Products Features
Good high-temperature strength and creep resistance (core advantage)
The core advantage of ASTM A335 P11 lies in its excellent high-temperature strength and creep resistance. Thanks to the addition of 0.5% molybdenum (Mo), P11 exhibits significantly superior high-temperature creep rupture strength compared to ordinary carbon steels (such as A106 Gr.B) within the temperature range of 450-550°C. Under 500°C conditions, the allowable stress of P11 is approximately 1.5 to 2 times that of carbon steel, enabling it to effectively resist slow plastic deformation (creep) of materials under high temperature and pressure, ensuring the safety and reliability of pipelines during long-term high-temperature service. With a minimum tensile strength of 415 MPa and a minimum yield strength of 205 MPa, it falls within the standard performance level of the A335 series and offers significant advantages in terms of cost-effectiveness.
Excellent welding performance and heat treatment adaptability
ASTM A335 P11 exhibits excellent welding performance, which is a key reason for its widespread adoption in the power and petrochemical industries. Thanks to its moderate alloy content and carbon equivalent (CE), P11 has a lower tendency for hardening in the heat-affected zone (HAZ) of welds. It requires moderate preheating temperatures before welding (typically 150-250°C), making it user-friendly for on-site welding operations. Its welding process is well-established, with welders finding it of moderate difficulty, suitable for large-scale on-site installation. Post-weld heat treatment (PWHT) is required after welding, involving heating to 690-760°C, holding at temperature, and then slow cooling to eliminate residual welding stresses and soften the heat-affected zone.
Good machinability and formability
ASTM A335 P11 exhibits good cold and hot working properties, allowing for various forming processes such as hot bending, cold bending, and forging. Its moderate alloy content provides excellent formability during cold bending, making it suitable for manufacturing pipe fittings like elbows, tees, and reducers. Its machinability is comparable to that of P1, enabling processing through conventional machining methods.
An excellent cost-performance ratio and balanced overall performance (distinct from the positioning of P1/P22)
ASTM A335 P11 is the most balanced grade in the chromium-molybdenum alloy steel series. Compared to P1 (0.5Cr-0.5Mo), P11 has a higher chromium content (1.25% vs 0.5%), offering superior oxidation resistance and high-temperature strength. In comparison to P22 (2.25Cr-1Mo), P11 has lower alloy content, resulting in better weldability and lower cost. For applications with operating temperatures ≤550°C, P11 is the most cost-effective chromium-molybdenum steel grade and the most widely used chromium-molybdenum steel pipe in power plants and refining industries worldwide.
Good organizational stability and long-term service reliability
ASTM A335 P11 exhibits good organizational stability when in long-term service at temperatures ≤550°C. Its 1.25% Cr-0.5% Mo composition design effectively enhances the material's high-temperature creep strength and oxidation resistance while inhibiting pearlite spheroidization and carbide coarsening and aggregation, ensuring a low rate of mechanical property degradation during prolonged high-temperature service. After normalization plus tempering (N+T) heat treatment, P11 obtains a uniform and fine ferrite + pearlite microstructure, guaranteeing organizational stability and reliability under high-temperature service conditions.
Technical Specifications
Chemical Composition(ASTM A335 / ASME SA335)
|
Element |
Standard requirements |
Note |
|
C |
0.05 - 0.15% |
Low-carbon design ensures weldability and toughness |
|
Mn |
0.30 - 0.60% |
Solid solution strengthening, improve strength |
|
P |
≤ 0.025% |
Harmful elements, strictly controlled |
|
S |
≤ 0.025% |
Harmful elements, strictly controlled |
|
Si |
0.15 - 0.35% |
Deoxidizer, improve high-temperature oxidation resistance |
|
Cr |
1.00 - 1.50% |
Core elements that provide excellent high-temperature oxidation and corrosion resistance |
|
Mo |
0.44 - 0.65% |
Core elements to improve high-temperature creep fracture strength |
|
Fe |
Remaining quantity(≈ 97%) |
Matrix element |
Physical Properties
|
Performance |
Numerical Value/Range |
Test conditions |
|
Density |
≈ 7.85 g/cm³ |
Room Temperature (20°C) |
|
Melting Point |
≈ 1390-1440°C |
- |
|
Electrical resistance |
≈ 0.32 μΩ·m |
Room Temperature |
|
Thermal Conductivity |
≈ 40 W/(m·K) |
Room Temperature |
|
Coefficient of Thermal Expansion (20-100°C) |
≈ 11.8 × 10⁻⁶ /K |
- |
|
Elastic modulus (Young's modulus) |
≈ 200 GPa |
Room Temperature |
|
Poisson's ratio |
≈ 0.28 |
Room Temperature |
|
Magnetism |
Ferromagnetic |
Ferrite structure, which is magnetic |
Mechanical Properties (Normalized + Tempered, Typical Values, ASTM A335)
|
Performance |
Typical value |
Implementation standards |
|
Tensile Strength |
≥ 415 MPa |
ASTM A335 |
|
Yield Strength (0.2% Offset) |
≥ 205 MPa |
ASTM A335 |
|
Elongation (gauge length 2in/50mm) |
≥ 30% |
ASTM A335 |
|
Hardness |
≤ 217 HB (typical value) |
- |
Note: The strength level of P11 is a standard grade in the ASTM A335 chromium-molybdenum steel series. Its advantage lies in the balanced combination of good comprehensive properties (strength, weldability, oxidation resistance, cost) rather than pursuing the highest strength or the highest oxidation resistance. For higher temperature grades, it is recommended to select P22 or P91.
High-temperature performance
ASTM A335 P11 maintains good strength levels at high temperatures and is suitable for long-term high-temperature service conditions up to 550°C:
|
Temperature |
Tensile strength (MPa, approximately) |
Performance retention rate |
|
Room temperature (20°C) |
≥ 415 |
100% |
|
400°C |
≈ 380 |
≥ 92% |
|
500°C |
≈ 340 |
≥ 82% |
|
550°C |
≈ 300 |
≥ 72% |
Long-term Thermal Stability and Microstructural Stability:
ASTM A335 P11 exhibits good microstructural stability during long-term service at temperatures ≤550°C. The addition of 1.25% Cr-0.5% Mo effectively enhances high-temperature strength and oxidation resistance. However, microstructural stability decreases and creep strength significantly drops when used for long-term service above 580°C; thus, it is not recommended for long-term service above 580°C. For higher temperature grades, P22 or P91 is recommended.
Heat treatment system
The final performance of ASTM A335 P11 is highly dependent on the heat treatment regime, with common specifications as follows:
1. Normalizing Treatment (Normalizing)
Heat to 900-955°C, hold for a sufficient time (approximately 1 hour per inch of wall thickness), then air cool. This results in a uniform fine ferrite + pearlite microstructure, preparing it for subsequent tempering.
2. Tempering treatment(Tempering)
Heat to 690-760°C, hold for sufficient time, then air cool. This eliminates stresses induced by normalizing, optimizes toughness and ductility, and achieves the final service properties.
3. Full Annealing (Optional)
Heat to 840-890°C, hold, then furnace cool to approximately 650°C, followed by air cooling to room temperature. Used to eliminate cold working stress or improve cold working formability.
Attention: Post-weld heat treatment (PWHT) must be performed after welding. It involves heating to 690-760 °C, holding at temperature, and then slow cooling to eliminate residual welding stresses and soften the heat-affected zone.
The heat treatment temperature and time must be strictly controlled to avoid grain coarsening or performance fluctuations.
For thin-walled tubes or small-diameter tubes, the insulation time can be appropriately shortened.
Applicable Media
High-temperature steam:
Main steam pipelines (≤550°C) of power plants, boiler headers, superheater tubes, and reheater tubes
Petroleum refining media:
High-temperature process pipelines such as atmospheric and vacuum distillation, catalytic cracking, and hydrotreating.
High-pressure process gas:
High-temperature and high-pressure pipelines for chemical equipment such as ammonia synthesis, methanol, and chemical fertilizers.
Hot water:
Heat network, heating system.
Heat transfer oil and thermal carriers:
Pipelines for chemical heat transfer systems
Note: ASTM A335 P11 is not suitable for strongly corrosive media such as strong oxidizing acids and high-temperature, high-concentration chlorides. Its upper limit for oxidation resistance is approximately 550-570°C; P22 or P91 is recommended above this temperature. In high-temperature hydrogen-containing environments, the risk of hydrogen corrosion should be evaluated.
ASTM A335 P11 is suitable for high-temperature and high-pressure conditions ranging from 450 to 550°C. It is the most balanced and widely applied grade in the chromium-molybdenum steel series, recommended for use in the following fields:
Application Fields
-
Fossil Fuel Power Generation (Core Application)
● Main Steam Piping of Subcritical Power Plants (≤550°C)
● Boiler drum, superheater drum
● High-temperature steam pipelines, water supply pipelines
● Boiler heating surface tube system -
Petrochemical Engineering (Core Applications)
● High-temperature pipelines of the atmospheric and vacuum distillation unit in a refinery
● Aromatics unit high-temperature process piping
● High-temperature and high-pressure pipelines in hydrotreating units
● Delayed Coking Unit Process Piping -
Chemical and Fertilizer Industry
● High-temperature process pipelines for ammonia synthesis plants
● Methanol Plant Conversion Gas Pipeline
● High-temperature and high-pressure pipelines in chemical fertilizer plants -
Combined Heat and Power and Central Heating
● High-temperature steam pipeline of a thermal power plant
● Urban centralized heating high-temperature hot water pipeline -
High-temperature and high-pressure pipe fittings
● High-temperature elbows, tees, and reducers
● Forged pipe fittings, flanges
Delivery and Customization
We offer flexible and reliable supply chain solutions to ensure you receive ASTM A335 P11 alloy steel pipes that perfectly match your project requirements.
Customizable material forms
We support producing various basic and special shapes according to drawings or specifications.
|
Form |
 Seamless Steel Pipe
|
 Large-diameter Thick-walled Pipe
|
 Alloy Steel Pipe
|
|---|---|---|---|
|
Conventional Range |
Outer Diameter: 10.3 - 1067 mm; Wall Thickness: 1 - 150 mm |
Outer Diameter: 219 - 1067 mm; Wall Thickness: 20 - 150 mm |
Outer Diameter: 10.3 - 610 mm; Wall Thickness: 1 - 50 mm |
|
Customization Capability |
Hot-rolled / cold-drawn seamless tubes, fixed-length cutting, bevel machining, pipe end threads, special heat treatment conditions (normalizing + tempering / annealing) |
Hot expansion, fixed-length cutting, bevel machining, special heat treatment conditions |
Cold-drawn precision tubes, fixed-length cutting, special surface treatment |
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Full traceability across key QC checkpoints throughout production. 100% compliant with ASTM/ASME, EN, and GB standards. Material test reports available with every shipment.
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FAQ
Q: What are the main advantages of ASTM A335 P11?
Q: What is the difference between ASTM A335 P11 and P1? How to choose?
Q: What are the differences between ASTM A335 P11 and P22? How to choose between them?
Q: What is the maximum service temperature for ASTM A335 P11?
Q: What is the welding performance of ASTM A335 P11?
Q: What is the corrosion resistance of ASTM A335 P11?
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