Non-Circular Wound Magnetic Core Stress Relief Nanocrystallization
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Solution Overview
Problem
There is a demand for non-circular wound magnetic cores with impedance characteristics equivalent to circular ones, particularly in applications where spatial constraints require unique shapes, but existing methods for manufacturing nanocrystalline alloy cores face challenges in maintaining magnetic properties and preventing deformation during heat treatment.
Innovation Solution
A two-step heat treatment process involving a first heat treatment at a temperature below the crystallization start temperature with a first inner shape correction jig, followed by a second heat treatment with a smaller second inner shape correction jig and application of a magnetic field, helps maintain a non-circular shape while minimizing stress and deformation, ensuring the magnetic core achieves high impedance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a non-circular wound magnetic core is manufactured by straightening the inner circumference with a non-circular inner shape correction jig, then the magnetic core can fit spatial constraints in device installations, but stress concentration and deformation occur during heat treatment, deteriorating magnetic properties
Solution Approach 1:
The patent applies preliminary stress relief heat treatment at 300-450°C before the nanocrystallization heat treatment. This preliminary action reduces residual stress from the non-circular shaping process, preventing stress concentration during subsequent high-temperature treatment and preserving magnetic properties while maintaining the non-circular shape
Solution Approach 2:
The patent divides the heat treatment into two stages with different temperature parameters: first stage at 300-450°C for stress relief, and second stage at 500-600°C for nanocrystallization. This parameter change approach allows sequential achievement of stress reduction and magnetic property enhancement without mutual interference
2Reliability
If nanocrystallization heat treatment is performed at high temperature, then magnetic permeability and other magnetic properties are enhanced, but thermal stress and deformation increase, particularly in non-circular shaped cores
Solution Approach 1:
The patent performs preliminary stress relief heat treatment at 300-450°C before nanocrystallization heat treatment. This preliminary action reduces residual stress from shaping operations, preventing stress concentration during high-temperature nanocrystallization and enabling magnetic property enhancement without excessive thermal stress
Solution Approach 2:
The patent segments the heat treatment process into two distinct stages: stress relief treatment (300-450°C) and nanocrystallization treatment (500-600°C). This segmentation allows each stage to optimize for its specific purpose, reducing overall thermal stress while achieving high magnetic permeability
3Shape
If the inner shape correction jig has a large cross section to maintain non-circular shape, then shape stability is improved, but stress concentration on the magnetic core increases during heat treatment
Solution Approach 1:
The patent removes the inner shape correction jig before performing nanocrystallization heat treatment. This preliminary removal eliminates the source of stress concentration, allowing the core to undergo uniform thermal expansion and contraction without localized stress from the jig, while shape stability is maintained through proper winding tension control
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 a non-circular wound magnetic core with impedance relative magnetic permeability of 45,000 or more at 100 kHz and 80,000 or more at 10 kHz, maintaining excellent magnetic properties and mechanical stability, suitable for applications like common mode choke cores.
Implementation Method 1
with a first inner shape correction jig for holding the wound magnetic core in a non-circular shape placed in an internal space of the wound magnetic core
Implementation Method 2
a second heat treatment step of subjecting the wound magnetic core to a heat treatment for nanocrystallization at a temperature equal to or higher than the crystallization start temperature
Implementation Method 3
a second heat treatment step of subjecting the wound magnetic core to a heat treatment for nanocrystallization at a temperature equal to or higher than the crystallization start temperature
Implementation Method 4
a magnetic field is applied to the wound magnetic core over a partial period of the second heat treatment step
Implementation Method 5
a first heat treatment step of subjecting a wound magnetic core, which is formed by winding an amorphous soft magnetic alloy ribbon capable of nanocrystallization, to a heat treatment at a temperature that is 300° C. or higher and below a crystallization start temperature
Data Source
AI summary
A method for manufacturing a wound magnetic core of a nanocrystalline soft magnetic alloy ribbon, the method including: a first heat treatment step of subjecting a wound magnetic core, which is formed by winding an amorphous soft magnetic alloy ribbon capable of nanocrystallization, to a heat treatment at a temperature that is 300° C. or higher and below a crystallization start temperature, with a first inner shape correction jig for holding the wound magnetic core in a non-circular shape placed in an internal space of the wound magnetic core; and a second heat treatment step of subjecting the wound magnetic core to a heat treatment for nanocrystallization at a temperature equal to or higher than the crystallization start temperature, with the first inner shape correction jig removed and with at least one second inner shape correction jig placed in the internal space of the wound magnetic core, wherein: a cross section of the second inner shape correction jig perpendicular to a direction in which the second inner shape correction jig extends is smaller than a cross section of the first inner shape correction jig perpendicular to a direction in which the first inner shape correction jig extends; and a magnetic field is applied to the wound magnetic core over a partial period of the second heat treatment step.