Control of Carbon Content in Steel by Introducing Proeutectoid Ferrite Transformation into Hot-Rolled Q&P Process

A processing strategy involving primary and secondary carbon partitioning is proposed for the hot-rolled quenching and partitioning process through the introduction of proeutectoid ferrite transformation after rolling. The microstructures of the steels were characterized using scanning electron microscopy, transmission electron microscopy, electron probe microanalysis, and x-ray diffraction, and the mechanical properties were evaluated using a universal tensile machine. The blocky retained austenite that distributed along the ferrite grain boundaries was promoted based on the coupling action of the primary and secondary carbon partitioning, which enhanced the transformation-induced plasticity effect during deformation despite the high carbon concentration. A ferrite formation temperature range of ~ 760 to 800 °C was proposed. In addition, from the perspective of industrialization, the observed ‘plateau trends’ for the retained austenite fraction and product of strength and elongation suggest the availability of a wide processing window of 215-362 °C for controlling the coiling temperature.