Salzgitter Flachstahl Gmbh

Peter Matthies

Joachim Schöttler

Thomas Schulz

Andreas Wedemeier

Sascha Kluge

Christian Meyer

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&#x2265;0.075 to &#x2264;0.115; Si&#x2265;0.200 to &#x2264;0.300; Mn&#x2265;1.700 to &#x2264;2.300; Cr&#x2265;0.280 to &#x2264;0.4800; Al&#x2265;0.020 to &#x2264;0.060; N&#x2265;0.0020 to &#x2264;0.0120; S&#x2264;0.0050; Nb&#x2265;0.005 to &#x2264;0.050; Ti&#x2265;0.005 to &#x2264;0.050; B&#x2265;0.0005 to &#x2264;0.0060; Ca&#x2265;0.0005 to &#x2264;0.0060; Cu&#x2264;0.050; Ni&#x2264;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 &#x2265;2.350 and &#x2264;2.500%, for strip thicknesses of over 1.00 to 2.00 mm the sum of Mn+Si+Cr is &#x2265;2.500 and &#x2264;2.950%, and for strip thicknesses of over 2.00 mm the sum of Mn+Si+Cr is &#x2265;2.950 and &#x2264;3.250%.

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Clausthal-Zellerfeld, Germany

Peter Matthies