Permanent Magnet Manufacturers
Certainly! Permanent magnets are materials that produce a magnetic field continuously. Unlike electromagnets, which require an electric current to generate a magnetic field, permanent magnets retain their magnetism without the need for an external power source.
As the name suggests, sintered NdFeB is an alloy material composed of Nd2Fe14B, a compound composed of three elements: neodymium Nd, iron Fe and boron B. However, sintered NdFeB is not a single phase. It consists of Nd2Fe14B phase and B-rich phase (also known as Nd1 .1Fe4B4 phase) and Nd-rich phase (also known as rare earth-rich phase), of which Nd2Fe14B phase is the main phase or basic term permanent magnet manufacturers.
Most rare earth elements (RE) form RE 2Fe14B compound, which is the basic phase of sintered rare earth iron boron permanent magnet materials and accounts for 96%-98% of sintered rare earth iron boron permanent magnets. All RE 2Fe14B compounds have the same crystal structure, but their magnetic properties are very different, which means that adding other rare earth elements instead of neodymium to sintered NdFeB can change some properties of the magnet.
The role of heavy rare earth metal Dy in replacing Nd
1. Significantly improve the coercive force of magnets
The anisotropic field HA of the Dy 2Fe14B compound is about 2.14 times higher than that of Nd2Fe14B. Therefore, replacing Nd with a small amount of Dy can significantly increase the coercive force Hcj of the magnet. Theoretically, every time 1% (atomic fraction) Dy is used instead of Nd permanent magnet manufacturers, the coercive force Hcj of the magnet can be increased by 11.4kA/m. However, in practical applications, the increase in coercive force Hcj is related to the presence of other components permanent magnet manufacturers.
2. Reduce the magnetic polarization intensity Js of the magnet, thereby reducing the residual magnetism Br and the maximum magnetic energy product (BH) m
Theoretically, every time 1% (atomic fraction) Dy is used to replace Nd, the magnetic polarization intensity Js of the magnet decreases by 90mT.
3. Reduce the temperature coefficient of the magnet’s residual magnetism Br and the maximum magnetic energy product (BH) m
It should be noted that adding the heavy rare earth element Dy will significantly increase the raw material cost of sintered NdFeB permanent magnets, so the relationship between cost and magnet performance needs to be considered comprehensively.
The role of heavy rare earth metal Tb in replacing Nd
Adding Tb to partially replace Nd in sintered NdFeB magnets has the same effect as replacing Nd with Dy above, but the anisotropic field HA of Tb 2Fe14B is higher, so it can more effectively increase the coercive force of the permanent magnet. However, Tb has fewer reserves in rare earth minerals than Dy, and its price is higher.
The role of metal Gd and metal Ho in replacing Nd
Gd has the highest reserves among heavy rare earth metals. Gd can also form Gd2Fe14B compound. The magnetic polarization intensity Js and anisotropic field HA of this compound are obviously low, but its Curie temperature Tc is the highest. Due to the high reserves and low price of Gd, some manufacturers add Gd in the form of gadolinium-iron alloy to partially replace Nd to produce low-cost sintered NdFeB permanent magnet manufacturers. But in fact, using Gd to replace Nd is a waste. Once Gd is found to have more important uses in the future, it will be found to be an irreparable loss. Replacing Nd with Ho has the same effect and problem permanent magnet manufacturers.
The role of light rare earth metals La, Ce and Pr in replacing Nd
Light rare earth elements are abundant in reserves and relatively cheap. The development of light rare earth metals for use in the manufacture of sintered NdFeB materials is worthy of encouragement.
It is relatively difficult for La, Fe, and B metals to form La2Fe14B, and the temperature is very narrow, but once formed, it is stable below 860°C. Nd accounts for 65%-75% of the cost of sintered NdFeB, and the current cost of La is about one-tenth of Nd.
Replacing Nd with La can reduce costs and promote the comprehensive utilization of rare earth resources. As the La content increases, the magnetic polarization Js, remanence Br, coercive force Hcj and maximum magnetic energy product (BH) m of the alloy will decrease. La is a non-magnetic atom, which causes a decrease in (BH)m due to magnetic dilution. It decreases much faster than Br permanent magnet manufacturers.
Ce2Fe14B has poor stability and is more difficult to form. As the Ce content increases, all magnetic properties decrease. At the same time, the addition of Ce will cause the Curie temperature and temperature stability of the magnet to decrease.
Pr2Fe14B compound has several basic conditions that can be used as a permanent magnet material permanent magnet manufacturers, and good magnetic properties can be obtained by sintering at around 1060°C permanent magnet manufacturers. Sintered NdFeB permanent magnets with good magnetic properties can be produced using (PrNd)-Fe metal as raw material. It should be noted that Pr is more easily oxidized than Nd, and the amount of Pr must be appropriately controlled for some materials that require high stability.
The role of other metals replacing Fe
The sintered NdFeB permanent magnet material has shortcomings such as low coercivity and Curie temperature, poor temperature stability, low operating temperature (about 80°C), and poor corrosion resistance. For this reason, people The effects of various elements on NdFeB permanent magnet materials have been extensively studied.
1. The effect of cobalt Co partially replacing Fe on sintered NdFeB
As the Co content increases, the Curie temperature of the alloy increases linearly, and the magnetic induction reversible temperature coefficient α decreases significantly. When the Co content is less than 5% (atomic fraction), (BH) m and Br hardly decrease permanent magnet manufacturers; when the Co content is greater than 30%, various magnetic performance parameters decrease significantly. The added Co content of less than 10% is very beneficial. It not only increases the Curie temperature of the alloy, but also maintains high magnetic properties. At the same time, the temperature coefficient of magnetic induction is also improved.
2. The role of Al partially replacing Fe
Scholars’ research results show that adding a small amount of aluminum can significantly improve the coercive force of the ternary Nd-Fe-B material. The research results point out that on the basis of Nd-Fe-Co-B permanent permanent magnet manufacturers materials, adding Al can compensate for the reduction in coercive force caused by the addition of Co, so Nd-Fe-Co-Al-Nd-Fe-Co-Al- with higher comprehensive performance can be obtained. B alloy.
3. The role of Cu partially replacing Fe pair
Research has found that adding a small amount of copper Cu to the (Nd,Dy)-Fe-B and (Nd,Dy)-(Fe, Co)-B systems can significantly increase the coercive force, while Br is almost Reduce, so that permanent magnets with high Hcj and high (BH)m can be manufactured.
4. Other elements partially replace the role of Fe pair
On the basis of the ternary Nd-Fe-B alloy, adding a small amount of niobium Nb or zirconium Zr to replace part of the iron can effectively improve the Hcj and squareness Hk of the alloy permanent magnet manufacturers, while the Br decreases very little. At the same time, it is impossible to reduce the magnetic flux of the alloy. loss. Experimental results show that the maximum content of niobium Nb in Nd-Fe-B alloy is 3% (atomic fraction). Adding excess Nb will cause the coercive force of the alloy to decrease rapidly and make Nd2Fe14B unstable.
The addition of gallium Ga can significantly increase the coercivity of the alloy and reduce the irreversible magnetic field hirr. In Nd-Fe-Co-B alloys, as the Co content increases, the Hcj of the alloy decreases, but when Ga is added In this case permanent magnet manufacturers, the coercive force increases permanent magnet manufacturers. It is expected that in Ga-added alloys, it will be possible to prepare Nd-Fe-B series permanent magnet materials with high Curie point and high Hcj.
The combined addition of gallium Ga and niobium Nb can significantly improve the temperature stability of the alloy.
Sintered Neodymium Iron Boron (NdFeB) magnets typically consist of the following elements:
Neodymium (Nd):
Neodymium is the key rare earth element in NdFeB magnets, contributing to their high magnetic strength. It forms the base of the magnet material.
Iron (Fe):
Iron is the primary magnetic element in NdFeB magnets. It forms a major portion of the magnet’s composition and provides ferromagnetic properties.
Boron (B):
Boron is added to the NdFeB alloy to improve its magnetic properties, particularly coercivity and remanence. Boron helps to stabilize the magnet’s magnetization.
Dysprosium (Dy):
Dysprosium is commonly added in small quantities to enhance the coercivity and thermal stability of NdFeB magnets, especially in high-temperature applications.
Terbium (Tb):
Terbium is another rare earth element often added to NdFeB magnets to improve their coercivity, particularly at high temperatures.
Other Trace Elements:
Small amounts of other elements such as praseodymium (Pr), samarium (Sm), gadolinium (Gd), and holmium (Ho) may also be included to further refine the magnetic properties of the NdFeB magnet.
The precise composition and ratio of these elements can vary based on the specific requirements of the magnet’s application. However, neodymium, iron, and boron are the primary constituents, while dysprosium and terbium are added in smaller amounts to tailor the magnet’s properties permanent magnet manufacturers.
Measurement of surface magnetism
Surface magnetism is the most easily measured magnet performance parameter in daily life. It can be measured directly with a gauss meter, which is very convenient. When the shape and size of the magnet are certain, people often judge and compare the performance of the magnet by comparing the surface magnetism (in the case of non-multipolar magnetization, etc.) permanent magnet manufacturers. For some magnets that are particularly large or small in size and have special shapes, it is difficult to measure the magnetic flux. At this time, measuring the magnetic flux of the meter becomes very important.
To measure magnet surface magnetism permanent magnet manufacturers, a Gauss meter, also called a Tesla meter, is generally used. The Hall sensing elements on the Gaussmeters of different manufacturers are different, and the surface magnetism measured for the same magnet is not exactly the same. In addition, it should be noted that the measurement standards of gauss meters used in different countries are different.
Surface magnetism measurement is not objective and is not a parameter that can fully reflect the performance of the magnet. Therefore, it is not recommended to be used as an evaluation index when trading products.
The relationship between surface magnetism and magnet performance (remanence)
Residual magnetism refers to the magnetic induction intensity retained in the ferromagnet when the external magnetic field is used to magnetize the ferromagnet to a saturated state and then gradually reduces the external magnetic field to zero permanent magnet manufacturers. Its full name is residual magnetic induction intensity (Br), and the unit is Tesla Or Gaussian permanent magnet manufacturers. The remanence is determined by the characteristics of the magnet itself. The remanence of the same magnet is unchanged under specific conditions and has a single value.
Residual magnetism determines the surface magnetism of a magnet to a certain extent, but magnets with the same residual magnetism do not have the same surface magnetism. The surface magnetism is also affected by the shape, size and magnetization method of the magnet.
Two magnets with the same shape and size, the one with higher residual magnetism also has higher surface magnetism.
For two magnets with different shapes and sizes, the residual magnetism cannot be determined simply by the surface magnetism.
The residual magnetism is tested in a closed-circuit state, while the surface magnetism is tested in an open-circuit condition with a Gauss meter. At the same time, the magnet itself has a demagnetizing field, so permanent magnet manufacturers the maximum surface magnetism of a single magnet is much smaller than its remanent magnetism. At present, the maximum residual magnetism of sintered NdFeB magnets is around 14000Gs, so we can say with certainty that the maximum surface magnetism of a single NdFeB magnet cannot exceed 14000Gs permanent magnet manufacturers. (Note that it is a “single magnet”. In some magnetic assemblies and magnet arrays, the surface magnetism of the magnet can be improved through special magnetic circuit design)
Calculation of surface magnetism of NdFeB magnet
Since the sintered permanent magnet manufacturers have extremely high magnetic anisotropy field and the magnetization vectors are arranged in the easy magnetization direction permanent magnet manufacturers, we can regard it as a uniformly magnetized body. In this way, the current shell model can be applied to calculate the magnetic field generated by the magnet in space. magnetic field. At present, many surface magnetism calculation models on the Internet are based on this principle to derive the calculation formula.
However, there are two assumptions in it. One is that the magnet is a completely uniform magnetized body, and the other is that the demagnetization curve is completely a straight line. The actual situation is not completely true. , so there is a certain difference between the calculated results and the actual measured results. In addition to residual magnetism, the surface magnetism of magnets is greatly affected by the shape and size. The calculation formulas for surface magnetism applicable to magnets of different shapes are different.
