PHYSICAL METALLURGY OF Fe-Cr-Mo FERRITIC STAINLESS STEELS - A REVIEW.

Toughness, ductility and weldability are improved when carbon and nitrogen are held to the lowest practical values. Either titanium or niobium can be used to stabilize ferritic stainless steels, but best properties are obtained when the minimum amount required to prevent intergranular corrosion is added. The use of a mixture of titanium and niobium offers an optimum combination of weld ductility and toughness. Fracture toughness should be considered. Hydrogen should be avoided in welding. Nickel additions improve toughness. Chi and sigma phases and 475 C embrittlement must be considered. These steels should not be used above about 320 C if room temperature toughness is a concern. The steels should be rapidly cooled from elevated temperatures.