Ferritic stainless steels

Definition and applications

Ferritic steels are stainless steels containing mainly chromium, in some cases with slight additions of other elements such as molybdenum, aluminum, niobium.


Both austenitic and ferritic steels, have no phase transformation and therefore cannot be  treated with heat to increase the mechanical characteristics and the only way to do this is by cold deformation.


The most common ferritic stainless steel is grade 430. Both 430 steel and its sulfur grade, 430F are suitable for chip removal. Grade 434 is characterized by the presence molybdenum in the alloy, The addition of molybdenum increases this alloy’s corrosion resistance and its attack to many chemicals. It combines good heat and oxidation resistance. On the other hand, a further addition of niobium makes grade 436, a steel with greater resistance to heat. Finally, there is grade 409, is widely used for vehicle exhaust systems.

Austenitic-ferritic stainless steels (Duplex)

Duplex stainless steel grades have a two-phase ferritic-austenitic microstructure, with a phase balance . While exact ratios vary by grade, most duplex steels have a structure that is roughly 50-percent austenite and 50-percent ferrite.

The two-phase structure combine many of the beneficial properties of ferritic and austenitic stainless steels in terms of mechanical properties. The duplex microstructure contributes to the high mechanical strength and high resistance to stress corrosion cracking in aggressive environments.