Short Answer
P235TR1 and P235TR2 are both non-alloy welded steel pipes for pressure service, specified in EN 10217-1 for applications with defined room-temperature properties. The number 235 is the minimum yield strength in MPa; TR1 and TR2 are two quality levels. TR2 adds three guarantees that TR1 does not carry: a minimum total aluminium addition for grain refinement, a Charpy V-notch impact requirement of 27 J at 0 °C, and full-length non-destructive examination of the weld seam. If your enquiry asks for certified impact values or ultrasonic weld inspection, the grade you are describing is TR2, not TR1.
What the Designation Means
EN 10217-1 covers electric resistance welded and submerged arc welded tubes of circular cross-section made from non-alloy quality steel with specified room-temperature properties. The current edition is EN 10217-1:2019; earlier versions are cited as EN 10217-1:2002 + A1:2005, and the edition should be stated in the purchase order. The grade name reads as follows:
P - pressure application
235 - minimum yield strength of 235 MPa for wall thickness up to 16 mm
TR1 - basic quality level: no specified aluminium content, no impact requirement, standard testing
TR2 - quality level with specified aluminium content, impact testing and additional examination of the weld
Chemical Composition
Both grades use the same base limits for carbon, manganese, phosphorus and sulphur. The decisive difference sits in the aluminium and nitrogen clauses, because the aluminium addition is what makes the guaranteed toughness achievable.
| Element | P235TR1 | P235TR2 |
|---|---|---|
| C, max % | 0.16 | 0.16 |
| Mn, % | 0.60 – 1.20 | 0.60 – 1.20 |
| P, max % | 0.025 | 0.025 |
| S, max % | 0.015 | 0.015 |
| N, max % | 0.012 | 0.012, unless total Al ≥ 0.020 % |
| Total Al, min % | not specified | 0.020 |
| Carbon equivalent CEV, max % | 0.36 | 0.36 |
The aluminium in TR2 is added deliberately to refine the austenite grain during rolling or normalizing, which is what allows the guaranteed impact values to be met. The carbon equivalent limit of 0.36 % keeps the weld zone hardenable to a level that permits standard ERW and SAW procedures without preheat in most wall thicknesses.
Mechanical Properties and Testing
| Property | P235TR1 | P235TR2 |
|---|---|---|
| Yield strength ReH, min MPa | 235 (t ≤ 16 mm) | 235 (t ≤ 16 mm) |
| Tensile strength Rm, MPa | 360 – 500 | 360 – 500 |
| Elongation A, min % | 25 (longitudinal) | 25 (longitudinal) |
| Charpy V-notch impact | not required | KV ≥ 27 J average at 0 °C, single value ≥ 19 J |
| Hydrostatic test | mandatory | mandatory |
| Weld NDT (ultrasonic / radiographic) | only if agreed at order | full length of weld seam |
The impact requirement is where most confusion appears. EN 10217-1 specifies the TR2 Charpy test at 0 °C with a minimum average energy of 27 J on full-size longitudinal specimens and a minimum individual value of 19 J. A value of -20 °C is sometimes quoted on supplier datasheets, but that temperature belongs to low-temperature specifications such as EN 10217-4, not to EN 10217-1. Designers should check the temperature actually required by the project specification before fixing the grade.
Manufacturing and Delivery
Both grades are produced on the same ERW and SAW lines. ERW is used for smaller diameters where productivity and tight dimensional control matter; SAW handles larger diameters and heavier walls. Pipes can be delivered in the as-welded or normalized condition depending on the agreed option, and TR2 orders normally call for the normalized condition so that the impact properties are secured.
Practical mill supply for these grades typically covers ERW from about 21 mm to 660 mm outside diameter and SAW above that range. EN 10217-1 itself does not restrict the diameter; the achievable range depends on the forming equipment, so the exact size matrix should be confirmed against the mill capability list before enquiry.
Selection Guidance
| Service condition | Recommended grade | Reason |
|---|---|---|
| Ambient-temperature water, air or non-hazardous fluid at moderate pressure | P235TR1 | Meets the pressure requirements at lower cost |
| Specification demanding certified impact values or full weld NDT | P235TR2 | Guaranteed 27 J at 0 °C plus full-length weld examination |
| Design temperature below 0 °C | verify against EN 10217-4 or additional testing | EN 10217-1 only certifies TR2 impact at 0 °C |
| Elevated temperature above about 350 °C | EN 10217-2 grades such as P235GH | Part 1 specifies room-temperature properties only |
| Corrosive environment | either grade, with protective coating | Neither grade is corrosion resistant by itself |
P235TR1 is the economical default for ordinary low-pressure water, gas and air lines where the buyer accepts standard testing. P235TR2 is the engineering answer whenever the design code, the insurer or the end user requires verified toughness and a fully examined weld.
FAQ
Q: What is the difference between P235TR1 and P235TR2?
TR2 adds three requirements that TR1 does not have: a minimum total aluminium content of 0.020 % for grain refinement, a Charpy V-notch impact requirement of 27 J at 0 °C, and full-length non-destructive examination of the weld seam. The base chemistry, yield strength and tensile range are the same.
Q: Is P235TR2 impact tested at -20 °C?
No. EN 10217-1 specifies the P235TR2 Charpy test at 0 °C with a minimum average energy of 27 J and a minimum single value of 19 J. The -20 °C figure belongs to low-temperature specifications such as EN 10217-4 and should not be used as the acceptance basis for this grade.
Q: What is the chemical composition of P235TR1?
C ≤ 0.16 %, Mn 0.60 – 1.20 %, P ≤ 0.025 %, S ≤ 0.015 %, N ≤ 0.012 %, with carbon equivalent CEV ≤ 0.36 %. Aluminium content is not specified for TR1.
Q: Can P235TR1 be used for low-temperature service?
EN 10217-1 gives P235TR1 no guaranteed impact values, so it cannot be certified for low-temperature duty on the strength of this standard. For design temperatures below 0 °C, use P235TR2 with its 0 °C certification or a dedicated low-temperature grade from EN 10217-4, and confirm the requirement with the project specification.
Q: Are P235TR1 and P235TR2 seamless or welded pipes?
They are welded pipes produced by ERW or SAW under EN 10217-1. Seamless equivalents with the same designation exist under EN 10216-1; the two specifications differ in manufacturing route, testing and typical size range.
Q: Which standard covers P235TR1 and P235TR2?
Welded pipes are covered by EN 10217-1:2019 (pressure welded steel tubes with specified room-temperature properties). The seamless counterpart is EN 10216-1. For elevated-temperature service the relevant specification is EN 10217-2, and for low-temperature service EN 10217-4.
