ASTM A335 Grade P11 Alloy Steel Seamless Pipe Chrome Moly Pipe for Power Plant Piping
ASTM A335 / ASME SA335 P11 Alloy Steel Seamless Pipe for High‑temperature Service
ASTM A335 Grade P11 is a seamless 1.25Cr-0.5Mo chrome moly alloy steel pipe designed for high-temperature power plant service, and Yuhong Group can supply it in a wide range of sizes with full certifications, third-party testing, and application-ready finishes. Because of its nominal composition of 1.25% Cr – 0.5% Mo provides enhanced creep strength and oxidation resistance up to ~570°C, making it suitable for superheater tubes, main steam lines, and headers in subcritical boilers and HRSGs. In power plants, P11 pipes are used in boilers, superheaters, heat exchangers, and high-pressure steam lines where materials must resist creep, oxidation, and thermal fatigue at elevated temperatures (typically up to ~570–600°C / 1050–1110°F).
Key Properties for Power Plant Use
| Property | Benefit |
|---|---|
| High-temperature creep resistance | Withstands long-term stress at up to ~570°C without excessive deformation. |
| Oxidation resistance | Chromium forms a protective oxide layer in steam/combustion gases. |
| Good thermal fatigue resistance | Handles cyclic heating/cooling in boilers. |
| Weldability | Acceptable with preheat (150–200°C) and post-weld heat treatment (PWHT). |
| Resistance to hydrogen attack | Suitable for high-pressure hydrogen service (e.g., refinery/power applications). |
Specifications of Alloy Steel Seamless Pipe
| Standard | ASTM A335, ASME SA335 |
| Grade | Gr. P5, P9, P11, P12, P21, P22 , P91, P92 |
| Size | 1/2" TO 24 "IN OD & NB or custom |
| Schedule | SCH 5- SCH XXS, or custom |
| Type | Seamless |
| Length | Single Random, Double Random & Cut Length |
| End | Plain End, Beveled End |
Chemical composition(%) of ASTM A335 P-series Alloy Steel Seamless Pipe
| Grade | C | Mn | P≤ | S≤ | Si | Cr | Mo |
| P11 | 0.05-0.15 | 0.30-0.60 | 0.025 | 0.025 | 0.50-1.00 | 1.00-1.50 | 0.44-0.65 |
| P22 | 0.05-0.16 | 0.30-0.60 | 0.025 | 0.025 | ≤0.50 | 1.90-2.60 | 0.87-1.13 |
| P5 | ≤0.15 | 0.30-0.60 | 0.025 | 0.025 | ≤0.50 | 4.00-6.00 | 0.45-0.65 |
| P9 | ≤0.15 | 0.30-0.60 | 0.025 | 0.025 | 0.25-1.00 | 8.00-10.00 | 0.90-1.10 |
| P91 | 0.08-0.12 | 0.30-0.60 | 0.020/0.010 | 0.020/0.010 | 0.02-0.50 | 8.00-9.50 | 0.85-1.05 |
| P92 | 0.07-0.13 | 0.30-0.60 | 0.020/0.010 | 0.020/0.010 | ≤0.50 | 8.50-9.50 | 0.30-0.60 |
Mechanical properties of of ASTM A335 P-series Alloy Steel Seamless Pipe
| Grade | Tensile strength | Yield strength | Elongation |
| P11, P22, P5, P9 | ≥415 | ≥205 | ≥30/20 |
| P91 | ≥585 | ≥415 | ≥20 |
| P92 | ≥620 | ≥440 | ≥20 |
Fabrication and Welding Requirements (for power plant)
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Preheating Required: 150–200°C (300–400°F) before welding.
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Post‑Weld Heat Treatment (PWHT) Mandatory: 700–760°C (1290–1400°F), hold 1 hour per 25 mm thickness.
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Filler metals – Use matching composition: AWS A5.5 E8018-B2 (electrode) or ER80S-B2 (wire).
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Nondestructive Examination (NDE) – Usually 100% radiography (RT) or ultrasonic (UT) for power plant high‑energy piping.
Applications
1. Superheater and Reheater Tubing
2. Main Steam Piping
3. Hot Reheat Piping
4. Boiler Headers and Manifolds
5. Heat Exchanger Tubing (Feedwater Heaters & Economizers)
6. High‑Pressure Steam Lines in Combined Cycle HRSGs
7. Chemical Injection / Sampling Lines
8. Power Plant
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