熱延複合組織鋼の製造プロセスに対する一考察

抄録

The effects of processing variables and chemistry on the microstructure and the mechanical properties of as-hot rolled dual phase steel were investigated in relation to transformation behavior in order to optimize the processing condition. As-hot rolled dual phase structures with good strength-ductility balance and low yield ratio below 0.60 were obtained, when C-Si-Mn steels with such plain compositions as 0.040.10%C-0.51.5%Si-1.21.7%Mn were rolled at finishing temperature above and near Ar₃ point and coiled at temperatures below 200°C. Si was so effective for strengthening without sacrifice of ductility, and for broadening the suitable range of the finishing rolling temperature.
Deformation of austenite accelerated the transformation into ferrite and raised the Ar₃ point. The rise of Ar₃ point was remarkably influenced by deformation temperature, holding time in austenitic region and Si content. The optimum thermomechanical process for producing the dual phase steel was discussed on the basis of transformation characteristics of deformed austenite.