A statistical study of inclusions in medium-grade non-oriented silicon steel

Abstract

There are always differences between the magnetic properties (core loss and magnetic induction) of the head and those of the tail, with the same chemical composition, in a medium-grade non-oriented silicon steel coil (or MGNO for short). To work out the reason leading to the differences and get methods to increase the magnetic properties, this paper studied the types and the distribution of the inclusions in MGNO, and the effects of the inclusions on the magnetic properties of the MGNO, by using SEM + FEEM observation and statistic analysis. The results show that there are oxide inclusions, sulfide inclusions, nitride inclusions and composite inclusions in the MGNO. More inclusions shorter than 500 nm are bad for the magnetic properties of the MGNO. On a lower order of the sizes, the number of the inclusions would more obviously affect the MGNO on its magnetic properties. The Al2O3 shorter than 1 µm and the MnS whose size is 100∼500 nm are the main inclusions that decrease the magnetic properties of the MGNO. In order to get better magnetic properties of the MGNO, the steelmaking process and the hot rolling process should be improved, chiefly the RH and the heat furnace.