Modelagem da precipitação de MnS em aços elétricos de grão orientado

Abstract

Grain oriented silicon steel has been used for electrical purposes since the beginning of the twentieth century. Their properties such as high permeability and resistivity reduce energy losses. The high permeability of these steels arises from a preferred orientation of grains in relation to the direction of rolling which leads to strong anisotropy of the magnetic properties. This preferential orientation is produced during hot rolling aided by secondary phases called inhibitors. To produce a preferential orientation in appreciable levels, one of the requirements it is that the hot rolling to take place between the beginning and end of precipitation of these inhibitors. In this work, the nucleation and growth of MnS in Fe-3% Si steels, the inhibitor most frequently used in the manufacture of grain-oriented electrical steel, were modeled. Initially, the mathematical tools to analyze the nucleation were proposed, in general terms. As the modeling was being carried through, information about the process inrelation to coherence, preferential nucleation sites, behavior during the growth and coarsening of precipitates have been clarified.Diagrams of temperature-time-precipitation that describe the kinetic profile of semi coherent precipitation at ferritic grain boundaries of MnS precipitates in Si steels at the temperature range of 800 to 900 oC were generated. Likewise, the behavior of the coarsening of this precipitated was described graphically. The predictions by the model were compared to experimental data reported in the literature. It can be conclude that, the model presented in this work shows results that are reasonably in agreement with the experimental data reported in the literature.