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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 2.00 mm the sum of Mn+Si+Cr+Mo is ≧3.000 and ≦3.450%.

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First Claim