NdFeB Magnet

l      Inspection standard for permanent magnet

l      Purchasing Guide

l      Permanent magnet supply direction

l      Surface protection and surface coating for the permanent magnet

l      Quality warranty

l      Safety principle for manual operation of permanent magnet


Inspection standard for permanent magnet

1) When the permanent magnet is not supplied with specific size and shape, the properties of material should be tested. The test standard is as per GB/T3217-95permanent magnet (hard magnet) material test trial method,GJB2453-95rare earth permanent magnet material general criterion and relevant enterprise standard. GB/T3217 stipulated the test method. Enterprise standard stipulated the test process and sampling method.

2)When the permanent magnet is supplied with specific size and shape, the properties of the magnetic component should be tested. The properties of the material are only tested for reference.

3) For different permanent magnetic components,  the test parameters and test methods are different. For magnetic ring, the test parameter is diametric flux density. For magnetic segment and block, the parameters can be surface field, magnetic flux etc.  The magnetic flux is better.

A digital tesla meter can test diametric flux density

With a transverse  sensor. Magnetic flux can be tested by permanent magnet tesla meter and Helmholtz coil.

For more information about the international standard, you may

turn to the following reference:

IEC 404-5(1982) magnetic material Part 5:test measure for hard magnet(permanent magnet) material properties.

JISC 2501-1989 Test method for magnetic material(Japan)

4) When the permanent magnet is supplied as magnetic assembly or component,the properties of the magnetic assembly or component should  be tested. The buyer and seller will negotiate and decide the specific test method with each other.

5) Unless specified by the user, we will adopt standard sampling method for the final test of the permanent magnet.

Purchasing Guide

1) Permanent magnetic component is not a  standard  mechanical component , but a functional component. It is generally produced as per the customer's demand. So a certain process period is involved. The lead time is about 10-15 days.

2) In order to meet the urgent need, we keep the following rough semi-finished products in stock. You may choose among them according to your design requirement to save the production time.

3)The maximum dimension of the magnet is 60mm,the maximum dimension in magnetization direction is 200mm;the minimum dimension of the magnet is 2mm. For small size, the waste during production is more, so the cost per unit weight is high.  Preferential size of the produc:

4) The products will be tested strictly as per relevant standard. Unless specified by the user, the discrepancy of the properties of the product is below 5%.For quality problem found by the user, please give reasons and return the products to us.

6) Shipment method: express air mail, transit time 2~4days,EMS,transit time3~7days.express transportation by train,transit time5~10days normal mail service Normal transportation by train. The specific shipment method is decided by the order quantity and the price.

Permanent magnet supply direction

1) Permanent magnet supplied under two conditions,Magnetized or no magnetized, is usually not marked its polarity. If the user require, we could mark the polarity by the means agreed on. When pacing the order, the user should inform the supply condition and if the mark of the polarity is necessary.

2) The magnetization field of permanent magnet is related to the permanent magnetic material type and its intrinsic coercive force. If the magnet need magnetization and demagnetization, please contact with us and ask for technique support.

There are two methods to magnetize the magnet: DC field and pulse magnetic field.

There are three methods to demagnetize the magnet:demagnetization by heat is a special process technique.demagnetization in AC field. Demagnetization in DC field. This asks for very strong magnetic field and high demagnetization skill.

3) geometry shape and magnetization direction of permanent magnet: in principle, we produce permanent magnet in various shapes. Usually, it includes block, disc, ring, segment etc. The detailed illustration of the magnetization direction is below:


As for the ring magnets magnetized radially (B),only the isotropic magnetic ring is available. The anisotropic ones are still in research.

4) Size and tolerance of the permanent magnet: Except for the dimension in the direction of magnetization, the maximum dimension of the permanent magnet is not exceed 60mm, which is limited by the orientation field and sintering equipment. The dimension in the magnetization direction is up to 200mm.

Usually the permanent magnet should be ground. The tolerance after grinding is usually +/-0.05.  Tolerance +/-0.02mm is available too, but the cost will be higher.

We suggest the user to refer to our national military standard GJB2453rare earth permanent magnet general criterion in the design of the tolerance of the permanent magnet.

Surface protection and surface coating for the permanent magnet

1) Surface protection: Under the normal atmospheric condition(room temp. humidity 50%),it is unnecessary for special surface protection to the permanent magnet. However, for many applications, the surface protection is a must. This is for the following reasons:

Anticorruption protection: The rare earth permanent magnet exposed to acid, alkaline solution,salt,cooling lubricant or deleterious gas is usually protected by a surface coating. For NdFeB material, it is easy to erode by high humidity or dew.

Protection from magnetic granules:rare earth permanent magnet is a sintered magnet,so the magnetic granules on the surface are unavoidable. For some applications, for example the hard disc machine or sound coil system, the soft magnetic granules will influence the function,even damage the magnetism system. The surface protection coating could protect the permanent magnet from extra accumulation and keep its surface clean thoroughly.

Operation protection: In a certain system, the permanent magnet is usually installed by mechanical pressure. Under some conditions, the pressure install process will cause smashes. The sharp brim is insecure. So we should consider the coating for every application. We suggest the user to choose the most appropriate coating for their application.

3) Types of the protection coating:©There are two basis coatings, metal coating and organic coating. To meet special requirement of the user, we could also adopt metal/metal,metal/organic double-coating and many other special coatings.

Metal coating: Usually, the metal coating is made by electrical plating technique. In addition to standard Nickel-plating and Zn-plating, other coating is also available, if the user require.

Organic coating:The basic organic coating is epoxy. Lacquer spraying is also adoptable.

Temporary anti-corruption coating/surface passivation:For the protection in transit or storage period, this temporary coating is usually used.

Quality warranty

1) Quality management of SmCo permanent magnetic product has been  approved by the China electronic component quality system (i.e. China military standard approval),GB/T9001-ISO9001 quality system, IECQ international electrotechnics committee quality assessing system, China national Exp. & Imp. Enterprise approving committee.

2) The sintered permanent magnet made from rare earth alloy is bristle, especially for the SmCo permanent component, for which the crack slimmer than a hair thread or crack brim is easy to occur. But this phenomenon won¡¯t influence the magnetic properties and mechanical characteristics greatly. For NdFeB permanent magnet, cracks are not very familiar.

3) Under the proper processing technic condition,the magnetized permanent magnetic component is usually adhered with little magnetic dust and small chips. To avoid this phenomenon, we could wipe them off manually and packed the component individually. To do this, the lead-time will be longer and the cost will be higher.

4) For the final inspection of permanent magnet, we usually adopt standard sampling method. Our sampling inspection is as per the National military standard GJB179A,inspection level class,AQL1.5.

Safety principle for manual operation of permanent magnet

1) The magnetized permanent magnets with strong magnetic field attract the iron and other magnetic matters around them greatly. Under common condition, the manual operator should be very careful to avoid any damage. Due to the strong magnetic force, the big magnet close to them takes the risk of damage. People always process these magnets separately or by clamps. In this case, we should ware the protection gloves in operation.

2) In this circumstance of strong magnetic field, any sensible electronic component and test meter may be altered or damaged. Please see to it that the computer, display  and magnetic media , for example the magnetic disc ,magnetic cassette tape and video record tape etc., are far from the magnetized components, say farther than 2m.

The collision of the attracting forces between two permanent magnets will bring enormous sparkles. Therefore, the flammable or explosive matters should not be placed around them.

4) When the magnet is exposed to hydrogen, it is prohibited to use permanent magnets without protection coating. The reason is that the sorption of hydrogen will destroy the microstructure of the magnet and lead to the deconstruction of the magnetic properties.  The only way to protect the magnet effectively is to enclose the magnet in a case and seal it.

 Permanent magnet  ||  Ferrite Magnet   ||  Flexible magnet  ||  Bonded magnet   ||  NdFeB magnet   /  Bonded NdFeB magnets   
Alnico magnets  /  Alnico Bonded magnets  /   Sintered Alnico   ||  SmCo magnet  /   Bonded SmCo magnet  
Ferrite cores   /  NiZn core   /   NiCuZn core   /  Iron Powder core  ||  magnetizer  /  Tesla Meter
Magnetic Powder   /  Ferrite powder   /   NdFeB powder   /  Alnico powder

Copy Right 2004 YUXIANG Magnetic Materials Ind. Co.,Ltd. All Rights Reserved
Add :F/16, Jinyuan plaza, # 57 South Hubin.Rd, Xiamen, CHINA 361004
Tel : (86)592 2295387 (86)592 2217138 Fax: (86)592 2207122
Email To Us:magnetcom@gmail.com