SUMMARY

Laser-arc hybrid welding can be simply described as a fusion-welding process where both a laser beam and welding arc are focused simultaneously in the same weld pool. This hybrid technology has a number of advantages, but in this context the most important is the use of external filler material to modify the metallurgical composition of the resulting weld. The objectives of the laser-arc hybrid welding experiments were to produce welded test samples for mechanical, corrosion and microstructural characterisation, and to develop process know-how for successful joining of these novel materials.

RESULT

hThese welding experiments provide new data and know-how on laser-arc hybrid welding of novel ferritic and duplex stainless steel grades. The results gave guidelines to and understanding of interdependencies between the welding process conditions and weld geometry, filler metal selection with respect to dilution behaviour, and effect of weld chemistry on weld solidification and resulting microstructures. The results can be used, for example, by steel manufacturers in their steel development and customer service, by OEMs in their product and production development, and by end-users in their maintenance and service activities.From the point characterisation method viewpoint, electron backscatter diffraction (SEM-EBSD) proved to be an excellent tool in phase balance determination of the weld cross-sections with respect to accuracy and resolution, ease of use and characterisation time.

Laser-arc hybrid welding (a) arrangement allowing, microstructural tailoring (b) for e.g., optimised corrosion resistance (c) of components in true service conditions

MOTIVATION

Fluctuation of the nickel raw material price in the global market has resulted in demand for low-Ni alloyed stainless steels, i.e. duplex, Mn-alloyed austenitic and ferric grades. The use of low-Ni grades is expected to grow in both pulp & paper and process industries. However, in order to substitute existing construction materials, there is a need for a comprehensive understanding of both joining and joint performance in the service environment. Comparable experimental data on corrosion properties, as well as instructions and codes of practice for welding manufacture for demanding structures, are not yet available.

APPLICATIONS/
IMPACT

The results will be used by steel manufacturers (e.g. Outokumpu Stainless) in their steel development and customer service, OEM´s and end-users (e.g. Andritz) in their product and production planning and maintenance service, and research institutes (e.g. VTT and Aalto) in their research services and educational purpose.

MAIN CONTACT

Hannu-Pekka Heikkinen, Outokumpu Stainless Oy,  

Mika Sirén, VTT Technical Research Centre of Finland

PROJECT PARTNERS

Outokumpu Stainless Oy, Andritz Oy, VTT Technical Research Centre of Finland, Aalto University School of Engineering

AUTHORS