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ALNICO MAGNETS

Alnico magnets are made primarily from aluminum, nickel, cobalt, copper, iron and sometimes titanium. They can be either cast or sintered. Not sure if alnico is the best material for your application? Click here for an attribute and application comparison for all of the magnetic materials we offer.

Choose from one of the following shapes:

  • Applications
  • Attributes
  • Tolerances
  • Machining
  • Magnetizing & Handling
  • Magnetic & Physical Properties
  • Compare & Contrast

Applications of Alnico Magnets

  • Magnetos
  • Separators
  • Sensors
  • Electron tubes
  • Traveling wave tubes
  • Radar Holding magnets
  • Coin acceptors
  • Clutches and bearings
  • Motors
  • Distributors
  • Relays
  • Controls
  • Generators
  • Receivers
  • Telephones Microphones
  • Bell ringers
  • Guitar pickups
  • Loudspeakers
  • Security systems
  • Cow magnets

CAST VS. SINTERED ALNICO MAGNETS

Cast Alnico is melted and poured into a mold. Once solidified, the material is rough ground and then heat-treated and cooled, sometimes in a magnetic field. When treated in the presence of a magnetic field, the magnet is called anisotropic. This orients the material to take on maximum magnetization and allows a higher gauss level. A cast magnet that is not heat-treated in a magnetic field is called isotropic. After heat treatment and cooling, the material can be ground to specific tolerances and then magnetized.

Sintered Alnico is made from a powdered mixture of ingredients that are pressed into a die under tons of pressure, sintered in a hydrogen atmosphere and then cooled either within a magnetic field or without (anisotropic vs. isotropic).

Attributes of Cast Alnico

  • Size parameters range from 1 ounce to about 70 pounds
  • Will cast to a variety of shapes and sizes

Attributes of Sintered Alnico

  • Size parameters range from about one ounce of material up to one cubic inch
  • Pressed to close tolerance/minimal grinding to finish
  • Mechanically strongest of alnicos

Attributes of Both Cast and Sintered Alnico

  • Very temperature stable, great for high heat applications
  • Maximum working temperature 975° - 1020° F
  • May be ground to size
  • Does not lend itself to conventional machining (hard and brittle)
  • High residual induction and energy product compared to ceramic material
  • Low coercive force compared to ceramic and rare earth materials (more subject to demagnetization)
  • Most common grades are 5 and 8

Tolerances

Unless otherwise specified, our tolerances on alnico material meet and often exceed International Magnetics Association (IMA, formerly MMPA) standards. For unfinished surfaces (as cast) the following tolerances apply: 0-1” ± .016 1-3” ± .031 3-5 ± .047 5-7” ± .062 7-9” ±.078 9-12” ± .094 Finished surfaces are normally ground to ± .005 (See MMPA standards for more details.)

Machining

Alnico is a very hard and brittle material and does not lend itself to conventional machining. The Magnet Source™ employs experienced machinists and the proper equipment to grind alnico to its required dimensions.

Magnetizing and Handling

Magnetizing is done after the magnet has been machined to the correct tolerances. Care should be taken when handling alnico material since it is brittle and can chip or break if dropped on a hard surface. Also, because it has a low resistance to demagnetization, it will lose power if it is stored improperly (poles repelling each other). For best results, store magnetized alnico so that pieces are attracting each other, or with a steel keeper.

Typical Magnetic and Physical Properties of Alnico Magnet Material
Magnetic
Material
Density
Max. Energy Product BH (max)
Residual Induction BR
Coercive Force HC
Intrinsic Coercive Force HC
Normal Maximum Operating Temp.
Curie Temp.
lbs/in
g/cm
MGO
Gauss
Oersteds
Oersteds
Alnico 5 (cast)
0.264
7.3
5.5
12800
640
640
975
525
1580
860
Alnico 8 (cast)
0.262
7.3
5.3
8200
1650
1860
1020
550
1580
860
Alnico 5 (sintered)
0.250
6.9
3.9
10900
620
630
975
525
1580
860
Alnico 8 (sintered)
0.252
7.0
4.0
7400
1500
1690
1020
550
1580
860

Compare and Contrast Magnetic Applications and Materials

Applications of Alnico Magnets

  • Magnetos
  • Separators
  • Sensors
  • Electron tubes
  • Traveling wave tubes
  • Radar
  • Holding magnets
  • Coin acceptors
  • Clutches and bearings
  • Motors
  • Distributors
  • Relays
  • Controls
  • Generators
  • Receivers
  • Telephones
  • Microphones
  • Bell ringers
  • Guitar pickups
  • Loudspeakers
  • Security systems
  • Cow magnets

Attributes of Cast Alnico

  • Size parameters range from 1 ounce to about 70 pounds
  • Will cast to a variety of shapes and sizes

Attributes of Sintered Alnico

  • Size parameters range from about one ounce of material up to one cubic inch
  • Pressed to close tolerance/minimal grinding to finish
  • Mechanically strongest of alnicos

Attributes of Both Cast and Sintered Alnico

  • Very temperature stable, great for high heat applications
  • Maximum working temperature 975° - 1020° F
  • May be ground to size
  • Does not lend itself to conventional machining (hard and brittle)
  • High residual induction and energy product compared to ceramic material
  • Low coercive force compared to ceramic and rare earth materials (more subject to demagnetization)
  • Most common grades are 5 and 8

Applications of Neodymium Magnets

  • Magnetic separators
  • Linear actuators
  • Microphone assemblies
  • Servo motors
  • DC motors (automotive starters)
  • Computer rigid disc drives, printers and speakers

Attributes of Neodymium Material

  • Very high resistance to demagnetization
  • High energy for size
  • Good in ambient temperature
  • Moderately priced
  • Material is corrosive and should be coated for long term maximum energy output
  • Low working temperature for heat applications, but higher levels of heat resistance materials are being introduced periodically

Applications of Ceramic Magnets

  • Speaker magnets
  • DC brushless motors
  • Magnetic Resonance Imaging (MRI)
  • Magnetos used on lawnmowers and outboard motors
  • DC permanent magnet motors (used in cars)
  • Separators (separate ferrous material from non-ferrous)
  • Used in magnetic assemblies designed for lifting, holding, retrieving and separating

Attributes of Ceramic Material

  • Least expensive material compared to alnico and rare earth magnets
  • High intrinsic coercive force
  • Available in simple shapes only due to manufacturing process
  • Lower service temperature than alnico, greater than rare earth
  • Finishing requires diamond cutting or grinding wheel
  • Lower energy product than alnico and rare earth magnets
  • Most common grades of ceramic are 1, 5 and 8 (1-8 possible)
  • Grade 8 is the strongest ceramic material available
  • Tooling can be expensive

Applications of Samarium Cobalt Magnets

  • Computer disc drives
  • Sensors
  • Traveling wave tubes
  • Linear actuators
  • Satellite systems
  • Motors where temporary stability is vital

Attributes of Samarium Cobalt Material

  • High resistance to demagnetization
  • High energy (magnetic strength is strong for its size)
  • Good temperature stability
  • Expensive material (cobalt is market price sensitive)