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? Review our Permanent Magnet Materials comparison for more information.

Cast Alnico -

Cast alnico magnets are made by casting molten metal alloys into molds. This process allows for the production of magnets in various geometric shapes to fit specific design requirements in the automotive industry. Typical shapes of cast alnico magnets include:

• Rectangular and Cuboid: Often used in applications where space is constrained, such as in small motors or sensors.
• Cylindrical and Disc: Ideal for applications requiring a uniform magnetic field, such as in magnetic sensors or small motors. The cylindrical shape also facilitates the use of alnico magnets in rotary applications.
• Ring: Often used in magnetic assemblies where the magnet needs to encircle a component or create a magnetic field in a cylindrical space. Common in applications like magnetic couplings and rotor assemblies.
• Horseshoe: Provides a concentrated magnetic field between the poles, making it suitable for applications such as magnetic holders or clamping devices.
  
• Custom Geometric Shapes: Cast alnico magnets can be customized into complex shapes to meet specific design needs, such as in automotive ignition systems, where unique geometries are required for optimal performance. 

Sintered Alnico

Sintered alnico magnets are manufactured by compressing alnico powder and

other ingredients using a pressing machine. The compacted powder is then sintered into strong alnico magnets in a process that allows for precise control over the composition and microstructure of the magnets.

 

Powder metallurgy is the process used in the manufacturing of sintered alnico magnets that enables the production of magnets with complex shapes, and ensures uniform distribution of elements, and minimizes material waste.

 

Sintered alnico magnets are ideal for applications where consistency and reliability are crucial. They maintain strong magnetic properties over a wide range of temperatures, ensuring dependable performance in critical components. Sintered alnico magnets are suitable for sensors, electric motors, and ignition systems in the automotive industry. 

Tolerances - Unless otherwise specified, our tolerances on alnico material meet and often exceed International Magnetics Association (IMA) 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".

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.

Machining - Alnico is a very hard and brittle material and does not lend itself to conventional machining. Master Magnetics offers grinding and cutting services for alnico material.

 

Alnico Material	Density		Max. Energy Product BH (max)	Typical Residual Induction Br (max)	Coercive Force Hc (min)	Intrinsic Coercive Force (Hci)	Maximum Operating Temperature		Curie Temperature
	lbs/in3	g/cm3	MGO	Gauss	Oersteds	Oersteds	F°	C°	F°	C°
Alnico 5 (cast)	0.264	7.3	5.5	12500	≥650	≥640	1022	550	1562	850
Alnico 8 (cast)	0.262	7.3	5.3	8200	≥1450	≥1860	1022	550	1562	850
Alnico 5 (sintered)	0.250	6.9	4.2	12000	≥600	≥630	842	450	1580	860
Alnico 8 (sintered)	0.252	7.0	4.0	8200	≥1500	≥1690	842	450	1580	860

Attributes of Cast Alnico

• Size parameters range from one 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 Alnico Magnets

• Automotive Industry
• 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