Production process of NdFeB magnet

NdFeB permanent magnet materials are developing rapidly and widely used because of their excellent properties and low price of abundant raw materials. Mainly used in electroacoustic devices, instrumentation industry, automotive industry, petrochemical, nuclear magnetic resonance, magnetic health care and other fields. Its use is very extensive, and our daily life is closely linked.

20210417222024 91761 - Production process of NdFeB magnet

NdFeB is a kind of magnetic material which can not be magnetic at room temperature, so it is also called permanent magnet. It’s mainly born
Ingredients —— Smelting ———— Pressing —— Sintering Fire —— Magnetic Testing —— Grinding —— Cutting and Electroplating

Adhesive is to lead the material according to a certain shape, the number of 502 glue to stick it together for easy processing.
Next is cutting: cutting is done by our inner circle slicer.

Our rough material can be divided into three types:

  • Cylindrical magnet: diameter from 2 mm to 100 mm, thickness above 0.5 mm can be processed, and round magnet processing is more convenient, it can be cut at one time, so in order to choose more round magnets, The biggest advantage of this magnet is fast processing and short delivery time. The drawback is that prices are generally low and profits are low.
  • Square magnet: square magnet is slow to process, because it needs to be cut on all six surfaces, a product needs to be processed three times to succeed, two more processes than circular magnets, and the bonding workshop is not as good as a cylinder. Therefore, the square magnet processing speed is slow, the delivery time has grown into its shortcoming, but its profit is OK, has become its advantage again.
  • Punching products: before the product is processed, a specified hole is made on the blank in advance and then processed. Square needs to be processed to a certain job in drilling, and then in cutting, more troublesome. Punching products in the market is also very widely cited, the situation is also very optimistic. At the same time, our factory can also process some special-shaped products, such as trapezoid, size empty and other magnets.

The black piece inspection is to carry on the qualified inspection to the slice workshop processing semi-finished product, generally does not have the special request the round piece thickness in ±0.05 mm the square in 0.07 mm.

The essence of cooking is to boil 502 glue with hot water to facilitate material collection and polishing.
Material collection is to check the quantity of the product in advance in order to deliver the quantity immediately
Polishing (also called chamfering) is the first step of electroplating. It is to grind the angle around the product to a certain degree according to the customer’s request, so that its surface is more smooth, so as to improve the appearance quality of the product.

Electroplating

Electroplating is an important process of product appearance and storage time.

Its surface treatment mainly includes zinc, nickel, copper, chromium, gold, black zinc, epoxy resin. Its surface electroplating is different its color is also different its preservation time is also different, each has the superiority, also has the shortcoming.

  • 1) Zinc: the surface looks silvery white, can do 12-48 hours salt spray, can be used in some glue bonding ,(such as AB glue) if electroplated can be stored for two to five years, its advantage is that the price is relatively low.
  • 2) Nickel: seemingly stainless steel color, left in the air surface is difficult to be oxidized, and good appearance, good gloss, electroplating can exceed 12——72 hours salt spray test. Its drawback is that it can not be bonded with some glue, which will make the coating fall off. Accelerate oxidation, now the market for nickel-copper-nickel electroplating this way to do 120——200 hours salt spray, but its electroplating costs are relatively high.
  • 3) Copper: mostly in the hardware industry, NdFeB industry is rarely used, its appearance is yellow.
  • 4) Chromium: chromium electroplating industry is also relatively rare, its electroplating costs are very high, the general company can not accept. But its ability to release corrosion is very strong, it is difficult to react with other substances. Mainly used in places with strong pH, domestic product prices are relatively low, so few people choose.
  • 5) Black zinc: according to customer requirements, the surface of its products is treated as black. In electroplating process, a black protective film is added through chemical treatment on the basis of galvanizing. This film can also be used to protect the product. Increase salt spray time and prolong oxidation time. But its surface is easy to be scratched, lose its protective effect. Now few people are used, mostly replaced by resin. Below we have some explanation.
  • 6) Gold: this industry is very popular now, we see some stalls on the street yellow gold ornaments are mostly gold-plated, or copper. Gold plating makes the product look as beautiful as gold, generally used in the hand decoration industry, our products can also be gold-plated, for magnetic hand decoration.
  • 7) Epoxy resin: after nickel plating, add a layer of resin paint outside, this industry has only been in the market for nearly two years, its development speed is fast, now a variety of electroplating products with a lot of people, Its biggest advantage is that you can do the color you want.

White film inspection is our last work, here we have to pick up all the non-conforming products out, and according to the requirements of magnetization, in storage.

The above is our post-processing general work.

Magnetic strength

According to market demand, NdFeB magnet‘s magnetic strength is divided int N35N38N40N42N45N48N50N52 these numbers represent the magnetic strength of magnets. The greater the number, the stronger the magnetic strength, then the main factor of magnetic size is the number of magnetic molecules inside it. The more magnetic the molecule, the higher its density. It can be seen that the strength of magnetism and molding pressing have a close relationship. There is no detailed explanation here. You just need to understand that the larger the number, the stronger the magnetic, you can.
According to the working temperature can be divided into the following materials: the above mentioned material is ordinary material, their operating temperature ≤80 degrees. N33M, and N35M-N45M the working temperature of this material is 100 degrees ≤, Next N33H-N45H the material works at ≤120 degrees, Then N33SN-N42SH the material works at ≤150 degrees, Moreover N33UH-N38UH its working temperature is 180 degrees ≤ and the working temperature of EH material is 200 degrees. As the temperature coefficient increases, The properties of materials will be on the low side EH materials are generally in N28 performance. Can do N35EH, at best But it’s best to use a magnet like this, Al, nickel, cobalt, Cobalt magnet. The magnets work at temperatures above 500 degrees, difficult demagnetization. There’s more ferrite in the market, Very cheap, So we need a lot of people, The market is also very optimistic. The latter two markets are rare, The price is also a little more expensive. In addition, there is glue magnetism: glue magnetism is a more flexible magnetic material, A material belonging to feroxap, It is divided into two types: same-sex magnetism is smaller than heterosexual magnetism, It also has multipolar and polar magnetizing, The multipole is higher than the polar magnetism. This is also done according to customer requirements. At the same time, it can also put static electricity, Non-conductive working energy.
Here’s how our NdFeB can also be multipolar magnetized (2-108 poles).

Remanence of material properties: the magnetic induction strength preserved when the magnet is magnetized and the external magnetic field is retreated. That is to say, we fill a magnet and then recede it. In essence, it is difficult for us to remove all the magnetism. At this time, we call it remanent (Br) unit Gao Si (gs) or Tesla (T).

Coercivity: it is divided into coercivity and internal coercivity. Units Oster (oe) or Ann/Mi (A/m).

  • Coercivity (bHc): on the demagnetization curve of a permanent magnet material, when the reaction magnetic field H increases to a certain value (bHc), the magnetic induction intensity of the magnet is B 0, and the H value of the reverse magnetic field is called the coercivity of the material bHc When the reverse magnetic field is H=bHc, the magnet does not show magnetic flux. Therefore, coercivity represents the ability of permanent magnet materials to resist external reverse magnetic fields or their demagnetization effects. Compulsive force is one of the important parameters in magnetic circuit design. Generally speaking, coercivity is the force needed to remove magnetism. The coercivity is always smaller than the remanence numerically, and the remanence is the theoretical limit of the coercivity numerically.
  • Intrinsic coercivity: (JHC) is an intrinsic ability of a magnetic material to maintain its original magnetization state. In the demagnetization process, the magnetism of the magnet is often not completely cleaned. Although the magnetic flux is not displayed, the vector sum of the microscopic magnetic dipole moment inside the magnet is not zero. That is to say, the magnetization (magnetic molecule) is still in the original direction. To reduce magnet magnetic induction to zero, it must be given a corresponding intrinsic coercivity.
    The coercivity is an important index of the temperature coefficient of the corresponding magnetic material, that is, the higher the coercivity, the higher the temperature coefficient is, the more stable it is. The higher the material temperature, the higher the coercivity, especially the intrinsic coercivity.
  • Maximum magnetic energy product: At any point of demagnetization curve of permanent magnet, the product of magnetic flux density B and magnetic field intensity H,. It is a measure of the energy stored in the external magnetic field produced by a unit volume permanent magnet. That is, the energy of the external magnetic field after the magnetic saturation of the magnet. The unit is KJ/m3.

Source: China Permanent Magnet Manufacturer www.ymagnet.com

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