

Materials specialists
One thing is certain where both materials and materials specialists are concerned: The next generation is here.

More than a million cars are on the road worldwide right now. It remains to be seen whether we will soon be filling our tanks with gasoline or electricity or powering our cars with hydrogen or sunlight, and whether we will be doing it ourselves or letting robots do it for us. The car is the ultimate individual mode of transportation, even if it won’t necessarily be the only one in the future.

New materials are needed

As a result, car manufacturers need new ideas and models. Automobiles have to become more environmentally friendly and use resources more efficiently. They need to offer more comfort and safety. And they must become less expensive to produce and maintain. For the Steel division of thyssenkrupp, this means orienting the division’s materials to the current and future requirements of automobile production. For example, the division needs to develop types of steel that offer greater potential for lightweight construction and a broader range of forming options, and in certain parts of the chassis it needs to offer both increased stability and greater flexibility.

Jens-Ulrik Becker | thyssenkrupp Steel Europe

We are a miniature smelting works

Jens-Ulrik Becker, Head of Process Development and Pilot Production

Progress in these areas is plain to see at Westfalenhütte in Dortmund, the site of an important branch of thyssenkrupp’s Research and Development division. It is here that the achievements of materials developers are cast in steel and become a reality. “At the end of the day, we’re a miniature smelting plant,” says Jens-Ulrik Becker, head of process development and pilot production. “Steel is smelted here just like at a big plant. It’s annealed and hot and cold rolled, the only difference being that the quantities are small.”

Rüdiger Mempel and Jens-Ulrik Becker | thyssenkrupp Steel Europe
The simpler the steel, the easier it is to copy: Rüdiger Mempel and Jens-Ulrik Becker (right) make complex visions of materials a reality.

The ideas for new materials come not only from the automotive industry, but from thyssenkrupp’s Steel division as a whole. “Our internal customer base, if you will, is not limited to the materials developers from the Steel division. It also includes our coworkers in precision hot strip, tinplate, heavy plate, and electrical steel,” says Becker. “That’s because we are able to reconstruct many different facilities and produce both the thinnest tinplate and the thickest heavy plate.” Ideas are in plentiful supply at the company, and there is always plenty to do, he reports.

In keeping with the pioneering spirit, the latest innovation from the thyssenkrupp Group was conceived here: tribond®, a composite material that combines various types of steel. Both the procedure and the materials technology were developed in Dortmund. “This time around, the development came entirely from our team,” says Becker, “and that’s what makes this composite material unique in many regards.”

tribond® got its start here

tribond® 1200 and 1400 were developed especially for hot forming and are ready for production. The products consist of two outer layers of a ductile steel surrounding an ultra-high-strength steel core. The composite material functions as a modular system whose properties can be modified to suit a particular application based on the configuration of the materials. The automotive industry will not only benefit from the product’s potential for lightweight construction. tribond® has a higher energy absorption capacity than standard hot-formed steels, and that makes it suitable for use in entirely new areas of application, for example, in side members, where the material undergoes severe compression in the event of a crash, dissipating a great deal of energy in the process.

Gas control installation
A question of configuration: The gas control installation maintains the right furnace atmosphere during hot forming.

This is an obvious application for cold-formed steels today. Under normal circumstances, however, Jens-Ulrik Becker and his team are service providers who implement other people’s ideas. Examples include new, high-strength DP steels with exceptionally high elongation for use in cold forming. Like tribond®, these high-strength steels are a good fit for the lightweight construction strategies of car manufacturers. And they are much easier to form, thanks to increased ductility and modern processing technologies. That makes them suitable for complex structural elements such as B-pillars, a typical area of application for hot-formed steels.

Researchers in Dortmund are also testing steel-plastic sandwich materials at a pilot plant to keep weight down. Not only could these materials exert a major influence on future automobile construction, they could also offer an interesting alternative material for many other areas.

The search for ideal surfaces

However, a new product at thyssenkrupp still has to pass through additional stages before it is ready for the market. The usual procedure is for Becker and his employees to pass the new material on to the Surfaces pilot production facility, where Bernd Schuhmacher and his team work on coatings for new steel grades. This is a crucial job, because more than 80 percent of thyssenkrupp’s rolled steel destined for automotive customers undergoes surface treatment prior to delivery.

The chemical composition of a steel grade strongly influences its coatability. “For example, we have a hot dipping laboratory where we can selectively reproduce the hot-dip coating process for new steels in small quantities,” says the head of the New Surfaces and Pilot Production department. The same holds true for the coil coating lab, where organic coatings are applied by means of rolling. These high-performance laboratories make it possible to save on a lot of costly operating tests, which now only become necessary once the product has achieved the required degree of maturity in the laboratory.

Bernd Schuhmacher | thyssenkrupp Steel Europe

If it works here, it usually works at a large plant, too.

Bernd Schuhmacher, Head of New Surface Technologies and Pilot Production

Another of the team’s core areas is the BPA 300 strip pilot plant, a modularly designed research facility for 300-millimeter-wide slit strip, which runs through the machine at a rate of 60 meters per minute. The facility is able to test a large number of coating and cleaning methods that have yet to become established in the steel industry. It functions as a kind of midwife, so to speak, for a number of different developments. One example is the zinc-magnesium product family, a hot dipping process that has recently come to occupy a regular position in the steel portfolio as an outer shell coating for the automotive industry.

Pilot plant for metal strip, hot dipping lab, and composite materials pilot plant
No innovation without investment: The Surfaces pilot production facility, with its pilot plant for metal strip (right), hot dipping lab (upper left), and composite materials pilot plant (lower left), is always state-of-the-art.

New material properties require innovative technologies. “Hot dipping and organic coil coating have really reached their limits in this regard,” reports Schuhmacher. “By contrast, vacuum deposition, where the coating is applied as a thin film on flat-rolled steel, markedly increases the degree of flexibility in choosing the coating process.” Developing and industrializing a technology like this is exactly what the strip pilot plant was built for. “Here at the pilot plant we can run tests under conditions that closely approximate those of large industrial plants. If it works here, it should be possible to develop an industry-compatible process.” And if not, the tests will help set the right priorities at an early stage.

Cohesion is everything

But the best base material is useless if it cannot be processed. This means that steel grades not only have to be lightweight and crash-proof, they also have to be easy to form and join. “The most perfectly shaped component is worthless if you can’t attach it to a car,” says André Marx of the Press Joining and Bonding team. Whereas in production forming always comes before joining, research in the area of application technology in Dortmund examines both areas in parallel. “In addition to its mechanical technological parameters, the steel is characterized on the basis of its ability to be formed and joined.”

Resistance spot welding
Resistance spot welding: Two electrodes come together, current flows, and steel joins together.

In practice, one also has to deal with differences in the thicknesses of the metal sheets, for example, when a thin outer skin is welded onto a thicker structural component. In addition, it is also sometimes necessary to weld different steel grades together. tribond® posed a unique challenge for joining technicians in this regard due to its three-layer structure. “Our expertise in joining technology enabled us to overcome these challenges as well, of course.”

But hybrid joining processes are also important, since not all components can simply be welded together. When two different materials such as steel and aluminum have to be joined together, bonding is used in some cases in combination with a mechanical joining procedure. The complications entailed by this process should not be underestimated. “Just think about using adhesive on the windshield of a car,” says Marx. “It has to withstand extreme temperature differences without losing its adhesive properties.” Hybrid joining processes are lately becoming increasingly popular in steel connections as well, due to the fact that using several kilograms of structural glue in a car increases the overall stiffness of the vehicle.

André Marx | thyssenkrupp Steel Europe

The most perfectly shaped component is worthless if you can’t attach it to a car.

André Marx, Press Joining and Gluing team

Finding the right form

Sascha Sikora | thyssenkrupp Steel Europe
Sascha Sikora heads the Cold and Hot Forming test area in Dortmund.

Sascha Sikora is responsible for forming in Dortmund. His department tests the application of new materials and technologies in cold and hot forming. With tribond®, he has already succeeded in creating an innovative material for hot forming that is ready for production. “We are currently developing new forming technologies and processes for cold forming that will help make it easier to deal with springback, one of the central problems associated with high-strength, cold formed steels,” says Sikora. “Until now, springback has often prevented manufacturers from using this material in geometrically complex components such as B-pillars.”

Given the rapidly increasing number of raw materials and technological concepts, automobile manufacturers will now have far more options for implementing their lightweight construction solutions in an individualized and customized way without sacrificing crash performance. These innovative solutions are not a product of chance, but of ongoing development and continuous research. They highlight the versatility and attractiveness of the material and prove that steel is still a long way from the scrap heap.

Forming – the customer decides

Any car manufacturer who wants to achieve optimum results for his car in the area of lightweight steel construction and crash safety must use hot forming on some parts and cold forming on others.

thyssenkrupp Steel is diligently expanding its portfolio to offer customers more freedom of choice with regard to hot and cold forming. Today, the company offers raw materials with multiple properties such as tribond®. Designed for hot forming, this composite material is suitable for manufacturing highly stable lightweight B-pillars because it combines ductility properties with extremely high resistance to deformation. It also features additional properties that enable it to absorb a great deal of energy, making it an excellent material for side members in the front ends of automobiles.

The new high-strength variants of dual-phase steel are another all-rounder. Apart from their ability to absorb large amounts of energy, they also offer increased strength and improved forming properties as compared to previous generations. As a result, highly complex structural components can now be formed via cold forming.

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