Fe-Gradient Metal Magnetic Powder for Oxidation-Resistant Coil Cores
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Solution Overview
Problem
High Fe content in metal magnetic materials leads to oxidation during heat treatment, compromising magnetic properties, and existing methods struggle to balance high Fe content with oxidation inhibition.
Innovation Solution
Metal magnetic powder with a high Fe content at the center and low Fe content at the surface, combined with an oxide film, is produced by heat-treating a material powder with 90-99% Fe and easily oxidizable elements in a controlled oxygen atmosphere, creating a gradient that inhibits oxidation and maintains excellent magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the content percentage of Fe in metal magnetic material is increased to obtain excellent magnetic properties, then magnetic properties are improved, but oxidation of Fe occurs more easily during heat treatment
Solution Approach 1:
The patent applies local quality by creating a non-uniform Fe distribution within the metal magnetic grains, where the center part has high Fe content (98% by mass or higher) to ensure excellent magnetic properties, while the contour part near the surface has lower Fe content to inhibit oxidation. This spatial variation in composition allows simultaneous achievement of high magnetic performance and oxidation resistance.
Solution Approach 2:
The patent employs composite materials by combining Fe-rich metal phase with an oxide film covering the surface. The metal phase contains high Fe content at the center for magnetic properties, while the oxide film layer provides protection against oxidation. This composite structure integrates the advantages of both metallic Fe (magnetic properties) and oxide (oxidation resistance).
2Strength
If oxide layers are formed through heat treatment to bond grains together, then mechanical strength is improved, but Fe oxidation occurs which compromises magnetic properties
Solution Approach 1:
The patent applies local quality by creating a composition gradient where the contour part has lower Fe content that facilitates oxide layer formation for strong grain bonding, while the center part maintains high Fe content for excellent magnetic properties. This spatial differentiation allows oxide layers to form effectively for mechanical strength without significantly compromising the magnetic properties of the bulk material.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting metal magnetic powder effectively inhibits Fe oxidation, enabling the production of magnetic bodies with superior magnetic properties, allowing for higher current capacity and reduced size in coil components.
Implementation Method 1
heat-treating the material powder in an atmosphere of 5 to 10 ppm in oxygen concentration... an oxide film covering the metal phase
Implementation Method 2
raising its temperature to 850° C. at a rate of rise in temperature of 100° C./min or higher... heat-treating the material powder in the atmosphere at a temperature of 850° C. or above but below 1000° C.
Data Source
AI summary
A metal magnetic powder is constituted by metal magnetic grains that each include: a metal phase where the percentage of Fe at its center part is 98 percent by mass or higher, while the mass percentage of Fe at its contour part is lower than that at the center part; and an oxide film covering the metal phase, so as to inhibit oxidation of Fe contained in the metal phase, despite the high content percentage of Fe in the metal phase.