Permalloy 80 (Hi-mu 80 / Alloy 80 / 1J85) Procurement Guide: How to Specify and Verify Ultra-High Permeability Strip

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Permalloy 80 is not a material you can specify by dimensions alone. Two strips with identical thickness and width can differ by an order of magnitude in initial permeability, depending on annealing atmosphere, impurity control, and final heat treatment. This guide explains what to put in your technical agreement, what to verify before accepting a shipment, and where the common procurement failures occur.

Why  "Permalloy 80"  Alone Is Not a Specification

The designation "Permalloy 80"  or  "1J85" describes a composition family: approximately 80% nickel, 4.8–5.2% molybdenum, balance iron. It does not describe magnetic performance.

Two suppliers can both deliver "1J85 strip"  to GB/T 15018, and one may have an initial permeability of 80,000 while the other measures 40,000. The difference is not fraud—it is the reality that final magnetic properties are determined by the annealing process, not by the mill certificate’s chemistry alone. Hydrogen or vacuum annealing temperature, holding time, cooling rate, and impurity level (especially carbon and sulfur) all shift the B-H curve.

Procurement implication: Your purchase order must specify magnetic parameters, not just the grade name. The table in Section 3 shows what to write.

The Three Failure Modes in Permalloy 80 Procurement

Failure mode 1: Correct chemistry, wrong annealing.
The supplier delivers strip with the right Ni/Mo content but anneals in a non-optimal atmosphere or at the wrong temperature. Initial permeability falls below 80,000, coercivity rises above 1.5 A/m, and your sensor or transformer core fails final inspection. This is the most common failure and cannot be detected by chemistry alone.

Failure mode 2: Insulation coating omitted or inconsistent.
For laminated cores, interlamination resistance matters as much as permeability. If the phosphate or MgO coating is missing, uneven, or too thin, eddy current losses rise and the core overheats at high frequency. Your PO must specify coating type and target surface resistance.

Failure mode 3: Dimensional tolerance ignored in favor of “magnetic grade”.
A strip with excellent permeability but ±0.01 mm thickness variation will produce inconsistent lamination factors and air gaps in the assembled core. For high-frequency toroids and stacked laminations, thickness tolerance of ±0.002 mm is not optional—it is part of the magnetic specification.

What to Put in Your Technical Agreement

The following table converts the material’s key properties into procurement language. Use it as a checklist when drafting the technical agreement with your supplier.

Supplier Verification: What to Ask Before Ordering

Ask for a sample with a full magnetic test report.
A supplier confident in their annealing process will provide a toroidal sample test report showing μi, Hc, and the B-H curve—not just a chemistry certificate. If they cannot provide this, the risk of batch-to-batch variation is high.

Ask about annealing furnace capability.
The final magnetic properties are set by the annealing furnace. Suppliers using hydrogen atmosphere furnaces with precise temperature uniformity (±5°C or better) and controlled cooling rates will produce more consistent results than those using vacuum furnaces without adequate cooling control. This is a legitimate technical question, not a trade secret.

Ask whether the test report is from the actual production batch or a “typical” value.
Some suppliers provide a “typical” datasheet that does not correspond to the shipped lot. Require batch-specific test data, with the heat number traceable to the delivered coil.

Ask about coating consistency.
If you are buying coated strip for laminated cores, ask for interlamination resistance data or a cross-section photo showing coating thickness uniformity. A coating that is present but uneven is worse than no coating at all, because it creates local hot spots.

Incoming Inspection: What to Check When the Shipment Arrives

For first articles or new suppliers: Do not skip the toroidal sample test. A chemistry certificate alone cannot confirm that the annealing was performed correctly.

When to Consider Alternatives

Permalloy 80 is the right choice when you need maximum initial permeability in weak fields and can accept relatively low saturation induction (~0.75–0.8 T).

Consider 1J79 (without molybdenum) if: Cost is the primary driver and magnetostriction is not critical. 1J79 has slightly lower permeability and higher magnetostriction but is more widely available.

Consider silicon steel or amorphous alloys if: Your application requires high saturation induction (>1.5 T) or operates at higher power levels where core loss dominates over weak-signal sensitivity.

Consider nanocrystalline alloys if: You need high permeability combined with higher saturation induction and better high-frequency stability, and the cost premium is justified.

Request a Technical Consultation

To receive a material recommendation and a quotation with batch-specific magnetic test data, please provide:

1. Application: Sensor, transformer, shielding, or magnetic head

2. Required magnetic parameters: μi, Hc, and operating frequency

3. Dimensions: Thickness, width, and length or coil weight

4. Surface requirement: Bare or insulated (specify coating type if known)

5. Quantity (kg or meters)

6. Certification: EN 10204 3.1 with batch-specific B-H curve data

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