P91 Buttweld Pipe Fittings
Grade 91 / EN 1.4903 (X10CrMoVNb9-1) — 9Cr-1Mo-V Chrome Moly fittings for supercritical power generation and high-temperature refinery service. ASME B16.9 and EN 10253 Type B. EN 10204 3.1 standard; 3.2 TPI on request.
½″–48″
Size Range
650°C
Max Service Temp
630 MPa
Min Tensile (EN)
EN 10204
3.1 Std / 3.2 On Req.
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P91 Grade Equivalents
| ASTM | EN W.Nr. | EN Name | DIN | BS | UNS |
|---|---|---|---|---|---|
| A234 WP91 | 1.4903 | X10CrMoVNb9-1 | X10CrMoVNb9-1 | — | K91560 |
| A182 F91 (forged) | 1.4903 | X10CrMoVNb9-1 | — | — | — |
| A335 P91 (pipe) | 1.4903 | X10CrMoVNb9-1 | — | — | — |
Chemical Composition — P91 / 1.4903
| Element | C | Cr | Mo | V | Nb | N | Ni | Mn | Si |
|---|---|---|---|---|---|---|---|---|---|
| ASTM A234 WP91 | 0.08–0.12 | 8.00–9.50 | 0.85–1.05 | 0.18–0.25 | 0.06–0.10 | 0.03–0.07 | ≤0.40 | 0.30–0.60 | ≤0.50 |
| EN 1.4903 | 0.08–0.12 | 8.00–9.50 | 0.85–1.05 | 0.18–0.25 | 0.06–0.10 | 0.03–0.07 | ≤0.40 | 0.30–0.60 | ≤0.50 |
Mechanical Properties — P91 / 1.4903
| Standard | Min. UTS (MPa) | Min. YS (MPa) | Elongation (%) | Max. Hardness | HT Condition |
|---|---|---|---|---|---|
| ASTM A234 WP91 | 585 | 415 | ≥20% | 265 HBW | N+T |
| EN 1.4903 (EN 10253-3) | 630–830 | ≥450 | ≥19% | 265 HBW | N+T |
N+T = Normalise and Temper. Typical normalising: 1040–1080°C. Tempering: 730–800°C minimum 1h/25mm.
Available P91 Fitting Types
90° LR Elbows
Long radius (1.5D). ASME B16.9 and EN 10253-3 Type B. ½″–48″.
45° LR Elbows
Long radius. ASME B16.9 / EN 10253-3 Type B.
Equal Tees
ASME B16.9 and EN 10253-3 Type B. All schedules.
Reducing Tees
All standard reducing combinations.
Concentric Reducers
ASME B16.9 / EN 10253-3.
Eccentric Reducers
ASME B16.9 / EN 10253-3.
End Caps
ASME B16.9 / EN 10253-3.
180° Returns
Long and short radius. ASME B16.9.
Stub Ends
Lap joint stub ends. MSS SP-43.
Critical Welding & PWHT Requirements
⚠ P91 Welding Warning — Do Not Skip PWHT
P91 is highly sensitive to incorrect welding procedure. Un-PWHTed P91 welds are prone to Type IV cracking at the fine-grain heat-affected zone — a failure mode that may not manifest until years into service at high temperature.
Pre-heat Temperature
200–250°C minimum. Do not allow joint to cool below 200°C during welding.
Inter-pass Temperature
Maximum 300°C. Strictly controlled to prevent martensite transformation issues.
Filler Metal
ER90S-B9 (GTAW/TIG) or E9015-B9 (SMAW). Never use P22 filler on P91 joints.
PWHT Temperature
745–775°C. Hold for minimum 1 hour per 25mm wall, minimum 1 hour total.
Cooling
Slow cool in furnace to 300°C, then air cool. Chart-recorded temperature cycles required.
Post-PWHT Hardness
Weld and HAZ hardness must be ≤265 HBW after PWHT. Report required.
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Specify size, schedule, fitting type, standard (ASME B16.9 or EN 10253 Type B), and required MTR. We respond within 1 business day.
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