Stainless steels can be readily welded, provided a suitable welding procedure specification (WPS) is defined and followed. The WPS guides welders on preparation, weld conditions and filler metals to achieve consistent welds, and is typically validated by first making test welds and subjecting samples to microstructural, mechanical and corrosion testing.
Because there are so many stainless steels, a large number of welding procedure specifications exist, often company-specific and reflecting in-house processes, the part geometry and the end use. Stainless steels can be affected by the formation of deleterious phases when exposed to elevated temperatures.
How different families weld
Austenitic stainless steels are relatively straightforward to weld, whereas ferritic stainless steels are more challenging. Duplex and super duplex stainless steels sit somewhere in between: the harmful sigma phase can form if the part is exposed to elevated temperatures, causing a dramatic loss of impact strength and corrosion resistance in the weld and the heat affected zone (HAZ) on either side.
To avoid elevated temperatures during welding, moderate the weld heat input and the inter-pass temperature.