The Final Secret of NdFeB - Key to High-Temperature Sintering

In the previous newsletter, we introduced how NdFeB magnetic powder can be transformed into pressed NdFeB blanks through orientation pressing and isostatic pressing, resulting in internally consistent powder orientation and high density. Now, we will discuss the last pre-sintering process in the manufacturing of NdFeB materials: high-temperature sintering.

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High-temperature sintering is also a widely used technology in the field of powder metallurgy, which can transform powdered materials into dense bodies. In the manufacturing process of sintered NdFeB, sintering is conducted to further increase density, improve the contact properties between powder particles, enhance strength, and create microstructural characteristics for high magnetic performance in magnets.

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The specific process of sintering involves placing the NdFeB blanks in a vacuum sintering furnace, heating them to a temperature below the melting point of the main phase, and holding them at this temperature for a period of time under high vacuum or in a high-purity inert atmosphere to densify the blanks. Sintering is one of the key technologies for manufacturing sintered NdFeB permanent magnets and has a significant impact on magnet performance. The sintering temperature for NdFeB is generally around 1050°C. After sintering, the magnets have low properties other than residual magnetism, so they undergo two tempering processes at around 900°C and 500°C, respectively, to improve coercivity and squareness. The blanks after sintering are referred to as rough blanks, which can be processed into NdFeB products of various specifications and shapes through grinding, cutting, and other processing methods.

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