Product Code: ICA12_1701

Effect of Gas Shielding and Heat Input on Autogenous Welding of Duplex Stainless Steel
Authors:
Antti Salminen, Laboratory of Laser Materials Processing, Lappeenranta Univ. of Technology, Machine Technology Centre Turku Ltd; Lappeenranta Finland
Elin Westin, Böhler Schweisstechnik Austria GmbH; Kapfenberg Austria
Esa Lappalainen, Laboratory of Laser Materials Processing, Lappeenranta Univ. of Technology; Lappeenranta Finland
Anna Unt, Laboratory of Laser Materials Processing, Lappeenranta Univ. of Technology; Lappeenranta Finland
Presented at ICALEO 2012

Laser welding is often used for welding of stainless steel. Typically the welding is performed as autogenous keyhole welding. The advantages of laser welding, high welding speed, low heat input and distortion, gives narrow and deep weld penetration with good weld quality. The amount of weld bead oxidation is also typically of lower magnitude as with arc welding since small melt pool. Duplex stainless steels are new promising group of materials used to replace austenitic stainless steels for various reasons. The high speed and low heat input of laser welding in case of autogenous welding cause problem with microstructural balance of weld metal. New lasers offer excellent beam quality and high power via optical fiber that typically leads into even higher welding speed and lower heat input. Small focal point, however, makes dynamic beam forming possible. This study concentrates on testing the effect of focal point size and shape of scanned beam and shielding gas on the weld microstructure in order to define the usability of dynamic beam forming for welding of thin duplex stainless steel sheet in butt joint configuration. The differences between these focal point configurations are analyzed in terms of weldability, absorption and resulting microstructure. The larger laser beam size on workpiece and better gas shielding results lower welding speed, lower absorption and longer cooling time thus changing the fraction of different microstructures in weld metal into more favorable result.