Patent ID: 6893510
Filing Date: 2005-05-17
Classification: C21D

Abstract:
1. A process for the production of grain oriented electrical steel strips in which a silicon steel is continuously cast in the form of a strip 1.5 to 4.5 mm thick, hot rolled, coiled and then cold rolled to a strip 0.15 to 1 mm thick, subjected to a primary recrystallisation and decarburisation annealing and to a further annealing for secondary recrystallisation at a temperature higher than the one of said primary recrystallisation annealing, and in which a first precipitation of non-metallic second phases is promoted to inhibit grain boundaries movement with a drag force specifically comprised in the interval: Iz being defined as Iz=1.9 Fv/r (cm −1 ), in which Fv is the volume fraction of said non-metallic second phases stable at a temperature below 800° C. and r is the mean radius of said second phases; a second precipitation of said non-metallic second phases is promoted after cold rolling, wherein said first precipitation of said non-metallic second phases is obtained though a controlled in-line deformation of the as cast strip before its coiling, utilizing a reduction ratio of between 15% and 60% at a temperature higher than 750° C.; said hot rolled strip is cold rolled in at least one stage, with intermediate annealing, with a reduction ratio of between 60 and 92% in at least one of the rolling passages; and said second precipitation of said non-metallic second phases is obtained during said decarburisation annealing by rising the nitrogen content in the steel strip, by means of a nitriding atmosphere.