What is Alloy Steel P11?
Alloy Steel P11 is a widely used chromium-molybdenum alloy steel with a nominal composition of 1.25% chromium and 0.5% molybdenum. It offers higher strength and better resistance to creep (deformation under long-term stress at high temperatures) compared to carbon steel. P11 is a workhorse grade in power generation and process industries for medium-to-high temperature piping and pressure vessels, providing an excellent balance of performance and cost.
Alloy Steel P11
Chromium (Cr)
Molybdenum (Mo)
Carbon (C)
Manganese (Mn)
Silicon (Si)
Phosphorus (P) Max
Sulfur (S) Max
Iron (Fe)
Types of Alloy Steel P11 Pipes & Tubes
We supply a comprehensive range of Alloy Steel P11 pipes and tubes, available in both seamless and welded configurations, to serve the robust needs of power and process industries.
P11 seamless pipes are the preferred choice for high-pressure steam services, boiler superheater and reheater tubes, and other critical high-temperature applications. Their seamless nature provides inherent strength and reliability, preventing potential failures at weld seams. This makes them essential for power plant main steam lines and other systems where pressure and thermal cycles are a constant challenge.
Offering a cost-effective solution, P11 welded pipes are ideal for large-diameter piping, low-to-medium pressure boiler circuits, and various process industry applications. They are manufactured from plate or coil and undergo full heat treatment to normalize the microstructure, ensuring consistent mechanical properties throughout the pipe, including the welded seam, for dependable service life.
P11 ALLOY STEEL PIPES EQUIVALENT GRADES
| STANDARD | Werkstoff /DIN | Other | Equivalent |
|---|---|---|---|
| A335 Grade P11 | 1.7335 | k11597 | 13CrMo4-5 |
Specification of Alloy Steel P11 Seamless / Welded Pipes & Tubes
| Specification | Details |
|---|---|
| Specification | ASTM A335 / ASME SA335 |
| Dimensions | ASTM, ASME and API |
| Outside Diameter | 6-2500mm; WT:1-200mm |
| Wall thickness | 0.3mm – 50 mm |
| Size | 1/8″NB TO 30″NB IN |
| Type | Seamless / ERW / Welded / Fabricated Pipes |
| Form | Round, Square, Rectangular, Oval, Hydraulic Etc |
| Length | Single Random, Double Random & Required Length |
| End | Plain End, Beveled End, Treaded |
| Schedules | SCH 40, SCH 80, SCH 160, SCH XS, SCH XXS, All Schedules |
| Inspection, Test Reports | Mill Test Certificates, EN 10204 3.1, Chemical Reports, Mechanical Reports, PMI Test Reports, Visual Inspection Reports, Third Party Inspection Reports, NABL Approved Lab Reports, Destructive Test Report, Non Destructive Test Reports |
| Packing | Packed in Wooden Boxes, Plastic Bags, Steel Strips Bundled, or as per Customers Requests |
| Specials | Sizes and Specifications other than above can be manufactured on request |
ALLOY STEEL PIPE & TUBES SCHEDULE DIMENSIONS WALL THICKNESS, WT./MTR. (KG)
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CHEMICAL COMPOSITION OF ALLOY STEEL P11 SEAMLESS PIPES AND TUBES
| Grade | C≤ | Mn | P≤ | S≤ | Si≤ | Cr | Mo |
|---|---|---|---|---|---|---|---|
| P11 | 0.05~0.15 | 0.30~0.61 | 0.025 | 0.025 | 0.50~1.00 | 1.00~1.50 | 0.44~0.65 |
MECHANICAL PROPERTIES OF ASME SA335 ALLOY STEEL P11 PIPE
| Grade | Tensile Strength, MPa | Yield Strength, MPa | Elongation, % |
|---|---|---|---|
| P11 | 415 min | 220 min | 30 min |
💡 Practical Difference in Use
Use P11 when: you need a good balance of strength, weldability, and resistance to hydrogen attack at temperatures up to ~550°C (1022°F).
→ Example: Boiler superheater tubes, pressure vessels, and process industry piping.
Use P11 over other grades when: its specific combination of 1.25% chromium and 0.5% molybdenum meets the design code requirements for a medium-temperature, high-pressure service. → Example: Power plant boiler tubes and headers in certain temperature ranges.
Uses of Alloy Steel P11 Pipes
P11 (1.25Cr-0.5Mo) is a widely used alloy for high-temperature pressure parts, known for its good creep strength and fabricability.
- Boiler Pressure Parts: Extensively used for superheater and evaporator tubes, as well as headers in power and industrial boilers.
- Process Industry Piping: Common in refineries and chemical plants for high-temperature pipelines carrying oils, gases, and process fluids.
- Heat Exchangers and Pressure Vessels: Used in the fabrication of vessels that operate at elevated temperatures and pressures.
Frequently Asked Questions About P11 & Alloy Steels
Straightforward answers about P11, its place between P5 and P22, and how it performs in high-temperature piping applications.
What is the maximum operating temperature for P11?
- Answer: P11 (1.25Cr-0.5Mo) is typically rated for continuous service up to about 550°C (1022°F). Beyond this temperature, creep strength diminishes, and higher-alloy grades like P22 or P91 become more suitable.
How does P11 compare to P5 (5Cr-0.5Mo)?
- Answer: P11 offers better weldability and is less prone to hardening during welding compared to P5. P5 provides superior oxidation resistance at higher temperatures but is more difficult to fabricate and requires stricter preheat and post-weld heat treatment.
Is P11 resistant to hydrogen attack?
- Answer: Yes, P11 is widely used in refinery hydrogen service due to its good resistance to hydrogen attack at moderate temperatures and pressures. For more severe conditions (higher temperature or partial pressure), P22 or P91 may be required.
When should I choose P22 over P11?
- Answer: Choose P22 when you need higher creep strength, better resistance to hydrogen attack at elevated temperatures, or when operating above 550°C. P22’s 2.25% chromium content provides improved oxidation and corrosion resistance.
Is P11 suitable for power plant applications?
- Answer: Yes, P11 is commonly used in fossil-fuel power plants for superheater and reheater tubes, as well as main steam piping, typically in subcritical units operating at moderate temperatures and pressures.
What are the welding requirements for P11?
- Answer: P11 requires preheating (typically 150–200°C) and post-weld heat treatment (PWHT) to prevent hydrogen-induced cracking and to ensure the weld zone maintains adequate creep strength and ductility. It is considered more weldable than higher-chromium grades like P5.
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Looking for premium Alloy Steel P11 Pipes & Tubes? Ratnadeep Steel supplies ASTM A335 P11 seamless pipes, ASTM A691 P11 welded pipes, ASTM A213 T11 seamless tubes, and ASTM A369 FP11 forged and bored pipes for high-temperature and high-pressure applications. Contact us today for superior quality, competitive prices, and reliable worldwide delivery.
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