R-T-B Magnet Coercivity via Dynamic RH Diffusion
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Solution Overview
Problem
Existing methods for producing sintered R-T-B based magnets face challenges in achieving high coercivity without decreasing remanence, particularly due to low diffusion rates of heavy rare-earth elements at moderate temperatures and issues with adhesion between magnet and diffusion source at higher temperatures, leading to inefficient processes and productivity concerns.
Innovation Solution
A method involving a processing chamber where the sintered R-T-B based magnet body and RH diffusion source are moved relative to each other at temperatures between 700 °C to 1000 °C, allowing for efficient diffusion of heavy rare-earth elements within the magnet body without adhesion, using a specific composition range for the magnet and diffusion source to enhance coercivity and prevent unwanted reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the temperature is increased to accelerate diffusion of heavy rare-earth elements, then diffusion rate increases, but adhesion occurs between magnet and diffusion source
Solution Approach 1:
A ceramic layer is formed on the surface of the sintered magnet body before diffusion treatment. This ceramic layer acts as an intermediary barrier between the magnet and the heavy rare-earth element diffusion source, preventing direct contact and adhesion while still allowing controlled diffusion of the heavy rare-earth elements into the magnet at elevated temperatures (800-1000°C).
Solution Approach 2:
The invention changes the surface parameter of the magnet by forming a ceramic coating layer with specific properties (porosity, thickness, composition) that enables high-temperature diffusion while preventing adhesion. This parameter change allows the diffusion process to occur at higher temperatures without the harmful adhesion effect.
2Length of stationary object
If diffusion time is extended to achieve sufficient diffusion depth, then diffusion depth increases, but productivity decreases
Solution Approach 1:
The invention changes the temperature parameter to 800-1000°C, which is sufficiently high to achieve rapid diffusion kinetics. This temperature increase reduces the required diffusion time from hours to minutes or seconds, thereby maintaining deep diffusion penetration while preserving production productivity.
Solution Approach 2:
The diffusion process is made dynamic by using high temperature to enable rapid atom migration, transforming a slow, time-consuming process into a fast, efficient operation. The ceramic layer also dynamically controls the diffusion rate, allowing deep penetration without excessive surface accumulation.
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 significantly increases coercivity while maintaining remanence and prevents adhesion issues, allowing for faster and more productive diffusion of heavy rare-earth elements, thereby improving the magnetic properties of the sintered magnets.
Implementation Method 1
performing an RH diffusion process by conducting a heat treatment on the sintered R-T-B based magnet body and the RH diffusion source at a temperature of 500 °C to 850 °C for at least 10 minutes
Implementation Method 2
conducting a heat treatment on the sintered R-T-B based magnet body and the RH diffusion source at a temperature of 500 °C to 850 °C
Data Source
Figure 1~2
Figure 3
AI summary
A method for producing a sintered R-T-B based magnet according to the present application includes the steps of: providing a sintered R-T-B based magnet body, of which the R mole fraction that is defined by the content of a rare-earth element falls within the range of 31 mass% to 37 mass%; 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 magnet body and the RH diffusion source into a processing chamber so that the magnet body and the diffusion source are movable relative to each other and readily brought close to, or in contact with, each other; and performing an RH diffusion process by conducting a heat treatment on the sintered magnet body and the RH diffusion source at a process temperature of 700 °C to 1000 °C while moving the sintered magnet body and the RH diffusion source either continuously or discontinuously in the processing chamber.