Rare Earth Magnet Powder Classification for Fire-Safe Grain Control
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Solution Overview
Problem
Existing methods for producing rare earth magnets face challenges with high reactivity of magnetic powders, leading to powder fires and difficulties in achieving optimal magnetization due to high volumes of fines and coarse particles, which affect remanence and coercitive field strength.
Innovation Solution
A method involving the pulverization of rare earth metal alloys followed by classification using dynamic and static classifiers to separate fractions by particle size and density, resulting in a starting material with a targeted particle size range of 2-8 µm, minimizing superfine and coarse particles, and subsequent sintering with a magnetization pulse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If magnetic powder is produced by milling alloys in fluidized-bed jet mills, then superfine milling with precise upper grain limit is achieved, but high-volume percentage of superfine particles causes high chemical reactivity and powder fires
Solution Approach 1:
The patent extracts and removes the harmful superfine particle fraction from the magnetic powder through classification processes. By separating out particles below a certain size threshold, the highly reactive fraction that causes powder fires is eliminated while retaining the beneficial finer particles that improve magnetization.
Solution Approach 2:
The patent changes the particle size distribution parameters by implementing multi-stage classification. This transforms the powder from having a broad size distribution with excessive fines to an optimized distribution where superfine particles are minimized, thereby reducing chemical reactivity while maintaining manufacturing precision.
2Manufacturing precision
If high-volume percentage of fines is present in magnetic powder, then superfine milling is achieved, but orientation of grains during sintering becomes difficult and remanence is reduced
Solution Approach 1:
The patent performs preliminary classification of the magnetic powder before sintering to establish an optimal particle size distribution. By pre-removing superfine particles and controlling the size range, the powder is prepared in advance for better grain orientation during sintering, ensuring high remanence and reliable magnetization.
Solution Approach 2:
The patent optimizes the particle size parameters by classifying the powder to achieve a specific size range (d50 between 2-8 µm). This parameter optimization ensures that particles are fine enough for good packing but not so fine that they cause orientation difficulties during sintering.
3Stability of the object's composition
If high-volume percentage of coarse particles is present in magnetic powder, then chemical stability is improved, but opposing field stability and coercitive field strength are reduced
Solution Approach 1:
The patent optimizes the particle size distribution by removing excessive coarse particles through classification. This creates an balanced distribution where particles are fine enough to provide good magnetic properties (coercivity and opposing field stability) but not so fine as to cause chemical instability and powder fires.
4Productivity
If broad particle size distribution is used in magnetic powder, then production efficiency is maintained, but difficult to achieve optimal remanence and coercitive field strength
Solution Approach 1:
The patent segments the broad particle size distribution into distinct fractions through multi-stage classification. By separating the powder into different size ranges and removing unwanted fractions (superfine and excessive coarse particles), it creates an optimized narrow distribution that delivers superior magnetic properties while maintaining production efficiency.
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 rare earth magnets with improved remanence, coercitive field strength, and thermal stability by optimizing the particle size distribution, reducing chemical reactivity and enhancing the homogeneity of the magnetic properties.
Implementation Method 1
at least one dynamic classifier for carrying out at least one classification directed at particle size and/or density for the powdered intermediate product and thereby separating a fraction from the powdered intermediate product
Implementation Method 2
pulverizing an alloy comprising at least one rare earth metal and thereby producing a powdered intermediate product from the one alloy
Implementation Method 3
In sintering, the pulverized constituents of the powder are bonded together by heating or compacted, but none of the starting materials, or at least not all of them, are melted
Implementation Method 4
the parallel alignment of the elementary streams can be restored by a sufficiently strong magnetization pulse after cooling the magnets
Data Source
AI summary
A method for producing a powdered starting material, which is provided for production of rare earth magnets, including the following steps: pulverizing an alloy, including at least one rare earth metal, wherein a powdered intermediate product is formed from the alloy including at least one rare earth metal, and carrying out at least one classification aimed at particle size and/or density for the powdered intermediate product, wherein a fraction of the powdered intermediate product, which is formed by means of the at least one classification, for fabrication of rare earth magnets. Furthermore, at least one dynamic classifier is provided, implementing at least one classification directed at particle size and/or density for the powdered intermediate product and thereby separates the fraction from the powdered intermediate product, which forms the starting material provided for manufacturing rare earth magnets.