Transport and energy are growth industries. Joining technologies that allow large, thick-walled components to be processed with short production times are required for developing wind power plants, pipelines and secure transport containers. The combination of laser and electric arc into a common welding process offers financial benefits. The development of superlative lasers in the multi-kilowatt range will enable the future use of hybrid laser-electric arc processes with big metal plate thicknesses.

Setup for laser-hybrid welding trials with a 20 kW fiber laser in the BAM laser lab. Photo: BAM

CO2 lasers have long been used in shipbuilding, for example, to join thick plates with one another. The low expansion of the melting baths that are typical for the laser means that only small cutting slits can be joined. The welding of molded components, such as pipeline segments, however, requires new degrees of freedom in the process.

To present and discuss laser material processing, the German Federal Institute for Materials Testing (Bundesanstalt für Materialforschung – BAM) organized a workshop on the “Lasers for macro-material processing” topic together with the Laserverbund Berlin-Brandenburg e.V. (German laser users association) in BAM on 25 November 2008. The trend was shown to be quite clear – the combination of laser and electric arc into one common welding process has tangible benefits.

By adding additional fluid material, the arc can also be used as an ideal partner for the laser in welding larger joints. The laser’s high welding speed can be maintained. The development of new, exceptional lasers in the multi-kilowatt range will enable the future use of hybrid laser-arc welding processes with higher plate gages. More extensive flexibility will be achieved with fiber-guided lasers in hybrid welding processes. Immersion into a three-dimensional component with robot-guided processing heads is therefore “state-of-the-art technology”. The growth industries, transport and energy, are markets for these indispensable high performance lasers. Welding processes that allow large components to be handled, and at the same time guarantee economical short production times, are required in the construction of wind power plants and pipelines in particular.

The technical properties of the produced components can be adapted without restriction with adjusted parameters of the hybrid process within physical limits, whereby steel materials can be welded with higher levels of cohesion.  Weight-optimized weld constructions in commercial vehicle construction, for example, which allow the payload to be increased without exceeding the permitted axle loads, are therefore possible. In close cooperation with the respective industrial and university bodies, numerous research projects for the further development of laser beam and hybrid welding are currently underway. In the V.5 “Sicherheit gefügter Bauteile” (joined components safety) section at BAM, for example, the safety of the welded connections in laser beam and hybrid welding processes are being tested and further developed, in order to identify the correlations between the process, the construction and the material’s behavior, and to develop strategies for producing high quality welding techniques.

In this respect a 20 kW fiber laser and in the future a 16 kW disk laser will be used for qualifying laser beam hybrid welding processes in the thick plate range of up to 20 mm. Research work in this area focuses in particular on applications in pipeline construction or shipbuilding. The welding processes of high and low-alloy steels, as well as titan and nickel-based alloys, are being tested, and the mechanisms of hot crack formation in laser beam and hybrid welding processes are being examined. These BAM-internal research projects and cooperation with further competent and expert research institutes are the basis for possible safety-related assessments.