Key Takeaways
- Four major standards name the same electrical steel differently: GB/T 2521 (China), JIS C 2552/2553 (Japan), EN 10106/10107 (Europe), and AISI M-series (United States) — and none of them use the same code structure.
- Every naming system encodes the same two facts — thickness and core loss — just in a different order and format. Once you know the pattern, any grade code becomes readable.
- Real example: Chinese grade 50W400, Japanese grade 50A400, and European grade M400-50A refer to the same non-oriented electrical steel — same thickness class, same core loss ceiling, different label.
- “Equivalent” grades can still differ in test condition (P1.5/50 vs. P1.7/50), thickness tolerance, or coating class — matching grade names isn’t the same as matching mill test certificates.
- Zhongxin Special Steel maintains a verified cross-reference table spanning GB, JIS, EN, and AISI M-series across nine major mills, built specifically so buyers don’t have to guess at equivalence.
Why the Same Steel Has Four Different Names
Electrical steel grade equivalents are cross-reference codes that let a buyer match a Chinese GB/T 2521 grade to its closest Japanese JIS, European EN, or American AISI counterpart, based on matching thickness and core loss values. They exist because four regions developed electrical steel standards independently, decades apart, and never converged on one naming format.
That’s the part worth sitting with for a second. This isn’t four countries labeling the same thing four different ways for no reason — GB/T 2521 came out of China’s own steel industry standardization process, JIS C 2552/2553 out of Japan’s, EN 10106/10107 out of the European steel industry’s harmonization, and the AISI M-series out of an American classification system that predates most of the others. Each one specifies its own reference test conditions, and those conditions don’t always match exactly, even when two grades are commonly treated as interchangeable.
For a buyer, this shows up as a very specific headache: your engineering team’s spec sheet says “M400-50A,” your only quote is for “50W400,” and nobody in the email thread can tell you with confidence whether those are actually the same steel or just close enough to be risky.
They’re usually the same steel. But “usually” isn’t a word that belongs in a purchase order, which is why this guide exists.
A Brief History: Why These Standards Never Merged
Worth understanding why nobody ever fixed this, because it explains why a universal grade code still doesn’t exist. Japan’s electrical steel standard (the predecessor to today’s JIS C 2552/2553) and America’s AISI classification both trace back to domestic steel industries that matured in relative isolation in the mid-20th century, each building test infrastructure and grading conventions around their own mills’ output. Europe’s EN 10106/10107 came later, as part of a broader post-war push to harmonize steel standards across European Union member states — but it harmonized within Europe, not with Japan or the US.
China’s GB/T 2521 is the youngest of the four, developed as the country’s domestic electrical steel industry scaled up production in the late 20th century. By the time China’s steel output reached a scale where standard harmonization with Japan, Europe, or the US might have made commercial sense, three incompatible systems were already deeply embedded in each region’s supply chains, procurement software, and engineering specifications. Replacing any of them industry-wide would have meant re-qualifying decades of existing designs — nobody had the incentive to go first.
The practical result: international buyers inherited four parallel systems instead of one, and cross-reference tables became the industry’s workaround rather than a permanent fix.
How to Decode Each Standard’s Naming System
Every one of these four systems encodes the same two numbers — thickness and core loss — just in a different position and format. Once you see the pattern, you can read any grade code without a lookup table.
GB/T 2521 (China). Format: [thickness in hundredths of mm][W or Q][core loss × 100]. 50W400 breaks down as 0.50mm thickness, “W” for non-oriented (无取向), and a core loss ceiling of 4.00 W/kg under the standard’s reference test condition. 23QG090 is 0.23mm, “QG” for Hi-B grain-oriented, and 0.90 W/kg core loss.
JIS C 2552 / C 2553 (Japan). Format: [thickness in hundredths of mm][A, P, or Z][core loss × 100]. Non-oriented grades use “A”; grain-oriented use “P” (conventional) or “Z” (Hi-B). 50A400 is 0.50mm non-oriented steel at 4.00 W/kg core loss — structurally the same code logic as GB, different letter convention.
EN 10106 / EN 10107 (Europe). Format: M[core loss × 100]-[thickness in hundredths of mm][letter]. Notice the order flips — core loss comes first. M400-50A is 4.00 W/kg core loss, 0.50mm thickness, “A” indicating non-oriented. M90-23P is 0.90 W/kg core loss, 0.23mm, grain-oriented.
AISI M-series (United States). The oldest and least granular system — grades like M2 through M6 for grain-oriented and M15 through M47 for non-oriented steel, numbered roughly in order of increasing core loss rather than encoding exact values in the code itself. This is the system where a lookup table matters most, because the number alone doesn’t tell you the core loss figure the way GB, JIS, and EN codes do.
A worked example ties this together. Say your spec sheet lists “M4” and your supplier only quotes GB grades. M4 sits in AISI’s mid-range grain-oriented band — cross-referencing against a GB/JIS/EN table puts it in roughly the same core-loss class as GB’s 27Q120 or JIS’s 27P120 family, all in the 0.27mm thickness class. That’s your starting point for a quote request — not the final word, since (as the next two sections cover) you still need to confirm the coating and test condition match.
Coating Suffixes: The Part Most Grade Charts Leave Off
Grade codes describe the base steel. They don’t describe what’s on the surface of it — and that’s usually appended as a separate suffix that’s easy to miss if you’re only scanning for the thickness and core loss numbers.
Insulation coating classes run roughly from C-2 through C-6 in the common international shorthand, moving from thin inorganic coatings suited to standard stamping applications up through thicker, higher-resistance coatings used where interlaminar insulation matters more — high-efficiency motor cores, for example. A grade quoted as “50W470-C5” is telling you two separate things at once: the base steel (50W470) and the coating class (C5). Drop a supplier’s coating suffix from your comparison and you can end up matching the steel correctly while still receiving a coil that doesn’t meet your stacking factor or dielectric requirement.
This is worth checking explicitly on every quote, because coating class doesn’t always show up prominently on a supplier’s marketing material the way thickness and core loss do — it’s the kind of detail that lives on the mill test certificate rather than the product page.
Real Cross-Reference Examples: GB, JIS, and EN Side by Side
Here’s what that decoding looks like applied to three real, verified equivalent groups.
| GB/T 2521 (China) | JIS C 2552/2553 (Japan) | EN 10106/10107 (Europe) | Type | Thickness | Core Loss Ceiling |
|---|---|---|---|---|---|
| 50W400 | 50A400 | M400-50A | Non-oriented | 0.50mm | P1.5/50 ≤ 4.00 W/kg |
| 50W470 | 50A470 | M470-50A | Non-oriented | 0.50mm | P1.5/50 ≤ 4.70 W/kg |
| 23QG090 | 23ZH90 | M90-23P | Grain-oriented, Hi-B | 0.23mm | P1.7/50 ≤ 0.90 W/kg |
Read across any row and you’re looking at the same underlying steel, described three ways. The GB and JIS codes for the non-oriented grades are almost mirror images of each other — same digits, different letter. The EN code just reorders the same two numbers with the core loss figure moved to the front.
This is a small slice of a much larger table. Zhongxin maintains a full cross-reference spanning nine major mills — Baosteel, WISCO, Nippon Steel, JFE, Cogent, ThyssenKrupp, POSCO, NLMK, and AK Steel — across the common thickness range for both CRGO and CRNGO. The complete version lives on our grade equivalents reference page, alongside the underlying grade and standards summary.
Why “Equivalent” Doesn’t Always Mean Identical
Here’s the caveat that gets skipped in most grade equivalency charts, including some of ours until a buyer’s engineer pointed it out directly: matching grade codes is a strong signal, not a guarantee.
Three things can differ even between “equivalent” grades:
- Test condition. Core loss figures are only comparable if they’re measured under the same magnetic induction and frequency reference — commonly P1.5/50 (1.5 Tesla, 50Hz) for non-oriented steel or P1.7/50 for grain-oriented. A grade tested at a different reference condition can look better or worse on paper than it actually performs in your application.
- Thickness tolerance. Two standards might both call a grade “0.50mm,” but their allowable tolerance bands aren’t always identical. For tight-tolerance winding equipment, that difference matters more than the headline thickness number.
- Coating class. Grade codes describe the base steel, not the surface coating. Two “equivalent” coils can carry different insulation coating classes (C-3 vs. C-5, for example), which changes stacking factor and interlaminar resistance independent of the steel grade itself.
None of this means the equivalency tables are wrong. It means they’re a starting point for a conversation with your supplier’s technical team, not a substitute for one.
How to Verify True Equivalence Before You Order
- Match the test condition, not just the number. Confirm both grades were tested at the same reference frequency and induction before comparing core loss figures directly.
- Request the mill test certificate, not the grade code alone. A mill test certificate reports actual measured values for your specific coil — core loss, magnetic induction, thickness tolerance — rather than the nominal grade ceiling.
- Confirm the coating class separately. Ask specifically which coating class ships with the grade you’re quoting; don’t assume it matches your previous supplier’s default.
- Run a small trial order before switching suppliers on a critical application. Especially true when substituting a Chinese-sourced grade for a European or Japanese one your design was originally qualified against — verify stacking and lamination behavior on your own equipment first.
- Ask for CNAS-accredited or equivalent third-party test data. Self-reported figures and third-party-accredited figures both exist in this industry; know which one you’re looking at. Zhongxin’s in-house testing runs through its own CNAS-accredited laboratory, which is worth confirming with any supplier you’re evaluating.
None of these five steps take long individually — a mill test certificate request is a same-day email, and a coating class confirmation is a one-line question on a quote form. The reason buyers skip them isn’t effort, it’s that a matching grade code feels like confirmation enough. It looks precise. It has a standard number attached to it. That’s exactly why it’s worth the extra step: a grade code match is the first filter, not the last one, and treating it as final is how a design that was qualified against one standard’s test data ends up running on steel that was only ever verified against a different one.
Applications: Matching Grade Class to Your End Product
Grade class isn’t just a naming exercise — it’s the first filter that narrows a wide catalog down to the handful of grades actually worth quoting for your application.
- Power and distribution transformers typically specify grain-oriented grades in the 0.23mm–0.30mm thickness range, favoring Hi-B (domain-refined) variants when the design targets the lowest achievable core loss, and conventional grain-oriented grades when cost per ton matters more than the last increment of efficiency. See grain-oriented silicon steel for the full grade list, or the power transformer and distribution transformer application pages for grade-to-use-case pairings.
- Motors, generators, and general rotating equipment specify non-oriented grades, usually in the 0.35mm–0.65mm range, where isotropic magnetic behavior matters more than directional core loss performance. See non-oriented silicon steel for the standard thickness and grade breakdown.
- High-frequency applications, including EV traction motors, push toward thinner grain-oriented gauges below 0.20mm, where fewer published cross-standard equivalency tables exist at all, and OEM-specific specs become more common than standard grade codes. Buyers sourcing at this gauge should expect to work from actual test data rather than a grade-code lookup, since the equivalency conventions covered in this guide get thinner (in both senses) below the 0.20mm mark.
If your spec sheet references a grade code from a standard your usual supplier doesn’t quote in, that’s exactly the situation this equivalency framework is built to resolve — decode the code, find the closest matching GB grade, and verify against a real mill test certificate before committing to volume.
FAQ
Is GB 50W400 the same as European M400-50A?
They reference the same thickness (0.50mm) and the same core loss ceiling (4.00 W/kg) under matching test conditions, which is what “equivalent” means in a grade cross-reference table. Whether they’re identical for your specific application depends on confirming the same test condition, thickness tolerance, and coating class — the grade code match is a strong starting signal, not a final confirmation.
Why doesn’t the AISI M-series list exact core loss values like GB or JIS codes do?
The AISI M-series predates the more granular encoding used by GB, JIS, and EN systems, and numbers grades roughly in order of increasing core loss rather than embedding the exact figure in the code. A lookup table against GB or JIS grades is the fastest way to get the actual core loss ceiling for a given M-series grade.
Can I substitute a Chinese GB grade for a European EN grade my design was originally qualified against?
Often yes, once you’ve confirmed matching test conditions, thickness tolerance, and coating class — but for a critical application, run a small trial order first rather than substituting directly into full production, especially the first time you switch standards.
What’s the difference between P1.5/50 and P1.7/50 core loss ratings?
These denote the reference test condition the core loss figure was measured under — 1.5 Tesla or 1.7 Tesla magnetic induction at 50Hz. Non-oriented steel is typically rated at P1.5/50; grain-oriented steel at P1.7/50. Comparing a P1.5/50 figure to a P1.7/50 figure directly will give you a misleading result, since a higher induction test condition produces a higher core loss number for the same steel.
Where can I find a full grade cross-reference table instead of individual examples?
Zhongxin’s grade equivalents page maintains a verified cross-reference across GB, JIS, EN, and AISI M-series spanning nine major mills, for both grain-oriented and non-oriented product lines.
Does a higher AISI M-number mean better or worse steel?
Higher M-numbers generally indicate higher core loss within the same grade family — M2 sits at the lower-loss end of the grain-oriented range, while grades further up the numbering carry higher core loss ceilings. Because the M-series doesn’t encode the exact figure the way GB or JIS codes do, always confirm the actual core loss value against a cross-reference table rather than assuming the number alone tells you where a grade ranks.
Do coating classes count as part of grade equivalency?
No — coating class (commonly C-2 through C-6) is specified separately from the base steel grade and describes the insulation coating applied to the surface, not the steel itself. Two coils can carry matching grade codes and still differ in coating class, which affects stacking factor and interlaminar resistance independently of the steel’s magnetic properties.
Working from a spec sheet in a standard your usual supplier doesn’t quote in? Contact Zhongxin Special Steel with the grade code you have, and we’ll confirm the matching GB grade against actual mill test data before you commit to an order.
