Study on the abnormal growth of goss oriented grains in Fe-3.2%Si steel: Role of thermomechanical processing and inhibitors

Abstract

Detailed characterization of Fe-3.2%Si steel after different stages of processing trails including hot-rolling, normalization annealing, cold-rolling with intermediate annealing, and finally, decarburization/primary annealing and secondary annealing has been carried out. The evolution of ferrite grain structure, grain boundary characteristics, and the micro-texture of the samples are characterized using electron backscatter diffraction (EBSD). The inhibiting precipitates such as MnS and CuS are studied under scanning and transmission electron microscopy (SEM and TEM). The evolution of ferrite grain structure and texture are explained considering the mechanisms (role of inhibitors, crystal orientation, special boundary, high energy medium angle boundary, grain boundary curvature) responsible for the abnormal growth of Goss oriented grains after final annealing treatment. Extremely coarse Goss oriented grains (as large as >20 mm) have been developed in this study. An analytical approach is presented at the end to explain the texture evolution during processing considering the Taylor factor maps (for different loading conditions) and the prediction of limiting ferrite grain size for abnormal grain growth, considering the size and fraction of the precipitates along with their coarsening and dissolution kinetics.