Metal Magnetic Powder With Fe Gradient for Low Iron Loss

The patent applies local quality by creating a non-uniform Fe distribution within the metal magnetic grains, where the Fe content varies from the center to the contour. Specifically, the Fe content at the contour part is higher than at the center part, forming a gradient structure. This allows different regions of the same material to serve different functions: the high-Fe contour region provides high saturation magnetic flux density, while the lower-Fe center region reduces iron loss, thereby resolving the technical contradiction between saturation density and energy loss.

The patent resolves this contradiction by spatially separating the functions of different elements through non-uniform distribution. Si and other iron-loss reducing elements are concentrated in the center part of the grains where Fe content is lower, effectively reducing iron loss. Meanwhile, the contour part maintains high Fe content to ensure high saturation magnetic flux density. This local differentiation allows both requirements to be satisfied simultaneously without compromising either performance metric.

The patent applies preliminary action by performing heat treatment to form oxide layers on the surface of metal magnetic grains before final product assembly. This preliminary oxidation step creates an electrical insulating barrier that prevents eddy current formation between grains, thereby improving electrical insulating property and reducing iron loss. The oxide layer formation is performed as a preparatory step that does not significantly alter the internal Fe distribution or magnetic properties of the grains, thus maintaining saturation magnetic flux density while improving electrical insulation.