Powder Magnetic Core via Composite Soft Magnetic Particles
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Solution Overview
Problem
Existing methods for manufacturing powder magnetic cores face challenges in reducing core loss and achieving high saturation magnetic flux density due to limitations in heat treatment temperatures and the degradation of insulating coatings during compaction and sintering, as well as difficulties in densification caused by the use of iron-based alloys with high hardness and low plastic deformation.
Innovation Solution
A method involving the use of a mixed powder comprising composite soft magnetic particles with a core-shell structure containing pure iron and an Fe-α alloy, along with an oxide powder, is compacted and sintered at temperatures between 900°C and 1300°C to form a dense powder magnetic core with an oxide insulating coating, enhancing electrical insulation and magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicone resin insulating coating is applied to soft magnetic particles and heat treatment is performed, then electrical insulation is improved, but the heat treatment temperature must be limited to about 800°C or less to prevent degradation of the resin coating
Solution Approach 1:
The invention changes the material parameter from organic silicone resin to inorganic oxide coating, enabling heat treatment temperatures to be raised from 800°C or less to 900°C or more while maintaining insulating properties. The oxide coating remains stable at high temperatures unlike the organic resin coating.
Solution Approach 2:
The invention uses oxide particles as a sacrificial material during sintering that decomposes to form a protective oxide insulating coating on the soft magnetic particles. This temporary sacrificial layer enables high-temperature treatment while protecting the magnetic particles.
2Reliability
If iron-based alloys with high hardness are used to increase saturation magnetic flux density, then magnetic properties are improved, but plastic deformation becomes low making densification difficult
Solution Approach 1:
The invention performs preliminary action by adding boron to the soft magnetic particles before sintering. This preliminary addition of boron enables subsequent high-temperature sintering to proceed effectively, achieving both high density and high saturation magnetic flux density without requiring high plastic deformation during compaction.
Solution Approach 2:
The invention changes the chemical composition parameter by adding boron (0.01-5 mass%) to the soft magnetic particles. This compositional change enables the material to achieve high saturation magnetic flux density (1.75 T or more) while maintaining manufacturability through normal compaction processes.
3Loss of energy
If sintering is performed at high temperature (900°C or more) to accelerate single crystallization and improve magnetic properties, then core loss is reduced, but the resin insulating coating is degraded by heat impairing electrical insulation
Solution Approach 1:
The invention uses oxide particles as a sacrificial material that decomposes during high-temperature sintering to form a protective oxide insulating coating on the soft magnetic particles. This temporary sacrificial layer enables high-temperature treatment (900°C or more) that reduces core loss while maintaining electrical insulation through the formed oxide coating.
Solution Approach 2:
The invention changes the insulating coating material from temperature-sensitive organic resin to temperature-stable inorganic oxide. This parameter change allows the system to withstand high sintering temperatures (900°C or more) without degradation, simultaneously achieving low core loss through single crystallization and maintained electrical insulation.
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
This approach results in a powder magnetic core with high density and low core loss, improving the magnetic properties and energy efficiency of electromagnetic components such as motors and reactors.
Implementation Method 1
a step of sintering the green compact at 900° C. or more and 1300° C. or less
Implementation Method 2
the oxide powder containing oxide particles containing at least one selected from Fe and an element β that forms an oxide having higher electrical resistance than Fe3O4
Data Source
AI summary
A method for manufacturing a powder magnetic core includes: a step of preparing a soft magnetic powder and an oxide powder and preparing, as a raw material powder, a mixed powder of the soft magnetic powder and the oxide powder, the soft magnetic powder containing composite soft magnetic particles containing pure iron and an Fe-α alloy having an element α more oxidizable than Fe, the composite soft magnetic particles each having a core-shell structure where a core is made of one of pure iron and the Fe-α alloy and a shell is made of the other, the oxide powder containing oxide particles containing at least one selected from Fe and an element β that forms an oxide having higher electrical resistance than Fe3O4; a step of compacting the mixed powder into a green compact; and a step o sintering the green compact at 900° C. or more and 1300° C. or less.