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Model No: Permalloy 50
ASTM A753 Permalloy 50 Alloy Bar
The Permalloy 50 supplied by Lork Group strictly complies with the GB/T 15018 standard and the corresponding ASTM A753 specification. It is accompanied by a comprehensive Certified Material Test Report (CMTR) that includes actual measured magnetic property data.
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Product Introduction
Permalloy 50 (Hy-Ra 49/50H, ASTM A753, UNS K94840) relies not on"hardness"to do its job, but on"softness"—specifically, the ease with which it can be magnetized and demagnetized. It is a crucial material for ensuring that signals remain intact and undiminished in weak magnetic field environments.
Who buys it?
- Engineers designing audio transformers who find that standard silicon steel sheets suffer from excessively high iron losses and severe overheating at frequencies above a few hundred hertz?
- Manufacturers of earth-leakage circuit breakers (ELCBs) who need a magnetic core capable of triggering a sensitive response at leakage currents of just a few milliamperes?
- Specialists building magnetic amplifiers who require stable magnetic gain within moderate magnetic fields?
- Suppliers of clock stators who need a core material that ensures reliable stepping action at microampere-level currents?
1J50 (Permalloy 50) is the material for these applications. With a nickel content precisely in the 49–51% range, it boasts the highest saturation magnetic flux density in the Permalloy family (approximately 1.5 T), offers magnetic permeability dozens of times higher than silicon steel, and features low iron losses.
If you are simply making a standard transformer core, silicon steel sheets will suffice. However, if you are working on precision magnetic circuits, signal coupling, or weak-current detection, Permalloy 50 is an essential choice.
Chemical Composition
The performance of Permalloy 50 relies fundamentally on precisely controlling the nickel content to between 49% and 51%; a deviation of even a single percentage point alters its magnetic properties.
Typical chemical composition supplied by Lork Group (compliant with GB standard 1J50 / ASTM A753)
Typical chemical composition supplied by Lork Group (compliant with GB standard 1J50 / ASTM A753)
| Material Type | C | P/S | Si | Ni | Mn | Cu | Fe |
|---|---|---|---|---|---|---|---|
| Content (%) | ≤ 0.03 | ≤ 0.020 | ≤ 0.15 - 0.30 | 49.5 - 50.5 | ≤ 0.30 - 0.60 | ≤ 0.20 | Balance |
Academic research—specifically studies published in IEEE journals—indicates that Permalloy 50 (~50Fe-50Ni) is widely used in electromagnetic components such as relays. While the addition of small amounts of chromium enhances corrosion resistance, it reduces saturation magnetization; specifically, the saturation magnetization drops by half for every 9 wt% of chromium added. Since the standard composition of Permalloy 50 does not include chromium, you should verify whether your operating environment requires a corrosion-resistant variant when sourcing the material.
Core Physical Properties
| Property | Typical Value | Notes |
|---|---|---|
| Electrical Resistivity | Approx. 45–60 μΩ·cm | Higher than pure iron; low eddy current loss. |
| Curie Temperature | Approx. 450–500°C | Loses magnetic properties above this temperature. |
| Tensile Strength | ~450–550 MPa | Soft state; good workability. |
| Elongation | ≥ 30% | Suitable for cold stamping, bending, and shearing. |
| Hardness | ~HV 150–200 | Depends on heat treatment and cold-working conditions. |
Key insight regarding magnetic properties:
The superior magnetic properties of Permalloy 50 are not inherent to the material itself but are"tuned"through heat treatment. Even with identical chemical composition, a difference of 50°C in heat treatment temperature or a twofold difference in cooling rate can result in a twofold difference in initial permeability. This is a critical pitfall that is easily overlooked during the procurement process.
The superior magnetic properties of Permalloy 50 are not inherent to the material itself but are"tuned"through heat treatment. Even with identical chemical composition, a difference of 50°C in heat treatment temperature or a twofold difference in cooling rate can result in a twofold difference in initial permeability. This is a critical pitfall that is easily overlooked during the procurement process.
Mechanical and Physical Properties
For Permalloy 50, tensile strength is not a concern (that is a consideration for structural steel); magnetic properties are what truly matter.
The following are the typical magnetic property specifications for 1J50 in various forms (in accordance with GB/T 15018):
The following are the typical magnetic property specifications for 1J50 in various forms (in accordance with GB/T 15018):
| Performance Indicators | Cold-rolled strip | Forged (or rolled) bar/plate | SWhat does this mean? |
|---|---|---|---|
| Initial Permeability (μ₀) | ≥ 3.8 mH/m | ≥ 3.1 mH/m | Magnetic permeability in weak magnetic fields—determines whether signals pass through smoothly. |
| Maximum Permeability (μₘ) | ≥ 62.5 mH/m | ≥ 31.3 mH/m | Permeability at the optimal operating point—representing peak efficiency. |
| Coercivity (Hc) | ≤ 9.6 A/m | ≤ 14.4 A/m | Lower is better. Represents the loss associated with the material's inability to fully demagnetize; lower values mean greater energy efficiency and higher sensitivity. |
| Saturation Magnetic Flux Density (Bs) | Approx. 1.5 T | Approx. 1.5 T | Permalloy 50's"trump card"—the highest in the Permalloy family. This means it can handle higher magnetic flux densities without reaching saturation. |
In other words, for the same magnetic flux, a transformer made of 1J50 is smaller in size, generates less heat, and has a lower no-load current. It is suitable for medium-to-high frequency transformers (400–8000 Hz) with a power rating of under 100 W.
Purchase advice: Choose according to your product type
The potential pitfalls with Permalloy 50 lie not in its chemical composition, but in the delivery condition and whether the heat treatment has been properly executed.
Scenario 1: You are manufacturing transformer or inductor cores (stamped laminations).
Recommended procurement form: Cold-rolled strip, 0.1–0.5 mm thick (selected based on operating frequency).
Recommended procurement form: Cold-rolled strip, 0.1–0.5 mm thick (selected based on operating frequency).
Why? The strip can be directly stamped into E/I laminations or toroidal cores. While the cold-rolled state already approximates the final magnetic properties, stamping introduces stress; stress-relief annealing (annealing at 800–900°C in a hydrogen atmosphere) is essential to restore magnetic permeability.
⚠️ Note: Without post-stamping heat treatment, the initial permeability may be only one-third of the standard value. Many purchasers mistakenly assume the material is"soft magnetic"right off the shelf, only to find the performance of the finished components is completely off-spec.
Scenario 2: You need to manufacture a magnetic shielding cover (a bent sheet metal part).
Recommended procurement form: Strip or sheet in the soft state (annealed).
Why? After bending or deep-drawing operations shape the component, a final stress-relief anneal is performed to restore magnetic shielding performance.
⚠️ Note: Magnetic performance requirements for shielding covers are lower than those for transformers, but stresses at bend points can locally reduce magnetic permeability. If shielding effectiveness is suboptimal, a low-temperature anneal at 400–500°C can partially restore performance.
Scenario 3: You need to manufacture precision instrument transformer cores (toroidal/rectangular).
Recommended procurement format: Finished cores (stamped, wound, and heat-treated to achieve final magnetic properties).
Why? Toroidal cores require whole-unit heat treatment after winding; performing this step in-house carries significant risks (related to furnace temperature uniformity and atmosphere control). Cores supplied by professional manufacturers have already undergone magnetic property testing, so you only need to handle coil winding and assembly.
⚠️ Note: When purchasing finished cores, you must insist on receiving actual measured magnetic property data for that specific batch (μ₀, Hc, Bs), rather than just"standard values."
Scenario 4: You need to manufacture stator laminations for clocks/watches or magnetic circuit components for relays.
Recommended procurement format: Cold-rolled strip (with stress-relief annealing performed in-house after stamping) or finished fine-blanked parts.
Why? These parts require high dimensional precision (±0.01 mm); Lork Group offers precision blanking services, saving you the trouble of commissioning your own tooling.
A point easily overlooked:
The magnetic properties of Permalloy 50 must be restored after processing. Operations such as stamping, bending, or turning introduce stress both on the surface and within the material; this stress"pins"magnetic domain walls, causing magnetic permeability to plummet. Stress-relief annealing is not optional—it is mandatory.
Testing and Delivery: How Lork Group Ensures Quality
The"certificate"of Permalloy 50 does not just look at the chemical composition - the magnetic performance data is the core.
Lork Group’s standard testing items:
Lork Group’s standard testing items:
1. Chemical composition (PMI): Spectral analysis of each batch. The nickel content must be 49.5-50.5% - this is the basis of magnetic properties.
2. Magnetic performance test (according to GB/T 15018/ASTM A773):
Initial magnetic permeability (μ₀) measured value
Maximum magnetic permeability (μₘ) measured value
Coercive force (Hc) measured value
Saturation magnetic induction intensity (Bs) measured value
Produce a complete hysteresis loop curve - this is hard evidence to judge whether the material is"real"
Initial magnetic permeability (μ₀) measured value
Maximum magnetic permeability (μₘ) measured value
Coercive force (Hc) measured value
Saturation magnetic induction intensity (Bs) measured value
Produce a complete hysteresis loop curve - this is hard evidence to judge whether the material is"real"
3. Size and appearance:
Strip: Thickness tolerance ±0.005-0.01mm (depending on specifications), width tolerance ±0.1mm
Rod: Diameter tolerance h6/h7/h8
Surface: No oxidation, no scratches, no folds
Strip: Thickness tolerance ±0.005-0.01mm (depending on specifications), width tolerance ±0.1mm
Rod: Diameter tolerance h6/h7/h8
Surface: No oxidation, no scratches, no folds
4. Grain size rating (according to ASTM E112): Required ≥5 levels. The fine-grained structure is beneficial to low coercivity and high magnetic permeability.
5.Heat treatment process records (if required): If the customer purchases products that have been heat treated to final magnetic properties, we provide the heat treatment temperature curve and atmosphere records of the batch.
Contact the Lork Group Technical Team
The price of Permalloy 50 is directly influenced by the price of nickel (LME); given its 50% nickel content, costs track nickel market fluctuations. Lork Group quotes are valid for 7 days.
Reference Price Range (2024 Market Rates):
Cold-rolled strip (thickness 0.1–0.5 mm): Approx. 330–680 CNY/kg (depending on thickness and precision)
Bars/Plates: Approx. 90–170 CNY/kg
Finished cores: Quoted individually based on specifications
⚠️ Important Notes:
Prices for ultra-thin strip (thickness ≤0.1 mm) are more than double the standard rate due to rolling difficulties and lower yields.
Products that have undergone magnetic heat treatment are 15–25% more expensive than those in the"as-rolled"(untreated) state.
Lead Time Reference:
Standard stock items: 3–7 working days
Custom thickness/width: 2–3 weeks
Finished cores (customized to drawings): 3–4 weeks
🔧 Lork Group Technical Q&A
"We purchased 1J50 strip from another supplier, stamped it into E-laminations to assemble a transformer core, and—without any heat treatment—wound a coil and tested it. The initial permeability was only 2,000, which is less than half the standard value (3,800). The supplier claims the 'material is fine' and that our processing method is at fault. Where exactly is the problem?"
"We purchased 1J50 strip from another supplier, stamped it into E-laminations to assemble a transformer core, and—without any heat treatment—wound a coil and tested it. The initial permeability was only 2,000, which is less than half the standard value (3,800). The supplier claims the 'material is fine' and that our processing method is at fault. Where exactly is the problem?"
Email: [daisy@lorkgroup.com]
WeChat/WhatsApp: [+ 86 175 1308 1871]
WeChat/WhatsApp: [+ 86 175 1308 1871]
