Ferrite Powder for Bonded Magnets with High Coercive Force
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Solution Overview
Problem
Ferrite bonded magnets used in low-temperature environments face challenges with low coercive force, leading to demagnetization, and existing solutions like rare earth magnets are expensive and prone to rusting, while ferrite bonded magnets have poor maximum energy product (BHmax) due to low filling content of ferrite powder, affecting productivity and magnetic force.
Innovation Solution
A ferrite powder with specific surface area between 2.20 m2/g and 3.20 m2/g, compression density between 3.30 g/cm3 and 3.60 g/cm3, and coercive force of 3250 Oe to 3800 Oe is produced by sintering coarse and fine powders at specific temperatures and applying mechanical pulverization, allowing for high filling content and improved magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the filling content of ferrite powder in the compound is increased to improve magnetic force, then the magnetic force increases, but the viscosity of the compound becomes high during kneading, increasing load and reducing productivity
Solution Approach 1:
The invention changes the particle size distribution parameters of ferrite powder, specifically controlling the D10, D50, and D90 values to create a optimized distribution. This parameter optimization allows high filling content (91-94 wt%) to be achieved while maintaining acceptable viscosity and fluidity, resolving the contradiction between magnetic force and productivity
Solution Approach 2:
The invention applies local quality by creating different particle size regions within the powder distribution. The presence of fine particles (D10 ≤ 2.0 μm) fills voids between larger particles, while intermediate particles (D50 between 3.0-5.0 μm) provide structural framework. This local particle size variation enables dense packing with maintained flowability, allowing high filling content without excessive viscosity increase
2Reliability
If the filling content of ferrite powder is increased to improve maximum energy product, then BHmax improves, but the fluidity of the compound becomes low at molding, reducing productivity
Solution Approach 1:
The invention optimizes particle size distribution parameters (D10, D50, D90) to achieve a balance between filling density and fluidity. The specific range D10 ≤ 2.0 μm, D50 between 3.0-5.0 μm, and D90 ≤ 8.0 μm ensures that high filling content (91-94 wt%) does not excessively reduce fluidity, enabling both high BHmax and acceptable molding productivity
Solution Approach 2:
The invention creates a composite particle size distribution system where particles of different sizes work together. The fine particles fill gaps, intermediate particles provide structure, and the overall distribution creates a packed configuration that maximizes filling while maintaining sufficient fluidity for molding operations
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 ferrite powder enables bonded magnets with high coercive force, maintaining magnetic strength even in low-temperature environments, reducing production costs, and enhancing magnetic force without the drawbacks of rare earth magnets.
Implementation Method 1
a first sintering step of sintering the granulated material at a first temperature, and a second sintering step of sintering the granulated material at a second temperature
Implementation Method 2
applying mechanical pulverization
Data Source
AI summary
A ferrite powder for bonded magnets having a high iHc value usable even in a low temperature environment, a method for producing the same, and a bonded magnet using the ferrite powder and having high iHc value which can be used even in a low temperature environment, wherein a specific surface area is 2.20 m2/g or more and less than 3.20 m2/g; a compression density is 3.30 g/cm3 or more and less than 3.60 g/cm3, and a compressed molding has a coercive force of 3250 Oe or more and less than 3800 Oe.