R-T-B Magnet Composition for Lower Magnetizing Field Motors
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Solution Overview
Problem
The R-T-B-based magnetic material described in existing patents has high remanence but requires a high magnetizing field for magnetization switching, exceeding the limit of stator coils in motors, and exhibits large magnetization variation with respect to magnetic field variation, leading to inefficient motor operation.
Innovation Solution
An R-T-B-based magnet with specific composition and structure, including rare earth elements, transition metal elements, boron, gallium, aluminum, and carbon, with a tetragonal R2T14B-type main phase and grain boundary phases, optimized to reduce coercivity, magnetizing field, and increase minor curve flatness, allowing high remanence and efficient magnetization control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If R-T-B-based magnetic material with high remanence is used, then magnetic flux is improved, but magnetizing field required for magnetization switching becomes excessively high, exceeding stator coil capabilities
Solution Approach 1:
The patent modifies the chemical composition parameters of the R-T-B-based magnet by adding gallium (0.01-5 at%) and aluminum (0.01-5 at%) elements, and controlling the Fe/Co ratio and crystal grain size (0.5-5 μm). These parameter changes reduce the magnetizing field requirement while maintaining high remanence (Br ≥ 1.0 T), enabling the magnet to be switched by stator coil capabilities.
2Stability of the object's composition
If conventional R-T-B-based magnet with high coercivity is used, then magnetic stability is improved, but magnetization variation with respect to magnetic field variation increases, reducing motor efficiency
Solution Approach 1:
The patent optimizes composition parameters (gallium 0.01-5 at%, aluminum 0.01-5 at%, Fe/Co ratio 90/10 to 10/90) and structural parameters (crystal grain size 0.5-5 μm) to achieve coercivity of 5-50 kOe. This balanced parameter set reduces magnetization variation (improving minor curve flatness) while maintaining adequate magnetic stability, thereby reducing energy loss and improving motor efficiency.
3Stability of the object's composition
If Sm-Co-based permanent magnet is used for variable magnetic flux, then magnetization reversibility is improved, but cost increases due to expensive cobalt and saturation magnetization is insufficient compared to neodymium magnet
Solution Approach 1:
The patent creates a composite R-T-B-based magnet system combining neodymium (Nd) or praseodymium (Pr) with transition metals (Fe, Co) and additive elements (Ga, Al). This composite structure achieves saturation magnetization of 1.2-2.0 T (exceeding Sm-Co), maintains magnetization reversibility through controlled coercivity (5-50 kOe), and reduces cost by using abundant Fe and optimized Co content (0-50 at%).
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 optimized R-T-B-based magnet achieves low coercivity and magnetizing field, high remanence, and improved minor curve flatness, enabling efficient motor operation with reduced energy consumption and increased efficiency across a wide range of speeds and loads.
Implementation Method 1
a remanence reversibly changes by applying an external magnetic field
Implementation Method 2
R-T-B-based magnet containing one or more of rare earth elements; one or more of transition metal elements, including iron, or two or more of transition metal elements, including iron and cobalt; boron
Data Source
AI summary
The R-T-B-based magnet contains one or more kinds of rare earth elements (R), a transition metal element (T) including iron or iron and Co as an essential element, B, an element M that is Ga or Ga and Al, and C. When ratios of the number of atoms of R, T, B, M, and C are set as a, b, c, d, and e, respectively, relationships of 14%≤a≤20%, 70%≤b≤82%, 4%≤c≤7%, 0.009≤d/b≤0.035, and 0.025≤e/b≤0.055 are satisfied. The R-T-B-based magnet includes main phase crystal grains having an R2T14B-type tetragonal structure, and a grain boundary phase including an R-T-M-C phase. When ratios of R, T, M, and C in the main phase crystal grains are set as RMP, TMP, MMP, and CMP, and ratios of R, T, M, and C in the R-T-M-C phase are set as RRC, TRC, MRC, and CRC, relationships of RRC>RMP, TRC<TMP, MRC>MMP, and CRC>CMP are satisfied, and a relationship of 0.07≤MRC/TRC≤0.65 is satisfied.