Alnico Magnets, the oldest modern magnets, were used extensively in all industries until the introduction of Ferrites in the early 1950’s. They are available by either Cast or Sintered production processes and are primarily made of Aluminum, Nickel and Cobalt. Because of their heavy Cobalt content, prices are somewhat volatile.
Alnico magnets, composed of primarily aluminum (Al), nickel (Ni), and cobalt (Co), were developed in the 1940s. This class of magnet remains a preferred material because of its excellent temperature stability, high magnetic flux density, and resistance to corrosion. Alnico magnets are manufactured through a casting or sintering process. The Strength of Alnico Magnets. Alnico has a high magnetic strength and a low resistance to being demagnetized and re-magnetized. Before the development of rare earth magnets, alnico magnets were the strongest type of magnet available. Today, alnico magnets have been largely replaced by stronger rare earth magnets, such as neodymium. Cast Alnico magnets are cast in sand molds and usually require finish grinding. Casting Alnico is the most typical manufacturing method and most cast Alncio is “orientated” and anisotropic. This means that the magnet can only be magnetized in one direction, but this improves the magnetic strength. For critical applications, Alnico magnets can be temperature stabilized to minimize these effects. Alnico magnet material is made by alloying aluminum, nickel and cobalt with iron. Some grades also contain copper and/or titanium. The alloying process is casting or sintering.
What is an Alnico Magnet?
Alnico magnets, composed of primarily aluminum (Al), nickel (Ni), and cobalt (Co), were developed in the 1940s. This class of magnet remains a preferred material because of its excellent temperature stability, high magnetic flux density, and resistance to corrosion.
Alnico magnets are manufactured through a casting or sintering process. The casting process allows the magnet to be manufactured into intricate and complex shapes. Sintered Alnico is made from a powdered mixture of ingredients that are pressed into a die under tons of pressure. The Sintering process allows for the magnets to be manufactured to tighter tolerances and higher mechanical strength.
Alnico Magnet Applications
- Guitar pickups
- Separators
- Sensors
- Radar
- Holding magnets
- Coin acceptors
- Motors
- Relays
- Controls
- Generators
- Receivers
- Telephones
- Microphones
- Bell ringers
- Loudspeakers
- Security systems
- And much more
Custom Alnico Magnet Shapes
Magnetic Hold is an alnico magnet manufacturer and supplier with capabilities to customize any magnet shape. We work with you to personalize your magnets for your application. Common magnet shapes include:
- Rods
- Bars
- Assemblies
- Horseshoe
- C-shaped
- Cylinders
- Rings
- Channels
- Arc
- Disc
- Block
- Sphere
- Plugs
Cast Alnico Magnets
The most common Alnico cast magnets are in grades 1, 2, 3, 5, 6, 8, and 9. They are best suited for applications exposed to operating temperatures above 400 ° Fahrenheit. They maintain approximately 85% of their room-temperature strength up to 1000 ° F. They become completely demagnetized at approximately 1600 °F. For best results with Alnico 5 magnets, the length should be no less than 5 times the cross-section diameter or the diameter of a circle equal in area to the cross-section.
See the table below for cast Alnico magnet properties.
Alnico Magnet Grades & Properties
Grade | Residual Induction Br(max) [Gs] | Max Energy Product BH (max) MGOe | Coercive Force Hcb Koe | Curie Temp. [˚C] | Temp. Coe of Br [%/˚C) | Max. Practical Operating Temp. [˚C] |
---|---|---|---|---|---|---|
Alnico 2 (Isotropic) | 7000 | 1.6 | 0.56 | 810 | -0.03 | 450 |
Alnico 3 (Isotropic) | 6000 | 1.2 | 0.48 | 810 | -0.03 | 450 |
Alnico 5 (Anisotropic) | 12500 | 5.5 | 0.64 | 860 | -0.02 | 525 |
Alnico 6 (Anisotropic) | 10000 | 3.5 | 0.78 | 860 | -.0.02 | 525 |
Alnico 8 (Anisotropic) | 8000 | 5.5 | 1.65 | 860 | -0.025 | 550 |
Alnico 9 (Anisotropic) | 10500 | 9.0 | 1.50 | 860 | -0.025 | 550 |
Br: Residual Induction
Gs: Gauss
Hc: Coercive Force
Oe: Oersted
˚C: Degree Celcius
MGOe: Mega Gauss Oersted
Gs: Gauss
Hc: Coercive Force
Oe: Oersted
˚C: Degree Celcius
MGOe: Mega Gauss Oersted
Standard Tolerances (inches);
Rod - Diameter (±0.002), Length (±0.005)
Rectangle - Length & Width (±0.01), Thickness (±0.005)
Ring - Outside Diameter (±0.002), Inside Diameter (±0.02), Thickness (±0.005)
Rod - Diameter (±0.002), Length (±0.005)
Rectangle - Length & Width (±0.01), Thickness (±0.005)
Ring - Outside Diameter (±0.002), Inside Diameter (±0.02), Thickness (±0.005)
Sintered Alnico Magnets
They have marginally lower magnetic properties, but better mechanical properties, than cast Alnico. Their fine grain structure results in highly uniform flux distributions and mechanical strength. So they are suited for applications requiring short magnets.
See the table below for grades and properties of cast Alnico magnets.
Sintered Alnico Magnet Grades & Properties
Grade | Residual Induction Br(max) [Gs] | Max Energy Product BH (max) MGOe | Coercive Force Hcb Koe | Curie Temp. [˚C] | Temp. Coe of Br [%/˚C) | Max. Practical Operating Temp. [˚C] |
---|---|---|---|---|---|---|
SAlnico 2 (Isotropic) | 7000 | 1.55 | 0.55 | 810 | 0.008 | 450 |
SAlnico 3 (Isotropic) | 5800 | 1.20 | 0.50 | 860 | 0.011 | 550 |
SAlnico 5 (Anisotropic) | 11000 | 4.25 | 0.62 | 890 | 0.009 | 525 |
SAlnico 6 (Anisotropic) | 10000 | 3.50 | 0.79 | 850 | 0.011 | 525 |
SAlnico 8 (Anisotropic) | 8800 | 5.25 | 1.50 | 850 | 0.011 | 550 |
SAlnico 8HC (Anisotropic) | 7000 | 4.13 | 1.80 | 860 | 0.011 | 550 |
Alnico Magnets Properties
Br: Residual Induction
Gs: Gauss
Hc: Coercive Force
Oe: Oersted
˚C: Degree Celcius
MGOe: Mega Gauss Oersted
Gs: Gauss
Hc: Coercive Force
Oe: Oersted
˚C: Degree Celcius
MGOe: Mega Gauss Oersted
Standard Tolerances (inches);
Rod - Diameter (±0.002), Length (±0.005)
Rectangle - Length & Width (±0.01), Thickness (±0.005)
Ring - Outside Diameter (±0.002), Inside Diameter (±0.02), Thickness (±0.005)
Rod - Diameter (±0.002), Length (±0.005)
Rectangle - Length & Width (±0.01), Thickness (±0.005)
Ring - Outside Diameter (±0.002), Inside Diameter (±0.02), Thickness (±0.005)
Magnetism Direction Options
Alnico Magnets Facts
- Square and rectangular Cast or Sintered Alnico magnets can be magnetized with two poles ('N' & 'S') through the length, width, thickness and multiple poles.
- Round Alnico magnet can be magnetized with two poles ('N' & 'S') the thickness, diametrically and with multiple poles.
- Ring Alnico magnet can be magnetized with two poles ('N' & 'S') through the thickness, diametrically and with multipoles. Contact us for the magnetism direction of irregular shapes.
Alnico Magnets Speakers
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