P235GH steel (1.0345): properties, composition, equivalents
P235GH (1.0345) is the entry grade of EN 10028-2: 235 MPa yield at room temperature and, unlike a structural steel, guaranteed proof strength up to 400 °C.
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What is P235GH?
P235GH is where the pressure-vessel standards begin, and its designation says what it is for: P for pressure purposes, 235 for minimum yield in MPa, G for other specified characteristics and H for elevated temperature. Its Werkstoff number is 1.0345.
On paper it looks like S235JR — the same 235 MPa yield, the same low carbon — and it is a different product. Three things separate them. First, EN 10028-2 guarantees proof strength at temperature, tabulated from 50 °C to 400 °C, which is the number a vessel or pipe wall thickness is actually calculated from. A structural steel has no such data and therefore cannot be used in a pressure calculation at all. Second, the chemistry is held far tighter: phosphorus to 0.025 % and sulphur to 0.015 %, with a minimum aluminium that forces a fully killed, fine-grained steel. Third, the plate is supplied normalised, not as-rolled.
The grade is the workhorse of low-pressure and moderate-temperature equipment — boiler drums, heat exchanger shells, steam pipework, air receivers and process vessels — and it is the reference point from which P265GH, P295GH and P355GH step up in strength. It is also the answer to the most common designation error in this family: there is no such grade as S235GH. S belongs to the structural standard, P to the pressure standard, and the two letters are not interchangeable.
P235GH chemical composition
| Element | Mass % | Note |
|---|---|---|
| C | ≤ 0.16 | |
| Si | ≤ 0.35 | |
| Mn | 0.6 – 1.2 | |
| P | ≤ 0.025 | tighter than any structural S235 grade |
| S | ≤ 0.015 | less than half the S235JR limit |
| Al | ≥ 0.02 | total aluminium — the grade is fully killed and grain refined |
| Cr | ≤ 0.3 | |
| Ni | ≤ 0.3 | |
| Mo | ≤ 0.08 | |
| Cu | ≤ 0.3 |
EN 10028-2:2017 ladle analysis. The residual elements are capped because they affect behaviour at temperature and in service ageing, and the aluminium minimum forces a fully killed, fine-grained steel. This is the same carbon level as S235JR bought under far tighter control.
P235GH mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| ≤ 16 mm, room temperature | 235 (34.1) | 360–480 (52.2–69.6) | 24 | ≈ 110–150 HB (typical) |
| > 16 ≤ 40 mm | 225 (32.6) | 360–480 (52.2–69.6) | 24 | — |
| > 40 ≤ 60 mm | 215 (31.2) | 360–480 (52.2–69.6) | 24 | — |
| > 60 ≤ 100 mm | 200 (29.0) | 350–480 (50.8–69.6) | 24 | — |
| 0.2 % proof at 200 °C (≤ 16 mm) | ≈ 165 (≈ 23.9) | — (—) | — | — |
| 0.2 % proof at 300 °C (≤ 16 mm) | ≈ 139 (≈ 20.2) | — (—) | — | — |
| 0.2 % proof at 400 °C (≤ 16 mm) | ≈ 121 (≈ 17.5) | — (—) | — | — |
The elevated-temperature rows are the point of the grade and are approximate: the governing values are the minimum 0.2 % proof strengths tabulated by thickness in EN 10028-2 Table 5, and a pressure calculation must take them from the standard rather than from a summary. Delivery condition is normalised (+N).
Impact toughness
P235GH requires a minimum Charpy V-notch energy of 27 J at 20 °C (longitudinal; transverse values are lower and set separately). EN 10028-2 requires impact testing at +20 °C with minimum average energies given for longitudinal and transverse specimens. Where a vessel code sets a lower design temperature, testing at that temperature is agreed as a supplementary requirement.
P235GH equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| P265GH | EN (European) | Near | The grade above in the same standard: 265 MPa yield and correspondingly higher proof strength at temperature. Same family, same delivery condition. |
| A516 Grade 70 | ASTM / ASME | Functional | ASTM A516 Gr. 70 is far stronger (260 MPa yield, 485–620 MPa tensile) and notch-toughness oriented; A285 Gr. C is the closer American match to P235GH. |
| A106 Grade B | ASTM / ASME | Functional | The American seamless pressure pipe counterpart; comparable duty to P235GH TC1/TC2 tube, different property basis. |
| S235JR | EN (European) | Functional | Same room-temperature yield and similar carbon, but no elevated-temperature proof values, looser P and S, and no normalising requirement. It cannot be substituted into a pressure calculation. |
Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for P235GH →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| H I | DIN 17155 (withdrawn) | The legacy German boiler plate designation; still quoted on older vessel drawings and in the Middle East. |
| St 35.8 | DIN 17175 (withdrawn) | The tube designation of the same class; St 35.8/I and St 35.8/III map onto P235GH TC1 and TC2. |
| Fe 360-1 KW | EURONORM 28 (withdrawn) | Pre-EN European designation for the same pressure quality. |
Product forms and tolerance standards
Product forms: normalised plate and wide flat (EN 10028-2), seamless tube as P235GH TC1 and TC2 (EN 10216-2), welded tube as P235GH TC1 (EN 10217-2), pipe fittings and flanges (EN 10222-2 forgings), strip for welded pressure tube.
Dimensional tolerances: plate: EN 10029; seamless tube: EN 10216-2 dimensional clauses; welded tube: EN 10217-2; surface condition: EN 10163-2 class A or B for plate.
Key property values
P235GH yield strength
235 MPa minimum up to 16 mm at room temperature, 225 MPa to 40 mm, 215 MPa to 60 mm and 200 MPa to 100 mm, with tensile 360–480 MPa. The room-temperature figure is the familiar one; it is rarely the number that sizes the component.
P235GH at temperature
The defining data. Minimum 0.2 % proof strength falls to roughly 165 MPa at 200 °C, 139 MPa at 300 °C and 121 MPa at 400 °C for material up to 16 mm, with the governing values tabulated by thickness in EN 10028-2. Above about 400 °C the grade runs out: creep governs, and the specification moves to 16Mo3 or a chromium-molybdenum steel.
P235GH chemical composition
C ≤ 0.16 %, Si ≤ 0.35 %, Mn 0.60–1.20 %, P ≤ 0.025 %, S ≤ 0.015 %, Al ≥ 0.020 % total, with Cr, Ni, Cu each ≤ 0.30 % and Mo ≤ 0.08 %. The residual ceilings and the aluminium minimum are what make it a pressure grade rather than a structural one with the same carbon.
P235GH TC1 and TC2
The tube designations from EN 10216-2 (seamless) and EN 10217-2 (welded). TC1 covers the standard test category and TC2 the enhanced one, with additional testing on each length. They correspond to the old DIN 17175 St 35.8/I and St 35.8/III, which is the equivalence most often asked for on boiler-tube enquiries.
P235GH vs P265GH
P265GH is the same steel family with 265 MPa room-temperature yield and proportionally higher proof strength at every temperature, at the cost of slightly more carbon and manganese. The choice is a wall-thickness calculation: P265GH buys thinner walls for the same duty, P235GH welds a little more easily and costs slightly less.
Weldability
P235GH is designed to be welded and is among the most forgiving pressure grades. Carbon equivalent is low, and preheat is generally unnecessary below about 30 mm; above that, 100–150 °C preheat is normal practice in restrained joints. Use consumables matched to the parent grade and qualified to the applicable vessel code — the procedure, not the material certificate, is what the inspector accepts. Post-weld heat treatment is governed by the design code and the thickness rather than by the steel: many thin-walled vessels in this grade are built without it. The tight sulphur ceiling is a direct welding benefit, reducing hot-cracking risk in heavy restrained welds.
Machining, forming and heat treatment
Machinability is good and comparable to other low-carbon normalised steels. Cold forming — rolling shells, dishing heads, bending tube — is straightforward, and the normalised fine-grained structure gives consistent springback. Where cold forming exceeds the strain limits in the design code, re-normalising after forming is required; that is a code question rather than a material one, and it is the usual reason a dished end carries a heat-treatment certificate of its own.
Typical applications
- Boiler drums, headers and low-pressure steam equipment
- Heat exchanger shells, channels and tube sheets in moderate-temperature duty
- Steam and hot-water pipework as P235GH TC1 or TC2 tube
- Air receivers, compressed-air vessels and buffer tanks
- Process vessels and reactors operating below about 400 °C
- Pipe fittings, flanges and forged components to EN 10222-2
P235GH compared with related grades
Frequently asked questions
What is P235GH steel?
P235GH (1.0345) is the entry grade of EN 10028-2, the European standard for non-alloy pressure-vessel steels with elevated-temperature properties. It has a 235 MPa minimum yield at room temperature and, crucially, guaranteed proof strength tabulated up to 400 °C.
What is the difference between P235GH and S235JR?
P235GH has elevated-temperature proof strength data, tighter phosphorus and sulphur (0.025 % and 0.015 %), a minimum aluminium content and a normalised delivery condition. S235JR has none of these, so it cannot be used in a pressure calculation even though its room-temperature yield is the same.
What does GH mean in P235GH?
G means other characteristics are specified and H means elevated-temperature properties. The P before the number marks the pressure-purposes standard EN 10028; a grade beginning with S, such as S235JR, belongs to the structural standard EN 10025 instead.
Is there a grade called S235GH?
No. It is one of the most common designation errors on drawings, mixing the S of the structural standard with the GH of the pressure standard. The grade being asked for is almost always P235GH, or occasionally S235JR where no pressure duty exists.
What is the maximum temperature for P235GH?
Design data runs to 400 °C, and that is the practical ceiling. Above it creep governs the design rather than proof strength, and the specification moves to a molybdenum-bearing grade such as 16Mo3 or to a chromium-molybdenum steel for higher duty.
What is P235GH TC1?
The tube version, from EN 10216-2 for seamless and EN 10217-2 for welded pipe. TC1 is the standard test category and TC2 the enhanced one; they correspond to the withdrawn DIN 17175 grades St 35.8/I and St 35.8/III.
What is the ASTM equivalent of P235GH?
A285 Grade C is the closest plate match on strength and duty. A516 Grade 70 is often quoted but is considerably stronger and toughness-oriented; for tube, A106 Grade B covers comparable service to P235GH TC1 and TC2.
Related grades
Verified against EN 10028-2:2017; EN 10028-2:2017 Tables 1, 4 and 5; EN 10216-2 / EN 10217-2 (tube designations TC1 and TC2). Last checked: November 2026.