Soft Magnetic Dust Core Compaction Below Crystallization Limits
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Solution Overview
Problem
Existing methods struggle to form dense green compacts of Fe-B-Si-P-Cu-based amorphous powder without damaging the insulation coating and preventing the crystallization of secondary phases that affect magnetic properties.
Innovation Solution
A method involving coated amorphous powder made of specific alloys, compacted at a temperature lower than the first initial crystallization temperature minus 100 K, and heated to a maximum temperature between the first and second initial crystallization temperatures with applied pressure, ensuring high density and favorable magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous powder is green compacted without heating, then the insulation coating is preserved, but the density is low and mechanical strength is insufficient
Solution Approach 1:
The patent applies temperature and pressure parameters during green compacting to soften the amorphous powder, enabling density improvement while preserving the insulation coating. By controlling temperature to remain below the crystallization point and applying appropriate pressure, the material achieves densification without compromising coating integrity or magnetic properties.
2Volume of stationary object
If heat treatment is performed to increase density, then density improves, but the insulation coating may be damaged and secondary phases may crystallize
Solution Approach 1:
The patent precisely controls temperature and pressure parameters during heat treatment to achieve density improvement while avoiding coating damage and unwanted crystallization. The temperature is maintained below the crystallization point of the amorphous powder, and pressure is applied to promote densification without causing secondary phase formation.
Solution Approach 2:
The insulation coating is applied to the amorphous powder particles before green compacting and heat treatment. This preliminary protective action ensures the coating is in place to prevent oxidation and maintain electrical insulation throughout subsequent processing steps.
3Reliability
If heat treatment is performed to nanocrystallize the powder, then magnetic properties improve, but the Vickers hardness exceeds 1000 making green compacting difficult
Solution Approach 1:
The patent performs green compacting of the amorphous powder before nanocrystallization heat treatment. By consolidating the soft amorphous particles into a dense green compact first, the material becomes easier to handle and process. Subsequent heat treatment then achieves nanocrystallization for improved magnetic properties without the handling difficulties of loose hard particles.
Solution Approach 2:
The patent utilizes the phase transition from amorphous to nanocrystalline structure through controlled heat treatment. The amorphous powder is heated to a temperature below its crystallization point to induce nanocrystallization, improving magnetic properties while maintaining the green compact form for ease of handling.
4Volume of stationary object
If compacting pressure is applied at high temperature, then density increases, but the crystallization temperature window becomes restricted
Solution Approach 1:
The patent optimizes the combination of temperature and pressure parameters to achieve effective densification within a practical temperature control window. By applying compacting pressure at elevated but controlled temperatures, the material softens to facilitate densification while remaining below the crystallization point, thus avoiding restricted temperature windows and complex control requirements.
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 achieves a soft magnetic dust core with high density and improved magnetic properties, maintaining insulation integrity and preventing secondary phase crystallization.
Implementation Method 1
amorphous powder made of an Fe-B-Si-P-C-Cu-based alloy... compacted at a temperature lower than the first initial crystallization temperature minus 100 K, and heated to a maximum temperature between the first and second initial crystallization temperatures with applied pressure
Implementation Method 2
a first insulation coating that prevents oxidation of the amorphous powder and a second insulation coating formed on the first insulation coating
Data Source
AI summary
Provided is a method of manufacturing a soft magnetic dust core. The method includes: preparing coated powder including amorphous powder made of an Fe-B-Si-P-C-Cu-based alloy, an Fe-B-P-C-Cu-based alloy, an Fe-B-Si-P-Cu-based alloy, or an Fe-B-P-Cu-based alloy, with a first initial crystallization temperature Tx1 and a second initial crystallization temperature Tx2; and a coating formed on a surface of particles of the amorphous powder; applying a compacting pressure to the coated powder or a mixture of the coated powder and the amorphous powder at a temperature equal to or lower than Tx1−100 K; and heating to a maximum end-point temperature equal to or higher than Tx1−50 K and lower than Tx2 with the compacting pressure being applied.