EN 10346 Steel Coil Explained: DX Grades, Coating Types & EU/UK Ordering Guide

“Continuously hot-dip coated steel flat products”

EN 10346 (EU / UK) — DX Grades, Coating Types & Ordering Logic

Engineering & Procurement Guide for Roll Forming Applications

EN 10346 is the primary European and UK standard governing:

“Continuously hot-dip coated steel flat products”

It covers:

Galvanized (Z)
Galvalume (ZA / AZ equivalent)
Aluminized (AS)
Zinc-magnesium (ZM)
Zinc-iron (ZF)

Unlike ASTM standards, EN 10346 uses a structured grade naming system such as:

DX51D
S320GD
S350GD

For roll forming manufacturers operating in:

UK
EU
Middle East using EU spec
Export projects into Europe

Understanding EN 10346 is critical for:

Structural compliance
CE/UKCA marking
Warranty alignment
Mechanical performance
Coating specification

This guide explains how to decode the grade logic and specify coil correctly.

1️⃣ Grade Naming Logic in EN 10346

EN 10346 grades fall into two primary categories:

A) DX Grades (Forming Grades)

B) Structural Grades (SxxxGD)

2️⃣ DX Grades Explained

DX grades are designed for forming and deep drawing.

Examples:

DX51D
DX52D
DX53D
DX54D

What DX Means

D = Flat product for cold forming
X = Unspecified minimum yield strength
Number = Increasing formability

DX51D is the most common commercial forming grade.

2.1 Mechanical Characteristics of DX51D

Moderate yield strength
Good ductility
Suitable for roofing and cladding
Not ideal for structural load-bearing sections

DX grades prioritize formability over structural strength.

3️⃣ Structural Grades (SxxxGD)

Structural grades are designated as:

S + Yield Strength + GD

Examples:

S250GD
S280GD
S320GD
S350GD

3.1 Example: S350GD

S = Structural steel
350 = Minimum yield strength (MPa)
GD = Hot-dip galvanized

S350GD ≈ G350 in global terminology.

These grades are used for:

Purlins
Stud & track
Structural decking
Solar mounting

4️⃣ Coating Designations in EN 10346

EN coating weight is expressed in g/m² (both sides total).

Common coatings:

Designation	Coating Type	Total g/m²
Z100	Zinc	100 g/m²
Z140	Zinc	140 g/m²
Z275	Zinc	275 g/m²
Z450	Zinc	450 g/m²
ZA	Zinc-Aluminum	Varies
AZ	Aluminum-Zinc	150–185+ g/m²
ZM	Zinc-Magnesium	Advanced
AS	Aluminized	Heat applications

Z275 is one of the most common structural galvanized coatings in Europe.

5️⃣ Zinc (Z) vs Aluminum-Zinc (AZ) vs Zinc-Magnesium (ZM)

Z (Galvanized)

Strong sacrificial protection
Good cut-edge performance
Standard structural coating

AZ (Al-Zn)

Superior atmospheric corrosion resistance
Better flat surface durability
Used in roofing

ZM (Zinc-Magnesium)

Improved corrosion resistance
Enhanced cut-edge behavior
Increasingly common in solar and structural systems

6️⃣ Mechanical & Forming Implications

6.1 DX Grades in Roll Forming

DX51D:

Good for roofing panels
Limited structural capacity
Lower springback

DX52D+:

Better deep draw
Not typical in structural roll forming

6.2 Structural Grades (S350GD)

Higher yield strength means:

Increased springback
Higher forming force
Larger shaft load
Increased risk of edge cracking

Pass design must compensate.

7️⃣ Bend Radius & Coating Cracking

EN coatings may crack at tight radii.

Critical variables:

Substrate strength
Coating thickness
Bend radius
Slit edge quality

Z coatings generally tolerate bending well, but high tensile S350GD requires careful overbend control.

8️⃣ Surface Finish Designations

EN 10346 defines surface finishes:

Normal spangle
Minimized spangle
Skin passed
Surface quality A/B/C

Surface selection affects:

Paint adhesion
Oil canning visibility
Cosmetic appearance

Skin-passed coil reduces stretcher strain markings.

9️⃣ Ordering Logic — Full Specification Example

A correct EN 10346 order should specify:

Example:

EN 10346 – S350GD + Z275 – 1.5 mm – Mill Edge – Skin Passed – CE Marked

Breakdown:

Standard: EN 10346
Grade: S350GD
Coating: Z275
Thickness: 1.5 mm
Edge condition
Surface condition
Compliance requirement

Failure to include grade often results in DX51D being supplied instead of structural grade.

🔟 CE / UKCA Compliance

In EU/UK markets:

Structural sections require traceability
Mill certificates mandatory
CE or UKCA marking required

Incorrect grade specification can cause regulatory non-compliance.

1️⃣1️⃣ Buyer Strategy (30%)

When to Choose DX51D

Roofing panels
Wall cladding
Light flashing
Non-structural components

When to Choose S350GD

Purlins
Stud systems
Load-bearing profiles
Solar mounting

When to Upgrade to ZM

Solar projects
Coastal zones
Long design life structures

Common Buyer Mistakes

Ordering DX51D for structural purlins
Confusing Z275 with AZ150
Not specifying coating mass
Ignoring edge condition
Not requesting CE documentation
Mixing EU and ASTM terminology incorrectly

6 Frequently Asked Questions

1. What is DX51D used for?

It is a forming grade used mainly for roofing and cladding.

2. What does S350GD mean?

Structural steel with 350 MPa minimum yield strength, hot-dip galvanized.

3. Is Z275 suitable for structural purlins?

Yes, Z275 with S350GD is common for structural sections.

4. What is the difference between Z and AZ in EN 10346?

Z is pure zinc; AZ is aluminum-zinc alloy coating.

5. Should I use DX grade for load-bearing sections?

No. Structural grades (SxxxGD) should be used.

6. Does EN 10346 cover zinc-magnesium coatings?

Yes, ZM coatings are included and increasingly specified.

Final Engineering Summary

EN 10346 defines both:

Mechanical strength (DX vs S grades)
Coating mass (Z, AZ, ZM, AS)

Correct specification must include:

Grade
Coating designation
Thickness
Surface condition
Compliance marking

Failure to follow proper ordering logic leads to:

Structural underperformance
Corrosion failure
Certification issues
Production instability

Understanding EN 10346 is essential for any roll forming operation serving EU or UK markets.