The significance of hot rolled microstructure controlled by fine-tuning Al content to texture evolution and magnetic properties of low silicon non-oriented electrical steels

Abstract

In non-oriented electrical steels, the initial hot rolled microstructure usually had important effects on the successive microstructure and texture development during cold rolling and annealing and the final magnetic properties. In this paper, we reported that the hot rolled microstructure of a 0.4 wt% Si steel could be controlled by designing Ar1 (γ/α phase transformation temperature), which was susceptive to the content of Al. Three steel slabs with different Al contents (0.41, 0.30 and 0.21 wt%) were produced and then subjected to the same hot rolling, cold rolling and annealing treatment in an industrial production line. Interestingly, it was found that, the heavily elongated deformed grains were reduced or even avoided in the hot rolled sheets by decreasing Ar1 with a slight decline of Al. As a result, after cold rolling and annealing, weak γ-fiber (〈111〉//ND) texture and bigger grains were obtained. Hence, the magnetic properties were significantly improved, i.e. high magnetic induction (B50) together with low iron loss (P1.5/50). The microstructure and texture evolutions of these three steels throughout the whole processing route were comparatively investigated in detail, and the effects on magnetic properties were discussed in terms of the classical loss separation theory. This work also provides a promising method to optimize the microstructure, texture and magnetic properties for other low silicon non-oriented electrical steels.