Effect of phosphorus content on microstructure and magnetic/mechanical properties of ultra-thin non-oriented Fe–3%Si ribbons prepared with planar flow casting

The planar flow casting process has drawn increasing attention because of its noticeable advantages including short process, low energy consumption and low cost. However, this process has its limits in that the high melting point and viscosity of silicon steel melt lead to poor formability, which will deteriorate the surface quality of the ribbons. Phosphorus can effectively lower the melting point and viscosity of silicon steel, improving the formability of non-oriented silicon steel ribbons prepared by planar flow casting. Therefore, this paper systematically investigates the effects of phosphorus content on the surface quality, microstructure and magnetic/mechanical properties of Fe–3%Si ribbons prepared with the planar flow casting. The results show that as phosphorus content increases, the surface quality of ribbons significantly improves and the average grain size of Fe–3%Si ribbons decreases. The magnetic induction of the Fe–3%Si ribbons decreases, while the iron loss first increases, then falls, and goes up again. After annealing at 925 °C for 30 min, the magnetic induction of the phosphorus-containing ribbons significantly increased and the iron loss decreased. The enhanced magnetic induction is mainly attributed to the suppression of unfavorable orientation <111> grain growth. Meanwhile, phosphorus and Fe–P precipitated phases increase the resistivity and the eddy current loss reduces. When the phosphorus content is 0.5%, the magnetic properties of the annealed ribbons are optimal, with a magnetic induction of 1.60 T and iron loss of 16.59 W/kg. The tensile strength, hardness and elongation of the Fe–3%Si ribbons before annealing both increase with the increase of phosphorus content.