S350GD steel (1.0529): properties, composition, equivalents
S350GD (1.0529): 350 MPa yield, 420 MPa tensile, 16 % elongation — EN 10346 galvanized structural sheet for deck, long-span purlins and racking. Chemistry, coatings, A653 SS Grade 50 and SGC440 equivalents.
What is S350GD?
S350GD is the structural galvanized grade for members that are designed to their limit: composite floor deck, long-span roof deck, heavy-duty purlins, pallet-racking uprights, highway guardrail and solar trackers. EN 10346 guarantees 350 MPa yield and 420 MPa tensile at 16 % elongation; Werkstoff number 1.0529. Ordered as S350GD+Z275 (Z350–Z600 or +ZM for exposed frames) and, for deck, usually with a surface quality B and a minimized spangle so the concrete-side embossing is uniform.
It is the top of the plain carbon-manganese structural class in EN 10346 — S390GD and above are micro-alloyed — and roughly 20 % stronger than S280GD from the same section, which is why deck manufacturers publish their span tables on S350GD. Ductility is lower (16 %); bend radii on deck ribs and racking hooks are sized accordingly.
ASTM A653 SS Grade 50 Class 1 and JIS SGC440 are the equivalents used in North American and Asian deck catalogues.
S350GD chemical composition
| Element | Mass % | Note |
|---|---|---|
| C | ≤ 0.2 | |
| Si | ≤ 0.6 | |
| Mn | ≤ 1.7 | |
| P | ≤ 0.1 | |
| S | ≤ 0.045 |
EN 10346:2015 Table 2 (S220GD–S350GD). Some mills reach 350 MPa with a small Nb or Ti addition within these limits; above S350GD the micro-alloyed classes (S390GD–S450GD) apply.
S350GD mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| S350GD, all thicknesses (longitudinal) | 350 (50.8) | 420 (60.9) | 16 | ≈ 80–90 HRB (typ.) |
| S320GD (for comparison) | 320 (46.4) | 390 (56.6) | 17 | — |
| S390GD | 390 (56.6) | 460 (66.7) | 16 | — |
| S420GD | 420 (60.9) | 480 (69.6) | 15 | — |
| S450GD | 450 (65.3) | 510 (74.0) | 14 | — |
| S550GD | 550 (79.8) | 560 (81.2) | — | — |
EN 10346 Table 5, minimum values, A80 longitudinal; minus 2 points below 0.7 mm. S550GD (full-hard) has no elongation requirement and is for stiffness-only roofing sheet, not for designed members.
S350GD equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| S350GD+Z | GB/T (China) | Identical | GB/T 2518 adopts the EN designation (also 350 by yield). |
| SS Grade 50 (A653) | ASTM / ASME | Near | ASTM A653 Structural Steel Grade 50 [340] Class 1: 340 MPa yield, 450 MPa tensile — the US deck and framing grade. |
| S280GD | EN (European) | Near | One class lower — the general purlin grade. |
| S390GD | EN (European) | Near | First micro-alloyed class above S350GD, for heavy racking and structural deck. |
| IS 277 Grade 340 | IS (India) | Near | Indian galvanized sheet, 340 MPa yield. |
| SGC440 | JIS (Japan) | Near | JIS G3302 SGC440: yield ≥ 335 MPa, tensile ≥ 440 MPa, A ≥ 18 %. |
| S355JR | EN (European) | Functional | Uncoated hot-rolled equivalent by yield, for profiles hot-dip galvanized after forming. |
| S250GD | EN (European) | Functional | Same chemistry family, 350 MPa yield; used where span tables require it. |
Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for S350GD →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| FeE350G | EN 10147:1992 | Pre-2000 designation. |
| StE350-2Z | DIN 17162 (withdrawn) | German structural galvanized grade. |
| Z35 | BS 2989 | British structural galvanized quality, 35 kgf/mm² ≈ 345 MPa. |
Product forms and tolerance standards
Product forms: hot-dip galvanized coil and sheet 0.60–4.0 mm (+Z, +ZM, +AZ), slit strip for deck, purlin and racking lines, pre-painted (EN 10169) base.
Dimensional tolerances: thickness/width/flatness: EN 10143; coating mass per EN 10346 (Z275 standard; Z350–Z600 or ZM for exposed use); surface A or B, finish N or M.
Key property values
S350GD yield strength
≥ 350 MPa (51 ksi), longitudinal. Typical 370–420 MPa.
S350GD tensile strength
≥ 420 MPa (61 ksi); typical 440–500 MPa.
S350GD elongation
≥ 16 % (A80, longitudinal); 14 % below 0.7 mm.
Design values
EN 1993-1-3: fyb = 350 MPa, fu = 420 MPa. For composite slabs EN 1994-1-1 uses the deck yield as fyp = 350 MPa. E = 210 GPa.
Coating and corrosion life
Z275 ≈ 20 µm/face for interior deck and purlins; Z450–Z600 or ZM140–ZM200 for guardrail, agricultural and coastal frames (EN ISO 14713-1 categories C3–C5). Hot-dip galvanizing after forming (EN ISO 1461, 70–85 µm) is the alternative for heavy exposed members.
Weldability
Shear studs on composite deck are welded through the deck to the beam (EN 1994-1-1, stud welding through galvanized sheet ≤ 1.25 mm total zinc-coated thickness). Other joints are screwed, riveted or bolted; MAG welding needs fume extraction and zinc-rich repair paint.
Machining, forming and heat treatment
Roll forming with embossing (deck), punching and slitting are routine; recommended inside bend radius ≥ 1.5 t transverse. The higher yield increases springback — profile tooling is set for S350GD specifically. Not a drawing grade.
Typical applications
- Composite floor deck and steel roof deck (the reference grade)
- Long-span and heavy-duty C/Z/sigma purlins
- Pallet-racking uprights and beams
- Highway guardrail W-beam and posts (often Z600 or post-galvanized)
- Solar trackers and ground-mount structures (+ZM)
- Light-gauge framing joists for longer spans
- Silo and tank wall panels (with S390GD–S450GD)
Frequently asked questions
What is S350GD used for?
Composite and roof deck, long-span purlins, racking, guardrail and solar structures — galvanized profiles designed with a 350 MPa yield to EN 1993-1-3 or EN 1994-1-1.
What is the ASTM equivalent of S350GD?
ASTM A653 SS Grade 50 [340] Class 1 (340 MPa yield, 450 MPa tensile); JIS G3302 SGC440 (335 MPa) is the Japanese counterpart.
S350GD vs S355JR — what is the difference?
Same nominal yield, different product: S350GD is a continuously galvanized thin sheet (0.6–4 mm) for roll forming to EN 10346; S355JR is uncoated hot-rolled plate, strip and sections to EN 10025-2 that would be galvanized after fabrication.
Can S350GD be bent as tightly as S280GD?
Not quite — elongation is 16 % vs 18 % and springback is higher. Use an inside radius of at least 1.5 t and set tooling for the grade; deck ribs and racking hooks are designed around this.
Which zinc coating for guardrail in S350GD?
Most highway specifications call for Z600 continuous coating or, more commonly, hot-dip galvanizing after forming to EN ISO 1461 with 70–85 µm; the sheet grade stays S350GD or S420GD.
Related grades
Verified against EN 10346:2015; EN 10346:2015 Tables 2 and 5; EN 10143:2006; EN 1993-1-3, EN 1994-1-1; ASTM A653/A653M-22; JIS G3302:2019. Last checked: September 2026.