Stainless Steels
Stainless steels comprise a group of iron alloys that contain some Cr, Ni, Mn, Mo, or Al, in addition to carbon. The presence of chromium makes them highly corrosion resistant and all stainless steels require at least 11 wt % of this element.  Their room temperature microstructure divides stainless steels into three classes: martensitic, ferritic, and austenitic. In the martensitic steels, martensite is the main microconstituent and the iron/ iron carbide ratio is controlled by the other alloying elements. In ferritic stainless steels the bcc-a-iron is the major phase, and for the austenitc steels alloying additions have stabilized the g-iron ( fcc-austenite) down to room temperature. The table below details some stainless steel alloys.
From: Callister, 
"Materials Science and Engineering," 
Wiley (1994)