Fe-Based Nanocrystalline Soft Magnetic Material Thermal Stability
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Solution Overview
Problem
Existing soft magnetic materials face challenges in maintaining high saturation magnetization and low coercive force while ensuring thermal endurance, as the coercive force increases under high temperature conditions, making it difficult to suppress crystalline phase coarsening and maintain magnetic characteristics.
Innovation Solution
A Fe-based nanocrystalline soft magnetic material is produced by heat-treating an alloy with a composition of Fe100-x-yBxNiy, where x satisfies 10≤x≤16 and y≤4, at a temperature region between the α-Fe crystal formation start temperature and the Fe—B compound formation start temperature, using rapid heating and short holding times to prevent grain growth and formation of Fe—B compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If elements that suppress grain growth are added to the material, then the coercive force is reduced, but the Fe content decreases and saturation magnetization decreases
Solution Approach 1:
The patent changes the heating rate parameter from conventional slow heating to rapid heating (10°C/s or more). This parameter change allows the material to achieve fine nanocrystalline structure with low coercive force without needing to add grain growth suppressor elements, thereby maintaining high Fe content and saturation magnetization. The rapid heating transforms the phase evolution path to form nanocrystals before significant grain growth occurs.
2Force
If the alloy is heat-treated at high temperature for extended periods, then grain growth is suppressed, but thermal endurance deteriorates
Solution Approach 1:
The patent applies rapid heating to quickly pass through the temperature range where harmful Fe-B compound formation occurs, and implements short holding times (0 to 80 s) to complete the phase transformation before significant grain growth or compound formation can occur. This rushing through the critical temperature zones achieves fine nanocrystalline structure while maintaining thermal stability and endurance.
3Stability of the object's composition
If conventional heat treatment is performed on amorphous phase, then crystalline phase forms, but grain coarsening occurs and magnetic characteristics deteriorate
Solution Approach 1:
The patent fundamentally changes the heating rate parameter from conventional slow heating to rapid heating (10°C/s or more). This parameter change transforms the phase evolution kinetics, enabling the formation of fine nanocrystalline grains before grain coarsening can occur. The rapid heating creates a non-equilibrium process that produces the desired fine-grained nanocrystalline structure with low coercive force.
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 results in a soft magnetic material with a coercive force of 20 A/m or less and a coercive force characteristic decrease rate of 20% or less after thermal endurance testing, maintaining low coercive force and high saturation magnetization even under high temperature conditions.
Implementation Method 1
heating the alloy at a heating rate of 10° C./s or more and holding the alloy at a temperature of a crystal formation start temperature or more to less than a Fe—B compound formation start temperature over 0 to 80 s
Implementation Method 2
a crystalline phase (α-Fe) forms easily from the amorphous phase
Implementation Method 3
heating the alloy at a heating rate of 10° C./s or more
Data Source
AI summary
There are provided a soft magnetic material having a high saturation magnetization and a low coercive force and excellent in thermal endurance, and a method for producing the same. The present disclosure relates to a soft magnetic material represented by the following composition formula: Fe100-x-yBxNiy, wherein x satisfies 10≤x≤16 in at %, and y satisfies 0<y≤4 in at %, having a coercive force of 20 A/m or less, and having a coercive force characteristic decrease rate after a thermal endurance test {[(coercive force after thermal endurance test−coercive force before thermal endurance test)/coercive force before thermal endurance test]×100 (%)} of 20% or less, wherein the thermal endurance test is carried out by allowing the soft magnetic material to stand in a constant temperature oven at 170° C. in the air for 100 h, and a method for producing the same.