What is the difference between a sintered and bonded square shaped magnet?

As a supplier of Square Shaped Magnets, I often encounter customers who are curious about the differences between sintered and bonded square shaped magnets. In this blog post, I'll delve into the characteristics, advantages, and applications of both types to help you make an informed decision when choosing the right magnet for your needs.

Manufacturing Process

The first significant difference between sintered and bonded square shaped magnets lies in their manufacturing processes.

Sintered Magnets:
Sintered magnets are produced through a high - temperature sintering process. First, the raw materials, which are usually rare - earth metals like neodymium, iron, and boron (NdFeB) for neodymium sintered magnets, are melted and cast into ingots. These ingots are then crushed into a fine powder. The powder is placed in a die and pressed under a high magnetic field to align the magnetic particles in a specific direction. After that, the pressed powder is sintered at high temperatures (typically around 1000 - 1100°C) to solidify the material. The final step often involves machining and surface treatment to achieve the desired square shape and protect the magnet from corrosion.

Bonded Magnets:
Bonded magnets are made by mixing magnetic powders with a bonding material, such as epoxy resin, nylon, or rubber. The mixture is then formed into the desired square shape through injection molding, compression molding, or extrusion. Unlike sintered magnets, there is no high - temperature sintering step. This allows for more complex shapes and precise dimensional control during the manufacturing process.

Magnetic Properties

Strength

Sintered Magnets:
Sintered magnets generally have a much higher magnetic strength compared to bonded magnets. This is because the high - temperature sintering process results in a dense structure with well - aligned magnetic domains. For example, sintered neodymium magnets are known for their extremely high energy product, which can reach up to 50 - 55 MGOe (Mega - Gauss - Oersteds). This makes them ideal for applications where a strong magnetic field is required, such as in electric motors, generators, and magnetic separators.

Bonded Magnets:
The magnetic strength of bonded magnets is relatively lower. The presence of the bonding material dilutes the magnetic particles, reducing the overall magnetic performance. However, for applications where only a moderate magnetic field is needed, bonded magnets can still be a suitable choice. Their energy product typically ranges from 1 - 12 MGOe.

Thermal Stability

Sintered Magnets:
Sintered magnets have better thermal stability to a certain extent. They can maintain their magnetic properties at relatively high temperatures. For instance, some grades of sintered neodymium magnets can operate at temperatures up to 200°C. However, at very high temperatures, they may experience a significant loss of magnetic strength over time.

Bonded Magnets:
Bonded magnets generally have lower thermal stability. The bonding material can start to degrade at relatively lower temperatures, which may affect the magnetic performance of the magnet. However, some special - grade bonded magnets can be designed to operate at higher temperatures, but their performance is still not as good as sintered magnets in terms of high - temperature resistance.

Physical Properties

Density and Hardness

Sintered Magnets:
Sintered magnets are denser and harder. Their high - density structure is a result of the sintering process, which compacts the magnetic particles together. This makes them more resistant to wear and deformation. However, their hardness also makes them more brittle, and they can break easily if subjected to high impact forces.

Bonded Magnets:
Bonded magnets are less dense and more flexible. The presence of the bonding material gives them a certain degree of elasticity, making them more resistant to impact and vibration. They are also easier to machine and can be cut or drilled without the risk of cracking as easily as sintered magnets.

Machinability

Sintered Magnets:
Machining sintered magnets is a challenging task due to their hardness and brittleness. Special tools and techniques are required to cut, grind, and drill them without causing damage. Any errors during machining can lead to cracks or chips, which will reduce the magnetic performance of the magnet.

Bonded Magnets:
As mentioned earlier, bonded magnets are much easier to machine. They can be shaped using conventional machining methods, such as milling, turning, and sawing. This makes them a preferred choice for applications where complex shapes or precise dimensions are required.

Applications

Sintered Square Shaped Magnets

• Electric Motors and Generators: The high magnetic strength of sintered magnets makes them ideal for use in high - performance electric motors and generators. They can generate a strong magnetic field, which increases the efficiency and power output of these devices.
• Magnetic Separators: In industries such as mining, recycling, and food processing, sintered square shaped magnets are used in magnetic separators to remove ferrous contaminants from materials.
• Speakers and Headphones: Sintered magnets are also used in audio devices like speakers and headphones to convert electrical signals into sound waves. Their strong magnetic field allows for better sound quality and higher power handling.

You can explore our Strong Square Magnets for high - performance applications.

Bonded Square Shaped Magnets

• Sensors and Switches: The flexibility and ease of machining of bonded magnets make them suitable for use in sensors and switches. They can be easily integrated into small - scale electronic devices.
• Automotive Applications: Bonded magnets are used in various automotive components, such as sensors, actuators, and micro - motors. Their resistance to vibration and impact makes them reliable for use in the harsh environment of a vehicle.
• Consumer Electronics: In consumer electronics like smartphones, tablets, and laptops, bonded magnets are used in components such as cameras, hard drives, and magnetic closures.

Our Flat Square Magnets and Large Square Magnets are available in both sintered and bonded types to meet different application requirements.

Cost Considerations

Sintered Magnets:
The production process of sintered magnets is more complex and energy - intensive, which generally makes them more expensive. The high cost of raw materials, especially rare - earth metals, also contributes to the overall cost. However, for applications where high magnetic strength and performance are crucial, the higher cost may be justified.

Bonded Magnets:
Bonded magnets are relatively cheaper to produce. The manufacturing process is less complex, and the use of bonding materials can reduce the amount of expensive magnetic powder required. This makes them a cost - effective choice for applications where high magnetic performance is not the primary requirement.

Conclusion

In conclusion, the choice between sintered and bonded square shaped magnets depends on your specific requirements. If you need a magnet with high magnetic strength, good thermal stability, and are willing to pay a higher price, sintered magnets are the way to go. On the other hand, if you require a magnet with more flexibility, better machinability, and a lower cost, bonded magnets are a better option.

As a Square Shaped Magnet supplier, we have a wide range of sintered and bonded square magnets to meet your diverse needs. Whether you are working on a small - scale consumer electronics project or a large - scale industrial application, we can provide you with the right magnets. If you are interested in purchasing our square shaped magnets or need more information about our products, please feel free to contact us for a detailed discussion on your specific requirements.

References

1. Handbook of Permanent Magnets, edited by Ramesh C. Pullar.
2. Magnetic Materials and Their Applications by Naval Research Laboratory.