P355GH vs S355J2: differences explained
P355 vs S355: the same 355 MPa yield at room temperature, but P is a pressure grade proven at 400 °C and S is a structural grade proven at −20 °C. The letter decides which code you may design in.
Last updated
Overview
The two grades are cousins with the same headline number and entirely different qualification. P355GH belongs to EN 10028-2, the standard for pressure-purpose plate: it carries guaranteed proof strength at elevated temperature, up to 400 °C or beyond, because a vessel wall gets hot. S355J2 belongs to EN 10025-2, structural steel: it carries a Charpy value at −20 °C, because a bridge gets cold.
One more thing worth saying plainly, because it is the single most common error in enquiries: there is no such grade as S355GH. The S prefix belongs to structural steel and the GH suffix to pressure steel; mixing them produces a designation no standard defines. What the enquiry almost always means is P355GH.
P355GH vs S355J2 side by side
| Property | P355GH | S355J2 |
|---|---|---|
| Standard | EN 10028-2:2017 (pressure purposes) | EN 10025-2:2019 (structural) |
| Material number | 1.0473 | 1.0577 |
| Purpose | Boilers, pressure vessels, heat exchangers | Structures, frames, bridges, machinery |
| Min. yield ReH, ≤ 16 mm | 355 MPa | 355 MPa |
| Yield at 200 °C | 255 MPa (guaranteed) | Not guaranteed |
| Yield at 300 °C | 213 MPa (guaranteed) | Not guaranteed |
| Yield at 400 °C | 181 MPa (guaranteed) | Not guaranteed |
| Tensile Rm | 510–650 MPa | 470–630 MPa |
| Impact test | 27 J at 0 °C (longitudinal, standard) | 27 J at −20 °C |
| Max C | 0.20 % | 0.24 % |
| Max Mn | 1.10–1.70 % | 1.60 % |
| Max P / S | 0.025 / 0.015 % | 0.035 / 0.035 % |
| Cleanliness | Tighter — designed for welded pressure joints | Standard structural limits |
| Delivery condition | N (normalised) | As rolled, N or M |
| Forms | Plate only, 5–150 mm | Plate, sections, hollow sections, bar |
| Design codes | EN 13445, AD 2000-Merkblatt, PED 2014/68/EU | EN 1993 (Eurocode 3) |
| ASTM counterpart | A516 Gr 70 (closest, not identical) | A572 Gr 50 |
| Certificate | EN 10204 3.1 with elevated-temperature data | EN 10204 3.1 with −20 °C Charpy |
| Price difference | 15–30 % over structural plate | Baseline |
| Does S355GH exist? | No — the designation is invalid | No |
Which should you choose?
P355GH whenever the steel is part of a pressure envelope or sees service temperature above about 100 °C — vessel shells, boiler drums, heat exchanger shells, steam pipework flanges. S355J2 for everything structural, especially where cold toughness matters. They are not substitutes in either direction: using S355J2 in a pressure vessel fails the code because there is no proof strength at temperature, and using P355GH in a cold outdoor frame pays 15–30 % more for a property the frame does not need while giving up the −20 °C impact guarantee.
- Pressure vessels and boiler parts designed to EN 13445 or AD 2000
- Anything inside the scope of the Pressure Equipment Directive
- Service above roughly 100 °C, where structural yield values stop being valid
- Heat exchanger shells, separator bodies, steam drums and their nozzles
- Where the specification asks for elevated-temperature proof strength on the certificate
- Beams, columns, bracing and baseplates designed to Eurocode 3
- Outdoor and cold-climate structures needing a −20 °C Charpy value
- Anything that has to be CE marked under EN 1090
- Hollow sections and rolled sections, which EN 10028-2 does not cover at all
- Cost-sensitive plate work with no temperature requirement
Frequently asked questions
What is the difference between P355GH and S355J2?
P355GH is a pressure-vessel plate with guaranteed proof strength at elevated temperature and tighter phosphorus and sulphur; S355J2 is a structural steel with a guaranteed Charpy value at −20 °C. Room-temperature yield is 355 MPa for both.
Is there a grade called S355GH?
No. The S prefix means structural (EN 10025) and GH means pressure purposes at elevated temperature (EN 10028). Enquiries asking for S355GH almost always mean P355GH.
Can I use S355J2 instead of P355GH?
Not in pressure equipment. The design code requires proof strength at design temperature, which S355J2 does not guarantee, and the notified body will reject the material certificate.
Can I use P355GH for a structure?
Technically it is strong enough, but it costs more, comes only as plate, and its standard impact test is at 0 °C rather than −20 °C. For a cold outdoor structure it is the wrong choice despite being the more expensive steel.
What is the ASTM equivalent of P355GH?
A516 Grade 70 is the usual counterpart — both are normalised pressure-vessel plates in the same strength class — but the chemistry and the elevated-temperature tables differ, so it is functional equivalence rather than a substitution.
Which is easier to weld?
Both weld with standard procedures. P355GH has tighter sulphur and phosphorus limits and is supplied normalised, which helps in thick pressure joints; S355J2 allows slightly more carbon, so above 30 mm preheat is checked from the actual CEV.
Related comparisons
Verified against EN 10028-2:2017 · EN 10025-2:2019. Last checked: October 2026.