RH Diffusion Source for R-T-B Magnet Coercivity
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Solution Overview
Problem
Existing methods for producing sintered R-T-B based magnets face challenges in maintaining coercivity at high temperatures without decreasing remanence, and involve complex and inefficient processes for diffusing heavy rare-earth elements like Dy or Tb, which can react with the magnet body and require repeated setup.
Innovation Solution
A method involving a processing chamber where a sintered R-T-B based magnet body and an RH diffusion source with 30-80% Fe are moved relative to each other at 870-1000°C, allowing for efficient diffusion of Dy or Tb without excessive supply, using a rotating or rocking chamber to promote contact and prevent reaction, enabling repeated use of the RH diffusion source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a heavy rare-earth element RH is added to increase coercivity, then coercivity increases, but remanence decreases
Solution Approach 1:
The heavy rare-earth element RH is selectively concentrated at the grain boundaries of the R2T14B phase through diffusion, rather than being uniformly distributed throughout the magnet. This local concentration at critical interfaces provides the necessary coercivity enhancement while minimizing the overall amount of RH needed, thereby preserving remanence.
Solution Approach 2:
A ferrous compound of heavy rare-earth element is used as an intermediary diffusion source. This compound serves as a reservoir that releases RH atoms during heat treatment, enabling controlled diffusion into the magnet body. The intermediary approach allows precise spatial and temporal control of RH distribution, achieving high coercivity with minimal remanence loss.
2Strength
If a heavy rare-earth element RH is added to increase coercivity, then coercivity increases, but the amount of rare natural resources used increases
Solution Approach 1:
By concentrating RH at grain boundaries rather than distributing it uniformly, the invention achieves the required coercivity enhancement with a significantly reduced total amount of heavy rare-earth element. This localized approach minimizes consumption of rare natural resources while maintaining high performance.
Solution Approach 2:
The invention applies a small, controlled amount of RH precisely where needed (at grain boundaries) rather than using excessive amounts throughout the entire magnet. This partial action approach is sufficient to achieve the desired coercivity improvement while conserving rare resources.
3Productivity
If the RH bulk body is heated in contact with the sintered R-T-B based magnet body, then diffusion efficiency increases, but the RH bulk body reacts with the magnet body causing property alteration
Solution Approach 1:
A ferrous compound of heavy rare-earth element serves as an intermediary diffusion source that can be heated in contact with the magnet body without reacting adversely. This intermediary compound releases RH atoms through controlled thermal decomposition or diffusion, providing efficient element transfer while maintaining the stability of both the diffusion source and the magnet body.
Solution Approach 2:
The invention changes the chemical form of the RH source from a reactive bulk body to a ferrous compound with controlled reactivity. This parameter change in the source material's chemical state allows for higher heating temperatures and better contact without harmful reactions, thereby improving diffusion efficiency while preserving source integrity.
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 method effectively increases coercivity while minimizing remanence loss and allows for repeated use of the RH diffusion source, simplifying the production process and avoiding contamination issues.
Implementation Method 1
performing an RH diffusion process in which the sintered R-T-B based magnet body and the RH diffusion source are heated to a processing temperature of 870°C to 1000°C while being moved either continuously or discontinuously in the processing chamber
Implementation Method 2
a sintered R-T-B based magnet body and an RH diffusion source with 30-80% Fe are moved relative to each other at 870-1000°C, allowing for efficient diffusion of Dy or Tb without excessive supply, using a rotating or rocking chamber to promote contact
Data Source
Figure 1~2
AI summary
A method for producing a sintered R-T-B based magnet includes the steps of: providing a sintered R-T-B based magnet body 1; providing an RH diffusion source including a heavy rare-earth element RH (which is at least one of Dy and Tb) and 30 mass% to 80 mass% of Fe; loading the sintered R-T-B based magnet body 1 and the RH diffusion source 2 into a processing chamber 3 so that the magnet body 1 and the diffusion source 2 are movable relative to each other and are readily brought close to, or in contact with, each other; and performing an RH diffusion process in which the sintered magnet body 1 and the RH diffusion source 2 are heated to a processing temperature of more than 850 °C through 1000 °C while being moved either continuously or discontinuously in the processing chamber.