Application of Transformation Treatment to Commercial Low-Grade Electrical Steels under Different Processing Conditions

Abstract

In this paper, two low-grade electrical steels are used to inspect the effect of initial columnar grains and final transformation treatment on the microstructure and textures. Results show that the Al and P elements, besides causing the surface oxidation or segregation, increase the critical transformation temperatures of steels, thus restricting the formation of strong {100} texture. Two-layer grain structure of typical surface-effect-induced transformation is developed in the steels without Al. The transformation textures in both steels are nearly random, which are much better than the {111} recrystallization texture or the memory type of transformation texture. The steel with initial columnar grained structure produces more {110}-oriented grains in finally transformed sheets, whereas the initial hot-rolled structure induces more {100}-oriented grains. In addition, high cold rolling reduction produces a one-layer grain structure in the final transformed sheets. It is confirmed again that the increase in final heating temperature leads to a transition from the memory type of transformation texture to surface-effect-induced transformation texture. For commercial steels containing harmful Al and P, the change in processing parameters during transformation treatment does not influence transformed structure and texture. Finally, the combined control of three stages of transformation during casting, hot rolling and final annealing is discussed.