Modelagem da precipitação de AIN em aços elétricos de grão orientado

Abstract

Electrical steels have been widely used in the construction of motors and transformers because of the lower energy losses when compared to common steel. Since the second half of the twentieth century, grain-oriented electrical steels have been achieving increasing efficiencies, and therefore its production phases have become more elaborate, thus, needing tighter control. In the manufacture of such steels, different compounds are precipitated in the matrix of the steel and used as grain-growth inhibitors. Among these inhibitors, special attention has been given to manganese sulfide and aluminum nitride, which, by preventing the growth of ferritic grains in the primary recrystallization, promote the accumulation of energy required for the secondary recrystallization process to occur, when the growth of grains having Goss texture is favored. In this work, the precipitation of AlN in grain-oriented electrical steels has been studied. The work includes a discussion of the thermodynamic and kinetic processes involved in precipitation through the modeling of various parameters, such as Gibbs free energy in the precipitation process, influence of interfacial energy and effects of precipitation in grain boundaries and in dislocations. PTT diagrams were constructed for the precipitation process in the temperature range between 500ºC and 1300ºC. Two models for assessing the influence of elastic energy matrix in precipitation and a model that treats both the nucleation and growth of precipitates in ferritic matrices were compared. Finally, the obtained data were compared with those obtained from the literature in order to assess the validity of the thesis and the conclusion was that it is able to reach, with reasonable accuracy, the experimental data reported in the literature.