Smaller and mid-sized manufacturing enterprises that use lasers to weld thin metal sheets typically find that lasers with continuous wave radiation are too expensive for their operations to afford. One reason for this is the high output powers necessary for the welding process.

However, pulsed Nd:YAG lasers are a cost-effective option, and offer an alternative to continuous wave lasers. Due to their high peak pulse output, it’s possible to weld with relatively low medium-output power (100 to 250 W), and investment costs can be reduced.

However, the narrower welding seams from the pulsed lasers are not as strong as the seams from continuous lasers. The results can be improved if the parameter selection is optimized. This was the goal of a project completed recently at the Laser Zentrum Hannover e.V. (LZH), a research center for laser technology, supported by the Ministry of Economic Affairs, Labor and Transport for the State of Lower Saxony (Niedersächsisches Ministerium für Wirtschaft, Arbeit und Verkehr).

The investigations were commissioned by the Research Association of the German Welding Society (DVS) and funded by the German Federation of Industrial Research Associations (AIF).

The results of the project would seem to simplify the parameter selection for pulsed laser welding, for example pulse duration, pulse form or pulse peak output. Also, reference parameters for welding with continuous wave radiation have been recorded. For both types of laser welding, high seams qualities could be qualified and weld imperfections avoided, as shown in surface testing and seam cross-sections.

For the investigations, both ferritic and austenitic steels with sheets thicknesses up to 1.5 mm were butt-joint welded.

Also, thin foils with a minimal thickness of 50 μm were butt-joint welded. To accomplish this, the LZH developed and constructed a high precision clamping unit, which not only assures a zero gap, but also avoids a lateral edge mismatch.

Smaller and mid-sized manufacturers especially can benefit from the results of these welding tests. They are available via an online database at the LZH site. The database provides welding and laser parameters as well as pictures of the expected seams surfaces, cross-sections and micro-hardness tests. Manufacturers are welcome to use this data to estimate welding results. Apart from simplifying the selection of appropriate parameters, users can easily contribute to the database by adding parameters of their own welding tasks to the database and accessing them when needed.