Papers by Author: Hector Mendoza León

Abstract: The present work is an attempt to understand the recrystallisation mechanisms in Fe-3% Si alloys used in transformer cores. After secondary recrystallisation silicon steels exhibit a Goss texture with a more or less important spread depending on the details of the processing route, namely, Conventional Grain Orientation CGO or High Permeability Hi-B. The mechanisms of Goss grain formation during hot rolling and primary recrystallisation, as well as those controlling the first steps of abnormal growth, are not yet well understood. The present work mainly deals with texture characterization of the hot rolled state. Surface, quarter and half thickness samples are prepared from hot-rolled sheet. Global and local textures are characterized by neutron diffraction and electron backscattered diffraction, respectively. The Orientation Distribution Functions and the volume fraction of the different texture components are calculated. The components from global texture measurements are (001)[1-10], (112)[1-10] (α fiber ), (011)[100] (Goss) and (111)[1-21] (111) [1-10](γ fiber). EBSD measurements have shown large variations of texture from the surface to the half thickness of the sheet. These local measurements are related to the global results by rotation about the transverse direction. Moreover, the grain size appears to be inhomogeneous.

Abstract: After secondary recrystallization, the Fe-3%Si alloys, grade Conventional Grain Oriented (C.G.O.), exhibit a Goss texture that is sought for minimizing watt losses in transformer cores. The mechanisms of Goss grain formation and their evolution during the processing route from hot rolling to decarburizing such as the early first steps of abnormal growth are not still well cleared up. This work deals with the influence of local microstructure and texture heterogeneities observed by X-ray diffraction (XRD) and Electron Back Scattered Diffraction (EBSD) at the hot rolling step. The present results complete those previously obtained by neutron diffraction [1]. Presence of Goss grain colonies at about the quarter of the hot rolled sheet is probably, as it has already been suggested, at the origin of the Goss grain presence at the primary recrystallized state.