CRGO lamination standards you’ll see on orders (IEC / ASTM / JIS overview)

1. Why the standard name shows up in your lamination PO

On transformer drawings from 15+ years ago you see “M4, 0.27 mm”. On today’s RFQs you see:

CRGO laminations, IEC 60404-8-7 grade M100-23P, 0.23 mm, C-5 coating

or

ASTM A876 grade 23P090, laser-scribed, 0.23 mm

or a JIS-style:

JIS C 2553 23P090, 0.23×80 mm, step-lap

Same physics. Different committee stamps.

The standards are doing three jobs at once:

• Locking in how the mill measures loss and flux density.
• Encoding thickness and loss level into short grade codes.
• Giving purchasing and QA a legal reference when something is off.

Everything below is about reading those codes fast, and specifying lamination stacks so that suppliers in different regions still land on the same steel.

2. IEC 60404-8-7 in practice: what your lamination vendor is really promising

IEC 60404-8-7 is the current reference for cold-rolled grain-oriented electrical steel strip and sheet in fully processed condition, with nominal thicknesses like 0.20 / 0.23 / 0.27 / 0.30 / 0.35 mm.

You already know that from the standard. What matters for lamination stacks is how it leaks into the datasheet and then into your PO line.

Typical IEC-style grade:

M100-23P5

Rough mental decoding (mill conventions differ):

• 23 → thickness 0.23 mm (×100).
• 100 → core loss at 1.7 T, 50 Hz ≈ 1.00 W/kg (×100).
• The suffix (here P5) → family / permeability / sometimes frequency family.

So when a lamination spec says:

“CRGO laminations, IEC 60404-8-7, grade M100-23P or better”

it’s really saying:

• 0.23 mm nominal thickness
• ≤ ~1.00 W/kg at 1.7 T / 50 Hz
• Fully processed GO steel, tested to IEC methods

Designers usually start from the loss number and induction. Purchasing tends to start from the thickness and the standard name. Both are in that single token.

On the lamination drawing, the IEC name is not enough. You still need:

• Thickness tolerance and delivery range
• Coating type (tied back to IEC 60404-1-1 surface insulation classes)
• Whether core loss guarantees are “as sheared” or “after stress-relief anneal”
• Lamination factor assumption used in stack height

Without those, “M100-23P” is only half a spec.

3. ASTM A876: the North-American habit that sneaks into global RFQs

ASTM A876 covers flat-rolled, grain-oriented, fully processed low-carbon silicon-iron electrical steel for transformer cores.

Two quirks:

1. Loss reference: grades are based on core loss in W/lb at 1.7 T, 60 Hz.
2. Grade naming: 23P060, 23P090, etc.

A876-style decoding:

• First two digits → nominal thickness in hundredths of mm
  • 23 ≈ 0.23 mm
• The last three digits → reference loss value ×100 in W/lb at 1.7 T, 60 Hz
  • 060 ≈ 0.60 W/lb
• Letter in the middle → family (regular, high-permeability, laser-scribed, etc.)

So:

ASTM A876 grade 23P090

says “0.23 mm GO steel, max core loss around 0.90 W/lb at 1.7 T, 60 Hz, high-permeability family”.

When you compare that to an IEC spec based on W/kg at 50 Hz, you know the usual drill:

• Convert lb → kg
• Convert 60 Hz values to 50 Hz (or vice versa) using the mill’s ratio or ASTM A677 guidance

On paper this all looks neat. In practice, RFQs often say something imprecise like:

“CRGO laminations as per ASTM A876”

which is like ordering “beer as per German purity law”. The family is clear. The strength is not.

4. JIS C 2553: the 23P090-style codes you keep seeing

JIS C 2553 defines cold-rolled grain-oriented electrical steel strip and sheet with insulation coating on both sides, in nominal thicknesses 0.23 / 0.27 / 0.30 / 0.35 mm.

A common JIS-style code:

23P090

Typical pattern:

• 23 → nominal thickness 0.23 mm
• 090 → max specific core loss 0.90 W/kg at 1.7 T, 50 Hz (notation P1.7/50)

This mirrors the logic in IEC and ASTM. The code is just aligned with Japanese practice and JIS measurement methods like JIS C 2550.

So in JIS language:

• “23P100” → 0.23 mm, ≤ 1.00 W/kg at 1.7 T, 50 Hz
• “27P110” → 0.27 mm, ≤ 1.10 W/kg at 1.7 T, 50 Hz

Cross-reference databases show that a single physical steel like M100-23P can appear as IEC, JIS and ASTM designations simultaneously (e.g. IEC 60404-8-7 grade M100-23P5, JIS 23P100, ASTM A876 grade 23P060 for roughly equivalent material families).

That’s what your lamination supplier is really juggling when they say “same steel, different name”.

5. One table, three worlds: typical CRGO grade cross-references

This table is illustrative, not a purchasing spec. Always check the mill datasheet.

¹ Example based on cross-reference where one EN/IEC grade M100-23P links to JIS 23P100 and ASTM A876 23P060; exact mapping shifts by producer and generation.

Use the table like this:

• Start from your design assumption (loss at B and frequency, plus thickness).
• Pick one family: IEC / JIS / ASTM.
• Use cross-reference tables only as a sanity check, not as a contract.

6. What purchasing actually needs to lock down on the RFQ

Most lamination problems start in purchasing, not in Maxwell’s equations.

When you send out an RFQ for CRGO lamination stacks, and the drawing just says “M4, 0.27 mm”, suppliers will fill in gaps based on their stock and comfort, not yours.

Bare minimum, per stack size:

1. Standard + grade + thickness
   • IEC: “IEC 60404-8-7, grade M100-23P, 0.23 mm”
   • JIS: “JIS C 2553, grade 23P100, 0.23 mm”
   • ASTM: “ASTM A876, grade 23P070, 0.23 mm”
2. Loss guarantee with conditions
   • “P1.7/50 ≤ 1.00 W/kg, measured by SST per IEC 60404-3, after stress-relief anneal at xxx °C for yy h”
3. Flux density guarantee (optional, but very useful)
   • “B8 ≥ 1.88 T” or “B50 ≥ [value] T” at defined field intensities, aligned to IEC/JIS test methods.
4. Coating and insulation
   • “Surface insulation class C-5 equivalent as per IEC 60404-1-1; minimum interlaminar resistance [value] Ω·cm²”
5. Stack-specific geometry
   • Lamination factor assumption (e.g. ≥ 0.96 at 50 psi, reference per mill spec)
   • Burr height limit
   • Max camber per length
   • Step-lap pattern and allowed tolerance on step length

If these items don’t exist in the RFQ, they will exist later in the NCR.

7. Engineering notes on lamination stacks that standards mostly ignore

The three standards care about strip and sheet. Your transformer cares about stacks.

Some details live outside IEC / ASTM / JIS text, yet change real-world performance:

1. Lamination factor vs. modelStandards and mill catalogues routinely show lamination factor values in the mid-90s % range, depending on thickness and coating. If your CAD model quietly assumes 100 %, you’ll either:
   • miss flux (undersized core) ormiss window (stack too tall)
   Both look like “magnetizing current is higher than expected” during FAT.
2. Burr and residual stressStandards talk about core loss on neat samples; your laminations are punched, sheared, maybe laser cut.
   • Higher burr → higher inter-laminar contact area → more eddy current paths.Heavy punching → more residual stress → worse loss and permeability unless annealed.
   On orders, burr limits and “as sheared vs annealed” conditions matter more than the logo on the mill’s datasheet.
3. Step-lap execution vs. drawingNothing in IEC 60404-8-7 explains how well the step-lap must be aligned on a stacked core. Yet your no-load loss and noise are very sensitive to it.Engineers will say “same steel, different core shop, different watts”.That’s not the steel’s fault. That’s stack repeatability, clamping pressure, corner fit, and orientation tracking.
4. Orientation markingAll three standards assume rolling direction is known. In the lamination shop, that ends up as paint marks, tags, or etched arrows.When a stack is rebuilt in the field and pieces are flipped, standards don’t help you. Clear marking on each lamination does.

8. Simple spec patterns you can reuse

A few short templates for lamination stacks. You adjust numbers to your design.

Example A — IEC-centric spec for a power transformer core

Material: Cold-rolled grain-oriented electrical steel, fully processed, as per IEC 60404-8-7. Grade: M090-23P or better. Thickness: 0.23 mm nominal; tolerance per mill datasheet, max deviation ±0.02 mm. Magnetic properties (after stress-relief anneal at 800 °C, 2 h, neutral atmosphere): – P1.7/50 ≤ 0.90 W/kg (SST per IEC 60404-3) – B8 ≥ 1.88 T Surface insulation: Equivalent to IEC 60404-1-1 class C-5; interlaminar resistance ≥ [value] Ω·cm². Lamination factor: ≥ 0.96 at 50 psi, verified per supplier method. Geometry and fabrication: – Step-lap configuration as per drawing xxx – Burr height ≤ 0.02 mm – Max camber [value] mm per 2 m – All laminations punched / cut with rolling direction labelled and kept consistent in stacking.

Example B — Cross-region spec that allows IEC / JIS / ASTM

Accepted standards: IEC 60404-8-7, JIS C 2553, ASTM A876. Target material class: – IEC: M100-23P (0.23 mm, P1.7/50 ≈ 1.00 W/kg) or better – JIS: 23P100 or better – ASTM: 23P070 or better (convert to W/kg at 50 Hz for verification) Supplier shall declare the exact grade code and standard on the inspection certificate, plus: – measured P1.7/50 and P1.5/50 – test frequency and method – measured lamination factor and coating type

This kind of spec lets you source from Europe, Japan or North America without rewriting the drawing every time, while keeping the physics aligned.

9. Key takeaways for your next lamination order

• IEC 60404-8-7, ASTM A876 and JIS C 2553 all encode the same story: thickness, loss at a defined B and f, and processing condition. The codes are short; the implied assumptions are big.
• Grade labels like M3 / M4 are only rough landmarks. They came from older AISI / ANSI conventions and still show up in colloquial speech, but actual GOES datasheets now anchor around precise P1.7/50 numbers and thickness bands
• For lamination stacks, the standard name is not enough. You also need loss conditions, coating class, lamination factor, burr limits and annealing assumptions. Those are usually outside the core standard text, buried in mill brochures and handling guides.
• Cross-region sourcing is safe if you write the spec in numbers, not slogans. If the drawing says “P1.7/50 ≤ X W/kg, thickness Y, lamination factor ≥ Z”, your supplier can map that to IEC / JIS / ASTM grade codes unambiguously, backed by cross-reference tables.
• The lamination stack is where standards meet reality. Magnetic performance that looks identical on strip test can diverge once you add burr, clamping, step-lap alignment and annealing history. So the lamination PO should talk about stacks and process, not just coils and committees.

If your next RFQ for CRGO lamination stacks makes an engineer, a buyer, and a mill all reach the same interpretation without a follow-up call, the spec is probably in good shape.