EN 10346 is the European reference for continuously hot-dip coated flat steel products, and its coating designation system is especially important when an aluminized tube is produced from pre-coated strip. The standard defines steel grades such as DX51D through DX57D and coating symbols including Z, ZF, ZA, ZM, AZ and AS. For aluminized applications, +AS identifies a hot-dip aluminium-silicon alloy coating, with the coating bath specified at about 8–11% silicon and the balance aluminium. 

1. What EN 10346 Controls

EN 10346 establishes requirements for continuously hot-dip coated steel flat products, including chemical composition, mechanical properties, coating type, coating mass, surface quality, tolerances and related testing. The designation combines the steel grade with the coating symbol.

For the cold-forming grades, EN 10346 includes DX51D, DX52D, DX53D, DX54D, DX55D, DX56D and DX57D. The available coating combinations are not identical for every grade. For example, DX55D is specifically listed with +AS, while DX51D through DX54D and DX56D/DX57D have broader combinations depending on the edition and grade. 

2. What +AS Means in the European System

+AS is the key designation for aluminium-silicon coated steel under EN 10346. The standard defines the coating as an aluminium-silicon alloy applied by the continuous hot-dip process. The coating bath contains approximately 8–11% silicon, with aluminium making up the balance. 

This is different from simply writing “aluminized steel”. For procurement, the complete designation provides much more useful information because it identifies both the substrate family and coating system.

3. DX51D to DX57D: Choosing the Substrate

The DX grades are not interchangeable names for the same steel. They represent different levels of cold-forming performance. As the grade progresses toward DX54D, DX56D and DX57D, the specified mechanical-property and forming requirements become increasingly relevant to complex forming operations. EN 10346:2015, for example, lists different yield-strength ranges, elongation values and forming parameters for these grades.

The important procurement principle is simple: select the steel grade from the forming requirement first, then specify the coating system. Do not assume that a heavier coating automatically requires a higher DX grade.

4. AS, AZ, Z and ZM Are Not the Same

One common European purchasing mistake is treating every aluminium-containing coating as an aluminized coating. EN 10346 separates the coating families by designation.

EN 10346 specifically defines AS as aluminium-silicon alloy coating and AZ as aluminium-zinc alloy coating. The distinction is therefore part of the material designation rather than merely a supplier's commercial terminology. 

5. EN 10346 AS vs ASTM and JIS Systems

European, ASTM and JIS specifications can describe similar aluminized products, but their designation systems should not be treated as direct one-to-one translations.

Do not automatically write “EN 10346 +AS = ASTM A463 Type 1 = JIS AS...” as if the three standards were identical. The coating chemistry may be conceptually similar, but steel grades, coating-mass designations, testing rules, dimensional tolerances and ordering requirements can differ. ASTM A463, for example, uses its own Type 1/Type 2 classification, while EN 10346 uses coating symbols such as AS. 

6. From EN 10346 Strip to European Aluminized Tube

For tube production, EN 10346 is often the material and coating starting point. The coated strip can be slit, roll formed and welded into round, square, rectangular or other tube profiles. The final tube specification then needs to address dimensions, weld condition, length, straightness, surface condition and any post-forming requirements.

This distinction is especially important when a buyer searches for an EN 10346 aluminized tube. The phrase normally describes a tube manufactured from steel complying with the EN 10346 coating system; it does not mean that EN 10346 alone specifies every finished-tube requirement.

7. European Project Applications

EN 10346 material designations are useful when a European project requires traceable control of both the substrate and coating. Potential tube applications include exhaust-related components, heat-resistant fabricated sections, equipment frames, agricultural equipment, ventilation components and other formed tubular products where an aluminium-silicon coating is required.

For higher-temperature service, the substrate grade, coating system, weld design and actual service temperature should be evaluated together. Coating selection should not be based on the word “aluminized” alone.

8. Correct Procurement Wording

A strong purchase specification should avoid simply stating “EN 10346 aluminized tube.” Instead, identify the material chain and the finished tube requirements.

The exact coating mass should be stated rather than relying on the word “AS.” EN 10346 defines coating mass as the total coating mass on both surfaces, and the coating designation is used together with the coating symbol.

9. Teda Ganghua Supply Support

For European buyers sourcing coated tube for repeat production, Teda Ganghua can coordinate the steel grade, coating designation, tube dimensions and inspection requirements as one procurement package. The focus should be on matching the DX grade + AS coating + tube geometry + forming/welding process to the final application rather than selecting the coating independently.

For project or production inquiries, see EN 10346 aluminized steel and provide the required steel grade, coating designation, coating mass, tube size, wall thickness, length, quantity and applicable inspection requirements.

10. FAQ

Is EN 10346 a tube standard?

No. EN 10346 primarily specifies continuously hot-dip coated steel flat products. A finished tube normally needs additional requirements covering tube dimensions, manufacturing, welding, tolerances and testing.

What does +AS mean in EN 10346?

+AS identifies a hot-dip aluminium-silicon alloy coating. EN 10346 specifies an aluminium-silicon bath containing approximately 8–11% silicon, with aluminium as the balance. 

Is DX51D+AS the same as ASTM A463 Type 1?

They describe related aluminium-silicon coating concepts, but they are not automatically identical specifications. The substrate grade, coating mass, mechanical requirements and testing system must be checked separately.

Can DX55D be used with an AS coating?

Yes. EN 10346:2015 specifically lists DX55D with +AS. This grade is associated with higher forming requirements and should be selected according to the actual tube-forming process. 

What should be written on a purchase order?

Specify the EN 10346 steel grade, coating symbol and coating mass, followed by tube shape, OD or section dimensions, wall thickness, length, manufacturing method, surface requirements, tolerances and inspection documentation. This is substantially clearer than simply writing “EN 10346 aluminized tube.”