High strength multi-phase steel, and method for producing a strip from said steel

A method for producing a cold or hot rolled steep strip, said method comprising:

• providing a high-strength multiphase steel with minimal tensile strengths of 580 MPa for a cold or hot rolled steel strip composed of the following elements in weight %:
• C 0.075 to ≤0.105
• Si 0.200 to ≤0.300
• Mn 1.000 to ≤2.000
• Cr 0.280 to ≤0.480
• Al 0.010 to ≤0.060
• P ≤0.020
• Nb ≥0.005 to ≤0.025
• N ≤0.0100
• S ≤0.0050
• remainder iron including usual steel accompanying elements not mentioned above, wherein boron is limited to unavoidable steel accompanying element amounts in the high-strength multiphase steel;
• producing a cold rolled or hot rolled strip from the high-strength multiphase steel;
• adjusting the Mn content of the high-strength multiphase steel as a function of a different thickness of the strip to obtain comparable material properties of the strip at different thicknesses of the strip, wherein the Mn-content is adjusted to ≥1.000 to ≤1.500% at strip thicknesses 0.50-1.00 mm, to ≥1.250 to ≤1.750% at strip thicknesses 1.00-2.00 mm and to ≥1.500 to ≤2.000% at strip thicknesses 2.00-4.00 mm;
• heating the cold or hot rolled steel strip in a continuous annealing furnace to an annealing temperature in the range of about 700 to 950° C. to produce an annealed strip;
• cooling the annealed strip from the annealing temperature to a first intermediate temperature of about 300 to 500° C. at a cooling rate between about 15 and 100° C./s;
• and
• cooling the strip to room temperature.