S250GD steel (1.0242): properties, composition, equivalents
S250GD (1.0242) is the entry structural galvanized grade of EN 10346: 250 MPa yield, 330 MPa tensile, 19 % elongation, Z100–Z600 coating. Chemistry, S220GD–S550GD ladder, A653 SS/HSLAS equivalents, purlin and decking use.
What is S250GD?
S250GD is the first of the structural hot-dip galvanized grades in EN 10346 — the ones ordered when a roll-formed profile has to carry load and the engineer needs a yield value to design to. The designation reads S (structural steel), 250 (minimum yield in MPa), G (hot-dip coated), D (for cold forming); the coating code follows, usually +Z275 (275 g/m² zinc both faces) or, increasingly, +ZM zinc-magnesium at ZM90–ZM120 for the same corrosion life at half the mass. Werkstoff number 1.0242.
Against the forming grade DX51D, S250GD trades some ductility (19 % vs 22 % elongation) for a guaranteed 250 MPa yield and 330 MPa tensile — enough for purlins, girts, light-gauge framing, composite floor deck and cable trays designed to EN 1993-1-3. The ladder continues S280GD (the usual purlin grade), S320GD, S350GD (deck and long-span profiles), up to S550GD full-hard for roofing sheets that only need stiffness.
ASTM A653 SS Grade 37 and JIS SGC340 are the nearest equivalents; Chinese and Indian standards use the EN name or the yield number directly.
S250GD 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 to S350GD share these limits). Strength comes from carbon/manganese and cold work, not micro-alloying; typical coil C 0.05–0.10, Mn 0.30–0.60.
S250GD mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| S250GD, all thicknesses (longitudinal) | 250 (36.3) | 330 (47.9) | 19 | ≈ 65–80 HRB (typ.) |
| S220GD (for comparison) | 220 (31.9) | 300 (43.5) | 20 | — |
| S280GD | 280 (40.6) | 360 (52.2) | 18 | — |
| S320GD | 320 (46.4) | 390 (56.6) | 17 | — |
| S350GD | 350 (50.8) | 420 (60.9) | 16 | — |
| S390GD | 390 (56.6) | 460 (66.7) | 16 | — |
| S450GD | 450 (65.3) | 510 (74.0) | 14 | — |
| S550GD | 550 (79.8) | 560 (81.2) | — | — |
EN 10346 Table 5: minimum yield ReH (or Rp0.2), minimum tensile Rm, minimum A80 longitudinal. Values apply to the base steel; for thickness < 0.7 mm elongation minus 2 points. S550GD has no elongation requirement (full-hard).
S250GD equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| S250GD+Z | GB/T (China) | Identical | GB/T 2518 adopts the EN designation (also listed as 250 by yield). |
| IS 277 Grade 250 | IS (India) | Identical | Indian galvanized sheet with 250 MPa yield. |
| SS Grade 37 (A653) | ASTM / ASME | Near | ASTM A653 Structural Steel Grade 37 [255]: 255 MPa yield, 360 MPa tensile — the closest US structural galvanized grade; SS Grade 33 [230] sits just below. |
| S280GD | EN (European) | Near | Next class up (280 MPa); the common purlin grade when S250GD is not stocked. |
| SGC340 | JIS (Japan) | Near | JIS G3302 SGC340: yield ≥ 245 MPa, tensile ≥ 340 MPa, A ≥ 20 % — Japanese structural galvanized. |
| S350GD | EN (European) | Functional | Same chemistry family, 350 MPa yield; used where span tables require it. |
| DX51D | EN (European) | Functional | Same substrate family without a guaranteed yield — for bending and profiling that is not load-bearing. |
| S235JR | EN (European) | Functional | Uncoated hot-rolled structural steel of similar strength for members that will be post-galvanized. |
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 S250GD →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| FeE250G | EN 10147:1992 | Structural galvanized designation before the S…GD names (EN 10147:2000). |
| StE250-2Z | DIN 17162 (withdrawn) | German structural galvanized grade; ≈ S250GD+Z. |
| Z25 / Z28 | BS 2989 | British structural galvanized qualities by yield in kgf/mm². |
Product forms and tolerance standards
Product forms: hot-dip galvanized coil and sheet 0.40–4.0 mm (+Z, +ZM, +AZ, +ZA, +ZF), slit strip for purlin, deck and profile lines, pre-painted (EN 10169) on S250GD base.
Dimensional tolerances: thickness/width/flatness: EN 10143; coating mass per EN 10346 (Z275 = 275 g/m² both faces, ≈ 20 µm per face); surface quality A or B; finish N or M.
Key property values
S250GD yield strength
≥ 250 MPa (36 ksi), longitudinal, ReH or Rp0.2. Typical measured values 270–320 MPa.
S250GD tensile strength
≥ 330 MPa (48 ksi). No upper limit is specified; typical 350–400 MPa.
S250GD elongation
≥ 19 % (A80, longitudinal); 17 % below 0.7 mm.
Design values
EN 1993-1-3 uses fyb = 250 MPa and fu = 330 MPa for cold-formed members in S250GD; the cold-forming strength increase (fya) may be used for fully effective sections. E = 210 GPa, density 7.85 g/cm³.
Coating and corrosion life
Z275 ≈ 20 µm/face: roughly 20–40 years in rural C2 air, 10–20 in urban C3, 3–8 near the coast (EN ISO 14713-1 guidance). ZM120 gives about twice the life of Z275 at equal mass and is the trend for solar mounting and agricultural framing.
Weldability
Spot welding and MAG welding as for DX51D+Z: zinc fume extraction, 10–20 % higher current for spot welds, zinc-rich repair paint on heat-affected areas. Structural connections in light-gauge framing are usually self-drilling screws, blind rivets or bolts rather than welds, to keep the coating intact.
Machining, forming and heat treatment
Roll forming, punching and slitting are routine; minimum inside bend radius about 1 t (transverse) — the coating passes the EN 10346 T-bend test without flaking. Not a drawing grade (no r-value). Cut edges are protected sacrificially by the zinc up to about 2 mm thickness.
Typical applications
- C and Z purlins, girts and eaves beams (S250GD–S350GD)
- Light-gauge steel framing studs and tracks for load-bearing walls
- Composite floor deck and roof deck (usually S280GD–S350GD)
- Cable trays, ladders and support channels
- Solar-panel mounting rails and ground-mount frames (+ZM preferred)
- Guardrail, agricultural and greenhouse structures
- Racking uprights and beams (higher grades for heavy racks)
Frequently asked questions
What is the difference between DX51D and S250GD?
DX51D is a forming grade with no guaranteed yield (tensile 270–500 MPa, 22 % elongation); S250GD is a structural grade with a guaranteed 250 MPa yield and 330 MPa tensile at 19 % elongation. Order S250GD when the profile is load-bearing and designed to EN 1993-1-3.
What does S250GD+Z275 mean?
Structural (S) steel with 250 MPa minimum yield, hot-dip coated (G) for cold forming (D), zinc coating of 275 g/m² total on both faces (+Z275, about 20 µm per side).
Is S250GD the same as SS Grade 37 or SGC340?
Near-equivalent: ASTM A653 SS Grade 37 [255] has 255 MPa yield and 360 MPa tensile; JIS G3302 SGC340 has 245 MPa yield and 340 MPa tensile. All three serve the same purlin and framing applications.
Which grade for purlins — S250GD, S280GD or S350GD?
S280GD is the most common purlin grade in Europe; S250GD is used for light spans and where stock dictates; S350GD where the span table needs it or for deck. Higher yield means smaller sections but slightly less ductility.
Can S250GD be supplied pre-painted?
Yes — pre-painted (PPGI) profiles to EN 10169 are usually on S250GD–S320GD substrate for purlins that stay visible, and on DX51D for non-structural cladding.
Related grades
Verified against EN 10346:2015; EN 10346:2015 Tables 2 and 5, coating tables; EN 10143:2006 (tolerances); EN 1993-1-3 (design of cold-formed members); ASTM A653/A653M-22 Table 2; JIS G3302:2019. Last checked: September 2026.