Low-Cost Grain Oriented Silicon Steels Manufactured by Continuous Annealing

Abstract

Low-cost grain oriented silicon steel produced by continuous annealing, low slab-heating temperature, and omitting normalization annealing is explored and analyzed. This type of grain oriented steel is designed to replace the non-oriented steels used for the production of transformers of medium and small sizes as specified in all GO steel producers catalogs. Fully secondarily recrystallized structure with magnetic properties of P1.7 = 2.04 W kg−1 and B8 = 1.76 T is obtained at temperature of 1050 °C within 10 min in the condition of two-stage cold rolling, whereas one-stage cold rolling method fails to initiate abnormal grain growth in the same processing parameters. The success of fully secondary recrystallization using two-stage cold rolling method is ascribed to the more important role of sufficient amount of Goss seeds in decarburized samples as in CGO steels than the stronger {111} texture as in HiB silicon steels. It is further determined that by two-stage cold rolling technique, a higher secondary stage rolling reduction leads to a lower secondary recrystallization starting temperature and a shorter secondary recrystallization staring time related with a finer grain size. The reasons for the high iron core loss related by continuous annealing are connected to the higher number of deviated Goss grains scattering toward {210} or Brass orientations, the residual inhibitors and the imperfect grain size and morphologies. The reasons for the failure in abnormal grain growth by one-stage rolling are also discussed.