Nitrogen-Gradient Soft Magnetic Iron Plate for Low-Loss High Flux
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Solution Overview
Problem
Current soft magnetic materials struggle to achieve high saturation magnetic flux density while maintaining low iron loss and cost-effectiveness, particularly for applications in rotating electric machines and transformers, where existing materials like Permendur are costly and have limitations in coercive force and hysteresis loss.
Innovation Solution
A soft magnetic iron alloy plate with a specific nitrogen concentration gradient distribution, formed through a nitrogen immersion and denitrification process, which includes an outer nitrogen concentration transition region, a high nitrogen concentration region, and an inner nitrogen concentration transition region, optimized to enhance saturation magnetic flux density without excessive iron loss, and manufactured using a combination of nitrogen concentration control heat treatment and phase transformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nitrogen concentration is introduced to increase saturation magnetic flux density, then saturation magnetic flux density is improved, but iron loss increases due to high coercive force
Solution Approach 1:
The patent applies local quality by creating a non-uniform nitrogen concentration distribution within the plate thickness direction. The nitrogen concentration is controlled to be higher in the central region and lower near the surface, forming distinct regions (first nitrogen concentration region with 3-9 at%, second nitrogen concentration region with 1-5 at%, and surface region with 0.1-3 at%). This spatial variation in nitrogen concentration allows the central region to provide high saturation magnetic flux density while the surface region maintains low coercive force and low iron loss.
2Quantity of substance
If Fe-Co-based alloy material is used to increase saturation magnetic flux density, then saturation magnetic flux density is improved, but material cost increases significantly
Solution Approach 1:
The patent applies parameter changes by modifying the nitrogen concentration parameter within the iron-based material rather than changing the base material composition to Fe-Co alloy. By controlling nitrogen concentration to be 1-11 at% (with specific regional variations), the patent achieves saturation magnetic flux density exceeding that of pure iron (2.1 T) while maintaining iron as the primary material, thus avoiding the high cost associated with Fe-Co-based alloys like Permendur.
3Quantity of substance
If uniform high nitrogen concentration is applied throughout the material, then saturation magnetic flux density is maximized, but coercive force increases and magnetic characteristics deteriorate
Solution Approach 1:
The patent applies local quality by creating a non-uniform nitrogen concentration distribution within the plate thickness direction. The nitrogen concentration is controlled to be higher in the central region and lower near the surface, forming distinct regions (first nitrogen concentration region with 3-9 at%, second nitrogen concentration region with 1-5 at%, and surface region with 0.1-3 at%). This spatial variation in nitrogen concentration allows the central region to provide high saturation magnetic flux density while the surface region maintains low coercive force and low iron loss.
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 solution provides a soft magnetic iron alloy plate with improved saturation magnetic flux density exceeding that of pure iron, while maintaining low iron loss and reducing material costs, making it suitable for high-output rotating electric machines and transformers.
Implementation Method 1
a nitrogen concentration distribution control heat treatment step of subjecting the starting material to predetermined nitrogen concentration distribution control heat treatment to form predetermined N concentration distribution along a thickness direction of the starting material
Implementation Method 2
a phase transformation and iron nitride phase generation step of subjecting the starting material in which the predetermined N concentration distribution is formed to martensite transformation and dispersing and generating an iron nitride phase
Data Source
AI summary
A soft magnetic iron alloy plate having saturation magnetic flux density higher than that of an electromagnetic pure iron plate without an excessive increase in an iron loss, a method for manufacturing the soft magnetic iron alloy plate, and an iron core and a rotating electric machine using the soft magnetic iron alloy plate are provided. A soft magnetic iron alloy plate according to the present invention includes chemical composition containing 2 to 10 at. % of N, 0 to 30 at. % of Co, 0 to 1.2 at. % of V, and a remaining portion including Fe and impurities, and in a thickness direction of the soft magnetic iron alloy plate, an outer nitrogen concentration transition region where N concentration on a main surface is 1 to 4 at. % and N concentration increases toward the inner side from the main surface, a high nitrogen concentration region where maximum N concentration is higher than N concentration of the main surface and less than 11 at. %, and a variation range of N concentration is within 1 at. %, and an inner nitrogen concentration transition region where N concentration decreases toward the inner side from the high nitrogen concentration region and minimum N concentration is lower than N concentration in the high nitrogen concentration region and is 1 at. % or more.