Lighter automobiles through laser beam welding

Fig. 1: Model for a segmented inductor: laser processing head (right), threepart inductor that can flexibly follow the course of the joint (left)

The automotive industry in Germany is working intensely on lightweight concepts to reduce vehicle mass and thus fuel consumption. This involves on the one hand the use of higher strength steels, or aluminum and magnesium alloys respectively, and on the other hand the use of customized sheet metals of different thicknesses and qualities known as tailored blanks.

Laser beam welding of tailored blanks composed of higher strength steels, however, cannot be considered as trivial, since the welded joints become brittle as a result of high heating and cooling rates. This can be significantly improved by integrating into the process inductive postheating of the welded joint directly after welding.

This process is the result of the Collaborative Research Center 362 “Sheet Metal Processing” (SFB 362) by the German Research Foundation (DFG), in which the Technical University of Clausthal, the University of Hannover, as well as the Laser Zentrum Hannover e.V. (LZH) participated. In addition, inductive postheating of welded joints was to be transferred to blanks of high-strength steel materials with virtually any weld joint geometry known as nonlinear tailored blanks. The main goal was to construct and qualify a flexible, processintegrated inductor that has to adjust itself to the course of the welded joint in order to guarantee constant postheating.

The LZH constructed a flexible multipart inductor for twodimensional welded joints. The inductor is guided mechanically across the welded joint by means of a matrix. It has a movement radius of 90° and a maximum feed rate of 3 m/min. Using this inductor, an adequate formability was achieved. More information about the system can also be obtained at the EuroBlech trade fair in Hannover (October 24-28, 2006 at booth C 21 in hall 12.

The knowledge already gained shall now be optimized in a subsequent DFG project that aims at transferring inductive postheating of linear tailored blanks to industrial manufacturing. Project partners are the LZH, Volkswagen AG, ThyssenKrupp Steel AG, Trumpf GmbH & Co. KG, as well as Huettinger Elektronik GmbH & Co. KG.

Business Development & Communications Department
Michael Botts
Public Relations
Tel.: +49 511 2788-151
Fax: +49 511 2788-100
The Laser Zentrum Hannover e.V. (LZH) carries out research and development in the field of laser technology and is supported by the Ministry of Economic Affairs, Labour and Transport of the State of Lower Saxony (Niedersächsisches Ministerium für Wirtschaft, Arbeit und Verkehr).