EN 10253-2 Type B buttweld pipe fittings in 1.7386 — P9 CrMo alloy steel (X11CrMo9-1, 9Cr-1Mo). The original 9Cr-1Mo grade for refinery service — excellent sulfidation resistance and Nelson curve advantage. P9 is commonly confused with P91, but they are entirely different materials: P9 has no vanadium or niobium additions and is an ASME P-No.5B grade, not P-No.15E.
P9 (1.7386) and P91 (1.4903) both start with "9Cr-1Mo" but are completely different grades:
| Property | P9 (1.7386) | P91 (1.4903) |
|---|---|---|
| EN Name | X11CrMo9-1 | X10CrMoVNb9-1 |
| V (Vanadium) | None | 0.18–0.25% |
| Nb (Niobium) | None | 0.06–0.10% |
| ASME P-Number | P-No.5B | P-No.15E |
| Allowable stress at 600°C | ~30 MPa | ~90 MPa |
| Weld filler | ER80S-B8 | ER90S-B9 only |
| PWHT | 720–760°C | 745–775°C |
| Primary use | Refinery hot piping | Power plant supercritical |
| W.Nr. | 1.7386 |
| EN Name | X11CrMo9-1 |
| ASTM Grade | WP9 / P9 |
| Composition | 9Cr-1Mo (no V/Nb) |
| ASME P-No. | P-No.5B |
Filler: ER80S-B8 (AWS A5.28). Preheat 200°C min. PWHT 720–760°C. Standard P-No.5B WPS applies.
DN15–DN600 and larger. Outside diameters follow the EN 10220 / EN ISO 1127 pipe series; wall thickness is matched to your connecting pipe.
| Size | OD (mm) |
|---|---|
| DN 15 | 21.3 |
| DN 20 | 26.9 |
| DN 25 | 33.7 |
| DN 32 | 42.4 |
| DN 40 | 48.3 |
| DN 50 | 60.3 |
| DN 65 | 76.1 |
| DN 80 | 88.9 |
| DN 100 | 114.3 |
| DN 125 | 139.7 |
| DN 150 | 168.3 |
| DN 200 | 219.1 |
| DN 250 | 273.0 |
| DN 300 | 323.9 |
| DN 350 | 355.6 |
| DN 400 | 406.4 |
| DN 450 | 457.0 |
| DN 500 | 508.0 |
| DN 600 | 610.0 |
P9 (EN 1.7386, X11CrMo9-1) and P91 (EN 1.4903, X10CrMoVNb9-1) both contain approximately 9% chromium and 1% molybdenum — but P91 also contains vanadium (0.18–0.25%) and niobium (0.06–0.10%) additions that create precipitation hardening through MX carbonitrides. These additions give P91 significantly higher allowable stress at elevated temperatures (P91 allowable at 600°C is approximately 90 MPa vs P9's ~30 MPa). P9 is the older grade used in refinery hot piping; P91 is the modern power plant supercritical steam grade. They are NOT interchangeable — different PWHT temperatures, different fillers, different ASME P-Numbers. P9 is ASME P-No.5B; P91 is P-No.15E.
In refinery service, where 9Cr-1Mo gives excellent sulfidation resistance and a favourable position on the Nelson curve.
X11CrMo9-1 (9Cr-1Mo). It is a different material from P91 (1.4903, X10CrMoVNb9-1).
Supplying an Indian boiler or ASME B16.9 project? The equivalent grade is listed on our group site ibrfittings.com: ASTM A234 WP9 fittings.
