R-T-B Magnet Tb Gradient for Br and HcJ
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Solution Overview
Problem
Existing rare earth permanent magnets with R-T-B composition face challenges in achieving high residual magnetic flux density (Br) and coercive force (HcJ) while maintaining corrosion resistance and production stability.
Innovation Solution
An R-T-B based permanent magnet with specific elemental compositions, including Tb, Fe, Cu, Co, Ga, and B, with a concentration gradient of Tb from the surface to the center, and optimized content ranges for other elements, enhances Br and HcJ, and improves corrosion resistance and production stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rare earth permanent magnet with R-T-B composition is used to achieve high residual magnetic flux density and coercive force, then magnetic properties are improved, but production stability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compositional parameters within specific ranges: Tb content at 0.05-5.0 mass%, Cu at 0.04-0.50 mass%, Co at 0.5-3.0 mass%, Ga at 0.08-0.30 mass%, and B at 0.85-0.95 mass%. These defined parameter ranges ensure reproducible manufacturing while achieving superior magnetic properties. The total rare earth content is controlled at 28.05-30.60 mass%, providing a narrow but optimized composition window for consistent production.
2Reliability
If Tb concentration is increased to improve coercive force, then magnetic properties are improved, but manufacturing complexity increases
Solution Approach 1:
The patent implements local quality through a controlled concentration gradient of Tb element, where the surface region contains higher Tb content than the center. This gradient structure can be achieved through directional solidification or diffusion processes during manufacturing, allowing the material to self-organize the desired composition distribution without requiring complex post-processing or multiple assembly steps.
Solution Approach 2:
The patent simplifies manufacturing by defining a specific range for Tb content (0.05-5.0 mass%) and establishing the concentration gradient parameter (higher at surface, lower at center). These parameter specifications provide clear manufacturing targets that can be controlled through standard metallurgical processes, avoiding the need for complex multi-step fabrication or assembly procedures.
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 magnet exhibits improved residual magnetic flux density, coercive force, corrosion resistance, and production stability, making it suitable for applications like motors and generators.
Implementation Method 1
a magnet body is immersed in slurry in which fine powder including rare earth element is dispersed in water or organic solvent, heated thereof, and the rare earth element is diffused into the magnet body along the grain boundaries
Data Source
AI summary
An object of the present invention is to provide an R-T-B based permanent magnet showing high residual magnetic flux density Br and coercive force HcJ. Provided is an R-T-B based permanent magnet in which, R is a rare earth element, T is an element other than the rare earth element, B, C, O or N, and B is boron. R at least includes Tb and T at least includes Fe, Cu, Co and Ga, and a total of R content is 28.05 to 30.60 mass %, Cu content is 0.04 to 0.50 mass %, Co content is 0.5 to 3.0 mass %, Ga content is 0.08 to 0.30 mass %, and B content is 0.85 to 0.95 mass %, relative to 100 mass % of a total mass of R, T and B, and Tb concentration reduces from outside to inside of the R-T-B based permanent magnet.