ASTM A335 ASME SA335 P9 Seamless Alloy Steel Pipe High Temp Creep Resistant for Petrochemical And Power Generation Supplier
ASTM A335/ASME SA335 P9 is a seamless ferritic alloy steel tube belonging to the 9Cr-1Mo chromium-molybdenum alloy system, specifically designed for high-temperature and high-pressure applications. The "9" in P9 comes from the nominal content of its primary alloying element, chromium (approximately 9%), while molybdenum (approximately 1%) imparts excellent high-temperature creep strength.
This standard covers tubes with both nominal and minimum wall thicknesses. The tubes must be suitable for bending, flanging, and similar forming operations, and possess good weldability.
A335 P9 seamless alloy steel tubes are a dedicated tube solution for petrochemical cracking furnaces, boiler superheaters, and high-temperature process pipelines in the metal temperature range of 538°C to 650°C (1000°F–1200°F), bridging the heat resistance gradient between low-chromium alloys (such as P5/P11) and high-grade alloys (such as P91).
| Chemical Composition |
| Element |
Content Range (%) |
Function Description |
| C (Carbon) |
≤ 0.15 |
Hardness & tensile strength control |
| Mn (Manganese) |
0.30 – 0.60 |
Hot workability & deoxidation |
| P (Phosphorus) |
≤ 0.025 |
Ductility & toughness retention |
| S (Sulfur) |
≤ 0.025 |
Ductility & toughness retention |
| Si (Silicon) |
0.25 – 1.00 |
Oxidation resistance |
| Cr (Chromium) |
8.00 – 10.00 |
Oxidation & scaling resistance |
| Mo (Molybdenum) |
0.90 – 1.10 |
Creep & rupture strength |
| Mechanical Properties (Minimum, Room Temperature) |
| Parameter |
Value |
| Yield Strength (0.2% offset) |
≥ 205 MPa (30 ksi) |
| Tensile Strength |
≥ 415 MPa (60 ksi) |
| Elongation (gage length 50 mm) |
≥ 30% |
| Hardness |
≤ 163 HBW |
| A335 Series Typical Grade Mechanical Properties Comparison |
| Grade |
Cr (%) |
Mo (%) |
Max. Service Temp. Reference (°C) |
Min. Yield Strength (MPa) |
Min. Tensile Strength (MPa) |
| P1 |
0.44–0.65 |
0.44–0.65 |
482 |
205 |
380 |
| P5 |
4.0–6.0 |
0.45–0.65 |
593 |
205 |
415 |
| P9 |
8.0–10.0 |
0.90–1.10 |
593 |
205 |
415 |
| P11 |
1.0–1.5 |
0.44–0.65 |
538 |
205 |
415 |
| P22 |
1.9–2.6 |
0.87–1.13 |
565 |
205 |
415 |
| P91 |
8.0–9.5 |
0.85–1.05 |
593 |
415 |
585 |
The ASTM A335/ASME SA335 standards cover a variety of seamless ferritic alloy steel pipes for high-temperature applications. Different grades balance strength, temperature resistance, corrosion resistance, and cost by adjusting the content of key alloying elements such as chromium and molybdenum to meet different application requirements.
Oil Refineries: High-chromium grades (P5/P9) offer better resistance to such environments and are the typical choice in this field.
Power Plants: P11/P22 are common choices for conventional boilers and piping. For power plants seeking higher efficiency and parameters, P91/P92 are almost essential.
Hydrogen Corrosion Resistance:In high-temperature, hydrogen-rich environments (such as hydrogenation reactors), the alloy's resistance to hydrogen corrosion is crucial. P22, with its higher chromium content, outperforms P11.
Budget Sensitive and Mild Operating Conditions: P11 is preferred. It strikes a good balance between cost, strength, and weldability and is one of the most widely used grades.
Temperature and Pressure are Primary Challenges:P22 is the main choice in conventional power generation and petrochemical applications. For high-efficiency power generation projects, P91 or P92 should be considered directly.
| Physical Properties |
| Parameter |
Value |
Unit |
| Density |
~7.85 |
g/cm³ |
| Elastic Modulus (20°C) |
~210 |
GPa |
| Thermal Conductivity |
~28 |
W/(m·K) |
| Specific Heat Capacity (20°C) |
~460 |
J/(kg·K) |
| Coefficient of Linear Expansion (20–400°C) |
~12.5 |
×10⁻⁶/°C |
| Dimensional Range |
| Parameter |
Range |
Standard Reference |
| Nominal Pipe Size (NPS) |
1/8″ – 24″ (DN6 – DN600) |
ASME B36.10M |
| Outside Diameter (OD) Range |
10 – 1000 mm |
Industry common |
| Wall Thickness Schedule |
SCH 20 to SCH XXS, including heavy wall |
ASME B36.10M |
| Wall Thickness Range |
1 – 100 mm |
Industry common |
| Length |
Single random, double random, or cut-to-length |
ASME B36.10M |
Application
- Petrochemical and Refining: Furnace tubes in refining units; high-temperature process piping; reactor effluent lines in hydrotreating units. Grades P5 and P9 under the A335 standard are widely used in the petrochemical and refining industries.
- Power Generation: Superheater tubes, reheater tubes, main steam lines, and high-temperature headers in thermal power plants.
- Industrial Heating Equipment: Industrial furnace tubes; pyrolysis furnace conveying lines; heat exchanger tube bundles under high-temperature conditions; high-temperature process piping in chemical plants.
- Special Purposes and Retrofitting Applications: High-temperature piping in biomass and waste-to-energy power plants; replacement of existing piping constructed with P9 material in power plants or refining units.
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