Abstract: Four kinds of non-oriented 4.5 % Si steels with different mass fraction of Y (0, 0.006 %, 0.012 %, 0.016 %) were analyzed for the effects of Y on microstructure and magnetic properties of annealed sheets. The results showed that Y effectively modified nano scale square TiN and Al2O3 inclusions into spherical TiO2, Al2O3 and Y2O2S composite inclusions, coarsened the size of inclusions and reduced the number of fine inclusions dispersed in 0-500 nm. Thus, adding appropriate amount of Y increased the grain growth rate and reduced the activation energy of grain boundary migration, and the interaction of magnetic domain with grain boundary and inclusions led to the decrease of loss and iron loss. However, excessive Y increased the fine inclusions, enhanced the effect of pinning grain boundary and reduced the grain size of the annealed sheets. The {111} oriented grains nucleated and grew preferentially around the fine inclusions during annealing, the addition of rare earth Y reduced the inclusion density, and the enrichment of rare earth Y at the grain boundary reduced the nucleation advantage of {111} grains at the grain boundary, so the addition of rare earth Y weakened the strength of γ texture. The results showed that the sample containing 0.012 % Y has the highest B50 (1.655 T) and the lowest iron loss at each frequency, P1.0/50=1.41 W/kg, P1.0/400=19.28 W/kg and P1.0/1000=77.69 W/kg respectively.

Key words: non-oriented silicon steel, rare earth Y, inclusion, grain size, texture