R-T-B Permanent Magnet Carbon Grain Boundary
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Solution Overview
Problem
The existing R-T-B based permanent magnets require a large magnetizing field to switch magnetization, leading to inefficiencies and uncontrollable magnetization changes, especially in low magnetizing fields, which limits their application in variable magnetic flux motors.
Innovation Solution
The development of an R-T-B based permanent magnet with a tetragonal structure and a grain boundary phase containing carbon, featuring a specific composition and atomic ratios of rare earth elements, transition metals, and boron, which reduces the coercive force and magnetizing field while maintaining high residual magnetic flux density and minor curve flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional R-T-B based permanent magnets are used, then high residual magnetic flux density is achieved, but large magnetizing field is required to switch magnetization
Solution Approach 1:
The patent modifies the chemical composition parameters of the R-T-B permanent magnet by adding specific amounts of Cu (0.5-0.6 atomic %) and Ni (0.1-0.3 atomic %) elements, and adjusting the rare earth element composition (R1, R2, Sm ratios). These parameter changes reduce the coercive force and magnetizing field requirements while maintaining high residual magnetic flux density, directly resolving the technical contradiction.
2Quantity of substance
If conventional R-T-B based permanent magnets are used, then high residual magnetic flux density is achieved, but magnetization becomes uncontrollable in low magnetizing fields
Solution Approach 1:
By changing the compositional parameters to include Cu and Ni elements with specific ratios, and adjusting the rare earth element composition, the patent achieves a balance between residual magnetic flux density and magnetization controllability. The modified composition allows controlled magnetization switching in low magnetizing fields, resolving the contradiction between maintaining high residual flux and achieving controllability.
3Ease of manufacture
If Sm-Co based permanent magnet is used as variable magnetic flux magnet, then low cost is achieved, but saturation magnetization is limited to about 12.5 kG
Solution Approach 1:
The patent creates a composite permanent magnet material by combining R-T-B base material with Cu and Ni additive elements. This composite approach leverages the high saturation magnetization of R-T-B (exceeding 12.5 kG) while using Cu and Ni to modify magnetic properties and reduce coercive force, achieving both high saturation magnetization and cost-effectiveness.
4Power
If R-T-B based permanent magnet with high residual magnetic flux density is used, then high power output is expected, but large magnetizing field requirement exceeds the upper limit of magnetic field that can be applied by stator coil
Solution Approach 1:
The patent adjusts the compositional parameters to reduce coercive force and magnetizing field requirements. By adding Cu (0.5-0.6 atomic %) and Ni (0.1-0.3 atomic %), and optimizing rare earth element ratios, the magnetizing field is reduced to within the applicability range of stator coils, while maintaining high residual magnetic flux density for high power output capability.
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
This solution enables the R-T-B based permanent magnet to operate efficiently with low coercive force and magnetizing field, achieving high residual magnetic flux density and minor curve flatness, even in low magnetizing fields, thus enhancing the controllability and efficiency of variable magnetic flux motors.
Implementation Method 1
a low coercive force Sm—Co based permanent magnet (a variable magnetic flux magnet), whose magnetization reversibly changes by applying an external magnetic field
Implementation Method 2
The R-T-B based permanent magnet comprises crystal grains including a rare earth element R, a transition metal element T, and boron B
Data Source
AI summary
An object of the present invention is to provide an R-T-B based permanent magnet having a low coercive force and a low magnetizing field, and having a high residual magnetic flux density and a high minor curve flatness even in the low magnetizing field. Provided is an R-T-B based permanent magnet including a main phase crystal grain including a compound having an R2T14B type tetragonal structure and a grain boundary phase existing between the main phase crystal grains, in which R is at least one rare earth element including scandium and yttrium, T is at least one transition metal element including iron, or at least two transition metal elements including iron and cobalt, an average diameter D50 of the main phase crystal grain is 1.00 μm or less, and a content of carbon included in the R-T-B based permanent magnet is 3,000 ppm or more.