Research on Evolution of Inclusions and Removal Rate of Oxides in Grain-Oriented Silicon Steel during RH Refining Process

摘要

The evolution of inclusions in grain-oriented silicon steel during the RH refining process was investigated by FE-SEM/ EDS, and the evolution mechanism was also discussed. The results show that there are not only a very small amount of micron-scale single MnS and complex inclusions containing Al_2O_3 compounding with SiO_2, but also a lot of nano-scale spherical (Al and Si)N and MnS. The number of small-sized nitride increases and that of large-sized oxide inclusions reduces with the increase of the refining time. At the end of RH, the inclusions are mainly A1N with MnS as the core. The average size of the inclusions in steel is minimal after the steel is being treated for 26 minutes. The proportion of inclusions which size ranges from 0.05μm to 0.5μm in the steel is the maximum and that of inclusions which size ranges from 0.5μm to lμm is the minimum. The number of inclusions which size is larger than 1 urn is the least when formation and removal of inclusions in the bath reach equilibrium. The content of total oxygen decreases linearly at first 26 minutes and then increases slowly to be a steady value. Its lowest value is 8×10~(-6). The apparent deoxidization rate constant is 0.068 min~(-1) at the experimental conditions. In the early 26 minutes of the refining process, the relationship between lnT[0] and the refining time is the same as that the amount of inclusions larger than lμm and the refining time.