Strongest neodymium magnet
Determining the “strongest” strongest neodymium magnet depends on what specific metric you’re using to define strength. strongest neodymium magnet are typically characterized by their maximum energy product, which is a measure of their magnetic strength. The maximum energy product is usually given in units of MegaGauss Oersteds (MGOe) or Tesla.
As of my last update in January 2022, strongest neodymium magnet with maximum energy products in the range of 40 MGOe to 52 MGOe were commonly available. However, it’s worth noting that research and development in magnet technology continue to advance, so there may be even stronger neodymium magnets available now.
When looking for the “strongest” strongest neodymium magnet, you would typically want to find one with the highest maximum energy product that suits your application. It’s also important to consider factors such as size, shape, and temperature stability, as these can affect the magnet’s performance in different applications.
Make the permanent strongest neodymium magnet into a certain shape, take the block magnet in the figure below as an example. If you measure the magnetization curve in the open circuit state along the x, y, and z directions of the magnet, you can find that magnetization along the x direction only requires a lower magnetic field. (H1), it can be magnetized to technical saturation, while measured along the y and z directions, respectively, a higher magnetic field is required to magnetize it to technical saturation.
This phenomenon is called the shape anisotropy of permanent strongest neodymium magnet. The direction that requires a smaller magnetic field to magnetize it to technical saturation is called the easy magnetization direction; the direction that requires the largest magnetic field to magnetize it to technical saturation is called the difficult magnetization direction.
Why do permanent strongest neodymium magnet of a certain shape (non-spherical) show shape anisotropy? This is related to the demagnetization field of the permanent magnet.
We know that block or cylindrical permanent magnets will always have N poles and S poles. The presence of magnetic poles will generate a magnetic field around it and inside the strongest neodymium magnet.
The magnetic field generated by the magnetic poles of a permanent magnet always goes from the N pole to the S pole, both around and inside the magnet. The demagnetization field inside the permanent strongest neodymium magnet are represented by Hd, and its direction is from the N pole to the S pole. The direction of the magnetic moment Mm of the permanent magnet or the direction of the magnetization intensity is from the S pole to the N pole. The Hd inside the permanent magnet is in the opposite direction to the magnetization intensity M and plays the role of demagnetization, so it is called a demagnetization field.
How is the demagnetization field of a permanent strongest neodymium magnet generated? We can think of a permanent magnet as consisting of two magnets, A and B. Magnet A is in the magnetic field generated by magnet B, and magnet B is also in the magnetic field generated by magnet A. These magnetic fields just go from N pole to S pole, so it is opposite to the magnetization direction of the strongest neodymium magnet, so it is called demagnetizing field.
The demagnetization field strength of the permanent strongest neodymium magnet is related to the shape and size of the permanent magnet. For example, the demagnetization field strength of an annular permanent magnet changes with the size of the gap in the annular permanent magnet (i.e., the length of the permanent magnet).
When the annular permanent strongest neodymium magnet is magnetized along the ring axis direction, no demagnetization field is generated; when half of the annular permanent magnet is cut off, the demagnetizing field of the semi-circular ring is Hd; the shorter the annular permanent magnet is cut, the shorter it is. , the absolute value of its demagnetizing field Hd also gradually increases. The order in which the absolute value of the demagnetization field gradually increases is Hd(e)>Hd(d)>Hd(c)>Hd(b)>Hd(a)→0.
It can be inferred that when the coercive force Hcj of the permanent magnet is not large enough, if the permanent magnet is made thin and magnetized along the thin direction, it may not be able to be charged because the demagnetizing field is too large.
The size of the demagnetizing field of a permanent magnet is related to the shape and size ratio of the magnet. Experiments and theoretical calculations can prove that the demagnetization field of the permanent magnet Hd=-NM, where M is the magnetization intensity of the permanent strongest neodymium magnet, N is the demagnetization factor, and the negative sign in the formula indicates that the direction of Hd is opposite to M.
For an infinitely long round rod-shaped permanent strongest neodymium magnet, the demagnetization factor N1 along the length direction and the demagnetization factor Nd in the diameter direction can be expressed as the following formula, where k is the size factor, k=l/d, d is the rod magnet Diameter, l is length.
Hot pressing and thermal deformation NdFeB strongest neodymium magnets were successfully researched and developed almost simultaneously with sintered NdFeB magnets. In 1985, the General Motors (GM) Research Center of the United States reported that using hot pressing technology to compress fast-quenching NdFeB magnetic powder in an argon environment at 700°C, a solid-density isotropic magnet can be obtained, which was later called MQ-Ⅱ magnet.
If the isotropic solid-density strongest neodymium magnet is subjected to thermal deformation processing, that is, the MQ-Ⅱ magnet is hot-headed to less than 50% of the original height at a temperature above 700°C, the easy magnetization axis can be increased to more than 75% in the heading direction. Orientation degree, solid density anisotropic thermal deformation magnets are made. These three strongest neodymium magnets are called MQ.
The figure below shows the demagnetization curve of high quenching speed (over-quenching) Nd0.13(Fe0.95B0.05)0.87 fast quenching powder, MQ-Ⅱ magnet, MQ-Ⅲ magnet, in which the pressing direction (∥) and perpendicular to the pressing direction (⊥) The difference between the measured curves can reflect the degree of orientation of the magnet. Obviously, the difference measured in the two directions of MQ-II is not big, but there is still some orientation, while MQ-III shows strong orientation. Characteristically, the demagnetization curve in the pressing direction (∥) is very close to the square shape of the sintered NdFeB magnet, while the large remanence maintained perpendicular to the pressing direction (⊥) indicates insufficient orientation.
Since the hot pressing and thermal deformation temperatures are not high and the action time is not long, the fine grain (nano or sub-micron) structure of the fast-quenched NdFeB magnetic powder is basically maintained, so the MQ-Ⅱ and MQ-Ⅲ magnets still have high HcJ, especially the HcJ of MQ-Ⅱ is only 1~2kOe lower than the original powder. For a long time after that, GM Company was producing MQ-Ⅱ and MQ-Ⅲ magnets. Until the beginning of the 21st century, they transferred the production of fast-quenched NdFeB magnetic powder to Tianjin, and the MQ-Ⅱ and MQ-Ⅲ magnet production lines were moved to Tianjin. Mexico ceased production shortly thereafter.
The chemical composition analysis of NdFeB strongest neodymium magnet materials generally includes:
1-Chemical composition analysis of raw materials, including the chemical composition of rare earth metal raw materials, as well as the chemical composition of industrial pure Fe, B-Fe alloys and other metals, such as Ga, Al, Nb, Zr, etc.;
2-The chemical composition of the magnet. If there is an unknown magnet or there is a problem with the magnet, it needs to be analyzed. If the product quality is normal, there is no need to analyze it. The chemical composition of the magnet includes rare earth metal elements, such as Nd, Pr, Ce, Dy, Ho, Gd, Tb, etc., and other metal elements, such as Cu, Al, Nb, Zr, Ga, Co, Ti, etc.;
3-Content analysis of other non-metal elements, such as hydrogen, oxygen, carbon and other elements.
In this article, we mainly introduce the composition analysis of raw materials and magnets. We will talk about the analysis of hydrogen, oxygen, and carbon in magnets in the next issue.
The composition analysis of NdFeB is the same as that of steel materials and non-ferrous metal materials, including traditional analysis methods and modern physical analysis methods.
The traditional analysis method is to use the color, mass and volume changes of the reactants produced by the chemical reaction between a certain element in the material and a certain substance to conduct chemical analysis. This method is time-consuming and labor-intensive, and personal experience has a significant impact on the analysis results. It is rarely used in the quality control of NdFeB materials.
Modern physical analysis methods mainly use the wavelength and intensity of the spectral lines emitted when electrons in atoms of a certain element jump in different shells to analyze the elements and content contained in the material. Modern physical analysis methods mainly use instruments for analysis, which can analyze multiple elements at the same time. The analysis speed is fast, but the cost is also high. There are three main categories of modern physical analysis methods: plasma spectrometry, atomic absorption spectrometry, and atomic fluorescence spectrometry. Plasma spectroscopy analysis is more commonly used in the composition analysis of steel materials, rare earth metals and compound materials, and rare earth permanent magnet materials.
The chemical composition of NdFeB (Neodymium Iron Boron) magnets is critical to their exceptional magnetic properties. Here’s an analysis of the typical chemical composition of NdFeB magnets:
Neodymium (Nd): Neodymium is the rare earth element that gives NdFeB magnets their name. It typically constitutes around 30-35% of the alloy by weight. Neodymium contributes to the high magnetization of the material.
Iron (Fe): Iron is a major component of NdFeB magnets, typically comprising around 60-65% of the alloy. Iron provides structural integrity to the magnet and helps maintain its magnetic properties.
Boron (B): Boron is another essential element in NdFeB magnets, typically making up around 1-1.5% of the alloy. Boron plays a crucial role in forming the crystal structure of the material, which is essential for its magnetic properties.
Other Elements: In addition to the primary elements, small amounts of other elements may be added to the alloy to improve its properties. These can include elements like dysprosium (Dy), terbium (Tb), cobalt (Co), and aluminum (Al). These elements are often added to enhance the magnet’s coercivity (its ability to resist demagnetization) and thermal stability.
The exact composition of NdFeB magnets can vary depending on the specific grade or formulation of the magnet, as well as any customizations made for particular applications. Manufacturers carefully control the composition and processing of the alloy to achieve the desired magnetic properties, including maximum energy product and coercivity, while also ensuring mechanical integrity and stability.
Overall, the combination of neodymium, iron, boron, and other elements in precise proportions results in NdFeB magnets with exceptional magnetic strength, making them indispensable in various industrial, commercial, and consumer applications.
