New alloying concepts are proposed to develop hot-rolled weathering-dual phase steels that combine good strength-ductility balance and enhanced atmospheric corrosion resistance. The proposed concepts comprise mainly the alloying elements that improve the atmospheric corrosion resistance (Cu, Ni, P and Cr) and those that facilitate the adjustment of dual phase microstructure during processing by hot rolling (C, Mn and Si). Moreover, Nb and combined Nb-Mo additions are utilized to enable the controlled-thermomechanical processing and to tailor the mechanical properties. The applicable processing window and cooling strategy for microstructure adjustment are designed on laboratory scale by means of thermomechanical simulation experiments. The most successful processing parameters are transferred to the pilot scale. The microstructures of the pilot hot-rolled sheets are investigated and the mechanical properties are evaluated by means of tensile, hole expansion and bending tests. The atmospheric corrosion behavior in comparison to a reference-dual phase steel is studied by conducting an accelerated cyclic atmospheric corrosion test. The developed weathering-dual phase steels achieve tensile strengths in the order of 730-940 MPa and average total elongation of 11-14%. Moreover, they corrode at an average corrosion rate of about 0.26 µm/week (under accelerated corrosion testing conditions), which is comparable to the corrosion rate of weathering steel (0.22 µm/week) and around 40% lower than that of the reference-dual phase steel (0.42 µm/week).
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