How Magnets Are Manufactured

Magnet manufacturing is a multistep, complex process. Each step necessitates substantial capital equipment investments and precision cutting, machining and grinding operations to produce magnets of desired shape and size. Depending on order quantity, part shape and complexity, customers may choose to have magnets machined from blocks or press-to-shape.

Magnets are composed of ferromagnetic metals such as cobalt, nickel and iron; or alloys thereof. While some simpler magnets can be made with pure iron or iron-cobalt alloys, more intricate high-power magnetic systems require highly specialized materials.

Neodymium (Nd) Magnets

NdFeB magnets are the most widely used permanent magnets in commercial and industrial settings. They power many hybrid and electric automobiles, wind turbines, audio devices, air conditioners and other components; additionally they’re utilized in robotics, aerospace applications and medical devices.

Ferrite magnets are almost 20 X stronger and weigh only one-tenth as much, making them a valuable resource for many new designs. Magnets are used in a range of high-power yet low-weight applications that demand sleek form factors and significant downstream economies.

NdFeB magnets boast an impressive magnetic force, but can also be tailored with various chemical and mechanical modifications for improved performance. For instance, adding manganese or other nonferrous elements may improve their remanence while adding boron increases density and durability in high temperature applications.

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Sintered NdFeB magnets are produced through a process known as strip casting. Ingots of NdFeB metal are cast into book molds that contain slots with cross sections smaller than the smallest dimension of the finished product; this helps maintain Nd in its elemental state throughout melting and sintering, avoiding precipitates of iron that would otherwise lead to poor remanence.

After fabricating, NdFeB magnets undergo various heat treatments. Calcination requires temperatures between 1250degC and 1300degC for proper chemical separation of spinodal components while maximising coercivity. If kept too low, iron in the NdFeB could amorphize and weaken it; conversely, raising temperatures leads to grain growth and decreased coercivity.

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Sintering NdFeB is a complex process that requires various furnace types. Sizes range from several cubic feet to hundreds of cubic feet and the temperature settings can be adjusted accordingly; pressure also plays an important role in controlling cooling rate. Finally, NdFeB in the sinter is typically cooled below peritectic temperature which helps prevent precipitates of iron.

Sintering NdFeB is essential for producing magnets with optimal properties. Sintering temperature also plays a significant role, as it affects chemical and physical characteristics such as remanence and density of the final magnets. Finally, balance must be achieved between BaCO3 and SrCO3 feedstock powders; too much BaCO3 or SrCO3 dilutes magnetic moments and reduces remanence, while too much Fe2O3 causes large grains which contribute to reduced remanence.