Magnets

Alnico magnets

The Alnico material (composed predominantly of aluminum, nickel, and cobalt with minor amounts of other elements including titanium and copper) is manufactured through either a casting or sintering process. Compared to modern materials alnico has a low coercivity. The main advantage of alnico is the very low temperature coefficient and the wide temperature range from -273 °C to more than +550 °C for practical use.

Alnico magnets is very hard and brittle. Machining or drilling cannot therefore be accomplished by ordinary methods. Holes are usually cored in at the foundry. Magnets are cast or sintered as closely as possible to required size so that abrasive grinding to finish dimensions and tolerances is minimized.

Fact:-

• - good temperature stability up to 550°C
• - Cast to from a vast range of complex shapes and sizes at economical cost
• - Good corrosion resistance
• - Material is so hard that the only machining possible is grinding

Cast alnico magnets - are use specialized casting techniques to achieve the unique crystalline grain orientation found in the alnico 5 and 8 grades. These anisotropic grades are designed to produce high magnetic output in a specified direction. Orientation is achieved during heat treatment, by cooling the casting from 1250°C at a controlled rate within a magnetic field which conforms to the preferred direction of magnetization. Alnico 5 and Alnico 8 are anisotropic and exhibit a preferred direction of orientation. Magnetic orientation should be specified on your drawing when you send an order to us.

Cast Alnico 5 is the most commonly used of all the cast Alnico's. it combines high indications with a high indications with a high energy product of 5 MGOe or more and is used extensively in rotation machinery, communications, meters and instruments, sensing devices and holding applications.

Sintered Alnico magnets - offer slightly lower magnetic properties but better mechanical characteristics than the cast Alnico materials. Sintered Alnico magnets are most suitable in small size (less than 1oz.) in this process. The desired mix of metal powder is pressed to shape and size in a die, than sintered at 1250°C in a hydrogen atmosphere. The sintering process is well suited to large volume production, and results in parts which are structurally stronger than cast magnets. Relatively close tolerances can be achieved without grinding.

Neodymium-Iron-Born magnets

NdFeB Magnet is being used to produce high performance motors, relays, holding systems, magnetic bearings, magnetic couplings, magnetic switches, etc.

Rare Earth are the Neodymium (Nd) Iron (Fe) Boron (B) types and Samarium (Sm) Cobalt (Co) classes. The most commonly produced material is neodymium iron boron (NdFeB). This group of magnetic materials provides the highest available magnetic energies of any material. NdFeB magnets allow small shapes and sizes with high magnetic fields. Energy products range from 26 MGOe to about 45 MGOe.

Sintered NdFeB magnets - will produce the highest magnetic properties. NdFeB is sensitive to heat and should not be used in the environments that exceed 180 °C. and both NdFeB and SmCo are available in sintered as well as bonded forms.

Fact: -
- Allowing small shapes and sizes with high magnetic field
- Sensitive to heat
- Some finishing operations required in order prevent corrosion

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Bonded NdFeB magnets - is composed of rapidly quenched NdFeB magnetic powder and epoxy or nylon resin. The material is Isotropic offering approximately 10 MGOe. Its isotropic nature allows it to be magnetized in any direction with multiple pole magnetization. Bonded NdFeB magnet has been used in the fields of the spindle Motor for CD/DVD-Rom driver and Hard disk drive, Stepping motor, Stepping motor.

Fact: -
- Produce with close tolerance off tools, with little or no finishing required.
- Can be magnetized in multi pole direction

Injection molded NdFeB - are use NdFeB powder blended with a plastic material and injection molded. Energy products are dependent upon the magnetic powders used in fabrication. The molding process allows for the manufacture of more complex shapes. These magnets are usually lower in magnetic strength as there are limitations to the degree of loading.

The main areas of Injection Molded NdFeB applications include:-
- DC motors;
- Brushless DC motors;
- Stepper motors;
- Magnetic torque couplers;
- Medical magneto-therapeutic equipment;
- Automotive: ignition system components, fuel pumps, position sensors, accelerometers (air bag sensors) and meters.

Ferrite magnets

Hard Ferrite Magnets are made of Barium or Strontium Ferrite. This class of magnets, aside from good resistance to demagnetization, has the popular advantage of low cost. Due to their low cost, Hard Ferrite magnets enjoy a very wide range of applications, from motors and loudspeakers to toys and craft, and are the most widely used permanent magnets today.

Sintered hard ferrite - Anisotropic grades are oriented in the manufacturing direction, and must be magnetized in the direction of orientation isotropic grades are not oriented and can be magnetized in any direction, although some degree of greater magnetic strength will be found in the pressing dimension, usually the shortest dimension. The energy products range from 1.1 MGOe to about 4.0 MGOe.

Fact:-
- Lower magnetic properties
- Good resistance to demagnetization
- Popular advantage of low cost
- Very hard and brittle

• Bonded / Injection molded hard ferrite magnets - both can be compression bonded or injection molded, it can be manufactured with either isotropic or anti-isotropic properties. They are comprised of magnetic ferrite powder and bonding nylon. They can be molded into highly precise and complicated shapes by injection. Bonded hard ferrite magnets are high growth products, They have low to medium magnetic strength but can be economically produce in a variety of complex shapes in high volumes.

  Fact:-
  - Can be molded into highly precise and complicated shapes
  - Can be economically produced in a variety of complex shapes in high volumes
  - Can be magnetized in multi pole direction
  

  Rubber / Flexible magnets - can be either isotropic & anisotropic. They are made from strontium ferrous oxide, K-resin (rubber) and some other trace elements. The result is a magnet material that can be bent, twisted, and coiled. They can be used without further machining, or it is possible to trim their shape to requested dimensions. The energy products range from 0.65 MGOe to 1.40 MGOe. Magnetic properties depend on the kind of the magnetic powder that is used.

  Fact:-
  - Material can be bent, twisted and coiled
  - Use without machining or possible to trim their shape to requested dimensions
  
  Typical Applications for Rubber magnet: Refrigerator, information notice holder, fastening elements to metallic bodies as advertisement, sheet magnets for toys, teaching materials, switches and sensor.

Samarium cobalt magnets

Samarium cobalt magnets - holds its standard property in higher maximum temperatures than neodymium, although its maximum strength is less. The cost of material is the most expensive, so it is recommended only when its performance in a high temperature environment is a concern.

Fact:-
- Maximum operation temperature up to 300°C

- Cost of material is the most expensive
- Very brittle need to be handle with care