What is S320GD galvanized steel?
S320GD fills the step between S280GD and S350GD in EN 10346: 320 MPa yield with 17 % elongation and a 1.5 × t bend radius, from a slightly stronger low-carbon heat (typically C 0.08–0.12 %, Mn 0.6–1.0 %) on a hot-rolled pickled or cold-rolled substrate. Mills produce it less often than its neighbours — most designers jump from 280 to 350 — so it is a made-to-order grade in Turkey, and EN 1993-1-3 allows S350GD to be substituted whenever the design does not rely on the softer grade's ductility. Where it does appear it is usually in composite floor decking (EN 1994 sheeting is often designed at 320 MPa), heavier purlins in 2.0–3.0 mm and solar mounting structures written to a German specification. Coating Z275 as standard, Z350 for agricultural and coastal use.
Chemical composition
| Element | C | Si | Mn | P | S |
|---|---|---|---|---|---|
| max. % (ladle) | 0.20 | 0.60 | 1.70 | 0.10 | 0.045 |
Typical heat: C 0.08–0.12, Mn 0.60–1.00.
Mechanical properties
| Property | Requirement | Typical value | Note |
|---|---|---|---|
| Yield strength ReH / Rp0.2 | ≥ 320 MPa | 340–390 MPa | fyb = 320 |
| Tensile strength Rm | ≥ 390 MPa | 420–470 MPa | |
| Elongation A80 | ≥ 17 % | 20–25 % | |
| Bend radius (180°) | 1.5 × t | passes |
Equivalent grades
| System | Grade | Note |
|---|---|---|
| EN 10147 (old) | Fe E 320 G | withdrawn |
| ASTM A653 | SS Grade 50 Class 1 (340 MPa) | near |
| JIS G3302 | SGC490 | |
| GB/T 2518 | S320GD+Z | |
| EN 10346 | S350GD | upward substitute |
Coating classes supplied on S320GD
| Class | Zinc mass (g/m², both sides) | Thickness per side (µm) | Typical life C3 | Where used |
|---|---|---|---|---|
| Z200 | 200 | ≈ 14 | 9–13 years | racking uprights, beams and internal framing |
| Z275 | 275 | ≈ 20 | 12–18 years | composite floor decking and exposed framing |
| Z350 | 350 | ≈ 25 | 15–22 years | humid plant, agricultural and coastal structures |
| Z450 / Z600 | 450 / 600 | ≈ 32 / 42 | 20–35 years | ground contact, tunnel and drainage components |
Composite floor decking is a special case: the top face is cast into concrete, which is alkaline and passivates zinc, while the soffit stays exposed. Z275 on both faces is the normal specification; heavier classes buy nothing on the embedded face and only help the soffit.
Thickness range and stock sizes
| Thickness | Widths × lengths | Availability |
|---|---|---|
| 0.60–1.2 mm | coil 1 000 / 1 250 mm | to order 2–3 weeks |
| 1.5–3.0 mm | coil 1 250 / 1 500 mm | to order 2–3 weeks |
| any | S350GD from stock as substitute | 3–5 days |
Weight per m² and per sheet
| Thickness | kg/m² | 1 000 × 2 000 (kg) | 1 250 × 2 500 (kg) | 1 500 × 3 000 (kg) |
|---|---|---|---|---|
| 0.6 mm | 4.99 | 10.0 | 15.6 | 22.4 |
| 0.7 mm | 5.77 | 11.5 | 18.0 | 26.0 |
| 0.8 mm | 6.56 | 13.1 | 20.5 | 29.5 |
| 1 mm | 8.13 | 16.3 | 25.4 | 36.6 |
| 1.2 mm | 9.70 | 19.4 | 30.3 | 43.6 |
| 1.5 mm | 12.05 | 24.1 | 37.7 | 54.2 |
| 2 mm | 15.98 | 32.0 | 49.9 | 71.9 |
| 2.5 mm | 19.90 | 39.8 | 62.2 | 89.6 |
| 3 mm | 23.83 | 47.7 | 74.5 | 107.2 |
Includes Z275 coating.
Forming, welding and design
Roll-forms decking and purlin profiles at 1.5 × t inside radius; spring-back higher than S280GD — set the tooling accordingly. Welding as for the other GD grades (fume extraction, zinc-rich repair); shear-stud welding through decking works with Z275 up to 1.25 mm. Design to EN 1993-1-3 / EN 1994-1-1 with fyb = 320 MPa, fu = 390 MPa, core thickness = nominal − 0.04 mm.
Where it is used
- Composite floor decking (EN 1994)
- Purlins and side rails in 2.0–3.0 mm for long bays
- Solar mounting rails, posts and trackers
- Heavy framing and mezzanine joists
- Silo and bin stiffeners
- Guardrail posts and lighter highway components
S320GD vs S350GD
S350GD gives 9 % more yield for the same price class and is stocked; S320GD is worth ordering only when a specification names it and forbids upward substitution, or when its slightly better elongation (17 vs 16 %) matters for a deep profile. See S350GD and, for lighter duty, S280GD.
Price
S320GD is priced about 25 USD/t over DX51D; the band below is indicative FOB Istanbul for mill-order coil.
Bands from our weekly export list (September 2026), FOB Istanbul, full-container quantities, excluding freight and certificates. Firm price per project on RFQ within one working day.
Export and packing
S320GD for decking goes out as coil or as slit strip at deck width, cradled eye-to-sky, VCI-wrapped and strapped; rolled deck sheets ship in nested packs under 3 t with timber bearers and the profile marked on the end of each pack. A 40' HC takes 24 t of coil or about 9 packs of deck. Customs code 7210.49.
| Term | Detail |
|---|---|
| MOQ | One coil (10–20 t) |
| Incoterms | FOB Istanbul · CIF / CFR Gulf, Africa · DAP EU, Balkans, Iraq, Caucasus · DAP Aktau |
| Lead time | To order 2–3 weeks; S350GD from stock as substitute |
| Packing | Coil eye-to-sky, VCI wrap |
| Container / truck | 20' one coil ≤ 20 t; 40' HC two coils |
| Documents | Invoice, packing list, EN 10204 3.1 (3.2 on request), certificate of origin; SASO / SONCAP / PVoC on request |
| Payment | 30% advance, balance against B/L copy; L/C at sight for orders above 100 t |
Certificates and testing
The EN 10204 3.1 certificate for S320GD gives the mechanical values at the delivered thickness and the triple-spot zinc mass. Decking projects often need those figures tied to the profile drawing, so we cross-reference the coil number on the pack list. A 3.2 certificate witnessed by SGS, TUV or BV can be arranged before rolling starts.
How to order
Specify thickness × width, coating, tonnage and whether S350GD from stock may be substituted; mill slot confirmed within a day.
Standards
- EN 10346:2015 — S320GD+Z, 1.0250
- EN 10143 — tolerances
- EN 1993-1-3 — cold-formed design (fyb = 320 MPa)
- EN 10204 3.1
Grades
Grade data sheets (chemistry, mechanicals, equivalents) are on our reference site: S320GD · S280GD · S350GD
Frequently asked questions
What is S320GD?
A structural hot-dip galvanized strip to EN 10346 (1.0250) with guaranteed yield ≥ 320 MPa and tensile ≥ 390 MPa, used for composite decking, heavier purlins and solar structures.
Can S350GD replace S320GD?
Yes in almost all designs — it exceeds the yield and tensile requirements; confirm if the design depends on the softer grade's elongation for a deep profile.
What is the ASTM equivalent of S320GD?
ASTM A653 SS Grade 50 Class 1 (340 MPa) is the nearest; there is no exact 320 MPa ASTM grade.