Effect of Deformation Temperature on the Hot Ductility of Non-Oriented Electrical Steels

Abstract

The hot tensile ductility of solution treated Si-Al electrical steels was investigated at temperatures between 850 and 1150 °C. Samples for mechanical testing were obtained from continuous cast thin slabs and hot rolled strips. A continuous decrease in ductility was observed up to about 1000 °C. After that, the ductility was recovered in strip samples while in slab samples the ductility remained constant at RA<10%. This behavior was associated with the presence of large quantities of undissolved AlN particles formed during slow cooling of the slab. In the case of strip specimens, where the starting slab is not cooled to room temperature, the 1000 °C ductility minimum was attributed to strain localization at grain boundary nucleated ferrite grains. Rapid nucleation and growth of microvoids at AlN particles formed during cooling to test temperatures in the vicinity of Ae3 resulted in intergranular tensile failure by microvoid coalescence.