The Difference between NdFeb Magnet Sintering And Bonding

NdFeB magnets, specifically sintered NdFeB and bonded NdFeB, are two distinct types of permanent magnets with unique characteristics and manufacturing processes. Below is an English introduction to the differences between sintered NdFeB magnets and bonded NdFeB magnets, with a focus on their composition, manufacturing processes, magnetic properties, and applications.

Sintered NdFeB Magnets

Sintered NdFeB magnets are made through a powder metallurgy process. The alloy is first melted and then turned into a powder. This powder is pressed into a shape in a magnetic field and subsequently sintered at high temperatures to achieve a dense structure. The sintering process typically results in rough, which then undergo further mechanical processing, such as wire cutting, slicing, and grinding, to achieve the desired shape and size.

Sintered NdFeB magnets are known for their high magnetic properties, with maximum energy product (BH)max reaching over 50MGOe. They are anisotropic, meaning their magnetic properties vary depending on the direction of magnetization. During production, a magnetic field orientation step ensures that the magnets have high magnetic strength when magnetized in the desired direction. However, they are brittle and hard to process, resulting in high costs, large material losses, and poor dimensional accuracy. Additionally, their corrosion resistance is relatively low, necessitating surface treatments such as plating.

Due to their high performance, sintered NdFeB magnets are widely used in electronics, electromechanical machinery, medical equipment, toys, packaging, metalworking machinery, aerospace, and other fields. Common applications include permanent magnet motors, loudspeakers, magnetic separators, computer disk drives, and magnetic resonance imaging equipment.

Bonded NdFeB Magnets

Bonded NdFeB magnets are made by mixing NdFeB magnetic powder with a binder and then molding or injection molding the mixture into the desired shape. The binder can be epoxy resin, nylon, or rubber, among others. The resulting magnets do not require secondary processing and can be made into complex shapes, which is a significant advantage compared to sintered NdFeB magnets.

Bonded NdFeB magnets are isotropic, meaning their magnetic properties are the same regardless of the direction of magnetization. However, their magnetic performance is generally lower than that of sintered NdFeB magnets, with a maximum energy product typically below 10MGOe, although some high-performance bonded magnets can reach up to 12MGOe. The presence of the binder also reduces the density and magnetic strength of the magnets by about 30% compared to sintered magnets.

Despite their lower magnetic performance, bonded NdFeB magnets are widely used due to their low cost, high dimensional accuracy, flexibility in shape, good mechanical strength, and light weight. They are commonly found in office automation equipment, electronic assemblies, audio-visual equipment, instrumentation, small motors, and metering machinery. Applications in mobile phones, CD-ROM and DVD-ROM drive motors, hard disk spindle motors, and other micro direct current motors and automated instrumentation are particularly common.

In summary, sintered NdFeB magnets offer superior magnetic performance but are difficult to process, while bonded NdFeB magnets are easier to shape and more cost-effective but have lower magnetic properties. The choice between the two types of magnets depends on the specific requirements of the application.