Laser welding of duplex stainless steel with nitrogen as shielding gas

• Laser welding with argon shield gas results in a reduced level of austenite in the weld metal.
• Higher welding speeds are linked to lower austenite levels and harder, more brittle welds.
• The use of nitrogen (instead of argon) as the weld shield gas increases the austenite content of the weld. This is probably linked to the uptake of nitrogen by the weld pool and this compensates to some extent for nitrogen lost by the weld pool as a result of the laser welding process.
• Nitrogen as a shield gas has minimal effects on weld hardness but improves weld toughness.

Nitrogen loss from laser welding melts pools and can have a deleterious effect on weld toughness for duplex stainless steels. This effect can be alleviated by using nitrogen as the shielding gas during laser welding. The use of nitrogen results in increased austenite levels in the weld metal and improved toughness levels.