R-T-B Permanent Magnet Composition With Low Heavy Rare Earth Use
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Solution Overview
Problem
Existing R-T-B based permanent magnets face challenges in maintaining excellent corrosion resistance and magnetic properties, particularly coercive force at room and high temperatures, while minimizing heavy rare earth element content.
Innovation Solution
An R-T-B based permanent magnet composition with specific content ranges of rare earth elements, Fe, Co, Si, Zr, Ga, and B, along with a distribution of heavy rare earth elements decreasing from the surface inward, and a core-shell structure formed through grain boundary diffusion, enhancing magnetic properties and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare earth element content is increased to improve coercive force, then magnetic properties improve, but material cost increases and corrosion resistance may deteriorate
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of heavy rare earth elements through grain boundary diffusion, where the surface region has higher concentration than the interior. This localized enrichment provides enhanced coercive force at the grain boundaries without requiring high bulk concentration, thus reducing overall heavy rare earth content while maintaining magnetic performance.
Solution Approach 2:
The patent utilizes parameter changes by controlling the diffusion process to achieve specific concentration gradients of heavy rare earth elements. By adjusting diffusion time, temperature, and surface treatment parameters, the patent optimizes the distribution profile to maximize coercive force while minimizing total heavy rare earth content.
2Reliability
If heavy rare earth element content is increased to improve coercive force, then magnetic properties improve, but material cost increases
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of heavy rare earth elements through grain boundary diffusion, where the surface region has higher concentration than the interior. This localized enrichment provides enhanced coercive force at the grain boundaries without requiring high bulk concentration, thus reducing overall heavy rare earth content while maintaining magnetic performance.
Solution Approach 2:
The patent utilizes parameter changes by controlling the diffusion process to achieve specific concentration gradients of heavy rare earth elements. By adjusting diffusion time, temperature, and surface treatment parameters, the patent optimizes the distribution profile to maximize coercive force while minimizing total heavy rare earth content.
3Ease of manufacture
If total rare earth element content is reduced to lower cost, then material cost decreases, but corrosion resistance and magnetic properties deteriorate
Solution Approach 1:
The patent applies local quality by concentrating heavy rare earth elements at grain boundaries through diffusion, creating a protective and magnetically active surface layer. This localized distribution maintains corrosion resistance at grain boundaries while using minimal total rare earth content in the bulk material.
Solution Approach 2:
The patent creates a composite structure with distinct regions: a grain boundary phase enriched with heavy rare earth elements providing magnetic and protective functions, and a bulk phase with lower rare earth content. This composite approach optimizes both corrosion resistance and magnetic properties while minimizing overall rare earth usage.
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 achieves improved residual flux density, coercive force, squareness, and corrosion resistance, while optimizing the use of heavy rare earth elements to reduce costs and maintain high magnetic performance.
Implementation Method 1
a distribution of concentrations of the heavy rare earth element decreasing from a surface of the R-T-B based permanent magnet inwards
Data Source
AI summary
An R-T-B based permanent magnet includes at least a rare earth element, Fe, Co, Si, Zr, Ga, and B. The rare earth element includes a heavy rare earth element. The R-T-B based permanent magnet has a rare earth element content of 28.50 mass % to 31.50 mass %, a heavy rare earth element content of 0.30 mass % or less excluding 0 mass %, a Co content of 0.20 mass % to 1.00 mass %, a Si content of 0.35 mass % to 1.20 mass %, a Zr content of 0.21 mass % to 0.85 mass %, a Ga content of 0.04 mass % to 0.40 mass %, a B content of 0.90 mass % to 1.02 mass %, and a C content of 0 mass % to 0.11 mass %.