Laser welding in cold-formed areas of high-strength steel sheet with Rm ⩾ 800 N/mm2.

To extend the possibilities of innovative lightweight construction, increasingly stronger steel sheet materials are being developed by steel manufacturers and increasingly used by the sheet metal processing industries. Typical representatives of this group are the so-called multiphase steels. Due to their higher strength compared with non-alloyed or low-alloyed steels, they allow the implementation of new design and safety-relevant aspects. Major applications are components made from cold-formed sheet metal, i.e. in automotive engineering for door impact beams or for strengthening the B-pillar as well as in the design of cranes or for wear-stressed components, for example in transport vehicles or agricultural equipment. This means that the sheet metal is subjected to a forming process before welding for virtually all applications, i.e. by bending or deep drawing. The changed material properties as a result of cold forming and stretching, such as increased springback behaviour and local changes in structural/stress conditions and hardness, may impair the suitability for welding or soldering. As part of a research project [1] at the Welding Training and Research Institute SLV Munich, investigations were therefore conducted into the laser welding and soldering of non-deformed and specifically deformed highstrength steel sheet and analysed with regard to changes in process and materials behaviour and bonding properties in terms of the fields of application. The effects on the suitability for laser welding are presented in the following. [ABSTRACT FROM AUTHOR]