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Products and solutions, 2009-04-27, 11:00 AM

Stainless steel ThyssenKrupp Tailored Strips in auto mufflers reduce weight and emissions

Lightweighting is an increasingly important objective for auto manufacturers. Every gram of weight saved reduces CO2 emissions and thus makes the vehicles eco-friendlier. To meet these requirements, ThyssenKrupp Nirosta has developed an innovative solution using ThyssenKrupp Tailored Strips, which comprise strips of different thickness matched exactly to the stresses acting on the part. For the first time, this new technology is now being used in a stainless steel production part – a rear muffler made by automotive supplier Eberspächer for the new BMW 730d in the diesel version. It was developed by ThyssenKrupp Tailored Blanks in conjunction with ThyssenKrupp Nirosta and Eberspächer as innovation partners.

Currently, stainless steel of uniform wall thickness is used in the construction of exhaust systems. The material thickness is selected to be able to handle the highest mechanical, temperature and corrosive stresses. ThyssenKrupp Tailored Strips now allow the thickness and properties of the materials used in exhaust systems to be matched exactly to various local requirements. This not only opens up completely new areas of application for tailored steel solutions, it also offers advantages for production. “The material is more readily formable in critical areas. In addition, the production process is highly flexible when it comes to combining different thicknesses and widths,” says Stefan Schuberth, head of the Applications Technology department at ThyssenKrupp Nirosta. “Tailored strips technology allows our customers to take entirely new approaches to production and cost cutting.” The new product will be offered by ThyssenKrupp Tailored Blanks.

Compared with a normal muffler with a constant wall thickness of 1.2 millimeters, ThyssenKrupp Tailored Strips allow in order to the demand wall thickness of between 0.7 and 1.2 millimeters. On the rear muffler of the BMW 730d, for example, this leads to a weight saving of 700 grams. Applying this process to other parts of the exhaust system can reduce the weight of a mid-size car by up to three kilograms.

ThyssenKrupp Tailored Strips are made by joining two or three coils of different grade, thickness or finish by laser welding. Another unusual feature of this unique process is that the slit strips can be welded continuously to lengths of several hundred meters. The technology was developed by ThyssenKrupp Steel and is used exclusively on the world’s only line of this kind at the Gelsenkirchen plant of ThyssenKrupp Tailored Blanks. This groundbreaking technology not only makes it possible to join strips of different thickness, it also allows combinations of different stainless steel grades within a material group. In the future, it will also be possible to combine grades from different material groups.

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