Product Code: ICA10_1903

Effect of Heat Input Modification on Duplex Stainless Weld Quality
Authors:
Antti Salminen, Laser processing research group, Lappeenranta University of Technology; Lappeenranta Finland
Elin Westin, Outokumpu Corporation; Avesta
Presented at ICALEO 2010

Laser welding is a perfect tool for welding of different steel grades especially stainless steel. Laser welding is often used as autogenous keyhole welding process that provides narrow deep penetration with good weld quality. New lasers offer excellent beam quality and high power via optical fiber that typically leads into improvement of welding speed. Even though increased speed increases productivity it also increases cooling rate and causes problems in weld properties in case of e.g. duplex stainless steel and low alloyed steel. Small focal point makes also dynamic beam forming possible. This study concentrates on testing the effect of focal point size and shape on the weld microstructure and properties in order to define the suitability of dynamic beam forming for welding of duplex stainless steel and low alloyed steel St52 in a butt joint configuration. The differences between these focal point configurations are analyzed in terms of weldability, resulting microstructure and weld hardness. The dynamic beam shaping can enable increase of heat input almost tenfold still using keyhole welding process. The effect of focal point size and shape can be seen as the larger spot results lower welding speed and longer cooling time thus changing the properties of the weld metal.