HDDR Decarburization of R-Fe-B Magnet Scrap
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Solution Overview
Problem
Current methods for recycling R—Fe—B based permanent magnet scrap, sludge, and used magnets are inefficient due to carbon content, leading to poor magnetic characteristics and high costs, as they either produce rare earth carbides or require large amounts of calcium as a reducing agent, resulting in low yield and environmental concerns.
Innovation Solution
Subjecting carbon-containing R—Fe—B based permanent magnet alloys to an HDDR treatment, which includes hydrogenation, disproportionation, desorption, and recombination steps, effectively removes carbon, producing a recycled alloy with reduced carbon content suitable for magnet production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If calcium metal or calcium hydride is used to remove carbon from carbon-containing R-Fe-B alloy, then carbon is converted into calcium carbide and removed, but rare earth carbide is produced prior to calcium carbide due to thermodynamic stability, resulting in poor yield of rare earth element in the recycled alloy material
Solution Approach 1:
The patent extracts carbon from the carbon-containing R-Fe-B alloy by converting it into calcium carbide and removing it from the system. The carbon is selectively removed as calcium carbide without forming rare earth carbide, achieving effective carbon extraction while preserving rare earth elements in the recycled alloy material.
Solution Approach 2:
The patent changes the thermodynamic parameters of the system by controlling the chemical potential and activity of calcium and carbon during the treatment process. By adjusting these parameters, the reaction pathway is directed toward calcium carbide formation rather than rare earth carbide formation, despite the latter's higher thermodynamic stability under standard conditions.
2Use of energy by moving object
If magnet scrap, magnet sludge, and used magnets are directly subjected to high-frequency heating in a vacuum melting furnace, then energy saving and cost reduction are achieved, but carbon contained in the magnet structure adversely affects the magnetic characteristics of the produced magnet
Solution Approach 1:
The patent applies preliminary carbon removal treatment to magnet scrap, magnet sludge, and used magnets before they are subjected to high-frequency heating in the vacuum melting furnace. This preliminary action eliminates carbon that would otherwise adversely affect magnetic characteristics, enabling direct recycling while maintaining product quality.
Solution Approach 2:
The patent converts the harmful effect of carbon in recycled materials into a benefit by using the carbon-containing scrap and sludge as a source for controlled carbon removal. The carbon that would normally degrade magnetic properties is instead systematically eliminated through chemical treatment, transforming a liability into an opportunity for efficient recycling.
3Reliability
If magnet scrap and magnet sludge are recycled by being fed to a vacuum melting furnace little by little together with virgin alloy material, then carbon content in the produced magnet can be controlled, but the amount of virgin alloy material that can be reduced is naturally limited and production efficiency is low
Solution Approach 1:
The patent fundamentally changes the carbon content parameter of recycled materials by removing carbon before recycling. This parameter change enables much higher proportions of recycled material to be used without compromising magnetic characteristics, thereby dramatically increasing production efficiency while maintaining quality control.
4Loss of substance
If calcium metal is used as a reducing agent to reduce rare earth oxide produced during oxidation and decarburization, then rare earth oxide is reduced, but a large amount of calcium metal is required resulting in high cost and calcium metal remains as an impurity in the recycled alloy material adversely affecting magnetic characteristics
Solution Approach 1:
The patent extracts carbon from the alloy through direct conversion to calcium carbide without requiring a separate reduction step. This extraction approach eliminates the need for large amounts of calcium metal as a reducing agent, removing the source of calcium impurities and associated costs while maintaining effective carbon removal.
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
The HDDR treatment effectively reduces carbon in recycled alloys, allowing for efficient recycling of magnet scrap and sludge, reducing the need for virgin materials and minimizing environmental impact, while maintaining magnetic properties and lowering production costs.
Implementation Method 1
a carbon-containing R—Fe—B based permanent magnet alloy is subjected to an HDDR treatment to remove carbon
Implementation Method 2
a carbon-containing R—Fe—B based permanent magnet alloy is subjected to an HDDR treatment to remove carbon
Data Source
AI summary
An object of the present invention is to provide a method for producing an alloy recycled material by effectively removing carbon from a carbon-containing alloy, which is produced as scrap or sludge of an R—Fe—B based permanent magnet, a used magnet, or the like. The method of the present invention as a means for resolution is characterized in that a carbon-containing R—Fe—B based permanent magnet alloy is subjected to an HDDR treatment to remove carbon. An alloy recycled material produced by the method of the present invention contains a reduced amount of carbon. Therefore, in the case where it is recycled for the production of a magnet, even when an increased amount is subjected to high-frequency heating in a vacuum melting furnace, a non-negligible increase in the amount of carbon contained in the produced magnet can be avoided.