S355J2
EN 10025-2 · 1.0577
S355J2 is a structural steel (Carbon-Manganese family) to EN 10025-2 (1.0577). It has a specified 0.2 % proof stress of 355 MPa and a typical tensile strength of about 510 MPa, with a uniform elongation of 22 %. Nominal carbon content is around 0.23 %. For nonlinear FEA, a bilinear model uses E = 210 GPa up to yield and a tangent modulus of 717 MPa above it. A plain-carbon steel: economical and predictable, strengthened by carbon content and heat treatment rather than alloying.
Bilinear material model — nonlinear FEA
Uniform elongation εu = 22.0% · conservative analysis limit ½εu = 11.0%
Bilinear (BISO) approximation. Elastic modulus E up to the 0.2% proof stress R_p0.2, then a single tangent slope Eₜ to the ultimate tensile strength: Eₜ = (Rₘ − R_p0.2) / (εu − R_p0.2/E − 0.002), where εu is the uniform elongation and Rₘ is a typical (nominal) UTS within the specified band. The half-εu figure is a conservative strain limit for the analysis. Treat these as guidance for first-pass models; for critical work use a measured true stress–strain curve for the actual product and condition.
Ratings — engineering judgement
Weldabilitygood
Readily weldable by all common processes (MMA, MIG/MAG, TIG, SAW). Preheat generally not required below 25 mm. CE typically ≤ 0.45; thick or high-restraint sections may need preheat per EN 1011-2.
Formabilitymoderate
Reasonable cold forming for a structural steel. Minimum bend radii depend on thickness and rolling direction. Not suitable for deep drawing.
Machinabilitymoderate
Machines adequately with standard HSS or carbide tooling. Not a free-cutting steel; surface finish varies with plate source.
Corrosion resistancepoor
No inherent corrosion resistance — requires paint, galvanising or coating in exposed environments. Weathering variant S355J2W exists if needed.
Hardenabilitylow
Not intended for hardening. Supplied normalised or as-rolled. Flame/induction hardening not applicable.
Toughnessgood
J2 guarantees 27 J at −20 °C. Good for outdoor and cold environments. For colder service consider S355K2 (40 J @ −20 °C) or S355NL (27 J @ −50 °C).
Expert notes
S355 is the workhorse structural steel across Europe and increasingly globally. It replaced the old BS 4360 Grade 50 steels and is the default where S235 doesn't cut it. The J2 variant is the most commonly specified for outdoor structures.
For thickness above ~40 mm, minimum yield drops to 335 MPa (EN 10025-2, Table 7) — a trap for the unwary. Design to the yield value for the actual product thickness, not the headline 355 MPa.
S355 plate from different mills can behave quite differently in surface quality and residual stress, particularly in thick plate. If you're welding thick sections, get the actual CE from the mill cert rather than assuming the maximum.
For bolted connections, S355 pairs well with Grade 8.8 and 10.9 fasteners. The higher yield vs S275 gives more efficient joints — but check bearing and block-tearing capacity, as the connected plate works harder.
Don't confuse S355J2 with S355J2+N: the '+N' means normalised delivery, giving more consistent through-thickness properties — often specified for thicker plate or where lamellar tearing is a concern.
Mechanical properties
| Condition | Section | Yield (MPa) |
|---|---|---|
| S355 · as-rolled / normalised | t ≤ 16 mm | 355 |
| 16 < t ≤ 40 mm | 345 | |
| 40 < t ≤ 63 mm | 335 | |
| 63 < t ≤ 80 mm | 325 | |
| 80 < t ≤ 100 mm | 315 | |
| 100 < t ≤ 150 mm | 295 |
UTS 470–630 MPa · Impact 27 J @ −20 °C · Hardness ~160 HB (150–190)
Physical properties
| Density | 7850 | kg/m³ |
| Elastic modulus | 210 | GPa |
| Shear modulus | 81 | GPa |
| Poisson's ratio | 0.30 | |
| Thermal expansion | 12.0 | ×10⁻⁶/°C |
| Thermal conductivity | 50 | W/(m·K) |
| Specific heat | 470 | J/(kg·K) |
Chemical composition (wt %)
Available forms
Equivalent grades
| Standard | Grade | Note |
|---|---|---|
| BS 4360 | 50D | |
| ASTM | A572 Grade 50 | |
| JIS | SM490B | |
| DIN 17100 | St 52-3 N | |
| GB/T 1591 | Q345D | |
| IS 2062 | E350C | Close equivalent; 'C' quality includes −20 °C impact, aligning with J2. |
| NFA 35-501 | E36-4 | |
| UNI 7070 | Fe 510 D |
Historical designations
| Standard | Grade | Note |
|---|---|---|
| BS 4360:1990 | 50D | Widely referenced in legacy UK drawings. See '50D' on an old drawing and this is almost certainly what was meant. |
| DIN 17100 | St 52-3 N | Common on German-origin equipment. 'N' denotes normalised. |
| BS 4360:1968 | 55C | Earlier BS designation — 1970s drawings may reference this. |
Common applications
- Structural steelwork — buildings, bridges, platforms, masts
- General fabrication and heavy plate work
- Crane structures and lifting equipment
- Offshore structural components (with coating)
- Pressure vessel shells (to EN 10028-2)
- Heavy vehicle chassis and frames
- Wind turbine towers
- Railway rolling stock structures
History
S355 emerged from the European harmonisation of structural-steel standards in the 1990s–2000s, replacing a patchwork of national grades — most notably BS 4360 Grade 50 in the UK and St 52-3 in Germany.
- 1968BS 4360 first published, defining UK Grade 50 structural steels
- 1970DIN 17100 establishes St 52-3 as the standard German structural steel
- 1990EN 10025 first published, beginning European harmonisation
- 2004EN 10025:2004 major revision — S355 designation fully established