Non-oriented electrical steel sheet with phosphorus segregation

The patent replaces expensive cobalt with a cost-effective composition strategy using conventional elements (Si: 1-4 mass%, Mn: 0.05-3 mass%, P: 0.03-0.2 mass%, S: not more than 0.01 mass%, Al: not more than 0.004 mass%) in optimized proportions. This substitution eliminates dependence on expensive rare earth elements while achieving the same magnetic flux density improvement (B50 ≥ 1.68 T), thereby dramatically reducing production costs.

The patent optimizes the compositional parameters of conventional steel elements to achieve high magnetic flux density. Specifically, it controls Si content at 1-4 mass%, Mn at 0.05-3 mass%, and P at 0.03-0.2 mass%, with strict limits on Al (≤0.004 mass%) and S (≤0.01 mass%). This parameter optimization allows the steel to achieve B50 ≥ 1.68 T without requiring expensive cobalt addition, thus resolving the cost-performance contradiction.

The patent precisely controls the interaction between Al and P by limiting Al to ≤0.004 mass% while adding P at 0.03-0.2 mass%. This specific parameter combination allows P to effectively segregate at grain boundaries and improve magnetic flux density (B50 ≥ 1.68 T) while maintaining isotropic magnetic properties. The controlled parameter range prevents excessive anisotropy that would otherwise result from unbalanced Al-P interactions.

The patent exploits the local segregation behavior of phosphorus at grain boundaries to improve bulk magnetic properties. By adding P at controlled levels (0.03-0.2 mass%) in the presence of reduced Al (≤0.004 mass%), P preferentially accumulates at grain boundaries, locally modifying the microstructure to enhance overall magnetic flux density while maintaining isotropic characteristics in the bulk material.