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Use of Ndfeb magnets

Use of Ndfeb magnets

2020-07-24


Ndfeb magnets

Ndfeb magnets applications

Ndfeb permanent magnet is a kind of energy storage material that can produce a constant magnetic field in a certain space. Due to its extremely high coerce and magnetic energy product, especially its excellent performance compared with other permanent magnets in the environment of 20℃~150℃, ndFeb permanent magnet has been widely used in many fields, especially in modern high-tech fields.From the physical principle, its application can be divided into the following categories:


1. electrical energy - mechanical energy conversion, such as: motor, speaker, VCM voice coil motor;

2. mechanical energy - electrical energy conversion, such as: generators, receivers, measuring instruments, etc.;

3. mechanical energy -- mechanical energy, such as: magnetic separation, magnetic suspension, magnetic transmission, magnetic lifting magnetic chuck;

4,.the use of the physical effects of magnetic field, such as: magnetic resonance, magnetization remove wax, magnetizing oil.

               
Ndfeb magnets

Ndfeb magnet is composed of what materials?


Main raw materials are of ndfeb permanent magnet neodymium rare earth metals, metal iron and nonmetal elements boron (sometimes adding aluminum, cobalt, praseodymium, dysprosium, terbium, gallium, etc.), the general expressions for the: RE2TM14B (RE = Nd, Pr, DyTM = Fe, Co), ndfeb permanent magnetic material based on Nd2Fe14B ternary compound as matrix, its content should be close to compound Nd2Fe14B formula.


However, when the composition of Nd2Fe14B is completely matched, the magnetic properties of magnets are very low or even non-magnetic. Only when the actual magnets contain more neodymium and boron than the compounds of Nd2Fe14B (i.e. forming neodymium-rich phase and boron-rich phase), better permanent magnetic properties can be obtained.


Nd2Fe14 phase

This phase is the main phase of the magnet, and its volume percentage (which is basically fixed after the ingot has been refined) determines the remanence (Br) of the magnet.

The maximum magnetic energy product ((BH)m), and the orientation of the magnetic field during forming is to achieve its permutation and distribution so that the easy magnetization axis (C) of this molecular structure is arranged orderly along the orientation, thus achieving higher magnetic energy.


Rich phase B

B-rich phase exists in a certain compound in the matrix. It is a non-magnetic phase, which is generally harmful to the magnetic properties. However, the presence of B-rich phase makes the ingots easily broken.


Rich Nd phase

Most of the nD-rich phase exists in ND-FE compounds, which plays an important role in increasing the density of magnets during sintering.

Due to its very active nature, it is easy to oxidize to form oxide phase, which is very unfavorable to the corrosion resistance of the magnet.

But relatively more nD-rich, for the ingot long crystal is good, can reduce the precipitation of -Fe.


The microstructure of sintered NdFeb alloys has the following characteristics:

(1) The grains of the matrix phase (the principal phase) are polygonal;

(2) B-rich phase exists in isolated blocks or particles;

(3) Rich Nd phase along grain boundary or grain boundary cross coupling distribution;

(4) In addition in the matrix there are other impurities, oxide phase and cavity.

               



How is the Ndfeb magnet made

Sintered NdFeb permanent magnet is manufactured by powder metallurgy process.

The main processes are: melting, powder making, forming orientation, sintering, mechanical processing, surface treatment and so on.

The control of oxygen content is an important index to measure the technological level.


How long can the magnetism of ndfeb magnets last

Its magnetism can last almost forever if kept at the right temperature, humidity, and without strong external magnetic fields, radiation, and other factors that affect it.


5. Will the performance of magnets decrease over time?

The loss of magnetic energy of a magnet will not be great even after a long period of use, assuming the proper environment.

Therefore, in practice, we often ignore the effect of time on magnetic properties.

What are the main factors that affect magnetic properties


Ambient temperature.

As sintered NdFeb magnets have a negative temperature coefficient (Br.

13% / ℃, alpha Hcj<

- 0.

6%/℃), so the instantaneous maximum temperature and the continuous maximum temperature in the operating environment will demagnetize the magnet itself to different degrees, including reversible and irreversible, recoverable and unrecoverable.


(2) Wet environment

Degrees.

Neodymium iron boron magnet itself is easy to be corroded and oxidized. Generally, we take the way of surface treatment to protect permanent magnet, but it cannot fundamentally solve the influence of environmental humidity on magnet.

The drier the environment, the longer the service life of the magnet.

There are three main parameters by which magnetic properties can be measured:

Residual magnets (Br) measure the strength of the external magnetic field provided by magnets;

The Coercive Force Hc(Coercive Force) and unit Oersteds are the parameters used to measure the anti-demagnetization capability.

The magnetic energy product BHmax, the gaUSs-Oersteds, is a physical quantity that represents how much energy can be stored.


What is a magnetic device

A complete assembly of a magnet and one or more other conductive materials that may enhance magnetic performance.


How to assemble magnetic devices

Assemble magnets and other accessories into required magnets by means of mechanical or viscose.

The assembly of magnetic devices requires special tooling, materials, and specialized personnel.

Our company has the ability to assemble magnetic devices. We can provide assembly services for NMR magnets, refrigeration magnets and other application products. Professional engineers and comprehensive machining capabilities are the basis for our guarantee of assembly quality.


What is the maximum temperature of sintered Ndfeb magnet

The maximum operating temperature of a magnet depends on its magnetic properties and the choice of working point.

The working point of the magnet can be expressed by the magnetic conductivity of the magnet.

For the same magnet, the higher the magnetic permeability of the magnetic circuit (i.e. the more closed the magnetic circuit), the higher the maximum operating temperature of the magnet and the more stable the performance of the magnet.

Therefore, the maximum operating temperature of a magnet is not a certain value, but varies with the degree of closure of the magnetic circuit.

Sintered NdFeb at a given working point, such as :Pc=0.


7. The maximum temperature of each brand is as follows :N brand ≤80℃, H brand ≤80℃, SH brand ≤80℃, UH brand ≤80℃, EH brand ≤80℃.

If the actual operating temperature is close to the maximum operating temperature, and the magnet has a relatively large demagnetization, then either the magnetic circuit must be improved to increase the permeability coefficient of the magnetic circuit;

Or a higher grade of performance must be selected to ensure the normal operation of the magnet.


How to process Ndfeb magnet

Ndfeb must be processed without magnetism;

Because the magnet itself is hard and brittle, it must be processed by special equipment and technology, such as grinding, slicing, drilling, wire cutting, etc.

Note that it must be done professionally.


How much is the processing cost of the magnet

The manufacturing cost of magnets is mainly affected by three factors: batch size, specification shape, and tolerance size.

The smaller the batch, the higher the processing cost;

The more complex the shape, the higher the processing cost;

The stricter the tolerance, the higher the processing cost.


How to shield or guide the magnetic field

Ferromagnetic materials can be used to shield magnetic fields.

However, it should be noted that the thickness of the iron plate. If the thickness is not reached, the iron plate is in the state of magnetic saturation, and only part of the magnetic field can be shielded, and part of the magnetic field line will still be emitted.

The key to guide the magnetic field to form magnetic circuit lies in selecting the material with high magnetic permeability and the appropriate size and shape to reduce the magnetic leakage, that is, the reasonable configuration of the yoke and pole boots in the magnetic circuit.


Can you use the magnet for magnetic separation directly

Can't be!

Ndfeb magnets are prone to corrosion and fracture. The magnet must be protected with magnetic separation material to separate the magnetic separation medium from the magnet.

What precautions should be taken in the storage and transportation of magnets

(1) To pay attention to the indoor humidity, must be maintained in the dry level, the temperature does not exceed room temperature;

(2) Black block or blank state of the product storage can be properly oiled (general oil can be);

(3) Electroplating products should be vacuum sealed or isolated air storage, in order to ensure the corrosion resistance of the coating;

(4) Magnetizing products should be pulled together and stored in boxes, so as not to suck up other metal bodies;


Magnetizing products should be stored away from magnetic disks, magnetic CARDS, tapes, computer monitors, watches and other magnetic field sensitive objects.

Magnet magnetizing state transport should be shielded, especially air transport must be completely shielded.


What are the precautions for magnet operation

The characteristic of ndFeb is hard and brittle. After magnetizing, the suction weight is more than 600 times of its own weight.

During operation, attention should be paid to avoid collision and damage for small specifications, and more attention should be paid to personal safety and protection for large specifications.

When the magnet is assembled and fastened, mechanical methods such as bolts or gluing can be used.


What is the performance-price ratio of Ndfeb magnet

The price of defective NdFeb magnet is generally between 100~300/kg yuan. The price of finished product is mainly composed of five parts: material cost, processing cost, surface treatment cost, packaging cost and labor cost.

17, The performance comparison of Ndfeb magnet and ferrite magnet

On the surface, it looks a lot higher than normal ferrite, but in terms of price-performance per unit volume, NdFeb has a significant advantage.

The magnetic flux density of NdFeb is nearly 10 percent higher than that of normal permanent magnet ferrites


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