Control of surface graded transformation textures in steels for magnetic flux carrying applications

Abstract

The magnetic anisotropy of ferromagnetic materials implies the consequence that the crystallographic texture of these materials needs to be controlled during processing in order to guarantee optimum magnetic properties. The equilibrium phase transformation between the high temperature austenite phase and the low temperature ferrite, is considered in the present work as the crucial solid-state transformation for developing appropriate textures in electrical steel sheets. Surface energy anisotropy may act as a driving force for orientation selection at the metal-vapour interface because BCC {100} and {110} crystallographic planes have a relatively low surface energy. It is demonstrated here that this affects the microstructure and texture evolution at the surface during phase transformation. Subsequently, through an appropriate selection of the technological parameters of rolling and annealing, the nucleation and growth of the desired {001}áuv0ñ texture can be achieved, which is an essential prerequisite for obtaining a material with excellent soft magnetic properties.