Page 50 - Best of 2019 English

It’s better to bend than to break
Steel remains the number one material in automotive engineering – not just economically speaking, but above all from the safety point of view. Salzgitter AG has also had its part to play here – through the development of innovative steel grades. Blending these is crucial to automotive body construction: Stronger steels protect occupants in the event of an accident, while softer ones absorb impact energy
In the 1930s, the development of new presses, sheet metal processing and welding methods made it possible to build steel structures out of profiles and sheet metal that supported
the engine and chassis, giving the vehicle stiff- ness: the self-supporting body was invented. It was not until the 1950s, however, that the focus shifted more to safety aspects, however. In August 1952, Daimler-Benz was granted patent no. DBP 854.157, filed in January 1951, for the invention of the crumple zone: here, the center of the vehicle is designed to be more stable than the front and rear, causing the latter to deform and dissipate kinetic energy in the event of a collision. Both physically and economically, this invention would not have been possible with any material other than steel. At the same time, a distinction now came to be drawn between hard and soft construction, laying the foundation for the use of different types of steel in vehicle construction.
Since the 1960s, steel has been used to improve numerous details of car design in the interests
of safety. Examples include headrests and the deformable steering column which no longer impales the driver in an accident, roll-over bars
50 STEEL AS A LIFE-SAVER
in convertibles, side impact protection, tubes for seatbelt tensioners and airbags.
Not only are passenger compartments much more stable today than they were 20 years ago, body design is also more sophisticated, due in part to the greater differentiation between the steel grades available. When a crash occurs nowadays, deformation energy is directed along precisely calculated load paths, as they are called, to be dissipated in small doses by means of differ- ent types of steel as well as other materials such as aluminum. When designing new car bodies, manufacturers take into account the varying strengths of the different steel types as well as their formability and energy absorption capacity. Since the material properties are precisely known, cracks and fractures along the load paths can be specifically incorporated in planning.
Research into new steel grades is only part of the challenge facing the Salzgitter Group’s ma- terial developers. Not only do these also have to be extensively documented (see next page), they are also subject to the constraints of economic efficiency and the requirements of lightweight engineering.