Abstract: A duplex stainless steel which is economical and balanced to provide a good combination of properties in the as-cast condition and resists thermal transformation to martensite due the high levels of manganese. This steel is particularly suited for thin-walled castings for automotive underbody components. It is 30% to 60% ferrite and balance austenite and, in weight percent, consists essentially of:C - up to 0.07,Cr - 17 to 21.5,Ni - greater than 1 to less than 4,Mn - greater than 4 to 8,N - 0.05 to 0.15,Si - less than 2,Mo - less than 2,Cu - less than 1.5 and balance essentially Fe.