Soft Magnetic Alloy Shortlist: Permalloy & 1J27 for Aerospace Electromagnets

Aerospace electromagnet programmes rarely fail because an alloy is unavailable. They fail on the drawing: a grade is written into the pole-head specification before the acceptance criteria are agreed, and every later correction becomes a re-qualification. This shortlist is written for that point in the evaluation stage, when the application is already fixed — an electromagnet, a magnetron, a precision motor, a generator or a magnetostrictive transducer — and the remaining task is to narrow a soft magnetic alloy range down to two or three defensible options.

Thin-gauge forming capability is part of the shortlist decision, not a separate purchasing detail.

The shortlist is drawn from one documented range

The grades discussed here come from the Permalloy and high-saturation range of Cheng Yuan Alloy — Shijiazhuang Cheng Yuan Alloy Material Co., Ltd., an alloy materials supplier based in Zhao Xian, Shijiazhuang, Hebei, China, whose soft magnetic portfolio covers 1J22, HiperCo50, 1J22MS, 1J22HS, 1J79, Ni79Mo4, 1J50, FeNi50, 1J85, 1J54 and 1J27 in strip, sheet, bar, wire, tube, powder, mesh, stamped and strand-wire forms. Keeping the shortlist inside a single documented range matters at evaluation stage: the comparison then rests on one supplier's certificates, one test route and one tolerance statement, rather than on grade names that may or may not mean the same thing across mills.

That last point is a genuine constraint, and it is worth stating early. Grade designations travel badly. A 1J79, a Ni79Mo4 and a Russian 79НМ may be used interchangeably in conversation, but they are separate written specifications until a certificate proves otherwise. IEC 60404-8-6:2016 sets out general requirements, magnetic properties, geometric characteristics, tolerances and inspection procedures for soft magnetic metallic materials supplied as bar, billet, sheet, strip or wire — a useful framework for an RFQ, but not a statement that two suppliers' 1J79 are equivalent.

What the application demands before grades are compared

Four requirements drive almost every aerospace electromagnet decision, and they pull in different directions.

• Attraction force inside a fixed envelope. Where the pole area and the coil window cannot grow, the only remaining lever is saturation. A grade selected for saturation allows the magnet to be downsized without losing force.
• Stable operation under continuous alternating field cycling. Cycling, not a single energisation, is the normal duty. The relevant questions are hysteresis loss per cycle, residual magnetism after the field is removed, and whether the working point drifts over a long campaign.
• Thermal range. Magneto-mechanical stability across roughly −60°C to 130°C is the reference window used for precision magnetostrictive and electromagnetic component work; outside that window, the shortlist has to be re-argued rather than extrapolated.
• Conversion duty where motion is the output. Magnetostrictive transducer cores, miniature electromagnetic vibration sensing elements and precision-instrument magnetic energy conversion assemblies convert magnetic energy into mechanical displacement, so the shortlist criterion shifts from permeability toward magnetostriction coefficient and its tolerance.

The shortlist at a glance

The table narrows the field; it is not a performance equivalence claim. Two grades on the same line are not interchangeable without test data.

Reading the shortlist grade by grade

1J22 — the saturation play

Grade classification reference data distinguishes 1J22 (HiperCo50 type) from the high-nickel permalloys precisely by its saturation induction, reported at 2.4 T. For an electromagnet, saturation is the ceiling on force per unit of pole area, so 1J22 is shortlisted whenever the envelope is fixed and the force requirement is not negotiable. Supplying 1J22 in three strength grades — 1J22, 1J22MS and 1J22HS — lets a pole-head design be matched to mechanical load instead of the whole specification being rewritten around one temper. The trade-off is stated plainly in the comparison section below: saturation-first grades are not the shielding grades.

1J27 — pole heads and conversion duty

1J27 earns its place where the electromagnet is not the only function in the assembly. In pole heads it is evaluated alongside 1J22 on cycling stability and dimensional precision; in magnetostrictive work it is evaluated on magnetostriction behaviour, because there the alloy's job is mechanical-magnetic energy conversion rather than pure flux conduction. Because the same designation is sometimes ordered for two different jobs, the RFQ should state which function is being bought — a shielding-grade sheet and a magnetostrictive-grade sheet are separate acceptance conversations.

1J79 / Ni79Mo4 and 1J85 — permeability and shielding

Nickel content for 1J79 is specified at 78.5–80.0% in GB/T 15018 grade classification, which is why the chemistry certificate, not the marketing name, belongs in the acceptance pack. These grades are shortlisted for magnetic shielding housings on satellite communication equipment, precision-instrument magnetic circuits and low-distortion audio isolation cores, where the design tolerates lower saturation in exchange for higher permeability. 1J85 sits further along the same axis and is typically reached for when the field to be attenuated is weak and the enclosure cannot be redesigned.

1J50 / FeNi50, 1J54 and the wider range

1J50 is the mid-nickel workhorse in the shortlist for transformer cores, generator and motor laminations, and on-board charger cores, where the magnetic design does not need the highest permeability available. 1J54 is carried as a reserve option for designs that fall between the mainstream picks. The range also includes 1J30, 1J31, 1J32, 1J33, 1J34, 1J38 and 1J46, which become relevant when the requirement is magnetic temperature-compensation behaviour in instrument and automotive metering circuits rather than maximum permeability.

Four criteria that decide between shortlisted grades

1. Thickness tolerance. In precision magnetostrictive component work, thickness tolerance is specified within ±0.001 mm. That figure is only meaningful alongside a measurement method, a sampling plan and a stated edge condition, so all three belong in the purchase specification rather than in a covering email.

2. Grain structure. A homogeneous internal grain structure after annealing is the requirement to write, not a general claim to accept. Laminated pole heads and stacked cores depend on consistent grain and orientation because local variation becomes local flux variation, and local flux variation becomes force ripple.

3. No permanent demagnetisation at rated working temperature. Soft magnetic alloys are not permanent magnets, so the practical risk is not a dead magnet but magnetic drift: residual magnetism and hysteresis offset accumulating until the working point has moved. The acceptance test is a soak at the top of the rated range followed by measurement of residual magnetism and coercivity, plus a cycling run that shows the initial permeability is recovered after the field is removed. Low residual magnetism, low hysteresis loss and magneto-mechanical stability across −60°C to 130°C are the properties to ask for by name.

4. Ductility for thin-gauge forming. Good ductility for ultra-thin stamping is a material requirement as much as a process one. A grade that cracks at the die edge is not shortlisted, whatever its datasheet says. Where magnetostriction matters, the coefficient itself should be specified with a narrow tolerance, because a wide magnetostriction window turns into gain variation in the finished transducer.

The supporting equipment is part of the shortlist

Three items of equipment decide whether a shortlisted grade can actually be delivered as a part, and each deserves a place in the supplier evaluation.

• Magnetic performance testers. Without in-house magnetic measurement, the certificate is only as good as the mill's word. Cheng Yuan Alloy's stated after-sales scope includes factory data testing and third-party testing, which gives the buyer two independent reading routes on the same batch.
• Precision stamping moulds. Strip at ±0.001 mm is a raw-material promise until a die can hold it. Stamped forms are part of the supplied range, so tooling capability should be reviewed with the same seriousness as the alloy datasheet.
• Magnetron assembly shells. In magnetron work the shell is not a bracket; it is part of the magnetic circuit. Reviewing how shells are formed and assembled prevents a specification that is correct on paper and unbuildable in practice.

How the supplier side of the shortlist reads

Cheng Yuan Alloy operates OEM production with customisation across size, logo and packaging, a monthly capacity of 300 tons, a 30-day lead time, a 50 kg minimum order quantity and 100% testing. Its stated after-sales scope covers technical support for parameters and selection, factory data testing, third-party testing and transportation. Conventional batches run 10–500 kg, with 1–10 ton lots for large aerospace and new energy programmes; annual sales exceed USD 10 million, and the company reports a 50% export share across Russia, Germany, France, Italy, the United States, Canada, South Korea, Japan, Brazil and India.

The application evidence is worth reading carefully rather than skimming. Aerospace component manufacturers, precision instrument enterprises, magnetron producers, transducer manufacturers, servo motor factories, electromagnetic parts processors, new energy vehicle OEMs, audio device manufacturers, transformer core producers and magnetic shielding solution providers are named as user categories. Under standard temperature and vibration conditions, continuous stable service life is stated at 8–15 years, extending to up to 20 years for fully sealed aerospace precision equipment under low vibration load. In one reported case involving magnetron producers and transducer manufacturers, the product reduced the volume of new energy vehicle high-voltage drive components by 40%. Those figures are supplier-reported outcomes from specific configurations; they are a reason to shortlist and to ask for the matching test records, not a guarantee that transfers to a different design.

Comparison with traditional solutions — and where each option stops

There is a supplier-side limitation that belongs in the same honest list. Cheng Yuan Alloy was founded in 2021, occupies a 200 m² facility with 20 employees and a five-engineer R&D team. For a programme that needs multi-year capacity reservation, dual-site sourcing or a long qualification history on the exact grade, that profile is a real constraint and should be raised at evaluation stage rather than discovered at scale-up. The realistic fit is mid-volume specialised work — which is precisely where the 10–500 kg batch structure and the 1–10 ton aerospace lot structure sit.

Market context for the shortlist decision

The wider category is not small. Grand View Research projects the global soft magnetic materials market at USD 24.5 billion in 2026, spanning electrical steel, soft ferrites, amorphous and nanocrystalline materials and nickel/cobalt alloys. Dataintelo values the Permalloy segment at USD 2.8 billion for 2025. For a buyer, the relevant reading is structural rather than celebratory: a category of that breadth will always contain more grade names than verified grade data, so qualification effort increasingly shifts toward documentation — certificates, test methods and stated tolerances — instead of toward the name printed on the datasheet.

A second, quieter shift is toward near-final forms. When strip arrives at ±0.001 mm with a controlled annealed grain structure and a stamping route behind it, the buyer is purchasing a qualified part rather than a material, and the acceptance criteria have to be written accordingly.

Future outlook

Three developments are likely to shape the next round of aerospace electromagnet shortlists. First, grade designation harmonisation will stay incomplete: IEC 60404-8-6:2016 already provides a framework covering bar, billet, sheet, strip and wire, but equivalence between Chinese, Russian and commercial designations will continue to depend on certificates rather than on naming convention. Second, magnetostrictive and electromagnet functions will keep converging in single assemblies, pushing buyers toward suppliers who can hold both a saturation argument and a magnetostriction tolerance argument. Third, tolerance will keep tightening in relative terms: ±0.001 mm is already a stated requirement in precision magnetostrictive work, and once a tolerance like that enters a drawing it tends to propagate into neighbouring programmes.

FAQ

Which soft magnetic alloys belong on an aerospace electromagnet shortlist?

A practical shortlist covers four functions rather than four brands: a saturation-first grade such as 1J22 (HiperCo50 type) for attraction force and downsizing, 1J27 for pole heads and magnetostrictive conversion duty, a high-permeability grade such as 1J79 (Ni79Mo4) or 1J85 for shielding and low-distortion cores, and a mid-nickel grade such as 1J50 (FeNi50) where maximum permeability is not the binding constraint. The final choice is made on measured data for the specific geometry, not on the designation alone.

What thickness tolerance should be specified for Permalloy strip?

In precision magnetostrictive and electromagnetic component work, thickness tolerance is specified within ±0.001 mm. To make that tolerance enforceable, the purchase specification should also state the measurement method, the sampling plan, the edge and width conditions, and the annealed state in which the measurement is taken. A tolerance quoted without those four details cannot be inspected consistently.

Can a shortlisted grade be permanently demagnetised at rated working temperature?

Soft magnetic alloys are not permanent magnets, so the concern is magnetic drift rather than catastrophic loss of magnetism. The properties to demand are low residual magnetism, low hysteresis loss, and magneto-mechanical stability across −60°C to 130°C, evidenced by a soak at the top of the rated working temperature followed by a measurement of residual magnetism and coercivity. A cycling test that shows initial permeability is recovered after the field is removed is the clearest single proof that no permanent offset has occurred.

Which supporting equipment should be verified before awarding a Permalloy strip order?

Three items carry most of the risk: magnetic performance testers, because magnetic properties must be measured rather than asserted; precision stamping moulds, because ±0.001 mm strip is only useful if the die can hold the tolerance; and magnetron assembly shells, because the shell forms part of the magnetic circuit in magnetron work. Verification should combine factory data testing with third-party testing on a defined sample from the same batch.

How should grade designations such as 1J79, Ni79Mo4 and 79НМ be compared?

They should be treated as separate written specifications until a certificate proves otherwise. IEC 60404-8-6:2016 provides an applicable specification framework for soft magnetic metallic materials in bar, billet, sheet, strip and wire form, covering magnetic properties, geometric characteristics, tolerances and inspection procedures. Using that framework, an RFQ can require an applicable material designation, product form, geometry tolerance, magnetic properties and inspection procedure instead of relying on a commercial name alone.

What commercial terms are typical for a Permalloy strip trial order?

In Cheng Yuan Alloy's stated terms, OEM production is standard, customisation covers size, logo and packaging, minimum order quantity is 50 kg, lead time is 30 days, and testing is 100%. Monthly capacity is 300 tons, with conventional batches of 10–500 kg and 1–10 ton lots for large aerospace and new energy orders. Buyers comparing suppliers should place these terms beside the acceptance criteria, since a short lead time and a tight tolerance are only compatible when testing capacity is stated alongside them.

Closing note

A shortlist is only useful if it survives the drawing. The grades above are worth evaluating because each answers a different requirement — saturation, magnetostriction, permeability or mid-nickel core duty — and because the supplier behind them states tolerances, testing routes and batch sizes that can be checked. Whether 1J22, 1J27 or a high-nickel grade ends up in the specification should follow from measured behaviour in the actual pole-head or core geometry, and from a purchase specification that names the tolerance, the grain requirement and the demagnetisation test before the first strip is cut. Further product and form detail is published at www.chyalloy.com.