EFFECT OF FINAL ANNEALING ATMOSPHERE ON SECONDARY RECRYSTALLIZATION BEHAVIOR IN THIN GAUGE MEDIUM TEMPERATURE GRAIN ORIENTED SILICON STEEL

The development trend of grain oriented silicon steel is reducing the slab reheating temperature and the thickness of final product. Medium temperature slab reheating grain oriented silicon steel bearing copper was characterized by omitting hot band annealing and larger range of secondary cold rolling reduction which was suitable for the preparation of thin gauge product. But less research were reported about thin gauge grain oriented silicon steel produced by medium temperature reheat technique. It was well known that the sharpness of secondary recrystallization Goss texture is deteriorated by the preparation of 0.18 mm thin gauge grain oriented silicon steel, poor secondary recrystallization and deviated Goss grains occurs by the influence of Goss seeds decreasing and inhibitor decrease. So the key point of producing thin gauge grain oriented silicon steel was controlling the precipitations ageing behavior. In order to improve the sharpness of Goss texture and the magnetic flux density after secondary recrystallization, secondary recrystallization behavior was controlled by annealing atmosphere in this work. The microstructure and texture of interrupted annealing specimens were measured by EBSD system. The results show that the magnetic flux density of 0.18 mm gauge specimen was 1.95 T after final annealing in 90%N-2 atmosphere. Due to the coarsening behavior of inhibitors was more strongly influenced by atmosphere in thin gauge silicon steel, the primary recrystallization grain size was smaller and secondary recrystallization duration was longer by improving volume fraction of N-2 during final annealing. In this condition, deviated Goss grains were inhibited while Goss grains have enough time for abnormal growth. As a result, sharp Goss texture and stable secondary re crystallization were guaranteed and high magnetic flux density of thin gauge fmal product was obtained.