Considerations for the weldability of types 304L and 316L stainless steel

The susceptibility of austenitic stainless steels to the formation of two distinct weld defects, solidification cracking and lack of penetration, is related to the chemical composition of the base and filler material. The propensity for cracking is determined primarily by the solidification mode and the amount of residual tramp elements such as phosphorous and sulfur. High sulfur levels can lead to weld centerline cracking and heat affected zone (HAZ) cracking while very low sulfur levels (less than ∼50 ppm) in types 304L and 316L are associated with lack of penetration weld defects and a distinct loss in puddle control during fusion welding. A calculated Creq to Ni eq ratio of 1.52 to 1.9 is recommended to control the primary mode of solidification and prevent solidification cracks in type 304L while the Cr eq/Nieq ratio of 1.42 to 1.9 is recommended for type 316L stainless steel. A lower limit of 50 ppm sulfur is recommended to avoid possible lack of penetration. These ranges should be validated by welding trials for specific weld processes and applications. © ASM International.