Ferritic steels

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Ferritic stainless steels are Iron-Carbon-Chromium alloys characterised by a lower carbon content compared to martensitic steels, while the chromium content typically varies between 11% and 30%. This type of steel exhibits good mechanical resistance and moderate corrosion resistance, with the latter improving as the chromium content increases. It is not responsive to hardening treatments and requires annealing. Weldability is poor because the crystalline grain of the material expands at high temperatures.

The addition of other elements to the alloy serves to enhance specific characteristics. For instance, Molybdenum increases resistance to localised corrosion, Aluminium improves resistance to hot oxidation, and Sulphur is known to facilitate machinability.

Ferritic stainless steels, generally known as the AISI 400 series in the United States, are characterised by a crystalline structure featuring a body-centred cubic lattice (BCC), which makes them magnetic.