What are the key technologies involved in the production process of neodymium iron boron block magnets?

1、 Raw material preparation and proportioning
In the production process of neodymium iron boron block magnets, the selection and ratio of raw materials are a fundamental and crucial step. The raw materials mainly include rare earth metals neodymium, pure iron, boron iron alloys, and other trace additives such as cobalt, aluminum, nickel, etc. The purity and chemical stability of these raw materials have a direct impact on the performance of the final product. In order to ensure the quality of raw materials, suppliers need to undergo strict screening and certification. At the same time, raw materials need to undergo strict inspections before being stored, including chemical composition analysis, impurity content testing, etc.
In terms of proportioning, the raw materials need to be accurately proportioned according to specific ratios based on the required magnetic properties and mechanical strength. This step requires a high degree of precision and consistency, as any slight deviation in the ratio can lead to significant changes in the performance of the final product. In order to achieve precise proportioning, an automated batching system is usually used, which can accurately control the input of various raw materials to ensure the accuracy of proportioning. At the same time, in order to further improve the uniformity of raw materials, mixing treatment is also required after batching to ensure that various raw materials are fully mixed evenly.

2、 Melting and alloying
Melting and alloying are important processes in the production of neodymium iron boron block magnets. During the melting process, the raw materials are heated to a molten state in an induction melting furnace. To ensure the smooth progress of the melting process, it is necessary to precisely control the melting temperature and protective atmosphere. The selection of melting temperature needs to be determined based on the melting point and chemical reaction characteristics of the raw materials to ensure that they can be completely melted and fully reacted. Meanwhile, in order to protect the melt from oxidation and contamination by impurities, the melting process is usually carried out under vacuum or inert atmosphere.
Alloying is a crucial step after melting, which determines the composition and properties of the final alloy. During the alloying process, elements in the melt undergo chemical reactions to form Nd-Fe-B alloy. This step requires precise control of reaction time and temperature to ensure uniform composition and stable performance of the alloy. At the same time, in order to avoid element segregation or precipitation in the alloy, it is necessary to thoroughly stir and homogenize the melt.

3、 Powder metallurgy treatment
Powder metallurgy treatment is one of the core processes in the production of neodymium iron boron block magnets. It mainly includes three steps: crushing, grinding, and forming.
During the crushing process, the melted and alloyed metal blocks are broken into small particles. This step usually uses methods such as mechanical crushing or airflow crushing to obtain the desired particle size distribution. The crushed particles need to be ground to further refine their particle size and remove surface oxides and impurities. During the grinding process, precise control of the grinding time and the type of grinding medium is required to achieve the optimal particle size distribution and surface quality.
Forming is one of the key steps in powder metallurgy processing. It determines the shape and size of the final magnet. In the forming process, the ground magnetic powder is compressed into a magnet of predetermined shape by spray forming, cold pressing forming or other forming technologies. Spray molding is a commonly used molding method. It forms magnets by mixing magnetic particles and adhesives, spraying them into the mold, and then drying and curing. Cold pressing molding is the process of placing magnetic powder directly into a mold and applying pressure to tightly bond them together to form a magnet. Regardless of the molding method used, precise control of molding parameters such as pressure, temperature, and speed is required to achieve optimal magnetic properties and mechanical strength.

4、 Sintering and heat treatment
Sintering and heat treatment are key steps in the production process of neodymium iron boron block magnets. They collectively determine the density, magnetic properties, and mechanical strength of the final magnet.
During the sintering process, the formed magnet is heated to a certain temperature in a high-temperature furnace, causing the magnetic powder particles to tightly bond and form a high-density magnet. The selection of sintering temperature needs to be determined based on the melting point, chemical reaction characteristics, and required properties of the magnetic powder. Meanwhile, in order to protect the magnet from oxidation and contamination by impurities, the sintering process is usually carried out under vacuum or inert atmosphere. The sintered magnet needs to undergo cooling treatment to achieve a stable structure and performance.
Heat treatment is one of the key steps after sintering. It adjusts its magnetic properties by heating and cooling the magnet. Accurate control of heating temperature, holding time, and cooling rate is required during the heat treatment process to obtain the desired magnetic properties. For example, by adjusting the heat treatment process, the intrinsic coercivity of the magnet, the squareness of the demagnetization curve, and the irreversible loss at high temperatures can be improved. Meanwhile, heat treatment can also improve the mechanical strength and corrosion resistance of magnets, making them more suitable for various application scenarios.

5、 Magnetization treatment
Magnetization treatment is the final step in the production process of neodymium iron boron block magnets, and it is also a key step in ensuring that the magnet has the predetermined magnetization direction and magnetic strength. Magnetization treatment is usually carried out using high-intensity pulsed magnetic fields. During the magnetization process, the magnet is placed in a pulsed magnetic field, and the direction of the magnetic field is consistent with the desired magnetization direction. By adjusting the intensity and duration of the pulsed magnetic field, the magnetic domains in the magnet can be aligned along the direction of the magnetic field, thereby achieving magnetization.
The effect of magnetization treatment depends on multiple factors, including the composition, structure, shape, and size of the magnet. To ensure the magnetization effect, precise measurement and positioning of the magnet are required to ensure that it is in the optimal position of the pulsed magnetic field. At the same time, precise control of the intensity and duration of the pulsed magnetic field is required to obtain the desired magnetization strength and direction. The magnetized magnet needs to be inspected and tested to ensure that it meets the predetermined performance requirements.