R-T-B Permanent Magnet Grain Boundary Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
R-T-B based sintered magnets have insufficient residual magnetic flux density and temperature properties, with complex manufacturing processes leading to low productivity.
Innovation Solution
An R-T-B based permanent magnet comprising R2T14B main phase crystal grains with a coverage ratio of 50.0% or more and an area proportion of 92.0% or more, along with a grain boundary structure, which includes controlling the content of C and O to prevent phase formation that degrades coercivity and magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional R-T-B based sintered magnet manufacturing methods are used, then the manufacturing process can be completed, but the residual magnetic flux density is not sufficiently high
Solution Approach 1:
The patent applies parameter changes by precisely controlling the content of rare-earth elements (27.5-31.5 mass%) and creating a specific microstructure with R2T14B main phase crystal grains having 50.0% or more coverage ratio and 92.0% or more area proportion. This optimized composition and microstructure achieve high residual magnetic flux density (14.0 kG or more) while maintaining manufacturing feasibility
Solution Approach 2:
The patent uses composite material principles by creating a multi-phase structure consisting of R2T14B main phase crystal grains and grain boundaries with controlled impurity distribution. The composite structure of main phase grains (providing magnetic properties) and grain boundaries (controlling coercivity) achieves both high residual magnetic flux density and good temperature properties
2Reliability
If conventional sintered rare-earth magnet manufacturing methods are used, then the magnet can be manufactured, but the temperature properties are not sufficient
Solution Approach 1:
The patent applies local quality by creating distinct regions with different functions: R2T14B main phase crystal grains (50.0% or more coverage ratio) providing high magnetic properties at room temperature, and grain boundaries with controlled impurity content (C: 500 ppm or less, O: less than 900 ppm) providing thermal stability. This spatial differentiation of material properties achieves excellent temperature characteristics while using a relatively simple sintering process
3Productivity
If conventional R-T-B based sintered magnet methods are used, then manufacturing can proceed, but productivity is low due to complicated manufacturing steps
Solution Approach 1:
The patent merges multiple process steps into a simplified sintering process that simultaneously achieves: (1) formation of R2T14B main phase crystal grains with 50.0% or more coverage ratio, (2) creation of grain boundary structure with controlled impurity distribution, and (3) achievement of high density (92.0% or more area proportion of main phase). This integration of multiple objectives into a single process dramatically improves productivity while maintaining excellent magnetic properties
Data Source
AI summary
An R-T-B based permanent magnet including R2T14B main phase crystal grains and a grain boundary. R represents one or more rare earth elements, T represents one or more iron group elements essentially including Fe or Fe and Co, and B represents boron. In a cross-section parallel to the alignment direction of the R-T-B based permanent magnet, the coverage of the R2T14B main phase crystal grains is 50.0% or more, and the area ratio of the R2T14B main phase crystal grains is 92.0% or more.