Product Overview
large ring magnets Magnetized High Precision and strong performance Custom NdFeB magnets, featuring extremely high magnetic strength, excellent demagnetization resistance, and precise dimensional accuracy. The product's precision can be customized according to customer requirements. Its sophisticated ring-shaped design meets high-performance magnetic needs in compact spaces, making it widely applicable in high-end electronic devices, audio equipment, premium perfume bottle caps, and other fields.
The magnet is manufactured using advanced wire cutting, center-less grinding, and double-disc grinding processes, ensuring neat edges and uniform dimensions. Surface treatment includes multi-layer metal coating (Ni+Cu+Ni) or optional Ni coating, effectively preventing oxidation and corrosion from environmental factors, thereby extending the product's service life.
Technical Specifications
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Product Name |
Large ring magnet |
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Material Grade |
N52 (Br ≥ 14.2 kGs, Hcj ≥ 12 kOe) |
|
Dimension |
Customize |
|
Dimensional Tolerance |
±0.05 mm (length/width/thickness) |
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Operating Temperature |
≤80℃ (high-temperature versions customizable) |
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Density |
≥7.5 g/cm³ |
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Surface Magnetic Field |
3200 ± 200 Gauss (measured with Japanese TM-801 Gauss meter)
|
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Magnetic Flux Value |
2.3 mWb (measured with fluxmeter) |
Manufacturing Process
Cold Isostatic Pressing (CIP)
After oriented compaction, the NdFeB green compacts are sealed in flexible containers and subjected to uniform high hydrostatic pressure in a cold isostatic press (CIP). This process effectively eliminates residual porosity within the compact, resulting in a more homogeneous and densely packed structure. Following CIP, the NdFeB compacts undergo slight dimensional shrinkage, accompanied by a significant improvement in density and structural uniformity, providing an ideal foundation for subsequent sintering.
Sintering and Annealing
The CIP-treated compacts are then placed into a high-temperature sintering furnace and heated to temperatures approaching the melting point of the NdFeB alloy, typically exceeding 1000°C. At these elevated temperatures, atomic diffusion becomes highly active, enabling strong intergranular bonding and allowing the alloy to fully develop its magnetic and mechanical properties. Throughout the sintering process, the magnetic domain orientation established during compaction is preserved, while the compacts densify and shrink to near-theoretical density.
Following sintering, residual stresses are introduced into the material as a result of intense atomic movement and thermal gradients. To relieve these stresses and stabilize the microstructure, a controlled annealing process is performed. The sintered blocks are reheated according to a predefined temperature profile, held at a higher annealing temperature, then gradually cooled to a lower holding temperature. After completing the holding stages, the stress-relieved blocks are slowly cooled to room temperature under controlled conditions, ensuring dimensional stability and long-term performance reliability.
Magnetization Patterns and Directions
Sintered NdFeB magnets are inherently anisotropic and can only be magnetized along a predetermined orientation. The magnetization direction is therefore carefully selected based on the magnet geometry and its intended application.
The most common magnetization modes include axial and thickness-direction magnetization. Cylindrical and disc-shaped magnets are typically axially magnetized, while square or rectangular magnets are generally magnetized through their thickness.
In addition to these standard configurations, NdFeB disc magnets can also be magnetized radially or diametrically, particularly in applications such as rotary position sensors where a specific magnetic field distribution is required. Beyond simple two-pole magnetization, sintered NdFeB magnets can be multi-pole or segmentally magnetized to produce tailored magnetic field profiles.
For example, ring-shaped sintered NdFeB magnets may be axially magnetized, radially magnetized, or magnetized in segmented radial patterns. Arc-shaped magnets are commonly magnetized in diametrically opposed pairs for use in electric motors, which is why they are often referred to as tile-shaped motor magnets.
Customization & Services
We offer extensive customization capabilities
- Custom dimensions, shapes, tolerances, and coating types
- Controlled magnetization direction and adjustable magnetic field strength
- Laser engraving (logo, serial number, batch code)
- Pull-force testing and application-specific packaging
- Engineering assistance for product integration and performance optimization
With strong R&D resources and deep expertise in magnetic materials, we support sectors such as EV motors, smart automation, consumer electronics, robotics, and renewable energy.
FAQ
Q1. What are the most common causes of NdFeB corrosion failure?
A: Coating pinholes, micro-cracks from mechanical stress, and poor surface preparation are the most common causes, especially in humid or salt-spray environments.
Q2. When should epoxy coating be preferred over Ni-Cu-Ni?
A: Epoxy coatings are preferred for complex shapes, harsh chemical environments, or applications requiring electrical insulation, though they generally have lower wear resistance.
Q3. Does coating thickness affect magnetic performance?
A: Yes. Thicker coatings slightly increase the magnetic gap and can reduce effective flux, which matters in precision or small-air-gap applications.
Contact Us
Phone / WhatsApp / WeChat: +86 13829120676
Email: Info@jinconn.com
Address: Xiaohe Industrial Zone, Daojiao Town, Dongguan City, Guangdong Province, China
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