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Company News, 2005-09-12, 11:02 AM

Tailored strips direct from coil

ThyssenKrupp Tailored Strips offer new perspectives to manufacturers of steel profiles or other formed parts. Seat rails, seat backrests, exhaust components and wheel rims could in the future all be manufactured from steel strips which are adapted from the outset to the stresses in the finished part. ThyssenKrupp Tailored Blanks GmbH supplies ThyssenKrupp Tailored Strips in coils of up to 15 metric tons. A unique line developed by ThyssenKrupp Tailored Blanks joins steels of different thickness, grade or coating by an uninterrupted laser weld several hundred meters long.

Steel profiles are formed by running slit steel strip through a profiling line with several roller sets arranged in sequence. The roller sets bend the steel strip step by step to the cross section required for its later use. ThyssenKrupp Tailored Strips can be made from steels of different thickness or strength, allowing the production of profiles which are ideally adapted to the actual stresses in the finished part. This eliminates the need for the subsequent reinforcement of highly stressed areas and allows customers to dispense with complete production steps.

Laser-welded strips also meet corrosion protection requirements more cost-efficiently: the strips can be made up of coated and non-coated steel or a combination of carbon and stainless steel. These stress-oriented strips also permit similar weight reductions to tailored blanks of over 20 percent.

Profiles are formed in a continuous process which requires the use of strip from a coil. Tailored blanks laser welded blanks developed in the 1980s comprising steels of different thickness, grade or coating are not suitable for this purpose. Until recently, joining long steel strips with an uninterrupted laser weld was regarded as technically impossible. Three-meter welds were the limit, and then only if the individual blanks were at least 200 millimeters wide.

The problem is that the laser beam melts the strip edges during laser welding. After a time, the strips heat up to such an extent that they distort, increasing the gap between them. However, this gap must not exceed 0.08 millimeters. The tailored strips line operated by ThyssenKrupp Tailored Blanks at its Dortmund plant is the first laser welding line in the world capable of coping with this problem, thanks to a newly developed weld cooling system. In addition, the stationary laser welding head under which the steel strips pass can swivel by five millimeters to each side, allowing it to follow irregularities in the joining gap.

To keep these irregularities to a minimum, the steel strips pass through levelers before they are guided to the welding station. The edges of the strips can also be prepared for welding by scraping, milling or rounding. The tailored strips line in Dortmund can process slit steel strips in widths of 50 to 700 millimeters and thicknesses of 0.8 to 2.5 millimeters.

ThyssenKrupp Stahl is exhibiting at IAA in hall 4.1, booth C50.

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