Effect of sulfur segregation/precipitation on microstructure and magnetic properties of Fe-3%Si non-oriented silicon steel ultra-thin ribbons prepared with planar flow casting

Sulfur segregation at grain boundaries induces hot brittleness in steel, necessitating strict control of sulfur content in conventional non-oriented silicon steel. The ultra-rapid solidification characteristics of the planar fiow casting process can effectively inhibit sulfur segregation, therefore avoiding hot brittleness of silicon steel ribbons caused by sulfur. The effect of sulfur segregation/precipitation on surface quality, microstructure and magnetic properties of Fe-3%Si ultra-thin ribbons prepared with planar fiow casting process is systematically investigated. Results indicate that extensive precipitation of FeS at grain boundaries and internal stresses induced by non-uniform solidification shrinkage leads to crack formation in 0.1%S ribbons. At 0.03%S, nanoscale precipitates (primarily FeS and MnS) distribute uniformly, when sulfur content exceeds 0.06%, and diffuse sulfur aggregation zones emerge. 001 \ 100 texture strength and magnetic induction of 0.03%S ribbons increase due to the optimized texture. Compared to 0%S ribbons, the magnetic induction of 0.03%S ribbons increases from 1.598 to 1.608 T. Higher sulfur raises iron loss due to increased grain boundaries and impeded magnetic domain motion. After annealing, 0.03%S ribbons achieve a magnetic induction of 1.625 T, attributed to sulfur inhibiting undesirable 110 and 111 grain growth. However, excessive sulfur restricts grain growth and texture evolution. Fe-3%Si-0.03%S ribbons possess the best magnetic properties after annealing at 1075 ℃, with a magnetic induction of 1.625 T, higher than 1.603 T of Fe-3%Si ribbons as well as a greater iron loss (17.51 W/kg vs. 12.33 W/kg).