Workability and Straining Behaviour of High Silicon Steels (3.0-6.3%Si) by Hot Torsion and RT Compression Tests

Abstract

High silicon steel (up to 6.5 wt.-%Si) is important for the electrical industry because of its magnetic properties. However, its production in low thickness by cold rolling is difficult due to extreme brittleness, mainly caused by ordering processes, making dislocation motion more complex. Nevertheless, these materials appear to be deformable at higher temperatures. The cooling rate after hot deformation, the temperature from which it is cooled and the time delay prior to cold deformation are important elements for the understanding of their workability. Hot torsion tests were performed on Fe-Si steel (4.2 and 5.6 wt.-%Si) under continuous cooling to study the influence of strain and interpass time on ordering and non-recrystallization temperatures. Compression tests at a constant strain rate were used to study the effect of continuous cooling to RT and the delay time between deformations for series of silicon alloys (from 3.3 to 6.3 wt.-% Si) with different thermomechanical treatments. An aging phenomenon due to an ordering reaction at RT was observed. Finally, extrapolating the hot torsion and compression tests parameters to the rolling mill a suitable schedule for hot rolling was found guaranteeing good conditions for further cold rolling.