The main neo magnets production process includes composition blending, magnetic powder preparation, molding, sintering, machining, etc. This series of steps produces neo magnets with high magnetic energy product and remanence, which meet the needs of various industries for high-performance magnets.
Raw Material Ratio
Main raw materials include Nd=neodymium (about 34%), Fe=iron (about 65%), and B=boron (about 1%).
Additives: Dy (dysprosium), Al (aluminum), Nb (niobium), Ga (gallium), Mo (molybdenum), Co (cobalt), Cu (copper), and so on.
According to the different requirements of magnetic performance, manufacturers carry out different raw material ratios. For example, the higher the remanence, the higher the content of neodymium; the higher the Hcj (intrinsic coercive force), the higher the content of heavy rare earth metal in the raw materials.
Image Source: Stanfordmagnets & Link.springer
Strip Casting
The purpose of smelting is to dissolve the raw metal lumps into liquid form in a high-temperature environment through the equipment of Vacuum Melting Furnace and mix them thoroughly. The temperature required for melting iron is 1400-1500℃, and the temperature required for melting neodymium, boron, and other ingredients is 600-700℃. The technical parameters are shown as follows.
The melted alloy material is 250*150*18mm square in shape.
The total weight of each raw material is 30 kg or 50 kg.
The time required is 2-3 hours.
Powdering
Because neodymium particles will oxidize rapidly when encountering oxygen, the entire powdering process is carried out in a vacuum or low-oxygen environment. It is necessary to add hydrogen and nitrogen to protect the raw materials from oxidation. It can produce 100 kg each time and takes 10 hours. Generally, there are two main steps in the powder-making process of high-performance NdFeB magnets:
Hydrogen Decrepitation | Put 250*150*18mm alloy block directly into the “hydrogen furnace” equipment, heated to 700-800 ℃. During the process, hydrogen is slowly absorbed into the solid alloy, making the alloy break and become fine powders.
Jet Milling | The powders from hydrogen decrepitation are fed into a grinding chamber to be ground into 3.1-3.2um particles.
Pressing & Molding
The molding process is to press the powdered magnetic powder into square, cylindrical, and circular shapes. To increase the density of the magnet, the molding requires two pressings: ordinary pressing and isostatic pressing.
During the secondary pressing, isostatic pressing can increase the density of the magnet by 5-6g/ cm3. If the plane diagonal does not exceed 220mm and the thickness does not exceed 50mm, magnets of this size can currently be pressed and formed.
Image Source: Hsmagnets & Link.springer
Sintering & Heat Treatment
The sintering temperature is controlled at about 1100 degrees Celsius. Firstly, the temperature is gradually increased and then gradually decreased. The weight of each sintering is 300 kg or 500 kg and the whole sintering time of the product is 2-5 hours.
Machining Process of Neo Magnets
Processing semi-finished products into shapes and sizes required by customers. Currently, there are three ways, as follows:
Internal Circular Machine Slicing | Ordinary square and disc magnets are cut by internal circular machines. The thickness of the blade is 0.27mm. Oil is added during the cutting process for lubrication and cooling.
Wire Cutting | Tile magnets are obtained by wire cutting. Wire cutting is through the high-speed operation of the molybdenum wire to split the magnet, The molybdenum wire diameter is 0.18mm, Due to the low production efficiency of wire cutting, the cost of wire cutting is higher.
Drilling | The tool used for drilling is made of alloy material and is very hard. The front end of the tool is a flat triangle. There are two types of drilling: straight holes and countersunk holes. When drilling a hole, a straight hole needs only one set of blades, while a countersunk hole needs two sets of blades, one big and one small, the big one is used to make a flared hole.
φ1.5mm holes need to be punched by ultrasonic punching tools, but the height of the product shall be limited to between 5-7mm, otherwise, the current level of technology will not be able to do so.
Attention: The higher the magnetic performance, the more brittle the magnet is and the more difficult it is to process.
Coating of Neo Magnets
Because right angles are easy to peel off and oxidize when coating, it is necessary to chamfer the product before coating. More information about magnet coatings is in this article: Coatings for Neodymium Magnets
Magnetization of Neo Magnets
For more knowledge about magnetization, please refer to this article: Magnetization Direction.
Packaging and Shipping of Neo Magnets
For detailed knowledge about the packaging and shipping of neo magnets, please refer to this article: Shipping Magnet and Magnet Package.
Neo Magnets Manufacturers in China
At Tengye, we’re thrilled to be early participants in your new projects. Our passion for neo magnets extends from material selection and design optimization to providing magnetic solutions. We hope to bring our knowledge and experience to the forefront by actively engaging in your upcoming projects.
