Mechanical Properties and Anisotropies of 0.2% Carbon Steel with Bimodal Microstructure Subjected to Heavy‐Reduction Controlled‐Rolling Process

The mechanical properties, anisotropies, and fracture behavior of 0.2% carbon steel sheets produced by a heavy-reduction single-pass controlled-rolling process with approximately 75% thickness reduction are investigated via a tensile test, field-emission scanning electron microscopy, and electron backscattering diffraction. The 900- and 1000 °C-heated specimens with less well-developed textures show relatively homogeneous anisotropies, whereas the 700- and 800 °C-heated specimens show strong V-shaped anisotropies, where the relative strength decreases and the relative elongation increases at 45° from the rolling direction in comparison with other directions. The uniform and total elongations of the 900- and 1000 °C-heated specimens in their rolling direction of roughly 12–14% and 23–28% are higher than those of the 700- and 800 °C-heated specimens, respectively, while maintaining high strength (610–670 MPa), as clarified from the nominal stress–strain curves. Additionally, the bimodal structure on the fracture surface consisting of submicron-size (<1 μm) and fine (2–5 μm) dimples lead to higher ductility while retaining outstanding strength. This is attributed to the submicron-size grains having excessive strength and the micron-size grains having high ductility.