New insights into the transformation behavior of AlN during high-temperature annealing of industrial low-temperature grain-oriented silicon steel

Industrial low-temperature grain-orientated silicon steel has very excellent magnetic properties in the rolling direction, which can be entirely attributed to the sharp Goss texture ({110}<001>) in the final product, and during the whole manufacturing process, the sharp Goss texture forms in the high-temperature annealing process. It is commonly believed that during high-temperature annealing, the inhibitor (e.g. AlN) will be gradually coarsened and will lose its inhibition force on grain boundary migration through the Ostwald ripening process, which in turn allows the Goss grains to grow abnormally. However, the results obtained in this work were different from the conventional concepts. In the 970-1050 degrees C high-temperature annealing process where the abnormal grain growth could occur, the AlN gradually became fine and dispersed through dissolution, leading to the improvement of the inhibition force of AlN, so that the AlN inhibition force and the grain boundary migration driving force, which were continuously improved with the increase of the temperature, could be matched with each other, which ensured that the Goss grains could undergo the desirable secondary recrystallization process. In addition, the dissolution behavior of AlN during the 970-1050 degrees C high-temperature annealing was analyzed and discussed in terms of microstructure, Thermo Calc calculation, and crystallographic characterization of AlN. The results of this work can provide important ideas and methods for the optimization of the industrial lowtemperature grain-oriented silicon steel manufacturing process, and the corresponding findings have also been successfully applied to the industrial production process.