P235TR1 and P235TR2 pipe steel: properties, the TR difference, equivalents
P235TR1 (1.0254) is the welded non-alloy pressure tube of EN 10217-1: 235 MPa yield, 360–500 MPa tensile. The TR1 and TR2 difference, and equivalents to A53 and A106.
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What is P235TR1?
P235TR1 is the plain welded steel tube for pressure purposes in the European system, and the grade name is self-describing once the convention is read: P for pressure purposes, 235 for the minimum yield strength in MPa. Material number 1.0254. Tensile strength is bounded at both ends — 360–500 MPa — and minimum elongation is 25 %. Its predecessor on German drawings was St 37.0, and that name is still in daily use.
The whole substance of this grade lies in the suffix, and it is routinely misunderstood because TR1 and TR2 have the same mechanical property table. Identical yield, identical tensile range, identical elongation. Nothing in a tensile certificate tells them apart. What separates them is everything around the tensile test:
TR1 is the basic quality. No impact test. Non-destructive testing of the weld only if the order asks for it. Inspection document 2.2 (a non-specific test report) is sufficient. TR2 adds a mandatory Charpy test at 0 °C, mandatory non-destructive testing of the weld, tighter control of residual elements, and a 3.1 inspection certificate. That is why most national pressure-equipment rules — and the Pressure Equipment Directive route in practice — accept TR2 and not TR1 for a pressure-retaining part.
The second boundary worth fixing is temperature. TR means "specified room temperature properties". There is no proof-strength table above 20 °C anywhere in EN 10217-1, so the grade cannot be used for a hot line no matter how modest the pressure. The grade for that is P235GH in EN 10216-2 or EN 10217-2, which tabulates proof strength to 400 °C and requires impact testing. P235TR1, P235GH and the structural S235JRH all carry the number 235 and are three different products.
Across systems the closest match is ASTM A53 Grade B: almost the same strength, the same market, and the same absence of an impact requirement. The structural difference is how each specification subdivides its product — A53 by manufacturing type, EN 10217-1 by test quality.
P235TR1 chemical composition
| Element | Mass % | Note |
|---|---|---|
| C | ≤ 0.16 | |
| Si | ≤ 0.35 | |
| Mn | ≤ 1.2 | |
| P | ≤ 0.025 | |
| S | ≤ 0.02 |
EN 10217-1:2019, grade P235TR1 (1.0254). TR2 (1.0255) is the same base analysis with the residual elements more tightly controlled and, in some editions, a slightly lower carbon ceiling. The **P prefix means pressure purposes** and the number is the minimum yield strength in MPa — the same logic as P265GH and P355GH, and not to be confused with the S prefix of the structural grades.
P235TR1 mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| P235TR1 / TR2 — specified, t ≤ 16 mm | 235 (34.1) | 360–500 (52.2–72.5) | 25 (longitudinal) | — |
| P195TR1 / TR2 — specified | 195 (28.3) | 320–440 (46.4–63.8) | 27 (longitudinal) | — |
| P265TR1 / TR2 — specified | 265 (38.4) | 410–570 (59.5–82.7) | 21 (longitudinal) | — |
| P235TR1, typical mill result | 280–350 (40.6–50.8) | 400–460 (58.0–66.7) | 28–35 | 115–145 HB |
| Leak tightness test | — | — | — | hydrostatic or eddy current, every tube |
| Flattening and weld bend test | — | — | — | required by size and route |
**TR1 and TR2 share the same mechanical table.** The yield, tensile and elongation figures are identical, which is precisely why the pair is so often confused — nothing in a tensile certificate distinguishes them. The difference is in the impact requirement, the non-destructive testing and the inspection document, all listed below. Older third-party data sheets quoting 215 MPa for P235 are reporting the **seamless** standard EN 10216-1, not EN 10217-1.
Impact toughness
P235TR1 requires a minimum Charpy V-notch energy of 40 J longitudinal average of three (27 J transverse) J at 0 °C °C (TR2 only. Tested on the parent metal; test frequency and specimen orientation follow the standard's tables, and sub-size specimens carry proportionally reduced requirements.). P235TR1 has **no impact requirement at all**. This single line is the difference between the two qualities and the reason most national pressure-equipment rules accept TR2 and not TR1.
P235TR1 equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| A53 Grade B | ASTM / ASME | Near | ASTM A53 Grade B: 240 MPa minimum yield and 415 MPa minimum tensile with **no upper bound** on tensile, no silicon requirement and no impact test. Very close in strength to P235TR1 and the same market position; the differences are that A53 publishes no maximum tensile and splits its product by manufacturing type (F, E, S) while EN 10217-1 splits it by test quality (TR1, TR2). |
| A106 Grade B | ASTM / ASME | Near | ASTM A106 Grade B at 240/415, seamless only, with a silicon minimum and published elevated-temperature allowables. Its EN counterpart is not this grade but **P235GH to EN 10216-2/10217-2**, whose property table runs to 400 °C. P235TR1 is a room-temperature specification — that is what the TR designation means. |
| A53 Grade B | ASTM / ASME | Near | EN 10217-1 P235TR1: 235 MPa minimum yield, 360–500 MPa tensile — the European welded pipe for general service. Slightly lower strength, and TR1 carries no impact requirement while TR2 does; A53 carries none either, which makes TR1 the closer match. |
| P235GH | EN (European) | Near | 1.0345: the same 235 MPa strength level, but specified for **elevated temperature** with proof-strength values tabulated to 400 °C, a silicon minimum and mandatory impact testing. The GH grade is what a boiler or process line needs; the TR grades stop at room temperature. |
| STPG370 | JIS (Japan) | Near | JIS G3454 STPG370: 215 MPa minimum yield, 370 MPa minimum tensile, carbon steel pipe for ordinary pressure service, welded or seamless. The closest Japanese counterpart. |
| S195T | EN (European) | Functional | EN 10255 S195T: the threadable general-purpose tube for water, gas and low-pressure service at 195 MPa minimum yield. One step below in both strength and test regime, and specified in light, medium and heavy series rather than by wall thickness. |
| S235JRH | EN (European) | Functional | EN 10219 S235JRH: 235 MPa minimum yield **structural** hollow section. The same strength number, and a frequent source of error — the H grade carries no pressure-purpose requirements and the TR grade carries no section-property or structural tolerance guarantees. The prefix decides which one the drawing means. |
| DC01 | EN (European) | Functional | EN 10130 DC01: the cold-rolled forming sheet that welded precision tube is often made from. Listed because enquiries confuse the two — DC01 is a forming grade with no strength guarantee, and a tube rolled from it is a precision tube to EN 10305-3, not a pressure tube. |
| E355 | EN (European) | Functional | EN 10217-1 P235TR1: the welded pressure tube at 235 MPa yield. A pressure tube is specified for leak-tightness and wall integrity; a precision tube is specified for dimensions and finish. Neither substitutes for the other, and a precision tube should not be used as a pressure-retaining part without checking the design code. |
| Q235 | GB/T (China) | Functional | Chinese welded pressure tube to GB/T 3091 and GB 9948 is usually rolled from Q235B, at a comparable carbon and strength level. The grade system and test regime differ, so an equivalence claim should be checked against the actual tube standard rather than the steel grade. |
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 P235TR1 →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| St 37.0 | DIN 1626 (withdrawn) | The German welded pressure tube grade P235 descends from; the .0 suffix marked the pressure-purpose quality as distinct from structural St 37-2. Still written on older drawings and in stockist catalogues. |
| St 37.4 | DIN 1630 (withdrawn) | The seamless, higher-quality counterpart; its modern equivalent is EN 10216-1 P235TR2 or EN 10305-4 for precision tube. |
| HFS 23 / ERW 23 | BS 3601 (withdrawn) | The British pressure tube grades at a similar strength level. |
| TU 37b | NF A 49-141 | The French welded pressure tube designation. |
Product forms and tolerance standards
Product forms: electric-welded tube (EW), submerged-arc welded tube (SAW) in larger diameters, black or galvanized, plain end, bevelled or threaded.
Dimensional tolerances: diameter, wall thickness and length: EN 10217-1 with the size tables of EN 10220; every tube leak tested; TR2 adds non-destructive testing of the weld as a mandatory requirement; seamless counterpart: EN 10216-1, same grade designations, different property table.
Key property values
P235TR1 mechanical properties
235 MPa minimum yield (ReH), 360–500 MPa tensile, 25 % minimum elongation longitudinal for wall up to 16 mm. The tensile upper bound is worth noting — unlike ASTM A53, EN 10217-1 caps it, because a pressure tube that must be bent, expanded or welded in the field should not be arbitrarily strong. Typical mill results run 280–350 MPa yield and 400–460 MPa tensile. The sister grades are P195TR1 at 195 MPa and P265TR1 at 265 MPa.
TR1 against TR2 — the actual difference
The mechanical table is the same. TR2 adds four things: a mandatory Charpy impact test at 0 °C (40 J longitudinal average of three), mandatory non-destructive testing of the weld seam, tighter limits on residual elements, and a 3.1 inspection certificate rather than a 2.2 test report. TR1 has none of these. The practical consequence is regulatory: a pressure-retaining component normally needs TR2, and ordering TR1 to save a few per cent produces tube that cannot be used for the job. Ask for the suffix on every enquiry — a quotation for "P235" is not a quotation for either.
What TR means and why it limits temperature
TR = specified properties at room temperature. EN 10217-1 contains no proof-strength values above 20 °C, so there is no basis on which to calculate a wall thickness for a hot line. The elevated-temperature family is separate: P235GH, P265GH, P355GH in EN 10216-2 (seamless) and EN 10217-2 (welded), each with a proof-strength table running to 400 °C, a silicon minimum and mandatory impact testing. A tube ordered as P235TR2 cannot be used where the design code calls for P235GH, and the substitution is not a matter of margin — the data simply does not exist.
P235TR1, P235GH and S235JRH
Three grades, one number, constant confusion. P235TR1 / TR2 (EN 10217-1) — welded pressure tube, room temperature only. P235GH (EN 10216-2 / 10217-2) — pressure tube for elevated temperature, with hot proof strength tabulated. S235JRH (EN 10219) — structural hollow section, with section properties and structural tolerances but no pressure-purpose requirements at all. The 235 is the minimum yield in each case and tells you nothing about which document applies. The prefix is the specification; the number is only the strength.
Welded against seamless: EN 10217-1 and EN 10216-1
The two standards use the same grade designations for different products: EN 10217-1 is welded, EN 10216-1 is seamless, and each has its own property table. This is the source of a persistent data error — third-party databases quoting 215 MPa yield for P235 are reporting the seamless standard's figure, not the 235 MPa of EN 10217-1. When comparing a certificate against a published figure, confirm which of the two standards the figure came from.
Physical properties
Density 7.85 g/cm³, E = 210 GPa, thermal conductivity ≈ 52 W/m·K at 20 °C, expansion 12.0 × 10⁻⁶/K (20–100 °C). At 0.16 % maximum carbon the carbon equivalent is low — typically 0.25–0.35 — which is why the grade is welded without preheat in any normal wall thickness and is the usual choice where a tube will be fabricated on site.
Weldability
Excellent weldability by every arc process with no preheat in normal wall thickness; the carbon ceiling of 0.16 % keeps the carbon equivalent at roughly 0.25–0.35. E6013/E7018 or ER70S-6 consumables, no post-weld heat treatment required below the code thickness limits. The tube's own longitudinal seam is made by high-frequency induction or submerged arc; on TR2 that seam is non-destructively tested as a matter of course, while on TR1 it is only leak tested unless the order says otherwise — relevant when a branch or support is welded near the seam. Galvanized tube must have the zinc removed from the weld zone before welding.
Machining, forming and heat treatment
Machines easily, around 70–75 % relative to 1 % C free-cutting steel, and threads cleanly — though for threaded service the proper specification is EN 10255 rather than a pressure tube. Cold bending is straightforward at this carbon level and the capped upper tensile strength helps, since springback is predictable; mandrel bending down to about 2.5 D is routine. Expanding, flaring and swaging are practical. Cutting by saw, abrasive wheel or plasma; keep the heat-affected zone modest if a leak-tight joint will be made at the cut. For close-tolerance mechanical work the grade to use is a precision tube to EN 10305, not a pressure tube.
Typical applications
- Water, compressed air and low-pressure steam service at ambient temperature
- Heating circuits, chilled water and HVAC pipework
- Pressure vessels and tanks — connections, nozzles and non-fired coils (TR2)
- Fire protection and sprinkler mains
- Hydraulic and pneumatic lines in larger diameters
- General fabrication where a leak-tight, weldable tube is needed
- Fluid handling in food, chemical and process plant at room temperature
Frequently asked questions
What is the difference between P235TR1 and P235TR2?
Not the mechanical properties — those are identical, which is why the two are so often confused. TR2 adds a mandatory Charpy impact test at 0 °C, mandatory non-destructive testing of the weld seam, tighter control of residual elements and a 3.1 inspection certificate instead of a 2.2 test report. TR1 has none of these. Most national pressure-equipment rules accept TR2 and not TR1 for a pressure-retaining part, so the suffix must be on the order.
What does TR mean in P235TR1?
Specified properties at room temperature. The standard contains no proof-strength values above 20 °C, so the grade cannot be used to size a hot line. For elevated temperature the corresponding grades are P235GH, P265GH and P355GH in EN 10216-2 and EN 10217-2, which tabulate proof strength up to 400 °C.
What is the yield strength of P235TR1?
235 MPa minimum, with tensile strength between 360 and 500 MPa and elongation at least 25 % for wall thickness up to 16 mm. Note that EN 10217-1 caps the tensile strength at the top as well as the bottom. Data sheets quoting 215 MPa are reporting the seamless standard EN 10216-1, not the welded EN 10217-1.
Is P235TR1 the same as St 37.0?
It is the direct successor. St 37.0 to DIN 1626 was the welded pressure tube grade — the .0 suffix marking the pressure-purpose quality, distinct from the structural St 37-2 — and EN 10217-1 replaced it with P235TR1 and TR2. The two names refer to the same material in practice, and stockists still list both.
What is the ASTM equivalent of P235TR1?
ASTM A53 Grade B is the nearest, at 240 MPa minimum yield and 415 MPa minimum tensile, with no impact requirement — the same absence as TR1. The structural difference is how each specification subdivides its product: A53 by manufacturing type (F, E, S) and EN 10217-1 by test quality (TR1, TR2). A106 Grade B is a seamless elevated-temperature pipe and corresponds to P235GH rather than to this grade.
What is the difference between P235TR1 and S235JRH?
The prefix. P is for pressure purposes and S is for structural, and they lead to different standards: P235TR1 is a welded pressure tube to EN 10217-1, while S235JRH is a structural hollow section to EN 10219 with section properties, structural tolerances and a J-quality impact class but no pressure-purpose requirements. Both have a minimum yield of 235 MPa, which is all the number tells you.
Can P235TR1 be used for a pressure vessel?
Generally not as a pressure-retaining part — that normally requires TR2, because the conformity route expects impact testing, non-destructive testing of the weld and a 3.1 certificate, none of which TR1 provides. TR1 is used for non-critical service lines, water, air and heating circuits. The design code or notified body determines what is acceptable, so the question should be settled before ordering rather than after.
Is P235TR1 weldable without preheat?
Yes, in any normal wall thickness. With carbon capped at 0.16 % the carbon equivalent sits around 0.25–0.35, which is low enough for every arc process without preheat and without post-weld heat treatment below the code's thickness limits. That weldability is one of the main reasons the grade is specified for site-fabricated pipework.
Related grades
Verified against EN 10217-1:2019; EN 10217-1:2019 — welded steel tubes for pressure purposes, non-alloy with room temperature properties; EN 10216-1 (seamless counterpart, different property table); DIN 1626 (St 37.0 comparison); ASTM A53/A53M (comparison). Last checked: October 2026.