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, said steel comprising the following elements in % by weight: C?0.075 to ?0.115; Si?0.200 to ?0.300; Mn?1.700 to ?2.300; Cr?0.280 to ?0.4800; Al?0.020 to ?0.060; N?0.0020 to ?0.0120; S?0.0050; Nb?0.005 to ?0.050; Ti?0.005 to ?0.050; B?0.0005 to ?0.0060; 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 rolled or cold rolled strips made from the steel a sum content of M+Si+Cr in the steel 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 is ?2.350 and ?2.500%, for strip thicknesses of over 1.00 to 2.00 mm the sum of Mn+Si+Cr is ?2.500 and ?2.950%, and for strip thicknesses of over 2.

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, said steel comprising the following elements in % by weight: C?0.075 to ?0.115; Si?0.200 to ?0.300; Mn?1.700 to ?2.300; Cr?0.280 to ?0.4800; Al?0.020 to ?0.060; N?0.0020 to ?0.0120; S?0.0050; Nb?0.005 to ?0.050; Ti?0.005 to ?0.050; B?0.0005 to ?0.0060; 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 rolled or cold rolled strips made from the steel a sum content of M+Si+Cr in the steel 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 is ?2.350 and ?2.500%, for strip thicknesses of over 1.00 to 2.00 mm the sum of Mn+Si+Cr is ?2.500 and ?2.950%, and for strip thicknesses of over 2.