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.
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.
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.
Hannu-Pekka Heikkinen, Outokumpu Stainless Oy,
Mika Sirén, VTT Technical Research Centre of Finland
Outokumpu Stainless Oy, Andritz Oy, VTT Technical Research Centre of Finland, Aalto University School of Engineering