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NdFeB Grades, Temperature Suffixes and Sourcing Risk
A procurement-oriented guide to N35–N52, M/H/SH/UH/EH suffixes and the composition evidence needed before comparing sources.
Reference note: Market prices and capacity figures are volatile reference points, not quotations or guarantees of current availability.
A grade is more than a strength label
NdFeB grade designations combine a number, such as N35 or N52, with an optional temperature/coercivity suffix such as M, H, SH, UH or EH. The number identifies a magnetic-performance family. The suffix identifies a higher-coercivity category intended for more demanding temperature or demagnetization conditions.
For sourcing, neither part should be treated as a decorative catalogue code. The grade affects raw-material choices, process capability, price, availability and qualification. It can also affect export controls when the composition contains dysprosium or terbium.
Reading N35 through N52
Within the commonly specified N35–N52 range, the higher number generally represents a higher maximum energy-product family. That does not mean the highest number is automatically the best design choice. Geometry, air gap, magnetic circuit, operating temperature, corrosion protection, mechanical retention and demagnetizing fields all influence the component requirement.
A sourcing RFQ should therefore preserve the engineer’s grade while also describing the application. If the grade is unknown, state that it is unknown and provide the operating conditions and required magnetic performance. A supplier can then quote against an explicit question instead of silently selecting a convenient grade.
What the suffix communicates
M, H, SH, UH and EH distinguish progressively more demanding coercivity or temperature categories. They are not interchangeable with the base number. N42 and N42SH may share the same number but represent different technical and sourcing cases.
In the verified August 2026 case, N42SH contains dysprosium. That composition places a China-produced N42SH magnet under the non-automatic export-licence regime introduced in April 2025. A standard N42 without the high-temperature suffix typically uses only light rare earths and remains outside that specific licensing rule. Composition must still be confirmed in writing; a suffix is not a country-of-origin certificate or chemical analysis.
Why composition evidence matters
Since April 2025, all SmCo magnets and all NdFeB magnets containing dysprosium or terbium require a non-automatic Chinese export licence. NdFeB made exclusively with neodymium, praseodymium, lanthanum or cerium continues to export freely under this specific control. Procurement therefore needs more than a generic statement that a product is “neodymium.”
Ask the potential supplier whether dysprosium or terbium is present, where the magnet is manufactured and which documents will support the answer. If a non-China source is required, define whether that means sintering origin, all major manufacturing steps, or another buyer-approved test. Commercial location and manufacturing origin are not the same fact.
Temperature belongs in the application section
A drawing that lists N42SH but omits operating temperature leaves part of the decision unexplained. A useful RFQ records normal and exceptional temperature conditions, duty cycle, nearby heat sources and the consequence of irreversible demagnetization. It also records coating and assembly conditions because corrosion or mechanical failure can be mistaken for a magnetic-material problem.
The sourcing process should not redesign the component. Its job is to make the questions visible so that each potential manufacturer quotes the same requirement and the buyer can review any proposed deviation through engineering.
Licensing changes the schedule model
Chinese licence applications for controlled magnets frequently remain unresolved for 60–120 days or longer. No statutory review period provides a dependable approval date. A quotation should therefore distinguish production lead time from licensing and export timing.
If the grade contains dysprosium or terbium, ask whether the supplier has included licence time, what end-use documentation is required, and whether the quote expires before approval could reasonably arrive. If the program cannot tolerate that uncertainty, the next question is not “Can the grade be changed?” but “Which qualified manufacturing options can meet the same approved specification without that exposure?”
A practical comparison framework
Compare quotations on the exact grade, composition statement, dimensions, tolerance, coating, magnetization, inspection method, origin, prototype quantity, annual volume and delivery assumptions. Separate deviations from omissions. A supplier offering a lower price against an unstated composition or a different suffix has not necessarily offered the same component.
Cardinal Magnetics can structure this comparison and identify potential manufacturing options. Grade approval, material substitution and supplier qualification remain with the buyer. The comparison should be refreshed whenever the drawing, operating condition, origin requirement or offered composition changes, and the revision date should remain visible to every reviewer.
Common RFQ mistakes
A common mistake is to request “N42 or equivalent” without defining what equivalence means. Another is to list a suffix but omit the operating-temperature context. A third is to ask for non-China supply without defining which manufacturing step determines origin. Each gap invites suppliers to answer a different question while appearing to quote the same part.
Avoid using a catalogue table as the only specification. Include the controlled drawing, application, magnetization, coating, tolerance, quantity and inspection expectations. Ask the supplier to repeat the offered designation in its quotation and sample documentation, so the response can be checked against the request. When a supplier proposes a different grade or composition, require the deviation in writing and route it to the responsible engineer. This preserves the distinction between a sourcing option and an engineering-approved component, especially when the change could also alter export-licence exposure.
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