What is P355NH steel plate?
EN 10028-3 is the pressure-vessel equivalent of the fine-grain structural standard EN 10025-3: the steels are micro-alloyed with niobium, vanadium and titanium, aluminium-killed for a fine grain, and delivered normalised. The family has four toughness levels at 355 MPa — P355N (−20 °C, 40 J), P355NH (−20 °C, 40 J, plus certified elevated-temperature properties to 400 °C: 216 MPa at 300 °C), P355NL1 (−40 °C) and P355NL2 (−50 °C). NH is therefore the all-round grade: it serves as a boiler plate like P355GH and as a cold-toughness tank plate like the NL grades. Carbon is limited to 0.18 % (lower than P355GH's 0.22 %), sulphur to 0.015 %, giving a carbon equivalent of 0.40–0.43 and slightly milder welding rules. It is the material most LPG vessel specifications in Europe and the Middle East name outright, alongside its DIN predecessor WStE 355.
Chemical composition
| Element | C | Si | Mn | P | S | Al | Nb | V | Ti | Ni | Cr | Mo | Cu | N |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| max. % (ladle) | ≤ 0.18 | ≤ 0.50 | 0.90–1.70 | ≤ 0.025 | ≤ 0.015 | ≥ 0.020 | ≤ 0.05 | ≤ 0.10 | ≤ 0.03 | ≤ 0.50 | ≤ 0.30 | ≤ 0.08 | ≤ 0.30 | ≤ 0.020 |
Nb + Ti + V ≤ 0.12 %. CEV 0.40–0.43 typical.
Mechanical properties
| Thickness | Yield ReH min (MPa) | Tensile Rm (MPa) | Elongation A min | Impact KV |
|---|---|---|---|---|
| ≤ 16 mm | 355 | 490–630 | 22 % | 40 J at −20 °C (long.) / 27 J trans. |
| > 16–40 mm | 345 | 490–630 | 22 % | 40 J at −20 °C |
| > 40–60 mm | 335 | 490–630 | 22 % | 40 J at −20 °C |
| > 60–100 mm | 325 | 470–610 | 21 % | 40 J at −20 °C |
| Rp0.2 at 100 / 200 / 300 / 400 °C (≤ 16 mm) | 304 / 265 / 216 / 194 | — | — | — |
Equivalent grades
| System | Grade | Note |
|---|---|---|
| DIN 17102 | WStE 355 | direct predecessor |
| EN 10028-3 | P355N / P355NL1 / P355NL2 | siblings: −20 / −40 / −50 °C |
| ASTM | A537 Cl. 1 | normalised C-Mn-Si pressure plate |
| ASTM | A516 Gr. 70 (normalised, CVN −20 °C) | near |
| JIS G3115 | SPV355 | |
| GB 713 | Q345R (N) |
Thickness range and stock sizes
| Thickness | Widths × lengths | Availability |
|---|---|---|
| 6–12 mm | 2 000 / 2 500 × 6 000–12 000 | to order 3–5 weeks |
| 15–40 mm | 2 500 / 3 000 × 6 000–12 000 | to order 3–5 weeks |
| 50–100 mm | 2 500 × 6 000–10 000 | to order 5–6 weeks, UT standard |
Weight per m² and per plate
| Thickness | kg/m² | 1 500 × 6 000 (kg) | 2 000 × 6 000 (kg) | 2 500 × 12 000 (kg) |
|---|---|---|---|---|
| 6 mm | 47.1 | 424 | 565 | 1 413 |
| 8 mm | 62.8 | 565 | 754 | 1 884 |
| 10 mm | 78.5 | 707 | 942 | 2 355 |
| 12 mm | 94.2 | 848 | 1 130 | 2 826 |
| 15 mm | 117.8 | 1 060 | 1 413 | 3 533 |
| 20 mm | 157.0 | 1 413 | 1 884 | 4 710 |
| 25 mm | 196.3 | 1 766 | 2 355 | 5 888 |
| 30 mm | 235.5 | 2 120 | 2 826 | 7 065 |
| 40 mm | 314.0 | 2 826 | 3 768 | 9 420 |
| 50 mm | 392.5 | 3 533 | 4 710 | 11 775 |
| 60 mm | 471.0 | 4 239 | 5 652 | 14 130 |
| 80 mm | 628.0 | 5 652 | 7 536 | 18 840 |
| 100 mm | 785.0 | 7 065 | 9 420 | 23 550 |
Nominal weights — mill tolerance to EN 10029 class A adds up to +4 % on thin plate; invoiced on theoretical weight unless agreed otherwise.
Welding, cutting and forming
Qualified procedures with basic low-hydrogen consumables matched for −20 °C toughness (E46 4 / G46 4 or better); preheat 75 °C above 25 mm and 100 °C above 40 mm (milder than P355GH thanks to the lower CEV), interpass ≤ 250 °C, heat input 1.0–2.5 kJ/mm to preserve the fine grain. PWHT 550–600 °C where the code requires (typically above 30 mm) — the grade is designed for it. Cold forming 2.5 × t; hot forming with re-normalising. Z25 quality recommended for nozzle reinforcement pads and skirt attachments on thick plate.
Where it is used
- LPG spheres, bullets and mounded vessels
- Ammonia and refrigerated-gas storage tanks
- Pressure vessels in cold climates (Kazakhstan, Balkans)
- Steam drums and boilers where −20 °C toughness is required
- Column and reactor shells to 400 °C
- Heat exchangers for refrigeration and petrochemical plants
P355NH vs P355GH
Same strength, two philosophies. P355GH (EN 10028-2) is a plain C-Mn boiler steel with elevated-temperature properties; toughness at −20 °C is an option. P355NH (EN 10028-3) is a micro-alloyed fine-grain steel with 40 J at −20 °C as standard, the same temperature curve up to 400 °C, lower carbon and easier welding — at a premium of about 30 USD/t. For boilers and hot service either works; for LPG, ammonia and any vessel with a design temperature at or below 0 °C, NH is the correct grade. See P355GH and the structural cousin S355NL.
Price
P355NH is priced about 250 USD/t over the S235JR base as an imported fine-grain pressure plate; UT, Z-quality and 3.2 inspection are added per ton. Indicative FOB Istanbul band below.
Bands from our weekly export list (September 2026), FOB Istanbul, full-container quantities, excluding freight and certificates. Firm price per project on RFQ within one working day.
Export and packing
We ship P355NH steel plate in strapped skid packs up to 5 t, each plate stencilled with its heat number so the certificate can be matched at the receiving end. One 40' HC carries 24–25 t of 6 m plate; short plate goes 20 t to a 20'. Plates longer than 6 m or heavier packs are booked on flat-racks or as breakbulk cargo out of Derince. Tariff heading 7208.51 / 7208.52.
| Term | Detail |
|---|---|
| MOQ | 20 t (mill lot) |
| Incoterms | FOB Istanbul · CIF / CFR Gulf, Africa · DAP EU, Balkans, Iraq, Caucasus · DAP Aktau |
| Lead time | To order 3–6 weeks (EU / Turkish mill programme) |
| Packing | Loose on bearers or skids ≤ 5 t, strapped, heat numbers stencilled |
| Container / truck | ≤ 6 m: 40' HC 24–25 t; 8–12 m flat-rack / breakbulk |
| Documents | Invoice, packing list, EN 10204 3.1 (3.2 on request), certificate of origin; SASO / SONCAP / PVoC on request |
| Payment | 30% advance, balance against B/L copy; L/C at sight for orders above 100 t |
Certificates and testing
Every lot of P355NH steel plate carries an EN 10204 3.1 inspection certificate listing heat, chemistry, mechanical and impact results. On request we add 3.2 witnessing by a classification society or inspector, EN 10160 ultrasonic testing and supplementary impact tests at the customer's design temperature.
How to order
Send thickness × width × length, tonnage, design temperature and pressure code, certificate (3.1 / 3.2 with inspector), UT class and Z-quality; for spheres we also need the petal cutting plan if you want plates cut to net shape.
Standards
- EN 10028-3:2017 — P355NH, 1.0565 (also P355N, P355NL1, P355NL2)
- PED 2014/68/EU; AD 2000 W1
- EN 10160 UT; EN 10164 Z15/Z25
- DIN 17102 — WStE 355 (withdrawn)
Grades
Grade data sheets (chemistry, mechanicals, equivalents) are on our reference site: P355NH · P355GH · S355NL
Frequently asked questions
What is P355NH steel?
A normalised, micro-alloyed fine-grain pressure-vessel steel to EN 10028-3 (1.0565) with 355 MPa yield, 40 J impact at −20 °C as standard and certified elevated-temperature properties to 400 °C; formerly DIN WStE 355.
What is the difference between P355NH and P355GH?
P355NH is a fine-grain steel with guaranteed −20 °C toughness and lower carbon; P355GH is a plain C-Mn boiler steel where cold toughness is only an option. Both have the same yield and temperature curve.
What is the difference between P355N, P355NH, P355NL1 and P355NL2?
N: −20 °C, no elevated-temperature guarantee; NH: −20 °C plus elevated-temperature properties; NL1: −40 °C; NL2: −50 °C. All 355 MPa, EN 10028-3.
Which steel plate is used for LPG tanks?
In Europe and the Middle East mostly P355NH (or P355NL1/NL2 for lower design temperatures); in the ASME world A516 Grade 70 normalised with impact testing or A537 Class 1.
What is the ASTM equivalent of P355NH?
ASTM A537 Class 1 is the closest (normalised C-Mn-Si pressure plate); A516 Gr. 70 normalised with −20 °C Charpy testing is often accepted.