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Products and solutions, 2010-02-02, 11:00 AM

Customized solution with “Tailored Orbitals”: New production process extends possibilities for eco-friendly use of stainless steel in car exhaust systems

Auto manufacturers are increasingly turning to lightweight parts. Every gram saved reduces CO² emissions and makes cars eco-friendlier. Innovative solutions from ThyssenKrupp support the auto industry in meeting these goals. For instance, ThyssenKrupp Tailored Blanks GmbH has developed a new production process that makes parts by joining together different materials with different thicknesses or coatings by laser welding. This principle of tailoring has also been extended to round parts, so-called Tailored Orbitals. Now stainless steel can also be used in these tubes – particularly for areas of the vehicle subject to corrosive attack. For this reason tailored orbitals are ideal for pipes in car exhaust systems.

ThyssenKrupp Tailored Blanks and ThyssenKrupp Nirosta have already worked together in developing the use of stainless steel in so-called tailored strips, with support from ThyssenKrupp Steel in testing the application. In the production of tailored strips, two or three coils of different thickness or coating are joined together length-wise by laser welding. The ends are then welded together to produce lengths of several hundred meters. Different stainless steels can also be combined in this way. Parts made from this material, with thicknesses and material properties matched precisely to local requirements, are already being used in the production of auto mufflers.

“With tailored orbitals, the principle of combining different materials to form a new part has been transferred from flat blanks to tubes,” explains Dr. Klaus Zimmermann, head of Tailored Orbitals. A patented, in-house-developed laser welding machine capable of joining up to five tube segments is used to manufacture the parts. The individual segments are cut from continuous tube and then joined together in their new configuration to form tailored orbitals in lengths up to 2.5 meters, diameters between 30 and 90 millimeters and wall thicknesses of 0.7 to 5 millimeters. Combinations of different steel grades including stainless steel are possible. “The use of stainless steel in tailored orbitals opens up whole new applications,” says Stefan Schuberth, head of applications technology at ThyssenKrupp Nirosta. To date the process has been used among other things to manufacture shock absorber components for cars. “Now we are able to make tubes for auto exhaust systems that are precisely tailored to the requirements of the application, for example in terms of resistance to corrosion and high temperatures or complex forming requirements,” says Schuberth.

For auto manufacturers, this groundbreaking technology has diverse advantages: The reduction in wall thickness means potential weight savings. With stainless steel parts, tailored orbital tubes can reduce material costs. “Also, the use of different materials in one tube creates wider design and forming possibilities. Particularly in critical areas the material can be more easily formed,” explains Dr. Zimmermann. Outside the area of exhaust systems, other possible uses for tailored orbitals are in car cockpit beams, seat systems, chassis parts and the capital goods industry.

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