What is Neodymium Magnet?
Sintered neodymium-iron-boron (Nd-Fe-B) magnets are licensed rare earth magnets which are the most powerful commercialized permanent magnets available today, with maximum energy product ranging from 26 MGOe to 52 MGOe. Neodymium Iron Boron is the third generation of permanent magnet developed in the 1980s. It has a combination of very high remanence and coercivity and comes with a wide range of grades, sizes, and shapes. With its excellent magnetic characteristics, Nd-Fe-B offers flexibility for new designs or as a replacement for traditional magnet materials such as ceramic, Alnico and Sm-Co for achieving higher efficiency and more compact devices.
Neodymium Magnets are very susceptible to losing their effective magnetic field at elevated temperatures. The Neo magnet grade should be carefully selected to account for the operational temperature of the application and the magnet’s geometry. All magnet alloy will gain or lose effective magnetic field as the temperature fluctuates. Neo magnets will lose effective field as the temperature increases and are said to have a Negative Temperature Coefficient. When compared to other magnet alloy options, neo magnets lose magnetic field at a faster rate. Neo magnets effectively have a higher Temperature Coefficient (TC) when compared to other commercial alloys.
Neodymium magnets have poor resistance to corrosion and they can also corrode from the inside-out if proper pre-treatment processes are not followed. Oftentimes, multi-layer Nickel-Copper-Nickel plating is applied to prevent failure from corrosion, but this preventative technique may not be sufficient for all applications.
Neodymium Magnets without coating or plating will fail immediately in the Salt Fog environment. The Salt Fog test is used to evaluate the performance of the plating or coating and it is not used to judge the quality of the Neo alloy itself. Various elevated temperature and humidity test can be used to evaluate the bare Neo alloy. The effective volume loss of the evaluated neo magnet is used to determine the quality of the neo magnet alloy. One compares the effective mass before and after the environmental testing exposure. (The “lost” volume is the portion of the Neo alloy which reacted during the environmental testing and “rusted”. The rust/oxidation is removed from the sample and the resulting mass difference between the initial state is quantified.)
Fully dense Neodymium Magnets (also known as neo magnets, neodymium iron boron, neo, or rare earth magnets) are usually manufactured by a powdered metallurgical process.Although sintered Neodymium magnet is mechanically stronger than Samarium Cobalt magnets and less brittle than other magnets, it should not be used as a structural component. Selection of Neodymium magnet is limited by temperature due to its irreversible loss and moderately high reversible temperature coefficient of Br and Hcj. The maximum application temperature is 200 °C for high coercivity grades. The neodymium magnet is more prone to oxidation than any other magnet alloys. If Neodymium magnet is to be exposed to humidity, chemically aggressive media such as acids, alkaline solutions salts and harmful gasses, the coating is recommended. It is not recommended in a hydrogen atmosphere.
Typical Magnetic Properties
|
Grade
|
Residual induction(Br)
|
Coercive Force(Hcb)
|
Coercive Force(Hcj)
|
(BH)max
|
Max.Operating
Temperature |
|---|---|---|---|---|---|
|
kGs(mT)
|
kA/m(kOe)
|
kA/m(kOe)
|
kJ/M3(MGOe)
|
°C
|
|
|
N27
|
10.3~10.8(1030~1080)
|
≥796(≥10.0)
|
≥955(≥12)
|
199~231(25~29)
|
80
|
|
N30
|
10.8~11.3(1080~1130)
|
≥796(≥10.0)
|
≥955(≥12)
|
223~247(28~31)
|
80
|
|
N33
|
11.3~11.7(1130~1170)
|
≥836(≥10.5)
|
≥955(≥12)
|
247~271(31~34)
|
80
|
|
N35
|
11.7~12.2(1170~1220)
|
≥868(≥10.9)
|
≥955(≥12)
|
263~287(33~36)
|
80
|
|
N38
|
12.2~12.5(1220~1250)
|
≥899(≥11.3)
|
≥955(≥12)
|
287~310(36~39)
|
80
|
|
N40
|
12.5~12.8(1250~1280)
|
≥907(≥11.4)
|
≥955(≥12)
|
302~326(38~41)
|
80
|
|
N42
|
12.8~13.2(1280~1320)
|
≥915(≥11.5)
|
≥955(≥12)
|
318~342(40~43)
|
80
|
|
N45
|
13.2~13.8(1320~1380)
|
≥923(≥11.6)
|
≥955(≥12)
|
342~366(43~46)
|
80
|
|
N48
|
13.8~14.2(1380~1420)
|
≥923(≥11.6)
|
≥876(≥11)
|
366~390(46~49)
|
80
|
|
N50
|
14.0~14.5(1400~1450)
|
≥796(≥10.0)
|
≥876(≥11)
|
382~406(48~51)
|
80
|
|
N52
|
14.3~14.8(1430~1480)
|
≥796(≥10.0)
|
≥876(≥11)
|
398~422(50~53)
|
80
|
|
N30M
|
10.8~11.3(1080~1130)
|
≥796(≥10.0)
|
≥1114(≥14)
|
223~247(28~31)
|
100
|
|
N33M
|
11.3~11.7(1130~1170)
|
≥836(≥10.5)
|
≥1114(≥14)
|
247~263(31~33)
|
100
|
|
N35M
|
11.7~12.2(1170~1220)
|
≥868(≥10.9)
|
≥1114(≥14)
|
263~287(33~36)
|
100
|
|
N38M
|
12.2~12.5(1220~1250)
|
≥899(≥11.3)
|
≥1114(≥14)
|
287~310(36~39)
|
100
|
|
N40M
|
12.5~12.8(1250~1280)
|
≥923(≥11.6)
|
≥1114(≥14)
|
302~326(38~41)
|
100
|
|
N42M
|
12.8~13.2(1280~1320)
|
≥955(≥12.0)
|
≥1114(≥14)
|
318~342(40~43)
|
100
|
|
N45M
|
13.2~13.8(1320~1380)
|
≥995(≥12.5)
|
≥1114(≥14)
|
342~366(43~46)
|
100
|
|
N48M
|
13.6~14.3(1360~1430)
|
≥1027(≥12.9)
|
≥1114(≥14)
|
366~390(46~49)
|
100
|
|
N50M
|
14.0~14.5(1400~1450)
|
≥1033(≥13.0)
|
≥1114(≥14)
|
382~406(48~51)
|
100
|
|
N30H
|
10.8~11.3(1080~1130)
|
≥796(≥10.0)
|
≥1353(≥17)
|
318~342(40~43)
|
120
|
|
N33H
|
11.3~11.7(1130~1170)
|
≥836(≥10.5)
|
≥1353(≥17)
|
247~271(31~34)
|
120
|
|
N35H
|
11.7~12.2(1170~1220)
|
≥868(≥10.9)
|
≥1353(≥17)
|
263~287(33~36)
|
120
|
|
N38H
|
12.2~12.5(1220~1250)
|
≥899(≥11.3)
|
≥1353(≥17)
|
287~310(36~39)
|
120
|
|
N40H
|
12.5~12.8(1250~1280)
|
≥923(≥11.6)
|
≥1353(≥17)
|
302~326(38~41)
|
120
|
|
N42H
|
12.8~13.2(1280~1320)
|
≥955(≥12.0)
|
≥1353(≥17)
|
318~342(40~43)
|
120
|
|
N45H
|
13.0~13.6(1300~1360)
|
≥963(≥12.1)
|
≥1353(≥17)
|
326~358(43~46)
|
120
|
|
N48H
|
13.7~14.3(1370~1430)
|
≥995(≥12.5)
|
≥1353(≥17)
|
366~390(46~49)
|
120
|
|
N30SH
|
10.8~11.3(1080~1130)
|
≥804(≥10.1)
|
≥1592(≥20)
|
223~247(28~31)
|
150
|
|
N33SH
|
11.3~11.7(1130~1170)
|
≥844(≥10.6)
|
≥1592(≥20)
|
247~271(31~34)
|
150
|
|
N35SH
|
11.7~12.2(1170~1220)
|
≥876(≥11.0)
|
≥1592(≥20)
|
263~287(33~36)
|
150
|
|
N38SH
|
12.2~12.5(1220~1250)
|
≥907(≥11.4)
|
≥1592(≥20)
|
287~310(36~39)
|
150
|
|
N40SH
|
12.5~12.8(1250~1280)
|
≥939(≥11.8)
|
≥1592(≥20)
|
302~326(38~41)
|
150
|
|
N42SH
|
12.8~13.2(1280~1320)
|
≥987(≥12.4)
|
≥1592(≥20)
|
318~342(40~43)
|
150
|
|
N45SH
|
13.2~13.8(1320~1380)
|
≥1003(≥12.6)
|
≥1592(≥20)
|
342~366(43~46)
|
150
|
|
N28UH
|
10.2~10.8(1020~1080
|
≥764(≥9.6)
|
≥1990(≥25)
|
207~231(26~29)
|
180
|
|
N30UH
|
10.8~11.3(1080~1130)
|
≥812(≥10.2)
|
≥1990(≥25)
|
223~247(28~31)
|
180
|
|
N33UH
|
11.3~11.7(1130~1170)
|
≥852(≥10.7)
|
≥1990(≥25)
|
247~271(31~34)
|
180
|
|
N35UH
|
11.8~12.2(1180~1220)
|
≥860(≥10.8)
|
≥1990(≥25)
|
263~287(33~36)
|
180
|
|
N38UH
|
12.2~12.5(1220~1250)
|
≥876(≥11.0)
|
≥1990(≥25)
|
287~310(36~39)
|
180
|
|
N40UH
|
12.4~12.8(1240~1280)
|
≥899(≥11.3)
|
≥1990(≥25)
|
302~326(38~41)
|
180
|
|
N28EH
|
10.4~10.9(1040~1090)
|
≥780(≥9.8)
|
≥2388(≥30)
|
207~231(26~29)
|
200
|
|
N30EH
|
10.8~11.3(1080~1130)
|
≥812(≥10.2)
|
≥2388(≥30)
|
223~247(28~31)
|
200
|
|
N33EH
|
11.3~11.7(1130~1170)
|
≥836(≥10.5)
|
≥2388(≥30)
|
247~271(31~34)
|
200
|
|
N35EH
|
11.7~12.2(1170~1220)
|
≥876(≥11.0)
|
≥2388(≥30)
|
263~287(33~36)
|
200
|
|
N38EH
|
12.2~12.5(1220~1250)
|
≥899(≥11.3)
|
≥2388(≥30)
|
287~310(36~39)
|
200
|