Abstract:
Consumable selection for stainless steel cargo tanks depends of course on the chemical composition of the base material. To increase the pitting resistance of the weld metal 317L type filler metal is used to weld 316L and 316LN base material. Duplex welding consumables have the same composition as the base material except that the Ni-content in the filler metal is increased from 5.5 to 9 %, in order to achieve the proper phase balance between ferrite and austenite in the weld metal.
Dissimilar joints between stainless steel 316L/LN and CMn-steel have traditionally been welded with an overalloyed filler metal - 22Cr12Ni+Mo (309L, MoL). However if dilution with the ferritic base material is too high this can give hot cracking problems. To overcome the problem 29Cr9N (312) consumables can be used.
Welding duplex stainless steel to unalloyed steels is basically straightforward. The risk of hot cracking is small and a standard duplex consumable can be used.
A computer software for selection of consumables for dissimilar welds – ConSel, is a powerful aid for the welding engineer and the risk of making expensive mistakes can be avoided.