Soft Magnetic Metal Powder Spheroidization for Low Core Loss

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Solution Overview

Problem

Current methods for producing soft magnetic metal powder struggle to achieve a balance of low coercivity, high roundness, and a small amount of fine powder, which are essential for improving DC superimposition characteristics and reducing core loss in electromagnetic circuit components like inductors and reactors.

Innovation Solution

A method involving the preparation of metal raw material powder with iron, silicon, and boron, followed by mixing with a carbon source and heat treatment in a non-oxidizing nitrogen atmosphere at 1,250°C or higher to achieve spherical particle formation and subsequent boron nitride removal, resulting in soft magnetic metal powder with improved properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If water-atomization method is used to produce metal powder, then low production cost and small average particle size are achieved, but particle shape becomes irregular and spherical particles cannot be obtained

Engineering Contradiction:

Improveproduction costVSAvoidparticle shape

Core Design Contradiction:

Ease of manufactureVSShape

Solution Approach 1:

The invention changes the physical-chemical parameters of the metal powder through heat treatment at high temperature (1273K or higher), transforming irregular water-atomized particles into spherical particles with single crystal structure, thereby resolving the shape issue while maintaining the cost advantage of water-atomization

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite structure where metal particles with specific composition (Fe-Si-B alloy) are transformed through heat treatment to achieve both spherical shape and single crystal structure, combining multiple desirable properties in one material system

Inventive Principle:

Principle #40Composite materials

2Shape

If gas-atomization method is used to produce metal powder, then spherical particle shape is achieved, but production cost increases and average particle size becomes larger

Engineering Contradiction:

Improveparticle shapeVSAvoidproduction cost

Core Design Contradiction:

ShapeVSEase of manufacture

Solution Approach 1:

The invention uses inexpensive water-atomized powder as the starting material, which is then transformed through heat treatment to achieve the properties previously only obtainable from expensive gas-atomized powder, effectively replacing a costly process with a cheaper one

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If heat treatment is performed to reduce coercivity, then magnetic properties are improved, but particle shape and particle size distribution cannot be improved

Engineering Contradiction:

Improvemagnetic characteristicsVSAvoidparticle shape

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

The invention performs heat treatment at a specifically high temperature (1273K or higher) to simultaneously achieve three effects: reducing coercivity for improved magnetic properties, forming spherical particle shapes, and creating single crystal structure, thereby resolving all three issues in one process

Inventive Principle:

Principle #35Parameter changes

4Reliability

If classification is performed to remove fine powder, then DC superimposition characteristics are improved, but production process complexity increases

Engineering Contradiction:

ImproveDC superimposition characteristicsVSAvoidproduction process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention performs heat treatment before classification, which causes coarsening of particles and formation of spherical shapes with single crystal structure. This preliminary action reduces the amount of fine powder and improves particle morphology, making subsequent classification more effective and reducing process complexity

Inventive Principle:

Principle #10Preliminary action

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 method produces soft magnetic metal powder with low coercivity, high roundness, and a reduced amount of fine powder, leading to enhanced DC superimposition characteristics and reduced core loss in soft magnetic metal dust cores.

Implementation Method 1

heat treatment step of performing heat treatment on the mixed powder in a non-oxidizing atmosphere containing nitrogen at a heat treatment temperature of 1,250° C. or higher and making the metal raw material particles spherical

Methodology Applied

Scientific EffectSpheroidization:

Implementation Method 2

mixing the metal raw material powder and a carbon source substance and obtaining mixed powder; performing heat treatment on the mixed powder in a non-oxidizing atmosphere containing nitrogen

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Data Source

PatentUS11854725B2Soft magnetic metal powder, method for producing the same, and soft magnetic metal dust core

Publication Date: 2023.12.26 TDK CORP

AI summary

A method for producing soft magnetic metal powder includes: a raw material powder preparing step of preparing metal raw material powder having metal raw material particles including iron, silicon, and boron; a mixture step of mixing the metal raw material powder and a carbon source substance and obtaining mixed powder; and a heat treatment step of performing heat treatment on the mixed powder in a non-oxidizing atmosphere containing nitrogen at a heat treatment temperature of 1,250° C. or higher and making the metal raw material particles spherical.