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Magnet grades

Bonded Magnet Grades

Bonded magnets are graded differently from sintered magnets. Because the binder dilutes the magnetic powder, a bonded grade is normally designated by its maximum energy product rather than by an N number, and the same material can be supplied at different outputs depending on how it is formed.

About Bonded Magnets

How Bonded Grades Are Designated

A sintered neodymium grade such as N42 takes its number from the maximum energy product in MGOe. Bonded grades follow the same underlying idea, but the achievable range is very different, so the designations are not interchangeable.

Two things set the grade of a bonded magnet. The first is the magnetic powder: neodymium, ferrite or samarium cobalt. The second is how much of that powder the process can pack into the finished part, which is decided by whether the magnet is compression bonded or injection moulded.

That is why the same powder can appear at more than one grade. A compression bonded part carries more magnetic material by volume than an injection moulded one, so it reaches a higher energy product from the same starting powder.

Do not read a bonded grade against a sintered one. A bonded neodymium magnet and a sintered neodymium magnet described by similar-looking numbers are not comparable parts, and substituting one for the other on the strength of the designation alone is a common and expensive mistake.

Bonded Magnet Grade Table

Compression bonded neodymium grades, with remanence, coercivity and maximum energy product in both CGS and SI units.

Compression bonded neodymium (NdFeB) magnet grades
Grade Remanence (Br) Coercivity (Hcb) Intrinsic coercivity (Hcj) Max. energy product (BHmax) Max. operating temp.
kGsmT kOekA/m kOekA/m MGOekJ/m3 °C
MS-B33.8–4.3380–4303.0–3.5239–2797.0–9.0557–7163.0–4.023.9–31.8100–120
MS-B44.2–4.7420–4703.5–4.0279–3187.0–9.0557–7164.0–5.031.8–39.8100–120
MS-B55.0–5.5500–5504.0–4.5318–3587.0–9.0557–7165.0–6.039.8–47.7100–120
MS-B65.5–6.0550–6004.2–4.7334–3747.0–9.0557–7166.0–7.047.7–55.7100–120
MS-B75.9–6.4590–6404.5–5.2358–4148.0–10.0637–7967.0–8.055.7–63.7120–130
MS-B86.2–6.7620–6705.0–5.8398–4628.5–10.0676–7968.0–9.063.7–71.6120–130
MS-B96.4–6.9640–6905.2–5.6414–4468.5–10.0676–7968.5–9.567.6–75.6120–130
MS-B106.7–7.2670–7205.2–6.0414–4778.5–10.0676–7969.0–10.071.6–79.6120–130
MS-B116.9–7.4690–7405.4–6.0430–4779.0–10.5716–83610.0–11.079.6–87.5120–130
MS-B127.0–7.5700–7505.6–6.1446–4859.0–11.0716–87510.5–11.583.6–91.5120–130
MS-B11L7.3–7.8730–7804.8–5.3382–4226.0–7.5477–59710.0–11.079.6–87.580–120
MS-B12L7.4–7.9740–7905.0–5.5398–4386.0–7.5477–59710.5–11.583.6–91.580–120
MS-B8SR6.4–6.9640–6905.0–5.8398–46211.0–14.0875–11148.0–10.063.7–79.6140–160
MS-B8HSR6.2–6.7620–6705.0–5.8398–46213.0–16.01035–12738.0–9.063.7–71.6140–160

Measurement conditions. These figures come from test results on a sample column of approximately 6.0 g/cc density at a permeance coefficient of Pc = 3, at room temperature. Values measured on a finished part of a different geometry or density will differ.

Grade codes. MS-B references are Magnet Store designations. There is no universal grade standard for bonded neodymium the way there is for sintered N grades, so every manufacturer uses its own scheme. We will cross-reference our code against the producer’s designation on any quotation.

Reference only. These are indicative ranges, not a guaranteed specification. Final values are confirmed against the material and process route actually being supplied, and can be adjusted to a requirement.

For sintered grades, see neodymium, samarium cobalt, alnico and ferrite grade tables.

Injection Moulded Grade Table

Injection moulded grades cover a wider spread than compression bonded, because the polymer and the magnetic powder can both be varied. The polymer sets the temperature ceiling; the powder and the orientation set the output.

Injection moulded magnet grades, isotropic and anisotropic
Grade Polymer / powder Remanence (Br) Coercivity (Hcb) Intrinsic coercivity (Hcj) Max. energy product (BHmax) Density Max. operating temp.
mTGs kA/mOe kA/mOe kJ/m3MGOe
Isotropic — magnetisable in any direction, including multi-pole
MS-INB30PA12 / NdFeB400–4504000–4500≥199≥2500≥334≥420023.9–27.83.0–3.54.8–5.1130
MS-INB40PA12 / NdFeB440–4804400–4800≥267≥3350≥597≥750030.2–36.63.8–4.64.4–4.6130
MS-INB50PA12 / NdFeB490–5404900–5400≥278≥3500≥597≥750039.0–43.04.9–5.44.8–5.0130
MS-INB60PA12 / NdFeB530–5805300–5800≥278≥3500≥557≥700046.2–54.15.8–6.84.9–5.3130
MS-INB70PA12 / NdFeB580–6105800–6100≥318≥4000≥597≥750054.1–58.96.8–7.45.2–5.4130
MS-INB80PA12 / NdFeB610–6606100–6600≥318≥4000≥557≥700062.1–70.07.8–8.85.4–5.8130
MS-INB90PA12 / NdFeB660–7106600–7100≥400≥5000≥700≥870070.0–77.98.8–9.85.8–6.0130
MS-INC20PPS / NdFeB300–3503000–3500≥159≥2000≥318≥400015.1–19.91.9–2.54.1–4.3180
MS-INC30PPS / NdFeB350–4003500–4000≥239≥3000≥621≥780022.3–27.12.8–3.44.0–4.3180
MS-INC35PPS / NdFeB400–4404000–4400≥239≥3000≥620≥780026.3–31.83.3–4.04.3–4.6180
MS-INC40PPS / NdFeB420–4704200–4700≥278≥3500≥796≥1000031.8–36.64.0–4.64.5–4.7180
MS-INC50PPS / NdFeB480–5204800–5200≥303≥3800≥796≥1000039.8–44.65.0–5.64.9–5.1180
MS-INC60PPS / NdFeB500–5605000–5600≥303≥3800≥796≥1000043.8–51.75.5–6.54.9–5.2180
MS-INC65PPS / NdFeB550–5805500–5800≥318≥4000≥597≥750050.9–56.56.4–7.15.1–5.4180
Anisotropic — pre-oriented during moulding, higher output, fixed direction
MS-IHNB100PA12 / NdFeB660–6906600–6900≥437≥5500≥875≥1100075.5–83.59.5–10.54.3–4.5130
MS-IHNB120PA12 / NdFeB720–7607200–7600≥469≥5900≥875≥1100091.4–99.411.5–12.54.6–4.8130
MS-IHNB140PA12 / NdFeB780–8307800–8300≥477≥6000≥875≥11000107.4–115.413.5–14.55.1–5.4130
MS-IHNB150PA12 / NdFeB820–8508200–8500≥477≥6000≥875≥11000115.2–123.214.5–15.55.2–5.4130
MS-IHNC90PPS / NdFeB635–6656350–6650≥420≥5300≥875≥1100068.4–74.78.6–9.44.6–4.8180
MS-IHNC100PPS / NdFeB650–7006500–7000≥414≥5200≥875≥1100075.6–83.59.5–10.54.6–4.8180
MS-IHNC110PPS / NdFeB740–7907400–7900≥420≥5300≥875≥1100083.4–91.410.5–11.54.9–5.1180
MS-IHSB70PA12 / SmFeN550–5905500–5900≥318≥4000≥437≥550054.1–59.76.8–7.53.8–4.0130
MS-IHSB80PA12 / SmFeN580–6205800–6200≥342≥4300≥477≥600062.1–67.77.8–8.54.0–4.2130
MS-IHSB90PA12 / SmFeN620–6606200–6600≥350≥4400≥477≥600068.5–75.68.6–9.54.2–4.5130
MS-IHSB120PA12 / SmFeN690–7406900–7400≥450≥5800≥630≥800091–10011.5–12.44.4–4.6130
MS-IHSNB100PA12 / SmFeN+NdFeB660–7106600–7100≥358≥4500≥517≥650075.6–83.59.5–10.54.4–4.6130
MS-IHSNB120PA12 / SmFeN+NdFeB740–7807400–7800≥398≥5000≥557≥700091.5–99.511.5–12.54.7–4.9130
MS-IHSNB140PA12 / SmFeN+NdFeB800–8408000–8400≥414≥5200≥637≥8000107.3–115.313.5–14.55.1–5.3130

Reading the code. I = injection moulded, H = anisotropic (no H means isotropic), N = NdFeB, S = SmFeN, B = PA12, C = PPS. The number is the nominal maximum energy product in MGOe multiplied by ten, so MS-IHNB150 is nominally 15 MGOe.

The two tables do not share a scale. On the compression bonded table the number is roughly the energy product in MGOe. Here it is ten times that figure. This is exactly why a bonded grade number should never be compared across ranges, and why the BHmax column is the one to read.

Reference only. Indicative ranges for the material and process route, not a guaranteed specification for a finished part. Higher Br and higher Hcj variants can be produced to a requirement.

How to Read a Bonded Grade Code

Unlike sintered neodymium, where N42 means the same thing worldwide, bonded neodymium has no agreed grade standard. Each producer numbers its own range.

What the schemes have in common is that the number tracks the maximum energy product in MGOe. A higher number means a higher energy product, and therefore more magnetic output from the same volume. The tracking is approximate rather than exact, so always read the BHmax column rather than inferring performance from the number alone.

The letter suffixes describe coercivity, not strength:

  • No suffix — the standard coercivity range for that grade
  • L — higher remanence with noticeably lower intrinsic coercivity, and a lower temperature ceiling
  • SR — raised intrinsic coercivity at similar remanence, rated to a higher temperature
  • HSR — the highest intrinsic coercivity in the range, for the most demanding demagnetising conditions

Coercivity is what resists demagnetisation from heat or an opposing field. If a part runs hot, sits close to other magnets, or works against a strong opposing field, the Hcj column matters more than Br.

Temperature and the Binder

On a sintered magnet the operating temperature is a property of the magnetic material. On a bonded magnet it usually is not.

Because the binder is a polymer, it commonly reaches its limit before the magnetic powder does. A bonded magnet can therefore be restricted to a lower maximum operating temperature than the same powder would allow in sintered form, and the binder chemistry matters as much as the grade.

This is the most frequent reason a bonded part is ruled out late in a design, so confirm the operating temperature at the specification stage rather than after tooling.

Bonded Grade FAQs

How are bonded magnet grades designated?

Bonded grades are normally designated by maximum energy product rather than by a sintered N number. The grade depends on both the magnetic powder used and how much of it the forming process can pack into the part.

Can I compare a bonded grade with a sintered N grade?

No. The two scales are not interchangeable. A bonded magnet contains a non-magnetic binder, so a bonded grade and a sintered grade with similar-looking numbers are not comparable parts.

Why does the same material appear at different bonded grades?

Because compression bonded parts carry more magnetic powder by volume than injection moulded parts. The same starting powder therefore reaches a higher energy product when compression bonded.

What limits the temperature rating of a bonded grade?

Usually the polymer binder rather than the magnetic powder. The binder commonly reaches its limit first, so a bonded magnet can be restricted to a lower operating temperature than the same powder in sintered form.