LOW ENERGY INPUT WELDING OF DUPLEX STAINLESS STEELS

There is a growing interest in the use of low energy input welding methods, often with little or no addition of filler material, for welding of duplex stainless steels. In the present study, therefore one lean, one standard 22%Cr and one superduplex stainless steel were autogenously laser welded bead-on-plate and MIG-laser hybrid welded with recommended fillers. The energy inputs ranged from 0.1-0.6 kJ/mm. Ferrite contents were generally high (65-99%) with autogenous laser welding resulting in the highest levels. The addition of fillers had a larger effect on ferrite content than increasing energy inputs. Evaluation of weld metal ferrite content and the tendency to form nitrides suggest that the superduplex steel, closely followed by the lean grade, are most suited for low energy input welding. The standard 22%Cr steel requires the most careful optimization of procedures to produce an acceptable weld metal microstructure. The overall conclusion is that low energy input welding methods could be applied to duplex stainless steels. However, high nitrogen grades are more suitable and care must be taken to ensure sufficient austenite formation.