A requirement for continuous operation at 350°C changes the magnet selection question. “Sm₂Co₁₇” names a material family, not a temperature rating for every grade or assembly. Before choosing a magnet, define the field the device must deliver at its working gap, the full temperature cycle and the conditions in which the finished assembly will operate.
This guide is for engineers and buyers evaluating a high-temperature permanent-magnet design. It is a specification checklist, not a claim that a particular Magnetstek grade or finished assembly has been qualified at 350°C.
Start with the proposed grade, not the material family
Sm₂Co₁₇ is often considered for elevated-temperature magnetic circuits because suitable grades can retain useful coercivity as temperature rises. The limit still varies. In Arnold Magnetic Technologies’ RECOMA grade summary, typical maximum operating temperatures differ between grades, including examples at 250°C, 300°C and 350°C. Those figures describe Arnold materials under the document’s stated assumptions. They do not establish a rating for a different supplier’s part or for an assembled device.
Specially engineered grades can extend the range. Arnold’s RECOMA HT paper discusses several high-temperature formulations. That is evidence that formulation matters, not evidence that every Sm₂Co₁₇ magnet will run continuously at 500°C or 600°C. Ask for the exact grade datasheet, demagnetization curves and conditions behind any proposed temperature figure.
What does “350°C continuous” mean in your assembly?
Give the supplier a temperature profile rather than one headline number. State the magnet’s expected temperature during steady operation, peak temperature, time at each condition, heating and cooling rates, number of cycles, and whether the surrounding atmosphere is air, inert gas, vacuum or a process fluid. Identify any opposing magnetic field from a coil, rotor or nearby magnet.
Separate three concepts. Curie temperature describes the loss of ferromagnetic order and is not a usable service rating. A datasheet’s maximum operating temperature is grade-specific and usually conditional. The finished assembly must be checked against its own magnetic circuit, mechanical retention and environment.
Check the magnetic working point
At elevated temperature, magnetic output changes even if the magnet is not permanently damaged. A reversible change returns on cooling. An irreversible loss does not return without remagnetization, and a permanent material change may not be recoverable. The risk depends on the grade’s coercivity at temperature, the magnet’s shape and load line, the working gap and any opposing field. Arnold’s magnetization-loss guidance explains why a room-temperature strength number alone cannot answer this question.
Specify the field or flux required at a defined location and temperature. If pull force is the acceptance measure, define the mating steel, contact surface, gap and direction of loading. Agree on whether the test is made hot, after cooling, or both. A room-temperature surface-field reading is not a substitute for an assembled-circuit test.
Review mounting, geometry and environment
SmCo is brittle. Thin sections, sharp internal corners, holes and long unsupported spans need a drawing review for machining, handling and assembly stress. At high temperature, the housing, magnet and retaining features expand differently. The design should define mechanical retention and allow for thermal movement without relying on an unverified adhesive or coating rating.
State the surrounding gas or fluid and any corrosion, cleanliness or outgassing requirement. Coating or encapsulation suitability depends on the actual environment and temperature; ordinary atmospheric corrosion resistance does not establish fitness for a hot, reactive or sterilized process. If the quote covers a complete assembly, identify all nonmagnetic components and their acceptance criteria separately.
Define a verification plan before approving a grade
- Record the proposed grade, datasheet revision, magnetization direction and finished dimensions.
- Measure the specified field, flux or force before thermal exposure, at temperature if required, and again after cooling.
- Define the number and duration of thermal cycles, the external field during the test, and the allowable irreversible loss.
- Inspect the magnet and retention features for cracking, movement and environmental damage.
The test method and acceptance thresholds should come from the actual device requirement. A supplier’s typical material table can help screen candidates; it is not a replacement for this qualification.
What to send with a high-temperature SmCo RFQ
- Part and assembly drawings, tolerances, pole layout and magnetization direction.
- Required field or force at a named working gap and operating temperature.
- Continuous and peak temperatures, dwell time, thermal cycling and any opposing field.
- Atmosphere or process fluid, mounting concept, coating or cleanliness requirement.
- Quantity, inspection method and acceptable change after thermal exposure.
See Magnetstek’s custom SmCo page for the material-family overview. Send the drawing and operating profile for a part-specific review; specify whether the request is for magnets alone or for a finished magnetic assembly. Grade availability, supply scope, minimum order and lead time can then be confirmed in the quotation.
