ALB Materials Inc
2360 Corporate Circle. Suite 400
Henderson, NV 89074-7739
United States
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Alnico Magnets

Neodymium Magnets 03/26/2020

Alnico Magnets - High Performance

Alnico Magnets

The most common magnetic materials in use today are alnico, ceramic (hard ferrites), samarium cobalt, and neodymium.

Each is made up of different elements used for different applications.

Short Timeline of Modern Permanent Magnets

A big step in the evolution of the permanent magnet materials used today came in the 1930s with the development of Alnico magnets.

In 1931, T. Mishima discovered that an alloy of iron, nickel, aluminum had a much higher coercivity than the best steel magnets of the time.

Further research created alnico, a term referring to a series of permanent magnet alloys which in addition to iron are composed primarily of aluminum (Al), nickel (Ni) and cobalt (Co).

Various alnico grades with different magnetic properties can be achieved by modifying the chemistry and manufacturing processes.

Today’s composition of alnico alloys is typically 8–12% Al, 15–26% Ni, 5–24% Co, up to 6% Cu, up to 1% Ti, with the balance being Fe. In addition to varying the alloy composition, specialized casting techniques can be used to achieve unique crystalline grain orientation.

Examples of this are alnico 5-7 and 9.

Once magnetized, Alnico magnets have between 5 and 17 times the magnetic force of magnetite or lodestone, a naturally occurring magnet that can attract iron.

Alnico magnets have the benefit of having the lowest temperature coefficient, or temperature stability of all of the permanent magnet materials.

Plus, they can be calibrated and have high residual induction. Before the development of rare earth magnets in the 1970s, alnico was the strongest type of permanent magnet.

Since that time, many applications using alnico have replaced it with less expensive or more powerful types of magnets.

However, the fact that alnico can be used in very high temperatures (up to 930°F or 500°C) makes them indispensable in certain applications.

Alnico magnets are also ideal for corrosive applications and are commonly used for various types of sensors.

They are stronger than ceramic magnets, but not as strong as rare-earth magnets.

Manufacturing Processes:

Alnico magnets are manufactured either by casting or sintering:

Cast alnico is produced by conventional foundry methods using resin bonded sand molds

Sintered Alnico magnets are formed using powdered metal manufacturing methods.

Sintering alnico is suitable for complex geometries.

permanent cast industrial alnico magnet ring

Most alnico produced is anisotropic, meaning that the magnetic direction of the grains is oriented in one direction.

This orientation is achieved via heat treatment after casting or sintering. The process involves heating the cast or sintered part above its Curie temperature and then cooling it at a controlled rate in the presence of a strong directional magnetic field.

Final shaping of the alnico materials is achieved by abrasive grinding and cutting where close tolerances are required.

Properties: Hard Ferrites

Ceramic magnets, like the ones used in refrigerator magnets and elementary-school science experiments, contain iron oxide in a ceramic composite.

Most ceramic magnets, sometimes known as ferrite magnets, aren’t particularly strong.

Ceramic permanent magnets are made from finely powdered barium ferrite or strontium ferrite formed under heat and pressure.

Their magnetic strength is enhanced by aligning the powder particles with a strong magnetic field during forming.

Ceramic magnets are somewhat comparable to alnico magnets in terms of magnetic force and have the advantage of being able to be pressed into various shapes without significant machining. However, hard ferrites are not magnetically stable at higher temperatures. They are typically used in magnets where price is a primary driver, rather than size or mass.

Alnico Magnet Choices

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

custom made cast alnico magnets

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.

alnico horseshoe magnet magnetic materials magnetic assemblies

Typical Magnetic and Physical Properties of Alnico Magnet Material Magnetic.

Available Grades of Alnico Magnets:

ALB Magnetics offers both cast and sintered Alnico Magnets in a variety of grades, including Alnico 2, Alnico 5, Alnico 5-7, and Alnico 8.

Our large selection of available Alnico magnetic alloys helps achieve the best balance of cost, magnetic performance, and operational temperature resistance for your specific application.

Corrosion Resistance: Alnico magnets exhibit a high degree of corrosion resistance and are typically employed in applications with no coatings or plating.

Temperature Effects: Alnico magnets offer the best temperature characteristics of any standard production magnet material available.

Alnico magnets can be used for continuous duty applications where temperature extremes up to 930°F (500°C) can be expected.

Magnetization Options: The lower coercive force of Alnico makes magnetizing a simple matter in most cases.

In order to optimize the performance of Alnico magnets, it is advisable to magnetize the magnet after assembly with other circuit components.

Compliance and Intellectual Property Considerations:

Alnico magnets manufactured by ALB Magnetics are compliant with Intellectual Property Rights, Environmental Restrictions, and Conflict Mineral usage.

DFARS Compliant

Handling and Storage of Alnico Magnets:

Alnico Magnets are very strong and brittle, requiring appropriate handling and packing to ensure safety and prevent damage.

Alnico Magnets for Sale

Alnico Magnets are Excellent for High-Temperature Applications!

Buy alnico magnets today! We carry a large inventory of grade 8 alnico disc magnets & grade 5 alnico rod magnets, available in a wide range of sizes and shapes, not all of which is shown on this website.

Alnico magnets, are part of the permanent magnet family, and relatively high in magnetic strength.

These powerful magnets offer excellent temperature stability & can be used at temperatures up to 1000⁰F (500⁰C).

Because of their relatively high strength and temperature stability, alnico magnets are commonly used for industrial applications such as rotating machinery, meters, instruments, sensing devices holding applications and more.

Alnico magnets are manufactured through either a casting or sintering process, so they can be made into complex shapes such as horseshoes, which is not possible to do with other magnet materials.

We can custom manufacture these to your exact specifications using our in-house manufacturing facilities and experienced team of engineers.

alnico bar block magnets for guitar pickup

Just let us know what you are looking for by sending us a request for a quote or contact us today, and we'll work with you to determine the most economical solution for your project.

Click on the images below for pricing and sizes:

Alnico Grade 8 Disc Magnets

Features & Characteristics of Alnico Magnets

What are the main characteristics of alnico magnets? Alnico magnets offer high magnetic strength, energies but low coercivities.

They are less brittle than Rare Earth magnets, are highly resistant to corrosion, have excellent temperature stability and can be used at very high temperatures.

Manufactured through either a casting or sintering process, they can be made into complex shapes (such as horseshoe shapes) that are not possible with other magnet materials.

What grades & shapes are available for alnico magnets? Grades 5 and 8 are the most commonly used Alnico grades.

Non-standard shapes can be custom fabricated to blueprint specifications from raw stock in sintered, or cast forms, & we can custom manufacture virtually any shape & size to meet your specialty requirements. Send us a request for a quote, and we'll work with you to determine the most economical way to manufacture your specialty project.

Are there machining constraints for alnico magnets? Alnico magnets are hard and brittle and prone to chipping & cracking.

They require very careful machining & it is not generally recommended that these materials be used for structural or decorative purposes.

Machining or drilling cannot be accomplished by ordinary methods.

Cutting & grinding should be done prior to magnetizing.

Holes must be made by EDM methods.

We are fully equipped to machine these materials to your blueprint specifications.

What are some common applications for alnico magnets? Instrumentation, meters, microwave devices, actuators, holding devices, sensors, are among the most common applications for Alnico magnets.

Do alnico magnets require surface treatments? Alnico magnets do not typically require a protective coating or plating since they exhibit excellent resistance to corrosion.

What are some safety precautions that should be taken into consideration when working with alnico magnets? Special care should be taken to assure that these magnets are not subjected to adverse repelling fields since these could partially demagnetize the magnets.

If Alnicos are partially demagnetized, they may be easily re-magnetized.

What is a permanent magnet? Permanent magnets represent the majority of magnetic materials available today.

A permanent magnet is made from ferromagnetic materials, which have magnetic fields that do not turn on and off like electromagnets.

We carry a large stock inventory of permanent magnets; neodymium, alnico, ceramic (ferrite) and samarium cobalt, in a wide range of sizes, shapes, and grades.

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