S355 Steel: EN 10025 Structural Steel Grades (S355JR, J0, J2, K2, NL)
EN 10025-2:2019 · Published: 2026-07-25 · Updated: August 2026
S355 steel (EN 10025-2:2019) is the standard European high-strength structural steel, delivering 355 MPa minimum yield strength for thicknesses ≤16 mm—2% higher than A572 Gr 50 and 42% higher than A36/S275. S355 is the default structural grade...
S355 steel (EN 10025-2:2019) is the standard European high-strength structural steel, delivering 355 MPa minimum yield strength for thicknesses ≤16 mm—2% higher than A572 Gr 50 and 42% higher than A36/S275. S355 is the default structural grade for European building construction, bridges, offshore platforms, and general engineering where Eurocode 3 (EN 1993) design applies. The S355 family includes sub-grades distinguished by impact test temperature: S355JR (27J at +20°C), S355J0 (27J at 0°C), S355J2 (27J at -20°C), S355K2 (40J at -20°C), and S355NL/NL1 (normalized for low-temperature service). Choose higher sub-grades for colder climates or fracture-critical applications. For thicknesses >16 mm, yield strength decreases progressively: 345 MPa for 16-40 mm, 335 MPa for 40-63 mm, 325 MPa for 63-80 mm, 315 MPa for 80-100 mm, and 295 MPa for 100-150 mm. S355 is also produced in weathering grade (S355J0W/J2W per EN 10025-5) with copper-chromium alloying for atmospheric corrosion resistance, similar to ASTM A588 Cor-Ten. For the most common sub-grade data sheets, see s355j2/">S355J2, s355j2-en10025/">S355J2 (EN10025), and s355k2/">S355K2. For the equivalent North American grade, see a572-steel/">A572 steel.
Quick Facts
| Category | Carbon Steel |
| Standard | EN 10025-2:2019 |
| Density | 7.85 g/cm³ |
| Yield Strength | 355 MPa (51 ksi) for t ≤ 16mm |
| Tensile Strength | 470-630 MPa (68-91 ksi) |
Detailed Mechanical Properties
| Elongation | 20% (in 200mm, J2 sub-grade) |
| Hardness | 140-200 HB |
| Charpy V Notch | 27J at -20°C (J2); 40J at -20°C (K2) |
| Modulus Of Elasticity | 210 GPa |
Physical Properties
| Melting Point | 1420-1530 °C |
| Thermal Conductivity | 50 W/m·K at 20°C |
| Electrical Resistivity | 0.0000180 Ω·cm |
| Specific Heat | 480 J/kg·K |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| EN S355 | Compare |
| ASTM A572 Gr 50 | Compare |
| GB Q345/Q355 | Compare |
| DIN St52-3 | Compare |
| CSA G40.21 350W | Compare |
Heat Treatment & Processing
| Normalizing | 870-920°C, air cool (specified for NL grades) |
| Stress Relieving | 530-580°C for stress relief after heavy fabrication |
| Note | S355 is supplied in as-rolled or normalized condition. Strength comes from chemistry, not heat treatment. Normalizing improves toughness for fracture-critical applications. |
Welding & Fabrication
| Preheat | Generally not required for t<25mm; 50-100°C for 25-50mm; per EN 1011-2 for thicker sections |
| Filler Metal | E7018 (SMAW), ER70S-6 (GMAW); match filler to sub-grade toughness for fracture-critical |
| Interpass Temp | Max 250°C for J2/K2 grades |
| Weldability Rating | Excellent for JR/J0/J2 grades; good for K2 with proper preheat |
Related Materials
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Frequently Asked Questions
What is the difference between S355JR, J0, J2, and K2?
The suffix denotes Charpy V-notch impact test temperature and energy. JR: 27J at +20°C (room temp). J0: 27J at 0°C. J2: 27J at -20°C. K2: 40J at -20°C (higher energy). For outdoor structures in temperate climates, J2 is typically specified; for arctic or fracture-critical applications, K2 or NL (normalized, -50°C) grades are used.
What is the ASTM equivalent of S355?
ASTM A572 Grade 50 (345 MPa / 50 ksi yield) is the closest equivalent, with 10 MPa lower yield but similar chemistry and weldability. ASTM A572 Gr 50, EN S355, and GB Q345/Q355 are generally considered cross-reference equivalents for international structural design.
What is the difference between S355 and S275?
Yield strength. S355 has 355 MPa minimum yield (t≤16mm); S275 has 275 MPa—29% lower. S355 enables lighter sections for the same design capacity, reducing weight, foundation loads, and total cost for most modern construction. S275 remains common for less critical structures and repair work.
Can S355 be welded?
Yes, S355 has excellent weldability with carbon equivalent typically 0.35-0.43 (sub-grade dependent). Use E7018 (SMAW) or ER70S-6 (GMAW) filler. Preheat is generally not required for thicknesses under 25 mm; for thicker sections or low-ambient-temperature fabrication, preheat per EN 1011-2 based on carbon equivalent.
Is S355 the same as A36?
No. S355 has 355 MPa yield—42% higher than A36's 250 MPa. S355 is the European equivalent of A572 Gr 50, not A36. The European equivalent of A36 is S275JR (275 MPa yield). Substituting S275 for S355 (or A36 for A572) without re-engineering can result in under-designed structures.
References & International Standards
- ASTM International. Standard Specifications for Steel & Metal Alloys. astm.org
- International Organization for Standardization (ISO). Metallic Materials — Cross-Reference Database. iso.org
- American Iron and Steel Institute (AISI). Steel Grade Designations & Equivalents. steel.org
- European Committee for Standardization (CEN). EN Steel Standards & Numbering System. cencenelec.eu
Structural & Carbon Steel — Engineering Reference
Structural steels are the backbone of construction and heavy industry. Grades in this category are specified primarily by their yield strength, tensile strength, and weldability — the three properties that determine whether a building stands or a bridge holds.
ASTM A36/A572/A516, EN 10025, JIS G3101/G3106, GB/T 700/1591
Building frames, bridges, pressure vessels, shipbuilding, offshore platforms, pipelines
When selecting a structural grade, match the required yield strength to the design load, but also verify Charpy impact values if the structure will operate below freezing — many structural steels undergo a ductile-to-brittle transition at low temperatures.