Sintered Ferrite Magnet Composition and Grain Control
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Solution Overview
Problem
Conventional sintered ferrite magnets have limitations in achieving high residual magnetic flux density (Br) and intrinsic coercivity (HcJ) with a small temperature dependency, which are essential for smaller, lighter, and more efficient rotating machines, particularly in automotive applications.
Innovation Solution
A sintered ferrite magnet with a composition of Ca, La, Ba, and Co, following a specific atomic ratio, is produced using a method that includes calcination, pulverization, and sintering, with the addition of SiO2 and CaCO3 to control grain growth, resulting in a magnet with improved magnetic properties and reduced temperature dependency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fine pulverization is performed to achieve small average particle size for high magnetic properties, then Br and HcJ are improved, but water removal time during molding becomes extremely long, drastically reducing molding efficiency
Solution Approach 1:
The patent changes the particle size parameter from ultra-fine (less than 0.7 μm) to a moderate range (0.7 μm or more), and combines it with optimized chemical composition (Ca content: 0.05-0.50 atomic ratio, R content: 0.05-0.50 atomic ratio, M content: 0.05-0.50 atomic ratio) to achieve high magnetic properties without the severe water removal problem. This parameter optimization resolves the contradiction between fine particle size benefits and molding efficiency.
2Productivity
If larger average particle size is used to improve molding efficiency, then productivity increases, but the resultant sintered ferrite magnets have low magnetic properties
Solution Approach 1:
The patent identifies an optimal particle size range (0.7 μm or more, but not excessively large) that balances molding efficiency and magnetic properties. Combined with specific compositional parameters (Ca, R, and M element ratios), this particle size optimization ensures both high productivity and high magnetic properties (Br of 4.0 kG or more, HcJ of 3.5 kOe or more).
Solution Approach 2:
The patent uses composite material composition with multiple elements (Ca, R rare earth elements, M transition metals like Co and Ni) in specific ratios to enhance magnetic properties. This composite approach allows achieving high Br and HcJ even with moderate particle sizes, thus maintaining both productivity and magnetic performance.
3Manufacturing precision
If conventional Sr ferrite composition is used, then production cost is controlled, but magnetic properties (Br and HcJ) and temperature stability are insufficient for high-performance applications
Solution Approach 1:
The patent develops a composite ferrite system containing Ca, R (rare earth elements like La, Nd, Pr), and M (transition metals like Co, Ni) elements in optimized ratios. This multi-element composite composition achieves superior magnetic properties (Br ≥ 4.0 kG, HcJ ≥ 3.5 kOe) and temperature stability compared to conventional Sr ferrite, while maintaining cost-effectiveness through optimized element selection and ratios.
Solution Approach 2:
The patent optimizes the compositional parameters including Ca content (0.05-0.50 atomic ratio), R content (0.05-0.50 atomic ratio), and M content (0.05-0.50 atomic ratio) to achieve the desired magnetic properties. By carefully controlling these parameters, the patent attains high performance while managing production costs through efficient material utilization.
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 resulting magnet exhibits high Br and HcJ values with minimal temperature-dependent degradation, enhancing the efficiency and reliability of rotating machines while also allowing for cost-effective production through recycling of waste materials.
Implementation Method 1
subjecting the calcined clinker to coarse pulverization and wet, fine pulverization to an average particle size of about 0.5 μm
Implementation Method 2
molding slurry of fine ferrite particles in a magnetic field
Implementation Method 3
sintering the resultant molding
Data Source
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AI summary
A method for producing a sintered ferrite magnet having an M-type ferrite structure, comprising Ca, an R element that is at least one of rare earth elements and indispensably includes La, Ba, Fe and Co as indispensable elements, and having a composition represented by the formula: Ca1-x-yRxBayFe2n-zCOz, wherein (1-x-y), x, y, z and n represent the contents of Ca, the R element, Ba and Co, and a molar ratio, meeting 0.3 ≤ 1-x-y ≤ 0.65, 0.2 ≤ x ≤ 0.65, 0.001 ≤ 0.2, 0.03 ≤ z ≤ 0.65, 4 ≤ n ≤ 7, and 1-x-y > y; a bonded magnet comprising ferrite powder having the above composition and a binder, and a magnet roll, at least one magnetic pole portion of which is made of the above bonded magnet.