Electrostatic Coating of Sintered Rare-Earth Magnets
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Solution Overview
Problem
Existing methods for producing rare earth magnets face challenges in uniformly and efficiently coating sintered magnet bodies with rare earth compound powders, leading to inconsistent coercivity and wasteful consumption of noble rare earth elements due to difficulties in controlling coating weight and forming a dense, tightly bonded powder coating.
Innovation Solution
The method involves electrostatically depositing a powder containing rare earth compounds onto a grounded sintered magnet body using a corona discharge, followed by a liquid application and drying before heat treatment, to achieve uniform and efficient coating with controlled weight and improved magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If immersion or spray method is used to coat rare earth compound powder on sintered magnet body, then coating process is simple, but coating weight cannot be controlled and powder coating is not dense
Solution Approach 1:
The patent replaces the mechanical immersion/spray coating method with an electrostatic field-based coating method. By applying electrostatic charge to the rare earth compound powder and using the electrostatic attraction between charged powder and grounded magnet body, the system achieves precise coating weight control without complex mechanical control systems. This substitution of mechanical coating with electrostatic field interaction resolves the contradiction between coating precision and process simplicity.
Solution Approach 2:
The patent changes the physical state and electrical properties of the coating system by electrostatically charging the powder particles. By controlling the electrostatic charge parameters (voltage, charge density) and powder properties (particle size, charge retention), the system achieves controlled coating weight and dense powder coating. This parameter change from neutral to charged state enables precise control over coating characteristics.
2Reliability
If excessive coating weight is applied to boost coercivity, then magnetic properties improve, but rare earth element consumption increases
Solution Approach 1:
The electrostatic coating method replaces indiscriminate powder application with controlled electrostatic attraction. The grounded magnet body selectively attracts only the necessary amount of charged powder, ensuring optimal coating weight that achieves maximum coercivity improvement without excessive rare earth element consumption. This electrostatic control mechanism prevents both under-coating and over-coating.
Solution Approach 2:
The electrostatic coating system provides inherent feedback control through the electrostatic field interaction. As powder accumulates on the magnet body surface, the charge distribution and field strength adjust automatically, preventing excessive coating. This self-regulating mechanism ensures optimal coating weight that achieves desired coercivity while minimizing rare earth element usage.
3Ease of manufacture
If powder coating is applied with weak adhesion, then coating application is easy, but heat treatment process efficiency decreases
Solution Approach 1:
The patent replaces mechanical adhesion-based coating with electrostatic field-based coating. The electrostatic attraction between charged powder and grounded magnet body creates strong initial adhesion, ensuring powder firmly bonds to the surface. This electrostatic bonding mechanism eliminates the need for complex mechanical adhesion systems while improving coating- substrate attachment and heat treatment efficiency.
Solution Approach 2:
The patent changes the adhesion mechanism from mechanical/chemical bonding to electrostatic field bonding. By maintaining electrostatic charge on powder particles during and after coating, the system achieves strong powder-substrate adhesion without complex mechanical systems. This parameter change in adhesion mechanism improves both coating application and subsequent heat treatment process 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
This approach allows for the production of rare earth magnets with enhanced coercivity and reduced waste, as the coating process is streamlined, and the magnetic properties are improved while minimizing the consumption of rare earth elements.
Implementation Method 1
the powder is electrically charged and sprayed to the grounded magnet body to electrostatically deposit the powder on the magnet body
Implementation Method 2
spraying the powder as electrically charged
Data Source
AI summary
A sintered magnet body is held in a grounded jig exhibiting excellent electrical conductivity, a rare-earth-compound powder is charged and sprayed on the sintered magnet body to electrostatically coat the sintered magnet body with the powder, and thus apply the powder to the sintered magnet body. The sintered magnet body having the powder applied thereto is heat treated to produce a rare-earth magnet. As a result, the rare-earth-compound powder can be uniformly applied to the surface of the sintered magnet body, and the application operating can be performed extremely efficiently.