Continuous Grain Boundary Diffusion Device for Nd-Fe-B Magnets
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Solution Overview
Problem
Current methods for grain boundary diffusion and heat treatment of Nd—Fe—B magnets face challenges in achieving consistent properties and efficient cooling rates, leading to oxidation and degradation of rare earth elements on the magnet surfaces.
Innovation Solution
A device and method for continuous grain boundary diffusion and heat treatment using airtight chambers with air cooling systems, where the alloy workpiece is processed in a relatively independent box with a diffusion source, allowing for controlled cooling rates and temperatures to optimize the microstructure and phase composition of the magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the sintered magnets are placed in a processing box with through holes for heat treatment, then the heating and cooling rates are increased, but the rare earth elements on the surfaces are oxidized and darkened due to contact with air
Solution Approach 1:
The patent uses a sealed processing box that maintains a vacuum or inert gas atmosphere throughout the heat treatment process. This prevents oxidation of rare earth elements on the magnet surfaces while still allowing for controlled heating and cooling rates through the sealed environment, eliminating the need for through holes that would expose the magnets to air.
Solution Approach 2:
The patent divides the heat treatment process into distinct stages with different atmospheric conditions. The processing box is sealed to create an isolated environment that can be independently controlled from the external atmosphere, allowing the magnets to be heated and cooled without exposure to oxidizing air.
2Manufacturing precision
If the sintered magnets are removed from the processing box after grain boundary diffusion and placed in a separate processing box for heat treatment, then the consistency of heat treatment process is improved, but the production efficiency is reduced due to additional handling and transfer steps
Solution Approach 1:
The patent designs a universal processing box that can serve multiple functions: it can be used for both grain boundary diffusion and heat treatment processes. The box maintains its sealed structure throughout both operations, eliminating the need to transfer magnets between different processing boxes and thereby maintaining production efficiency while ensuring consistent heat treatment.
Solution Approach 2:
The patent combines the grain boundary diffusion and heat treatment processes into a single continuous operation within the same sealed processing box. This merging of operations eliminates intermediate handling steps, maintains the sealed atmosphere throughout, and improves production efficiency while ensuring process consistency.
3Speed
If the cooling air temperature is significantly lower than the heat treatment temperature, then the cooling rate is increased, but the temperature difference may cause thermal stress and deformation
Solution Approach 1:
The patent employs a dynamic cooling process where the cooling air temperature is adjusted in stages rather than applying a single fixed temperature. The cooling process starts with a moderate temperature difference to reduce thermal stress, then progressively increases the cooling rate as the magnet temperature decreases, optimizing both cooling speed and stress management.
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 approach significantly improves the consistency and magnetic properties of Nd—Fe—B magnets by enhancing cooling rates and maintaining the integrity of the magnet surfaces, preventing oxidation and ensuring uniform heat treatment.
Implementation Method 1
both the first cooling chamber and the second cooling chamber adopt an air cooling system
Implementation Method 2
grain boundary diffusion and heat treatment for an alloy workpiece or a metal workpiece
Data Source
AI summary
Disclosed are a device and method for continuously performing grain boundary diffusion and heat treatment, characterized in that the alloy workpiece or the metal workpiece are arranged in a relatively independent processing box together with a diffusion source; the device comprises, in successive arrangement, a grain boundary diffusion chamber, a first cooling chamber, a heat treatment chamber, and a second cooling chamber, and a transfer system provided between various chambers for delivering the processing box; each of the first cooling chamber and the second cooling chamber uses an air cooling system, and the cooling air temperature of the first cooling chamber is above 25° C. and at least differs by 550° C. from the grain boundary diffusion temperature of the grain boundary diffusion chamber; the cooling air temperature of the second cooling chamber is above 25° C. and at least differs by 300° C. from the heat treatment temperature of the heat treatment chamber; and the cooling chamber has a pressure of 50 kPa to 100 kPa. The device provided by the present invention can increase the cooling rate and production efficiency, and improve product consistency.