Characterizing changes in microstructures, mechanical and magnetic properties of non-oriented silicon steel due to pulsed current

Abstract

In this paper, the influence of electrical pulse treatment (EPT) on the evolution of microstructure and texture and the resultant magnetic and mechanical properties of a cold rolled Nb-alloyed non-oriented silicon steel (NOSS) was investigated carefully. When the temperature rise caused by Joule heat is higher than the starting temperature of dissolution, more precipitates are dissolved in the EPT specimens than those subjected to the conventional heat treatment (CHT) at the same temperature, and higher current density resulted in Laves precipitates dissolved at lower temperature. The permeability of all the EPT and CHT specimens increase first and then decrease with the increasing temperature, and it reaches the maximum at the temperature for nearly the complete recrystallization. B50 is higher for the EPT specimen than CHT before the completion of recrystallization due to enhanced recrystallization, but lower than CHT after the completion because the athermal effect of pulsed current promotes the growth of γ-fiber grains, disfavoring the permeability. Moreover, the EPT specimen has the lower iron loss and lower yield strength than the CHT one at the same annealing temperature, because the dissolution of precipitates, recrystallization and grain growth in cold rolled matrix are all enhanced due to the athermal effect of pulsed current.