Abstract: A high-strength air-hardenable multiphase steel having minimal tensile strengths in a non air hardened state of 750 MPa and excellent processing properties includes the following elements in % by weight: C?0.075 to ?0.115; Si?0.600 to ?0.750; Mn?1.000 to ?1.950; Cr?0.200 to ?0.600; Al?0.010 to ?0.060; N?0.0020 to ?0.0120; S?0.0030; Mo?0.0200; Nb?0.005 to ?0.040; Ti?0.005 to ?0.030; B?0.0005 to ?0.0030; Ca?0.0005 to ?0.0060; Cu?0.050; Ni?0.050; remainder iron, including usual steel accompanying smelting related impurities, wherein for a widest possible process window during continuous annealing of hot strips or cold strips made from the steel a sum content of M+Si+Cr+Mo in the steel strips is a function of a thickness of the steel strips according to the following relationship: for strip thicknesses of up to 1.00 mm the sum content of M+Si+Cr+Mo is ?2.450 and ?2.800%, for strip thicknesses of over 1.00 to 2.00 mm the sum of Mn+Si+Cr+Mo is ?2.600 and ?3.150%, and for strip thicknesses of over 2.