Abstract: It is a frequently observed quality problem for new producers that the low temperature heating and subsequent nitriding grain oriented silicon steel products show a full abnormally grown grain structure but with a low magnetic property and its reason and solution are crucial to reduce production costs. In this work the products with above-mentioned phenomenon in two groups of grain oriented silicon steels were analyzed by determining their corresponding grain orientations in primary recrystallized sheets, in the interrupted samples during secondary recrystallization annealing including matrix grains and secondary grains and detecting their secondary recrystallization temperatures. Results showed that the reason for the decrease in magnetic properties lay in the higher scattering of Goss orientation mainly towards to {110}<227> which was related with a smaller average grain size of primary recrystallized sheets leading to low starting secondary recrystallization temperature by about 50 ℃. The earliest secondary grains showed large orientation scattering to Goss orientation. The difference in magnetic properties of the two group sheets were not related to their starting secondary recrystallization temperature, but to their degree in orientation scattering, which were ascribed to the slight differences in primary recrystallization textures and inhibitors as well as the turbulence in key elements contents.

Key words: low temperature heating and nitriding grain oriented silicon steel, secondary recrystallization, texture, magnetic properties