8 Factors to Affect the Magnetic Force of Permanent Magnet

China-Magnets-Source-Material.com | Best Magnetic Solution

The magnetic force for permanent magnet can stay for a long time but it is not really permanent. There are 8 factors which will affect magnetic force.
1. The material formulation
Material formulation limits magnetic properties fundamentally. Sintered ndfeb magnet is the strongest and alnico is the weakest. There is also difference for the same material based on formulation. The magnetic force for grade N45 is higher than grade N35 for the same size magnet.
2. Magnet size and shape
3. The magnetization saturability
Only when full charged, magnetic force can be achieved completely.
4. Design of magnetic circuit
Different magnetized direction, the magnetic force is different. For a cylinder magnet, magnetic force by axial-magnetized is stronger than diameter-magnetized.
5. Working temperature
Magnet is very sensitive to working temperature, especially for sintered ndfeb magnet. The momentary and continuous highest temperature of environment may cause certain demagnetization including recoverable and unrecoverable, reversible and irreversible. According to working temperature range 80-200 celsius, sintered ndfeb magnet is divided into several grade series (N, M, H, SH, UH, AH etc.). The cost will be expensive for high working temperature grade. So you need to consider your working temperature and choose the right grade. The loss of magnetic force can be ignored under working temperature permitted range. But magnetic force will decrease rapidly while working under a limit working temperature for a long time.
6. Working humidity
Sintered ndfeb magnet is easy to be oxidized and then loss its magnetic force. We use coating to avoid this problem. But this is not a permanent solution. So the dryer, the better.
7. External magnetic field
Magnetic force will reduce while placing opposite poles around magnet, only when the magnetic field of opposite poles is several times larger than magnet itself, the reduction will be evident.
8. Strong shock
It will reduce magnetic force, but needs long time.

Hast Neodymium Magnets

China-Magnets-Source-Material.com | Best Magnetic Solution

With the development of scientific research, requirement on the NdFeB application technology becomes higher and higher. China Magnets Source Material Limited adopts the most advanced technology and equipment to manufacture Hast Neodymium Magnets, which are different from traditional Sintered Neodymium Magnets. Hast Neodymium Magnets have the advantage of low weight loss, high consistency, high temperature resistance, excellent bonding strength, good adhesive affinity etc.

Hast Neodymium Magnets are mainly used in motors, magnetic coupling etc. As per IEC HAST standard, after 168 hours’ test in the high temperature, high pressure and high humidity cooker, the weight loss of the Hast Neodymium Magnets manufactured by China Magnets Source Material Limited is less than 2mg/cm2. That is to say, lifetime of Hast NdFeB in motors will be more than 10 years.

Depending on unique technology, Hast Neodymium Magnets of China Magnets Source Material Limited have very high corrosion resistance and reach the international leading level.

The Special Manufacturing Technique For Hast Neodymium Magnets

Weight loss of Hast NdFeB of China Magnets Source Material Limited in a HAST test (130°C, humidity 95%, vapor pressure 2.7bar)

Generally speaking, we make HAST Neodymium magnets with customer’s different HAST requirements.You are welcome to contact us for more information. Our engineers also are ready to provide technical assistance.

Permanent Magnet for Motor

China-Magnets-Source-Material.com | Best Magnetic Solution

Permanent magnet for motor is one of important and high-end applications. In order to achieve optimal performance of PM motor, motor designers need to continually change their design and find best material for motor. Several factors will affect the choice of motor magnet.

1. Magnetic Material: Sintered NdFeB, Bonded NdFeB, Ferrite, SmCo, AlNiCo

• Sintered NdFeB magnet has high magnetic performance (including high magnetic flux, remanence, coercive force, resistance to magnetic demagnetization, and low temperature coefficient, loss of irreversible). It can improve motor performance and reduce the volume as well. It is main magnet material for PM motor.
• Bonded NdFeB magnet is well known for good plasticity. It suits for complex shape magnet or magnet with multipole magnetization direction. Usually, mould is needed for its production.
• Ferrite is an old magnet material which used on PM motor. It’s heavy weight but cheap price.
• SmCo can work under high working temperature. The magnetic force is weaker than Sintered NdFeB magnet, but also very powerful.
• AlNiCo with very high working temperature 450-550℃ is the oldest magnet material for motor and replace by ferrite later.

2. Magnet Max. Working Temperature: Sintered NdFeB magnet 150℃ (N35SH, N38SH, N42SH, N45SH), 180℃ (N35UH, N38UH, N40UH) , 200℃ (N35EH, N38EH); Sm2Co17 300℃

 

3. Magnet Working Environment: low weight loss (high corrosion resistance)

 

4. Magnet Coating: NiCuNi, Zn, Black epoxy, Grey epoxy etc. To make full use of magnet performance and control tolerance well, sometimes the plating of magnet uses phosphorization or passivated for temporary protection

 

5. Magnet Shape: segment (arc), wedge, bread, block, ring, or special shape

 

6. Magnetized direction: it depends on magnet design. In order to get best performance, magnetic declination can’t be ignored.

 

7. Magnet tolerance: a lot of motor magnets are made of segment magnets, and small tolerance is very important to reduce air gap and assemble a ring.



Segment NdFeB Magnet For Motor

China Magnets Soure Material Limited is rich in experience of motor magnet manufacture, such as magnet for flat brushless motor, DC Motor, AC motor, stepper motor , servo motor, synchronous motor; magnet for mini motor or special motor; magnet for high temperature to high humidity; magnet for regular shape or irregular shape.

You are welcome to contact us for more information. Our engineers also are ready to provide technical assistance.

Price of Magnet is Keeping Increasing And No Reduction Nowadays

As we all know, the rare earth (the raw material of magnet) is non-renewable resources. 

However, China has exported the magnets at low price over 10 years. 
Now the goverment has to regluate and control the rare earth mine and the whole rare earth industry because of the rare earth will be less and less day by day.
So price of magnet is keeping increasing and no reduction nowadays. 

Overview on the Worlds’ Magnet Supply

 

China: Ferrites 60%, Neo 70%, SmCo 70%, Alnico 50%, Bonded magnets 25% 

Japan: Ferrites 20%, Neo 20%, Bonded magnets 20% 

India: Ferrites 5% 

Thailand: Bonded magnets 20% 

USA: Ferrites 10%, SmCo 10%, Alnico 20%, Bonded magnets 10%, 

Europe: Neo 10%, SmCo 10%, Alnico 20%, Bonded magnets 15%

The Use of NdFeB Magnet by china-magnets-source-material.com

Here, let’s introduce the use of NdFeB magnet in the market.

As the third generation permanent magnet material, NdFeB magnet has rather high properties. The NdFeB magnets apply to the industries for energy sources, transportation, machinery, medical treatment, IT, and home appliance. Especially with the development of information technology, it brings so many new uses for the NdFeB magnets.

In the electro-acoustic industry, the loudspeaker, receiver, microphone, annunciator all are using NdFeB.

In the electrical machine industry, they also can’t work without NdFeB magnet, such as VCM, CDDVD-ROM, dynamo, electromotor, micro machine, ac motor and so on.

In conclusion, it is a new sight to use more and more NdFeB products in our modern daily life.

Neodymium Rare Earth Magnets by china-magnets-source-material.com

Neodymium-Iron-Boronpermanent Magnet is also named as Neodymium Rare Earth Magnet, which contains rare earth metal. The Neodymium Rare Earth Magnets have powerful magnetic force. Its chemical formula is Nd2Fe14B, is a kind of man-made magnet. Until now, the Neodymium Rare Earth Magnets is the most powerful permanent magnet in the world.

In the coming two decades, there is no magnetic material which can replace the Neodymium Rare Earth Magnet. The main raw materials are rare earth metal Neodymium, pr, pure iron, aluminum, boron, and other rare earth material.

The core technology of Neodymium Rare Earth Magnet is mainly reflected in manufacturing. The advantage of Neodymium Rare Earth Magnets products is strong magnetic force, high consistency of magnetic force, high coercive force and so on. 

Cast Alnico by china-magnets-source-material.com

According to the productive technology, the alnico divides into Sintered Alnico and Cast alnico. There are round, rectangle, segment, and different irregular shapes. It can be manufactured into different sizes and shapes by casting technique. Comparing to casting technique, the Sintered magnets products are limited in small size. The tolerance of semi-finished product of Sintered Alnico is better than the semi-finished product of Cast Alnico, but the magnetic properties is lower than Cast alnico.

The advantage of Cast alnico is high in remanence (max 1.35T), low in temperature coefficient (T.C.), and the highest temperature can be 550°C. However, what is the disadvantage of Cast alnico? Its coercive force is very small. The demagnetizing curve of cast alnico is irregular. Therefore, the cast alnico is easy to magnetize, and easy to demagnetize in the same way.

ALNiCo Magnet by china-magnets-source-material.com

Alnico magnet is the first generation permanent magnetic material. It is a kind of alloy that contains aluminum, nickel, cobalt, iron and other microscope metallic element.

The Alnico magnet manufacture successfully in the 1930 s. At that time, the Alnico is the best in magnetic performance, and its temperature coefficient is very small. Therefore, the Alnico magnet is mainly used on producing the permanent motor at that time. After the 1960s, with the development of ferrite permanent magnet and rare earth permanent magnet, the alnico magnets are replaced to use in producing motor.

SmCo Magnets by china-magnets-source-material.com

SmCo magnet is a kind of rare earth magnets. According to different compositions, it is divided into SmCo5 and Sm2Co17. Sm1Co5 came out first, and then Sm2Co17. The price of SmCo magnet is very expensive for its raw material is very scarce. This limits its development.

 

SmCo magnet, as the second generation of rare earth magnets, is not only high in magnetic energy and coercive force, but also good for temperature characteristic. Comparing with the neodymium magnets, the SmCo magnet is more suitable for working in the environment with high temperature.

Magnetic Therapy Products by china-magnets-source-material.com

With magnet further study, the use of permanent magnet material in biological treatment health care become widely. There are more and more magnetic therapy products appeared in market, such as magnetic back support, magnetic elbow, and magnetic insoles and so on. All these products use very small magnets which can regulate your blood circulation.

 

How magnets connect with letter pigeon? By china-magnets-source-material.com

Magnet material also brings us many unexpected pleasure.

We all know letter pigeons, but seldom person know why the letter pigeons are good at recognizing the road to home. If let the pigeons fly away for hundreds of kilometer, they still can get home safe.

Why the pigeons can do this?

In fact, the pigeons are sensitive to earth magnetic field. They can estimate and position themselves by the strong and weak of earth magnetic field in the different place. If we bind magnet on the head of the pigeons, they will disorientation. If they overfly radio towers, powerful electromagnetic interference will also make them become disoriented.

How to choose a magnetic material? By china-magnets-source-material.com

When choose a magnet material, you need to figure out the requirement you need magnet to do in your application, but not blindly pursue high performance magnetic material; and then get a comprehensive understanding of different magnetic materials. If you have confusion on some point, you can ask for technical help from magnet specialist or manufacturer.

Material	Magnetic Property	Working Temperature	Corrosion Resistance	Price	Remark
NdFeB Magnet	high	low	low	high	1
Ferrite / Ceramic	middle	middle	high	low	3
SmCo Magnet	high	high	high	high	2
AlNiCo Magnet	low	high	high	middle	4

Ferrite and ndfeb magnet can be processed by sintering or bonding method. The Sintered magnet has high magnetic force, but poor formation. The bonded magnet has good formation, but low property.
Alnico can be processed by casting and sintering, the cast alnico has high property, but poor formation. The bonded alnico has good formation, but low property.

This is a brief introduction for choosing magnetic material, for more information, please visit our website www.china-magnets-source-material.com

The magnetic field orientation for permanent magnet by china-magnets-source-material.com

Orientation direction: The direction where anisotropic magnets can obtain the best magnetic property.

Permanent magnets are divided into two types: Isotropic and Anisotropic.

Isotropic magnet: The magnet has same magnetic property in any direction.

Anisotropic magnet: The magnet has different magnetic property in different direction. And there is one orientation which can obtain the best magnetic property.

Sintered NdFeB magnet is anisotropic magnet. So the orientation (magnetized direction) should be decided before production.

Bonded NdFeB magnet is Isotropic magnet. If you buy uncharged magnet, there is no necessary to confirm magnetization direction.

How long can magnetic force of NdFeB magnet last? By china-magnets-source-material.com

Neodymium magnet has high coercive force. 

 

That means it doesn't lose its magnetic force and change magnetic property under ordinary circumstances. 

 

We assume that the environment is stable, it’s just few lose on magnetic force even after a long time use. 

So in an actual application, we can ignore the influence of time factor on magnetic force.

The composition of Neodymium Magnet by china-magnets-source-material.com

Neodymium IronBoron Magnet contains rare earth metals like neodymium (Nd), metallic element iron (Fe), non-metallic element boron (B) and little trace elements, such as dysprosium (Dy), terbium (Tb), cobalt ( Co), niobium (Nb), gallium (Ga), aluminum(Al), copper (Cu), etc. 

 

Neodymium Iron Boron Magnet is based on compound Nd2Fe14B. The molecular formula is similar with Nd2Fe14B. But the magnetic force will be very low or even no magnetic force with exact proportion of Nd2Fe14B. Only when the content of neodymium (Nd) and boron (B) in magnet is higher than nd and B in Nd2Fe14B, it can obtain better magnetic properties.

The grade explanation for Sintered Neodymium Magnet by china-magnets-source-material.com

N: general coercive force Hcj ≥12Koe, for example: N40

M: medium coercive force Hcj ≥14Koe, for example: N48M

H: high coercive force Hcj ≥17Koe, for example: N45H

SH: very high coercive force Hcj ≥20Koe, for example: N42SH

 

UH: great high coercive force Hcj ≥25Koe, for example: N438UH

EH: super high coercive force Hcj ≥30Koe, for example: N35EH

 

AH: Top high coercive force Hcj ≥35Koe, for example: N28AH

T: high requirement for corrosion resistance, for example: N45T

L-T: low temperature coefficient and high requirement for corrosion resistance, for example: L-38SHT

PS: Figure represents the max energy product

Magnetic Property Parameter transformation by china-magnets-source-material.com

Description	Abbreviation	Unit SI	Unit CGS	CGS / SI
Remanence	Br	T	kGs	10
Coercive force	Hcb	KA/m	kOe	4π/10³
Intrinsic coercive field	Hcj,Hic	KA/m	kOe	4π/10³
Magnetic energy product	BH max	KJ/m³	MGOe	4π/10³
Magnetic force on Surface	H	KA/m	kOe	4π/10³
Magnetic flow	φ	Wb, Vs	Mx	108
Magnetic moment	Mm	A.m ²	Vs.cm	10³
Magnetization intensity	M	T	kGs	10

Note: Gs and Oe are the same numerical value, but two different physical significance units. So the magnetic field is the same by 1 Gs and 1 Oe.

10³/4π=79.6