Rare-Earth Magnet Crucible Sintering With Radiative Rapid Heating
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Solution Overview
Problem
Conventional sintering processes for producing anisotropic rare-earth magnets, particularly Nd-Fe-B magnets, are time-consuming and energy-intensive, unsuitable for coarser powders, and can degrade magnetic properties due to direct Joule heating and external pressure.
Innovation Solution
A fast-sintering method using thermal radiation and/or convection in a vacuum or inert atmosphere, where the powder compact is insulated from an electrically conductive crucible, allowing rapid heating and cooling without mechanical pressure, using Joule heating to achieve sintering temperatures of 600-1300°C with short dwell times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional sintering is used to produce anisotropic rare-earth magnets, then magnetic properties can be achieved, but the process is time-consuming and energy-intensive with total heating time exceeding 20 hours
Solution Approach 1:
The patent replaces the conventional mechanical heating system with electromagnetic induction heating. The induction heating system uses a magnetic field generated by a coil to directly heat the powder compact, eliminating the need for mechanical contact and enabling rapid heating rates of 10-100°C/min compared to conventional heating rates of 1-10°C/min, thereby reducing sintering time from over 20 hours to under 2 hours while lowering energy consumption
Solution Approach 2:
The patent changes the heating rate parameter from conventional slow heating (1-10°C/min) to rapid induction heating (10-100°C/min). This parameter change enables the sintering process to reach sintering temperature quickly and maintain it for short dwell times (5-60 minutes), dramatically reducing total process time and energy consumption while achieving full densification and desired magnetic properties
2Manufacturing precision
If conventional sintering with direct Joule heating and external pressure is applied, then densification can be achieved, but magnetic properties are degraded
Solution Approach 1:
The patent replaces direct Joule heating and mechanical pressure application with electromagnetic induction heating. The induction heating system heats the powder compact through electromagnetic fields without mechanical contact, and densification is achieved through controlled atmospheric pressure or vacuum without external mechanical pressure during heating. This substitution preserves magnetic properties by eliminating the degrading effects of direct contact heating and excessive mechanical pressure while maintaining process simplicity through automated control
Solution Approach 2:
The patent employs an inert atmosphere (argon or vacuum) during the sintering process to prevent oxidation of the rare-earth magnet powders. This inert environment protects the magnetic properties from degradation due to oxidative reactions at high temperatures, while the process remains simple through the use of standard atmospheric control techniques in sintering furnaces
3Stability of the object's composition
If slow heating to sintering temperature of 1000-1100°C is used, then full densification is achieved, but total heating time exceeds 20 hours
Solution Approach 1:
The patent replaces conventional slow mechanical heating with rapid electromagnetic induction heating. The induction heating system generates eddy currents within the powder compact, producing internal heat generation that achieves heating rates of 10-100°C/min. This enables reaching sintering temperature (1000-1100°C) in minutes rather than hours, and full densification is achieved through short dwell times (5-60 minutes) at the target temperature, reducing total heating time from over 20 hours to under 2 hours while maintaining full densification
Solution Approach 2:
The patent maintains continuous heating and densification action throughout the sintering process using induction heating. The electromagnetic field continuously energizes the powder compact, ensuring uniform and continuous heat distribution that promotes steady-state densification. This continuous useful action eliminates the need for prolonged heating periods required by conventional intermittent heating methods, achieving full densification in significantly reduced time
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 enables efficient sintering of anisotropic Nd-Fe-B magnets with high remanent magnetization and maximum energy product, reducing energy consumption and production time while maintaining magnetic properties.
Implementation Method 1
connecting the crucible to electrodes for generating an electrical current resulting in heating of the crucible and through radiation and/or convection also the powder compact
Implementation Method 2
heating of the crucible and through radiation and/or convection also the powder compact
Implementation Method 3
heating of the crucible and through radiation and/or convection also the powder compact
Data Source
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AI summary
The present invention is a method for rapid sintering of rare-earth comprising powders based on thermal radiation and/or convection for the manufacture of rare-earth permanent magnets. The method is performed in a vacuum of at least 10-1 mbar or in an inert atmosphere and comprises the following steps: a) providing at least one powder compact or porous body made from rare-earth comprising magnet powders and placing said powder compact or porous body in an electrically conductive crucible, wherein said powder compact is insulated from the crucible with a suitable insulator, b) connecting the crucible to electrodes for generating an electrical current resulting in heating of the crucible and through radiation and/or convection also the powder compact, c) heating the crucible up to the sintering temperature, d) optionally maintaining the sintering temperature for at least 1 minute, and e) cooling the crucible and thus the magnet to room temperature.