Low core loss non-oriented silicon steels

Low core loss non-oriented silicon steels are produced with high ( Si + Al) content to reduce eddy current losses. However, high alloy content has detrimental effect on mechanical properties, saturation polarization and thermal conductivity. A new generation of medium and, particularly, low core loss non-oriented silicon steels was developed, with lower alloy content than the conventional grades, based on improved purity and texture. The development allowed the production of new low loss grades, with maximum core loss ( W(1.5/50)) of 2.30 W/kg at 0.50 mm and 1.95 W/kg at 0.35 mm, with high permeability (J(50) of 1.7 and 1.72 T, respectively). Texture improvement was based on hot band structure control and higher boundary mobility. Large hot band grain size and low [ 1 1 0]parallel to RD fiber fraction in the hot band texture contribute to reduce the intensity of [ 1 1 1]parallel to ND and slightly increase the intensity of [ 0 0 1]parallel to RD in the final product. Higher grain boundary mobility and/or a two-stage cold rolling process, with an intermediate annealing, increase the fraction of [ 0 0 1]parallel to RD and reduce the fraction of [ 1 1 1]parallel to ND on recrystallization and lead to favorable texture evolution on grain growth. (C) 2008 Elsevier B.V. All rights reserved.