Superduplex Nitrogen Solubility Limit
The maximum concentration of dissolved nitrogen in the liquid and solid phase that can be retained without nitride precipitation within the microstructure. Nitrogen primarily serves here for austenite stabilization and strength enhancement.
When welding superduplex, you have to be careful that the nitrogen in the material doesn't escape from the melt. If too much nitrogen is released, the phase balance tips, and harmful precipitates form that can make the material brittle. That means for you: keep the heat input in check and don't let the weld get too hot. A weld pool that's too wide and too hot is the most common mistake. Use a cooler filler material that compensates for nitrogen loss, and make sure the joint preparation is clean and dry. If you cool the weld too quickly after welding, too much ferrite remains. The part should not go into cold water afterwards, but should cool slowly to room temperature. That way you get a balanced microstructure and no cracks.