EN 10253-2 Type B buttweld pipe fittings in 1.7386 — P9 CrMo alloy steel (X12CrMo9-1, 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 | X12CrMo9-1 | 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 | X12CrMo9-1 |
| 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.
