Ordering Information
Purchasers must specify the following when ordering:
- Quantity (length or number of pipes)
- Material grade (e.g., P11, P22, P91)
- Size (NPS or DN and schedule or wall thickness)
- Length (random or specific)
- ASTM designation (A335 or A335M for metric units)
- Optional requirements (e.g., additional testing, special finishes)
- Any supplementary requirements (S1–S7)
Material and Manufacture
- Process: Pipes shall be made by seamless process (hot-worked or cold-worked followed by heat treatment).
- Heat Treatment: All pipes must undergo proper heat treatment (e.g., normalization, tempering) to meet mechanical properties.
Chemical Composition
Each grade has specific limits for carbon, manganese, phosphorus, sulfur, silicon, chromium, molybdenum, and other alloying elements.
Mechanical Properties
- Tensile Strength, Yield Strength, and Elongation: Requirements vary by grade (e.g., P91: min. tensile strength 585 MPa, yield strength 415 MPa).
- Hardness Testing: Optional unless specified.
Test Requirements
- Hydrostatic Testing: Each pipe must withstand a specified hydrostatic pressure without leakage.
- Nondestructive Electric Testing (NDE): Optional unless required (e.g., eddy current, ultrasonic testing).
- Flattening Test, Bend Test, or Flange Test: Required for certain sizes and grades.
- Impact Testing: Required if specified (e.g., for low-temperature service).
Inspection & Certification
- Manufacturer must perform tests and provide a Certificate of Compliance.
- Third-party inspection may be required if specified in the purchase order.
Marking
Each pipe must be marked with:
- Manufacturer's name or trademark
- ASTM designation (A335 or A335M)
- Grade (e.g., P11, P22)
- Heat number
- Size and schedule
Supplementary Requirements
Optional additional tests (e.g., grain size analysis, special NDE methods) may be specified.
Keywords
Seamless pipe, alloy steel, high-temperature service, ferritic steel, P-grade steels.
Main Grades in ASTM A335/A335M
| Grade | UNS Number | Key Alloy Composition | Common Applications |
|---|---|---|---|
| P1 | K11522 | 0.5Mo | Low-alloy boilers, piping |
| P2 | K11547 | 0.5Cr-0.5Mo | Power plants, refineries |
| P5 | K41545 | 5Cr-0.5Mo | High-temp/pressure service |
| P9 | S50400 | 9Cr-1Mo | Petrochemical, boilers |
| P11 | K11597 | 1.25Cr-0.5Mo-Si | Power generation, steam lines |
| P12 | K11562 | 1Cr-0.5Mo | Similar to P11, boilers |
| P21 | K31545 | 3Cr-1Mo | High-temp strength |
| P22 | K21590 | 2.25Cr-1Mo | Widely used in power plants |
| P91 | K91560 | 9Cr-1Mo-V-Nb | Advanced high-temp/pressure |
| P92 | K92460 | 9Cr-2W-0.5Mo-V-Nb | Ultra-supercritical boilers |
| P122 | K91640 | 11Cr-2W-1Cu-Mo-V-Nb | High-efficiency power plants |
Key Notes
- Grades P5 to P92 are chromium-molybdenum (Cr-Mo) steels, offering increasing resistance to oxidation and creep at elevated temperatures.
- P91, P92, and P122 are advanced high-strength steels used in modern power plants for ultra-supercritical (USC) applications.
- P1 and P2 are lower-alloy grades for less severe conditions.
- These grades are selected based on temperature, pressure, and corrosion resistance requirements in industries like power generation, oil & gas, and petrochemical plants.
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Frequently Asked Questions
What is ASTM A335/A335M and what is it used for?
ASTM A335/A335M is a standard specification covering seamless ferritic alloy steel pipes designed for high-temperature service. These pipes are widely used in power generation, oil & gas, and petrochemical industries where elevated temperatures and pressures demand superior material performance.
What are the most commonly used grades in ASTM A335?
The most commonly used grades include P11 (1.25Cr-0.5Mo-Si) for power generation and steam lines, P22 (2.25Cr-1Mo) widely applied in power plants, and P91 (9Cr-1Mo-V-Nb) for advanced high-temperature and high-pressure applications. P92 and P122 are used in ultra-supercritical (USC) boiler systems.
What heat treatment is required for ASTM A335 pipes?
All ASTM A335 pipes must undergo proper heat treatment to meet the required mechanical properties. This typically includes normalization and tempering processes, which ensure the correct microstructure and strength levels for high-temperature service conditions.
What testing is required for ASTM A335 pipes?
Required tests include hydrostatic testing to verify pressure integrity, and mechanical tests such as tensile, flattening, bend, or flange tests depending on grade and size. Optional tests include nondestructive electric testing (NDE) such as eddy current or ultrasonic testing, hardness testing, and impact testing for low-temperature service applications.
What information must be marked on each ASTM A335 pipe?
Each pipe must carry the manufacturer's name or trademark, the ASTM designation (A335 or A335M), the material grade (e.g., P11, P22, P91), the heat number, and the pipe size and schedule. This marking ensures full traceability and compliance with the specification.
What should be specified when placing an order for ASTM A335 pipes?
When ordering, purchasers should specify the quantity, material grade, pipe size (NPS or DN with schedule or wall thickness), required length, ASTM designation, any optional or supplementary requirements (S1–S7), and whether third-party inspection or special certifications are needed. Providing complete ordering information ensures the correct product is delivered on time.