# What are the different performance grades of sintered NdFeB magnets?

NdFeB strong magnetic grade is in the magnetic material related industry friends will contact every day, so what is behind these complex grades? What are the differences between NdFeB magnets of different grades? How to choose the appropriate NdFeB magnetic materials by grade name?
The performance parameters of sintered NdFeB magnets are small. We will talk about the inner door.
First, the common sintered Nd-Fe-B grades can be divided into seven categories: N, M, H, SH, UH, EH and AH. Except for class n, each type will appear in the grade of product, for example, N38M is M series, n38sh is sh series, and if there is no letter after “N38”, then it is n series. (of course, there are some unusual and higher performance grades. You can understand them by yourself. We only introduce the more common ones today.)
Their magnetic energy products are the same, that is to say, the magnetic force is the same with the products made of them, no matter what suffix mark is taken behind. The biggest difference between them is temperature resistance, such as the maximum operating temperature of N38 is 80 ℃, the maximum operating temperature of n38m is 100 ℃, the maximum operating temperature of n38h is 120 ℃, the maximum working temperature of n38sh is 150 ℃, the maximum operating temperature of n38uh is 180 ℃, and the maximum working temperature of n38eh is 200 ℃.
Secondly, the following four indexes are used to measure the properties of sintered Nd-Fe-B products;
Br remanence: Tesla (T) and Gauss (GS), 1gs = 0.0001t. It refers to the magnetic induction strength of sintered NdFeB magnet when a magnet is magnetized by external magnetic field in closed circuit environment to technical saturation and then the external magnetic field is withdrawn. It can be understood as magnetic force of magnet after magnetization.
Coercivity of HCB: unit: OE or a / M (a/m), 1a/m=79.6oe. When the magnet is magnetized in reverse direction, the value of the reverse magnetic field strength required to reduce the magnetic induction strength to zero is called the magnetic sense coercivity force. But at this time, the magnetization of the magnet is not zero, but the interaction between the added reverse magnetic field and the magnetic intensity of the magnet is counteracted. At this time, if the external magnetic field is withdrawn, the magnet still has certain magnetic energy.
Intrinsic coercive force of Hcj: the reverse magnetic field strength required to reduce the magnetic intensity of the magnet to zero. We call it intrinsic coercive force, whose measurement unit is the same as coercive force. The classification of magnetic material grade is divided according to the intrinsic coercive force. Low coercivity n, medium coercivity m, high coercivity h, uh, eh, th. The intrinsic coercive force of NdFeB strong magnet will decrease with the increase of temperature. Therefore, when choosing to use NdFeB magnet, we must choose the grade suitable for us. In the next period, we will introduce the emperor of magnet further
(BH) max maximum magnetic energy product: represents the magnetic energy density established by the two pole space of the magnet, that is, the static magnetic energy per unit volume of the air gap, which is the maximum value of the product of Br and Hcj. Its size directly indicates the performance of the magnet. The number in the magnetic material grade represents the theoretical maximum magnetic energy product of the product.
Again, we can see that there are two units of measurement for each performance index, because they use different units – Si and CGS, i.e. international and Gaussian units, as if they were the differences between “meters” and “Li” in length units. There is a certain conversion relationship between the international unit system and the Gauss system, but it is more complex, so we will not introduce it.
What are the different performance grades of sintered NdFeB magnets? In fact, the added rare earth components dysprosium is different, so the high temperature resistance is different. Finally, it is not difficult to find that the properties of sintered Nd-Fe-B products under each grade are not the only fixed values, but a numerical range. The performance range of different manufacturers is not completely consistent. When you choose, you should pay special attention to whether the performance of the magnet supplier products can meet your requirements.