Microstructure and Texture Evolution of Fe-Si Steels after Hot Dipping and Diffusion Annealing

Abstract

A homogenous intensity distribution along the cube texture fibre is important to achieve an easy magnetization in non-oriented electrical steels. Several alternatives have been discussed in literature to achieve this goal namely, tertiary recrystallization (surface energy controlled), decarburization annealing, two step cold rolling (strain induced boundary migration), twin-roll thin strip casting (directional solidification), phase transformation (surface energy anisotropy) and columnar grains formation (selective grain growth). In the present study, a hypoeutectic Al-Si alloy was deposited on the surface of cold rolled Fe-Si steels with a hot dipping simulator and subsequently annealed at 1000°C for different times. This procedure was developed previously in order to enrich the substrate with Al and/or Si and consequently improve their resistivity. Of specific interest was the formation of columnar grains in the low Fe-Si steel after annealing. These columnar grains were found to grow from the surface towards the centre of the substrate. The microstructure and texture in the columnar grains were significantly different than those in the middle of the material. Therefore, the evolution of these features during processing was studied in detail in this work.