A rustproof austenitic cast steel having tensile strength greater than 550 MPA and elongation at break over 30%, characterized in that the cast steel having an aluminum content of 0 to 4% and a silicon content of 1 to 4% is within an alloy range that is determined by the coordinates of four points (Cräqu=14; Niäqu=8), (Cräqu=14; Niäqu=14), (Cräqu=22; Niäqu=8) and (Cräqu=22 Niäqu= 16), wherein the chromium and nickel equivalents are calculated from the chemical composition of the cast steel using the relations (1) and (2): Cräqu = %Cr+ %Mo + 1.5%Si + 0.5 %W + 0.9%Nb + 4%A1 +4%Ti + 1.5%V + 0.9%Ta ( 1 ) Niäqu = %Ni + 30%C + 18%N + 0.5%Mn + 0.3%Co + 0.2%Cu - 0.2%Al (2), wherein the information used is in percent mass and the remainder substantially comprises iron and other elements usually present in cast steel (O, P, S). Said cast steel exhibits a TRIP effect and serves as a material for plant and refrigeration engineering, particularly for facilities and components for obtaining gases and for liquefying and fractioning of gases and as a material in the construction of special vehicles and airplanes for the transport of liquid gases and for components exposed to low temperatures, in addition to crash relevant castings.