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Sintered Alnico Magnets

Sintered Alnico magnets are permanent magnets manufactured through a powder metallurgy process, combining aluminum (Al), nickel (Ni), cobalt (Co), iron (Fe), and copper (Cu). Unlike cast Alnico, sintered variants offer better mechanical strength and tighter dimensional tolerances, making them suitable for small, complex shapes (e.g., micro-motors, sensors). They exhibit moderate magnetic properties (Br: 0.5–1.2 T) but excel in temperature stability (up to 550°C) and corrosion resistance, often requiring no coatings. Their isotropic or anisotropic microstructures are achieved through pressing and sintering in hydrogen atmospheres, followed by heat treatment.

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Overview

Product Specifications

Material Composition:

Primary Elements: Aluminum (8–12%), Nickel (15–26%), Cobalt (5–24%), Copper (3–6%), Iron (balance)

Magnetic Properties:

Residual Induction (Br): 0.5–1.2 T (5,000–12,000 Gauss)

Coercivity (Hc): 30–60 kA/m (lower than rare-earth magnets)

Energy Product (BH)max: 1.1–9 MGOe (9–72 kJ/m³)

Temperature Performance:

Operating Range: -65°C to 550°C (Curie temp: 760–890°C)

Reversible Temp Coefficient (αBr): -0.02%/°C

Physical Properties:

Density: 6.9–7.3 g/cm³; Hardness: 520–630 HV (brittle)

Product Grades

Sintered Alnico magnets are classified by magnetic orientation and performance:

Isotropic Grades: Uniform magnetization (e.g., Alnico 3), lower Br but easier to machine

Anisotropic Grades: Directional magnetization (e.g., Alnico 5/8), higher Br (1.1–1.2 T) for precision applications like sensors and relays

Coatings

While inherently corrosion-resistant, optional coatings include:

None: Standard due to oxidation resistance

Nickel (Ni): For solderability in electronics (e.g., PCB-mounted sensors)

Epoxy: Mechanical protection in industrial environments

Applications

Sintered Alnico magnets are used in:

Electronics: Micro-motors, relays, and magnetic switches (small size tolerance <1 oz)

Automotive: Fuel level sensors, speedometers (stable output under heat)

Industrial: Magnetic separators, holding devices (corrosion-resistant)

Consumer Audio: Guitar pickups (high acoustic clarity)

Packaging Information

Standard: Anti-static foam or plastic wraps, packed in cartons with spacers to prevent attraction damage

Bulk Orders: Palletized with moisture barriers; magnetic shielding for air freight

FAQs

How do sintered Alnico magnets compare to cast Alnico?

Sintered variants have slightly lower Br but better mechanical strength and precision for small parts

Can they be machined?

Yes, but only with diamond tools or EDM due to brittleness

Why choose sintered Alnico over NdFeB?

Superior temperature stability (NdFeB degrades above 150°C) and no coating needs

Are custom shapes available?

Yes, complex geometries like rings or rods can be sintered (e.g., Alnico 5 rods for sensors)

Cost drivers?

Cobalt content and sintering process increase costs (~$20–50/kg)

Application

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