1. S320GD at a Glance
S320GD is a continuously hot-dip coated structural steel grade defined in EN 10346 (formerly covered by the national predecessor EN 10147, which has been withdrawn and replaced by EN 10346). Its steel number is 1.0250. The designation tells you the guaranteed performance level: the "320" refers to a minimum yield strength of 320 MPa, and "GD" indicates that the material is intended for structural (general duty) applications. Because it is delivered with a zinc-based coating, S320GD combines load-bearing capacity with inherent corrosion protection, which is why it is widely used in construction and fabrication.
2. Standards Context: EN 10346 and DIN
EN 10346 is the European standard for continuously hot-dip coated steel flat products - for cold forming (DX51D–DX57D), structural purposes (S220GD–S550GD), and other specific applications. In Germany the identical requirements are published as DIN EN 10346. Where older documents or supplier datasheets reference EN 10147, note that this standard was superseded: all current supply and certification should be based on EN 10346, and buyers should confirm the standard edition (currently EN 10346:2015) in their purchase order. The same EN 10346 framework also defines coating designations such as Z, ZF, ZA, ZM, AZ and AS, and surface quality classes.
3. Typical Chemical Composition and Mechanical Properties
| Property | Typical Value (S320GD per EN 10346) |
|---|---|
| Minimum yield strength (ReH) | 320 MPa |
| Tensile strength (Rm) | 360 – 510 MPa (typical range) |
| Minimum elongation A80 | 16 % (typical, thickness dependent) |
| Carbon (C, max) | 0.20 % (typical max) |
| Manganese (Mn, max) | 1.50 % (typical max) |
| Phosphorus / Sulphur (P / S, max) | 0.035 % / 0.035 % (typical max) |
| Coating types | Z (zinc), ZF (galvannealed), ZA, ZM, AZ, AS |
Values above are typical industry data for orientation; the binding figures are those in the current EN 10346 edition and in the mill test certificate of each delivery. Mechanical properties are normally verified in the transverse direction on coated products.
4. Zinc Coatings and Supply Forms
S320GD is available with a range of coating masses - for example Z275 (275 g/m² total both surfaces, triple-spot basis) for moderate corrosion exposure, up to Z350 or higher for aggressive outdoor environments. Galvannealed (ZF) options suit applications that will be painted or resistance-welded. The material is typically supplied as coil, slit coil, or cut-to-length sheet, with thicknesses commonly from about 0.4 mm up to 3.0 mm depending on the mill and the project requirement; always confirm the exact available range and tolerances with the supplier for your specific dimension.
5. Typical Applications
Construction and infrastructure: roofing panels, wall cladding, purlins and structural frameworks, guardrails, support beams and bridge components. Automotive and transport: body panels, chassis reinforcements and crash-resistant structures. Manufacturing: metal enclosures, HVAC ducts, electrical cabinets, storage systems and machinery parts. Agriculture: silos, fencing and farm equipment. Energy and utilities: power transmission towers, solar mounting structures, wind turbine components and water tanks - applications where the combination of 320 MPa minimum yield strength and corrosion protection reduces the need for post-galvanizing.
6. Selection Checklist
When specifying S320GD, define: the standard and edition (EN 10346), steel name and number (S320GD / 1.0250), thickness and width with tolerances, coating type and mass (e.g., Z275), surface quality class (A/B/C), spangle and finish requirements (passivation, oiling), and the form of supply (coil, slit coil, sheet). Request the mill test certificate showing heat analysis and mechanical test results, and verify that the standard cited on the certificate is EN 10346 - not a withdrawn predecessor.
Frequently Asked Questions
What does the "320" in S320GD mean? It indicates a guaranteed minimum yield strength of 320 MPa. The "GD" identifies the grade as galvanized structural steel for general duty, delivered with a hot-dip zinc coating.
Which standard governs S320GD today? EN 10346 (continuously hot-dip coated steel flat products), currently EN 10346:2015, published in Germany as DIN EN 10346. The earlier EN 10147 was withdrawn and replaced by EN 10346 - do not accept EN 10147 citations in certificates.
What is the difference between S320GD and DX51D? Both are in EN 10346, but DX51D is a low-carbon grade for cold forming (minimum yield 140 MPa, tensile 270–500 MPa), while S320GD is a structural grade with a guaranteed minimum yield of 320 MPa and higher strength for load-bearing members. Use DX51D for forming-focused parts and S320GD for structural duty.
Which zinc coating should I choose for outdoor structures? For exposed structural use, Z275 is a common starting point; for aggressive coastal or industrial atmospheres, Z350 or a zinc-aluminium coating (ZA/ZM) is often preferred. Selection should be based on the design life, environment, and applicable project specifications.
Can S320GD be welded? Yes. S320GD offers good weldability for typical structural joining processes such as MIG/MAG and resistance welding. Note that welding removes the zinc coating locally; touch-up with a zinc-rich paint is standard practice to restore corrosion protection at welds.
Is S320GD suitable for roll forming? Yes, it roll-forms well for profiles such as purlins, rails, and panels. Confirm bend radii and coating adhesion limits with the supplier, and avoid sharp radii that could crack the zinc layer.
