Permanent Magnet Demagnetization Using Reducing Atmosphere
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Solution Overview
Problem
Existing methods for demagnetizing and reusing permanent magnets in electric motors often result in oxidation, leading to a decrease in magnet performance and a limited number of reuse cycles, which wastes rare earth elements and increases CO2 emissions.
Innovation Solution
Demagnetization is performed under a reducing atmosphere to minimize oxidation, using a demagnetization apparatus that heats the magnets in the presence of a reducing substance like carbon monoxide, which suppresses the formation of an oxidation layer and maintains magnet performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If permanent magnets are heated under conventional atmospheres (argon, nitrogen, or vacuum) for demagnetization, then the demagnetization process can be completed, but oxidation occurs on the magnet surface leading to decreased magnet performance and limited reuse cycles
Solution Approach 1:
The patent applies an inert atmosphere (argon or nitrogen) during the heating process to prevent oxidation of the magnet surface. The atmosphere is maintained throughout the heating and cooling phases, creating a protective environment that eliminates oxygen contact with the magnet material, thereby resolving the contradiction between achieving demagnetization and preventing oxidation.
Solution Approach 2:
The patent introduces a reducing atmosphere (carbon monoxide or hydrogen) as an intermediary medium during heating. This reducing atmosphere acts as a mediator that actively prevents oxidation by providing a chemical environment that suppresses oxygen reaction with the magnet surface, thereby protecting magnet performance while enabling the demagnetization process.
2Loss of substance
If permanent magnets are reused multiple times, then rare earth elements are conserved, but oxidation accumulates over cycles leading to performance degradation
Solution Approach 1:
By maintaining an inert atmosphere throughout multiple heating cycles, the patent prevents oxidation accumulation that would otherwise limit the number of reuse cycles. This allows permanent magnets to be reused many times without performance degradation, thereby conserving rare earth elements while extending the service life of the magnets.
Solution Approach 2:
The patent ensures continuous protection against oxidation throughout the entire heating and cooling process by maintaining the inert or reducing atmosphere without interruption. This continuous protective action enables multiple reuse cycles without performance loss, allowing the full benefit of rare earth element conservation to be realized.
3Productivity
If heating temperature is increased to improve demagnetization efficiency, then the process time is reduced, but oxidation risk increases
Solution Approach 1:
The patent uses an inert atmosphere to enable higher heating temperatures without increasing oxidation risk. The inert environment provides a safety buffer that allows rapid heating and demagnetization at elevated temperatures while preventing oxidative damage, thereby resolving the contradiction between processing speed and oxidation prevention.
Solution Approach 2:
The reducing atmosphere serves as a protective intermediary that allows aggressive heating conditions to be applied without causing oxidation. By introducing this chemical mediator, the system can achieve fast demagnetization at high temperatures while the reducing atmosphere continuously suppresses oxidation reactions.
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 extends the number of reuse cycles for permanent magnets, effectively utilizes scarce rare earth elements, and reduces CO2 emissions by preventing oxidation and maintaining magnetic properties.
Implementation Method 1
heating the permanent magnet in a state where a concentration of the reducing substance in the atmosphere gas is 99.9% or more... suppresses the formation of an oxidation layer
Data Source
AI summary
A magnet material producing method includes demagnetizing, by thermal demagnetization in an irreversible manner, a molded permanent magnet, by heating the permanent magnet in a presence of a reducing substance having a reducing property stronger than nitrogen molecules, and cooling the demagnetized permanent magnet to create a molded magnet material. A magnet material with a thickness of 30 µm or more contains, as main components, a rare earth element and a transition metal element. In the above described magnet material, a ratio of (b) a carbon concentration in a surface layer region that is a region within 10 µm from a surface of the magnet material to (a) a carbon concentration in an interior region that is a region arranged in a position away from the surface of the magnet material by more than 10 µm and having a thickness of 10 µm is 1.1 or more.