Sintered vs Bonded NdFeB Magnets: How the Two Processes Differ and When to Use Each

Sintered NdFeB is made from alloy powder that is oriented and compacted, sintered and heat-treated, then finished and magnetized. Processing establishes the anisotropic easy-axis structure; the later magnetizing operation establishes magnetization within what that structure supports. Confirm the actual route, dimensions and magnetic properties with the supplier.

Mainrich’s sintered NdFeB range is N30 to N56, with no AH grades. The top grade depends on the temperature series: N56, N54M, N52H, N52SH, N50UH and N45EH. Grades up to N52SH can be made without a Chinese export licence, so we offer those first; UH and EH grades need a licence, applied for per order.

Confirm the grade, suffix, geometry and production route for each drawing. This summary does not offer every combination; grades outside it in educational examples are not Mainrich supply offers.

Polymer-bonded magnets combine magnetic powder with a binder, using a specified compression or injection process. Powder orientation, loading and binder determine the material properties. Magnequench’s product documentation distinguishes MQP powders used for MQ1 bonded magnets from MQU powders for fully dense anisotropic MQ3 magnets.

Hot-pressed and hot-deformed fully dense routes are separate from polymer bonding; MQ1/MQ2/MQ3 are not interchangeable powder choices for one bonded RFQ.

Compare the manufacturer’s Br, Hcj, BHmax, density and hot curves for the exact grades. Isotropic injection-bonded and anisotropic compression-bonded products have different property windows. A single upper energy-product limit for all bonded magnets is misleading. The polymer content changes the magnetic volume fraction, but it cannot support a fixed percentage performance loss for every circuit.

Confirm dimensional capability on the required geometry. Sintered material is brittle; polymer-bonded material also needs a qualified mounting and stress design. Thermal performance depends on both magnetic material and binder. Electrical resistivity depends on loading and inter-particle contact, so a polymer matrix does not prove zero magnet eddy loss. Use data for the specified compound and process.

Compare tooling, machining, cycle time, yield and inspection at the intended volume. No universal annual-volume crossover or tooling price is established by this guide. Ask for the same finished-part acceptance criteria in both quotations.

Compare sintered and bonded routes against the field requirement and the geometry. Motor rotors, sensors and encoders can use different materials depending on their duty. Permanent-magnet MRI refers to the main-field system of particular scanner designs; MRI gradient coils are electrically driven coils. A moulded part still needs a defined magnetizing operation and pole pattern.

For sintered parts, specify the material properties, finished dimensions, coating and magnetization. For polymer-bonded parts, additionally identify the actual powder grade and vendor, binder and process, loading or density, orientation and magnetizing fixture requirements. Keep fully dense hot-pressed or hot-deformed candidates as separate process proposals. Agree tests and sample traceability for the selected route.