Welding Metallurgy of Stainless Steels

Stainless steels are generally grouped into five distinct alloy families and are primarily classified by the phase that dominates the microstructure. The five families of stainless steels are martensitic, ferritic, austenitic, duplex, and precipitation hardened. Duplex stainless steels consist of a nearly equal mixture of ferrite and austenite, while the PH stainless steels can be either martensitic or austenitic. A constitution diagram predicts the microstructure of the stainless steel based on the type and amount of various alloying elements. Dilution of the filler metal by the base metal is often an important consideration when welding certain stainless steels. This chapter discusses excessive base metal dilution in austenitic stainless steels that is known to increase the susceptibility to solidification cracking. Constitution diagrams are a powerful tool for predicting stainless steel weld microstructures, and therefore, anticipating potential weldability problems.