Technical
Sintered NdFeB grades
A grade name encodes two things: the number indicates the nominal maximum energy product in MGOe; the letters after it indicate coercivity, which influences the maximum operating temperature. Higher-coercivity grades often use heavy rare earths (dysprosium, terbium), including through grain-boundary diffusion; heavy-rare-earth-free alternatives also exist.
Indicative family ranges at room temperature; confirm the selected supplier’s grade specification.
| Grade family | Br (T) | HcJ (kA/m) | (BH)max (MGOe) | Max. operating temp.* |
|---|---|---|---|---|
| N35 – N52 | 1.17 – 1.48 | ≥ 955 | 33 – 52 | 80 °C |
| N33M – N50M | 1.14 – 1.44 | ≥ 1114 | 31 – 50 | 100 °C |
| N30H – N48H | 1.08 – 1.42 | ≥ 1353 | 28 – 48 | 120 °C |
| N30SH – N45SH | 1.08 – 1.37 | ≥ 1592 | 28 – 45 | 150 °C |
| N28UH – N42UH | 1.04 – 1.32 | ≥ 1990 | 26 – 42 | 180 °C |
| N28EH – N40EH | 1.04 – 1.29 | ≥ 2388 | 26 – 40 | 200 °C |
| N28AH – N35AH | 1.04 – 1.22 | ≥ 2786 | 26 – 35 | 230 °C |
*Maximum operating temperature depends on the magnetic circuit (permeance coefficient) and load, not only on the grade. A thin magnet in an open circuit can demagnetise below the nominal figure. We check this against your operating point before quoting.
Reduced-heavy-rare-earth grades produced by grain-boundary diffusion reach SH/UH coercivity with a fraction of the dysprosium. They are used in motor applications. When exported from China, grades containing dysprosium or terbium still require an export licence — see Export licences.
Technical references
Updated
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