The steels of type ASTM 304, 316, 304L, and 316L have very good weldability. The old problem of intergranular corrosion after welding is very seldom encountered today. The steels suitable for wet corrosion either have carbon contents below 0.05% or are niobium or titanium stabilised.
They are also very unsusceptible to hot cracking, mainly because they solidify primarely ferritic. The higher-alloy steels such as 310S and N08904 solidify with a fully austenitic structure when welded. They should therefore be welded using a controlled heat input, and a recommended welding procedure. Steel and weld metal with high chromium and molybdenum contents may undergo precipitation of brittle sigma phase in their microstructure if they are exposed to high temperatures for a certain length of time. The transformation from ferrite to sigma or directly from austenite to sigma proceeds most rapidly within the temperature range 750-850 °C. Welding with a high heat input leads to slow cooling, especially in light-gauge welds. The weld's holding time between 750-850 °C then increases, and along with it the risk of sigma phase formation.