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Products and solutions, 2006-10-24, 09:05 AM

ThyssenKrupp Tailored Strips open up new possibilities

ThyssenKrupp Tailored Blanks GmbH is opening up further areas of application for its steel tailored products with the introduction of new, 1,200 millimeter wide tailored strips. While the previously available tailored strips in widths of up to 700 millimeters were mainly used for weight-optimized profiles, the new product has been specially developed for use in progressive/compound dies, used by auto manufacturers and suppliers to produce roof frames, roof cross rails and seat cross members among other parts.

In the past, it was not possible to process laser-welded tailored products in progressive/compound dies. Such lines are unsuitable for use with tailored blanks - made from sheets of differing grade, thickness or finish - because they cannot process individual sheets. Instead they use steel strip from a coil. During the forming process, the strip is indexed through several die stations, achieving its final shape in the last of these stations before being separated off. With the introduction of wide tailored strips, ThyssenKrupp Tailored Blanks GmbH has now made it possible to apply the tailored blank principle to parts which can only be manufactured from coil in a continuous process rather than from individual sheets.

The company operates a line - the only one of its kind in the world - which can continuously join steel strips of different thickness, grade or finish along their outer edges over a length of several hundred meters by laser welding. The products made using this technology can be ideally tailored to the stresses which will be encountered in the finished component. In tailored strips, available in coils of up to 15 metric tons, the right steel is in the right place from the outset. For example, tailored strips can be used to produce roof cross rails with thicker steel at the sides where they will later be attached to the pillars and thinner in the middle. This saves weight and reduces the number of steps required for assembly. Strips with different coatings can also provide a more cost-efficient solution to special anti-corrosion requirements. Combinations of carbon and stainless steel or all-stainless tailored strips are also possible.

For many years, joining long steel strips with an uninterrupted laser weld was regarded as technically impossible. Three-meter welds were the limit. The reason 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 and making it impossible to form a laser weld. The tailored strips line operated by ThyssenKrupp Tailored Blanks is the first laser welding line in the world capable of coping with this.

This is thanks to a combination of a newly developed weld cooling system, special edge treatment and a sophisticated strip guide system. In addition, the stationary laser welding head under which the steel strips pass can swivel to each side, allowing it to follow irregularities in the joining gap. The starting material for the up to 1,200 millimeter wide coils is 50 to 1,000 millimeter wide slit strip in thicknesses of 0.8 to 3.0 millimeters.

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