Rare-Earth Magnet Powder Classification for Safer Grain Size Control
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Solution Overview
Problem
Existing methods for producing rare earth magnets result in magnetic powders that are chemically reactive, leading to powder fires, and often exhibit poor orientation and impaired remanence due to high volumes of fine and coarse particles, affecting the magnetic properties of the final magnets.
Innovation Solution
A method involving the comminution of alloys with rare earth metals, followed by particle size-oriented classification using static and dynamic classifiers to produce a starting material with a targeted particle size range of 1µm to 10µm, reducing the volume percentage of particles >8µm and <2µm to ≤2%, thereby minimizing chemical reactivity and improving magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If magnetic powder is produced by grinding alloys in fluid bed jet mills or similar grinding systems, then fine grinding with defined upper grain limit is achieved, but a high volume percentage of fine particles is generated leading to chemical reactivity and powder fires
Solution Approach 1:
The patent extracts and removes the harmful fine particles from the magnetic powder mixture through classification processes. By separating out particles below a certain size threshold, the chemical reactivity and powder fire risks are eliminated while retaining the beneficial fine grinding characteristics for the majority of particles.
Solution Approach 2:
The patent changes the particle size distribution parameters by implementing multi-stage classification. This transforms the particle size profile from a broad distribution with excessive fines to a controlled distribution where fine particles are minimized, thereby reducing chemical reactivity while maintaining manufacturing precision.
2Manufacturing precision
If magnetic powder contains high volume percentage of fine particles, then fine grinding is achieved, but orientation during pressing is poor and remanence is impaired
Solution Approach 1:
The patent applies local quality by creating different particle size zones within the magnetic powder. Rather than uniform fineness, it maintains optimal particle sizes in specific ranges that balance fine grinding benefits with adequate magnetic orientation capabilities, thereby preserving remanence while achieving sufficient fineness.
Solution Approach 2:
The patent introduces dynamic classification processes that adaptively control particle size distribution. By using adjustable classification thresholds and multi-stage separation, the system dynamically optimizes the balance between particle fineness and orientation quality, ensuring adequate remanence is maintained.
3Stability of the object's composition
If magnetic powder contains high volume percentage of coarse particles, then chemical stability is improved, but opposing field stability and coercive field strength are reduced
Solution Approach 1:
The patent optimizes the particle size distribution parameters by implementing controlled classification that prevents excessive coarse particle formation. This maintains the chemical stability benefits of coarser particles while limiting their volume percentage to levels that do not compromise coercive field strength and opposing field stability.
4Reliability
If multiple classification stages are implemented to reduce fine and coarse particles, then magnetic properties are improved, but device complexity increases
Solution Approach 1:
The patent segments the classification process into distinct stages, each handling specific particle size ranges. This segmentation allows for optimized classification at each stage rather than attempting to handle all particle sizes in a single complex system, thereby improving magnetic properties while managing device complexity through modular design.
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 method produces a starting material with improved magnetic properties, enhancing the remanence and coercive field strength of rare earth magnets by reducing the proportion of fine and coarse particles, thus improving the stability and orientation of the magnetic powders.
Implementation Method 1
comminution of an alloy comprising at least one rare earth metal with a comminution device to a powdery intermediate product
Implementation Method 2
a first static classifier is fed with the powdery intermediate product from which a coarse fraction is separated
Implementation Method 3
a dynamic classifier is fed with the portion separated from the powdery intermediate product by means of the at least one static classifier from which a fine fraction is separated
Data Source
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AI summary
The invention relates to a method for producing a powdered starting material (AM) intended for the manufacture of rare-earth magnets. The method comprises the following steps: - comminution of an alloy comprising at least one rare-earth metal, wherein a powdered intermediate product (ZP) is formed from the alloy comprising at least one rare-earth metal, and - performing at least one classification of the powdered intermediate product (ZP) based on particle size and/or density, wherein a fraction of the powdered intermediate product (ZP) formed by the at least one classification constitutes the starting material (AM) intended for the manufacture of rare-earth magnets.Furthermore, at least one dynamic classifier is provided, which implements at least one dynamic classifier for the powdered intermediate product (ZP) based on particle size and/or density, thereby separating the fraction from the powdered intermediate product (ZP) that forms the starting material (AM) intended for the manufacture of rare earth magnets.