Chromium-molybdenum grades for high-temperature pressure service: refinery hydroprocessing, power generation boilers, HRSG, and supercritical steam systems. PWHT documentation on every 3.1 certificate.
Post-weld heat treatment (PWHT) is required for all chromium-molybdenum alloy steel grades without exception. Time-temperature charts and hardness test results are included on the EN 10204 3.1 inspection certificate for every CrMo fitting order. Weld without PWHT on CrMo creates a hard, brittle HAZ susceptible to hydrogen-assisted cracking.
Entry-level CrMo grade. HRSG, refinery fractionation, moderate-temperature steam service. PWHT 690–730°C. Filler ER80S-B2.
Hydroprocessing workhorse. Nelson curve compliance for H₂ service. PWHT 700–750°C. Filler ER90S-B3. Widely used in refinery and petrochemical hydrogen atmospheres.
5% chromium for superior Nelson curve protection. Refinery furnaces, catalytic reforming, high-temperature H₂ service. PWHT 720–760°C. Filler ER80S-B6.
Original 9Cr-1Mo. ASME P-No.5B. Filler ER80S-B8. Not interchangeable with P91 — no vanadium or niobium. PWHT 720–760°C.
3× higher allowable stress than P9. V+Nb+N microalloying. ASME P-No.15E. Filler ER90S-B9 only. PWHT 745–775°C. Supercritical power generation, HRSG high-pressure drums.
Highest performance CrMo grade. 1.5–2.0% W addition for creep strength beyond P91. USC and AUSC power plant steam systems. PWHT 750–780°C. Filler ER90S-B9M.
Silicon-enhanced P11 variant. Elevated Si (0.60–1.00%) improves oxidation resistance. Boiler headers, steam drums. PWHT 690–750°C. ASTM WP12 equivalent.
| Grade | EN Number | Cr% | Mo% | ASME P-No. | Max Temp | Primary Use |
|---|---|---|---|---|---|---|
| P11 | 1.7335 | 1.00–1.50 | 0.44–0.65 | 4 | 550°C | HRSG, steam headers |
| P22 | 1.7380 | 1.90–2.60 | 0.87–1.13 | 5A | 580°C | Hydroprocessing, H₂ service |
| P5 | 1.7362 | 4.00–6.00 | 0.44–0.65 | 5B | 650°C | High-temp refinery, catalytic reforming |
| P9 | 1.7386 | 8.00–10.00 | 0.85–1.20 | 5B | 600°C | Original 9Cr, legacy power plant |
| P91 | 1.4903 | 8.00–9.50 | 0.85–1.05 | 15E | 650°C | Supercritical power, HRSG HP |
| P92 | 1.4901 | 8.50–9.50 | 0.30–0.60 + W | 15E | 650°C | USC/AUSC steam, highest creep |
| P12 | 1.7337 | 1.00–1.50 | 0.45–0.65 | 4 | 540°C | Boiler headers, oxidising service (Si 0.60–1.00%) |
P9 (1.7386) and P91 (1.4903) are both 9Cr grades but have fundamentally different metallurgy, weld procedures, and allowable stresses. P91 contains vanadium, niobium, and nitrogen — P9 does not. P91 has 3× the allowable stress of P9 at 600°C. Always verify which grade is specified. Using ER80S-B8 filler on P91 weld joints is a serious error — P91 requires ER90S-B9 exclusively. See full P9 vs P91 comparison.
EN 10253-2 Type B. PWHT documentation included. EN 10204 3.1 with time-temperature chart and hardness results. Contact us with grade, size schedule, and delivery location.
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