S235, S275 and S355 steel: differences and how to choose
Published on 25 October 2026 by Metal S.r.l.
In fabrication drawings the material is almost always one of three grades: S235, S275 or S355. They are non-alloy structural steels covered by EN 10025-2. They look alike, but they are not interchangeable.
What the designation means
S stands for structural steel. The number is the minimum yield strength in MPa, measured on thicknesses up to 16 mm. The letters that follow (JR, J0, J2, K2) indicate impact toughness: the temperature at which the steel withstands impact without brittle fracture.
Quick comparison
| Grade | Min. yield (≤16 mm) | Tensile strength (3–100 mm) | Typical use |
|---|---|---|---|
| S235 | 235 MPa | 360–510 MPa | Light fabrication, brackets, railings, frames |
| S275 | 275 MPa | 410–560 MPa | Medium structures, commercial beams and sections |
| S355 | 355 MPa | 470–630 MPa | Loaded structures, machinery, lifting |
Toughness letters
| Letter | Impact test at |
|---|---|
| JR | +20 °C |
| J0 | 0 °C |
| J2 | −20 °C |
| K2 | −20 °C, higher energy |
For outdoor structures, cold areas or parts exposed to impact, designers often specify J2 instead of JR.
How to choose
- S235: when the part does not work at its limit. The easiest to find in sheet and to bend.
- S275: a middle ground, common in stock sections.
- S355: when strength matters. For the same load it allows thinner sections and less weight, but costs a little more and springs back more when bent.
The grade is chosen by the designer or the structural calculation, not by the workshop. If the drawing does not state it, we ask before cutting.
Welding and fabrication
All three weld well with MIG/MAG and TIG. Thick S355 may need preheating, according to the procedure. In bending, S355 has more springback and needs larger inside radii.
Certificates
If the part goes into a structure, a 3.1 EN 10204 material certificate is usually required: it states grade, heat number and tests performed. Ask for it at quotation stage. See Material certificates 3.1 EN 10204.
Conclusion
Always state the grade on the drawing, with the toughness letter if needed. If in doubt, send us the drawing and we will tell you right away how to proceed.
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