Effect of annealing atmospheres on secondary recrystallization in thin-gauge grain-oriented silicon steel: Microstructures and textures

Abstract

By controlling the onset temperature of secondary recrystallization and the temperature interval for grain growth, the annealing atmosphere is the key factor affecting the grain size and texture of grain-oriented silicon steel. The thin-gauge cold-rolled grain-oriented silicon steel (TG-CRGO) is not only more sensitive to annealing atmosphere than the thick-gauge grain-oriented silicon steel, but also requires a different annealing atmosphere. In this paper, the evolution of microstructures and textures in 0.18mm TG-CRGO steel during high-temperature annealing in five different annealing atmospheres are detected through EBSD technique. The results show that excellent magnetic properties (B8=1.93 T) can be obtained when annealing atmosphere as 75%N2+25%H2 (volume ratio). Secondary recrystallization occurs in all the specimens that were prepared in five different annealing atmospheres, which causes significant differences in secondary recrystallized microstructures and textures. As N2 content rises, the average secondary recrystallized grain sizes increased and reaches a maximum average grain size in 75%N2 atmosphere and then decreases along with N2 content over 75%. When N2 content is 75%, Goss grains show preferential abnormal growth at 1050–1055°C, which is a very narrow temperature range for secondary recrystallization. In conclusion, proper annealing atmosphere is one of the important measures to control and enable the grain-oriented silicon steel to get the sharp Goss texture.