R-T-B Permanent Magnet Composition Balancing Br and Coercivity
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Solution Overview
Problem
Existing R-T-B based permanent magnets face challenges in achieving a balanced improvement in residual magnetic flux density (Br) and coercivity (HcJ) at room temperature, along with a high squareness ratio (Hk/HcJ).
Innovation Solution
The R-T-B based permanent magnet composition includes specific ranges of rare earth elements (Nd and Pr), transition metal elements (Fe and Co), boron, and additional elements (Al, Cu, Ga, Zr) with controlled amounts of impurities, combined with a production process involving alloy preparation, pulverization, pressing, sintering, aging, and grain boundary diffusion to enhance magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the amount of heavy rare earth element is increased to improve coercivity (HcJ), then HcJ is improved, but residual magnetic flux density (Br) decreases
Solution Approach 1:
The patent optimizes the composition parameters by limiting heavy rare earth element content to 0.05-0.20 mass% and precisely controlling the Pr/TRE ratio (0.35-0.45) and boron content (0.95-1.05 mass%). This parameter optimization achieves a balance between coercivity and residual magnetic flux density without requiring excessive heavy rare earth additions that would harm Br.
Solution Approach 2:
The patent creates a composite microstructure consisting of main phase grains (R2T14B type) and grain boundary phases with specific compositions. The grain boundary phase contains heavy rare earth elements, Pr, and boron in controlled proportions, forming a composite structure that simultaneously provides high coercivity through heavy rare earth at grain boundaries and high residual magnetic flux density through the main phase composition.
2Quantity of substance
If the amount of Pr is increased to improve residual magnetic flux density (Br), then Br is improved, but the balance with coercivity (HcJ) deteriorates
Solution Approach 1:
The patent establishes an optimal Pr content range of 16-20 mass% and controls the Pr/TRE ratio between 0.35-0.45. This precise parameter control ensures that Pr contributes sufficiently to residual magnetic flux density while maintaining the correct balance with heavy rare earth elements for adequate coercivity, achieving optimal magnetic property balance.
3Quantity of substance
If conventional production methods are used to achieve high Br at low temperature, then Br at low temperature is improved, but Hk/HcJ ratio decreases
Solution Approach 1:
The patent optimizes multiple composition parameters simultaneously: rare earth element composition (Pr/TRE ratio), boron content (0.95-1.05 mass%), and heavy rare earth content (0.05-0.20 mass%). This multi-parameter optimization achieves high Hk/HcJ ratio (95% or more) while maintaining high Br at low temperature, resolving the contradiction between low-temperature performance and squareness ratio.
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 resulting magnet achieves improved Br and HcJ in good balance, along with a high Hk/HcJ ratio, optimizing magnetic performance.
Implementation Method 1
a diffusion heat treatment is then performed on the sintered body
Implementation Method 2
a method for producing an R-T-B based sintered magnet
Data Source
AI summary
An R-T-B based permanent magnet includes rare earth elements, transition metal elements, boron, and M. An amount of boron is within a range between 0.90 mass % or more and 1.00 mass % or less. An amount of carbon is within a range between 0 mass % or more and 0.10 mass % or less, an amount of oxygen is within a range between 0 mass % or more and 0.15 mass % or less, an amount of nitrogen is within a range between 0 mass % or more and 0.15 mass % or less, an amount of M is within a range between 0.30 mass % or more and 1.50 mass % or less, an amount of the rare earth elements based on mass represented by TRE is within a range between 29.00 mass % or more and 31.00 mass % or less, and a value represented by Pr/TRE is within a range between 0.30 or larger and 0.50 or smaller.