EN 10346 — Continuously hot-dip coated steel flat products for cold forming. Technical delivery conditions
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Scope
Hot-dip zinc (+Z), zinc-iron (+ZF), zinc-aluminium (+ZA), aluminium-zinc (+AZ), aluminium-silicon (+AS) and zinc-magnesium (+ZM) coated sheet and strip: forming grades DX51D–DX57D, structural grades S220GD–S550GD, HSLA HX grades, and multiphase steels. Specifies base chemistry, mechanical properties, coating masses (Z100–Z600, ZM70–ZM310…), surface qualities A/B/C, finishes and tests (T-bend, adhesion).
Grades covered by EN 10346
| Grade | No. | Type | C % | Yield MPa | Tensile MPa | Nearest equivalents |
|---|---|---|---|---|---|---|
| DX51D | 1.0226 | Hot-dip coated low-carbon steel for bending and profiling | ≤ 0.18 | — (no minimum; typ. 200–320) | 270–500 | CS Type B (A653), SGCC, DX51D+Z |
| DX52D | 1.0350 | Hot-dip coated low-carbon steel for drawing | ≤ 0.12 | 140–300 | 270–420 | dx51d, sphc, s250gd |
| S250GD | 1.0242 | Hot-dip coated structural steel, guaranteed 250 MPa yield | ≤ 0.2 | 250 | 330 | SS Grade 37 (A653), SGC340, S250GD+Z |
| S280GD | 1.0244 | Hot-dip coated structural steel, guaranteed 280 MPa yield — the purlin grade | ≤ 0.2 | 280 | 360 | SS Grade 40 (A653), SGC400, S280GD+Z |
| S350GD | 1.0529 | Hot-dip coated structural steel, guaranteed 350 MPa yield — deck and long-span profiles | ≤ 0.2 | 350 | 420 | SS Grade 50 (A653), SGC440, S350GD+Z |
Revision history and superseded standards
| Year | Change |
|---|---|
| 2009 | EN 10346:2009 — merged EN 10326 and EN 10327 |
| 2015 | EN 10346:2015 — current; ZM coatings and new grades added |
Supersedes: EN 10142 (zinc); EN 10147 (structural zinc); EN 10214 (ZA); EN 10215 (AZ); EN 10292 (HSLA); EN 10327/10326 (2004); DIN 17162 (St02Z…).
Where to buy the standard
The full text is copyrighted by CEN and is not reproduced here. Purchase the current edition from CEN or your national standards body. The values on this site are the normative limits as published; the standard's own tables, notes and test methods govern.
Related standards
Two grade families under one standard
EN 10346 covers continuously hot-dip coated steel strip, and it carries two quite different sets of grades that are easy to confuse.
The DX grades — DX51D, DX52D, DX53D, DX54D — are forming grades. They are specified by how far the material will bend, draw and roll-form without cracking, and the standard deliberately guarantees no yield strength for them: a forming grade with a strength floor would have to be rejected for being too soft, which is the opposite of what the buyer wants.
The S grades — S220GD to S350GD and beyond — are structural. The number is the minimum yield in MPa and GD marks continuous hot-dip coating. Purlins, cable tray, framing and profiled decking are ordered from this family; roofing sheet, ducting and drawn parts from the first.
The coating designation, and the conversion nobody remembers
A coating is written as a letter plus a number: Z for zinc, ZM for zinc-magnesium, AZ for aluminium-zinc, AS for aluminium-silicon. The number is the coating mass in grams per square metre counted over both faces together.
So Z275 is 275 g/m² across both faces, which is 137.5 g/m² per face, and at zinc's density of 7.14 g/cm³ that is about 19.3 µm per face. Comparing a Z number directly with the micron figure of a hot-dip galvanized fabrication under EN ISO 1461 — where 45 to 85 µm sits on every surface — is comparing two different quantities, and the difference is a factor of three to four.
Z100 ≈ 7 µm per face, Z275 ≈ 19 µm, Z600 ≈ 42 µm.
ZM gives two to four times the life of Z at equal mass.
AZ150 (galvalume) is a roofing material, weak at cut edges in alkaline contact.
EN ISO 1461 microns and EN 10346 g/m² are not interchangeable numbers.
What continuous coating cannot do
The coating is applied to strip, before the strip becomes a part. Every cut, punched hole, sheared edge and weld made afterwards exposes bare steel, and the zinc beside it protects that exposure only across a short distance — a couple of millimetres on thin gauge, less as the material thickens.
That is the entire reason hot-dip galvanizing after fabrication exists as a separate trade. A roll-formed purlin with sheltered ends is fine in Z275. The same section welded into an exposed frame is not, whatever its coating class says, because the coating never reached the weld. Where the part is finished before it is coated, EN ISO 1461 is the standard; where it is formed from coated coil, this one is.
faq.h
How many microns is Z275?
About 19–20 µm per face. Z275 means 275 g/m² counted over both faces, so 137.5 g/m² per face, divided by zinc's density of 7.14 g/cm³. Coating classes under this standard are always stated for both faces together.
What is the difference between DX51D and S250GD?
What they guarantee. DX51D is a forming grade with no specified yield strength, judged on bending and drawing behaviour. S250GD is a structural grade with a 250 MPa minimum yield. Roofing sheet and ducting use DX; purlins and framing use S.
What does GD mean in S250GD?
G marks a coated product and D that the coating was applied by continuous hot dipping. The number before it is the minimum yield strength in MPa, so S250GD is a 250 MPa structural grade in continuously hot-dip coated strip.
Is EN 10346 the same as EN ISO 1461?
No, and the two are the commonest mix-up in galvanized specification. EN 10346 covers strip coated continuously at the mill, in g/m² over both faces. EN ISO 1461 covers finished parts dipped after fabrication, in microns on every surface including welds and cut edges.
What replaced EN 10142 and EN 10147?
EN 10346, which merged them in 2009. EN 10142 held the low-carbon forming grades and EN 10147 the structural ones; the current standard carries both families with the DX and S designations, plus the zinc-magnesium and aluminium-zinc coatings that were added later.