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ASTM A335 pipe

ASTM A335 Alloy Steel Pipes for High-Temperature Service (Gr. P5, P9, P11, P22, P91)

ASTM A335 pipe

ASTM A335 Alloy Steel Pipes for High-Temperature Service (Gr. P5, P9, P11, P22, P91)

Learn about the alloy steel pipes specification ASTM A335 that covers “chrome-moly” seamless pipes with remarkable resistance to corrosion and good tensile strength at high-temperature service. Generally, ASTM A335 P11, P22, and P91 pipes are used in power generation, and in downstream oil and gas, P5 and P9 grades are for refinery applications.



ASTM A335 is a specification that covers seamless ferritic alloy-steel pipe for high-temperature serviceThese pipes are commonly used in high-temperature and high-pressure applications such as power generation, oil refineries, and chemical plants.

ASTM A335 P91 alloy steel pipes
Alloy Steel Pipes ASTM A335

Here are some key features of ASTM A335 alloy steel pipes:


  • ASTM A335 specification covers seamless ferritic alloy-steel pipe for high-temperature service. The pipes are categorized into several grades based on their chemical composition and mechanical properties.
  • Common grades include P1, P5, P9, P11, P22, P91, and P92, among others. Each grade has specific requirements regarding chemical composition, tensile strength, yield strength, and hardness.


Chemical Composition

  • The chemical composition of ASTM A335 alloy steel pipes varies depending on the grade. However, common alloying elements include chromium, molybdenum, vanadium, and sometimes nickel.
  • The presence of these alloying elements enhances the high-temperature properties of the steel, such as creep resistance, oxidation resistance, and strength at elevated temperatures.


Mechanical Properties

  • ASTM A335 pipes undergo various mechanical tests to ensure compliance with specified requirements. These tests may include tensile testing, hardness testing, impact testing, and flattening/flaring tests.
  • Mechanical properties such as tensile strength, yield strength, elongation, and hardness vary depending on the grade and heat treatment condition.


Dimensions and Sizes

  • ASTM A335 pipes are available in a wide range of sizes and dimensions, ranging from 1/8 inch to 26 inches in nominal diameter. The wall thickness can vary depending on the nominal pipe size and grade.
  • Standard pipe schedules such as SCH 40, SCH 80, SCH 160, and XXS are commonly available for ASTM A335 pipes.



ASTM A335 alloy steel pipes are widely used in high-temperature and high-pressure applications, such as:

  • Power generation: Boiler tubes, superheater tubes, and reheater tubes in steam boilers and power plants.
  • Oil and gas industry: Downhole tubular, production tubing, and piping systems in refineries and petrochemical plants.
  • Chemical industry: Piping systems for corrosive environments and high-temperature chemical processes.
  • Alloy steel pipes are used in the energy industry for high-temperature and very low-temperature service (cryogenic), or for applications with very high pressures.



  • ASTM A335 pipes can be welded using conventional welding methods such as SMAW (shielded metal arc welding), GTAW (gas tungsten arc welding), and GMAW (gas metal arc welding).
  • Preheating and post-weld heat treatment may be necessary to avoid cracking and ensure proper mechanical properties, especially for higher alloyed grades.

Overall, ASTM A335 alloy steel pipes are widely used for their excellent high-temperature properties, corrosion resistance, and strength characteristics. When selecting ASTM A335 pipes for a specific application, it is essential to consider factors such as grade, size, wall thickness, and end connections to ensure they meet the specific requirements and performance criteria.


ASTM A335 pipes have superior features than standard carbon steel pipes due to the addition of high-value elements such as Molybdenum, Chromium, and other alloying materials.

The addition of Molybdenum (“Moly”) increases the strength of the steel and its elastic limit, enhancing the steel’s resistance to wear, impact qualities, and hardenability. It also improves the resistance to softening, makes chromium steel less prone to embrittlement, and prevents pitting.

Chromium, a key element also for stainless steel alloys, prevents steel oxidation at elevated temperatures and increases the resistance of steel to corrosion. It enhances the tensile, yield, and hardness properties of low-alloy pipes at room temperature.

Other alloying elements, present in various degrees in pipes of all grades are
Alloying ElementProperties Conferred to Steel
Aluminum (Al)Increases grain refinement and control, enhancing strength and toughness. Also improves corrosion resistance and acts as a deoxidizer.
Boron (B)Enhances hardenability, allowing steel to achieve greater depth of hardness with less quench severity.
Cobalt (Co)Improves strength at high temperatures, making steel more resistant to thermal fatigue and wear.
Manganese (Mn)Increases hardenability, tensile strength, and wear resistance. Acts as a deoxidizer and improves toughness.
Nickel (Ni)Enhances overall strength and toughness, especially at low temperatures. Improves corrosion resistance in certain environments.
Silicon (Si)Strengthens steel and acts as a deoxidizer. In certain amounts, it can also increase magnetic properties and electrical resistivity.
Titanium (Ti)Combines with carbon to form titanium carbides, preventing grain growth and enhancing strength at high temperatures.
Tungsten (W)Significantly increases hardness and high-temperature strength, making steel more resistant to wear and deformation.
Vanadium (V)Improves hardenability while retaining fine grain size, leading to better wear resistance and toughness, especially at high temperatures.


As previously explained, ASTM A335 alloy pipes distinguish themselves from standard carbon steel pipes by containing elevated levels of alloying elements such as Molybdenum (Mo), Chromium (Cr), and occasionally Nickel, among others.

These pipes are categorized as “low-alloy” due to the total concentration of alloying elements typically remaining below 5%. In contrast, a higher concentration of alloying elements would classify the steel as “higher-alloy,” resembling stainless steel, duplex, or even super-alloys like Inconel, Hastelloy, Monel, and others.


ASTM A335 alloy steel pipes fit ASTM A234 WPx series buttweld fittings (WP5, WP9, WP91) and A182 Fx forged fittings and flanges (A182 F5, F9, F11, F22, F91). All these materials have similar chemical and mechanical properties and can be joined or welded.


The marking requirements for ASTM A335 pipes are specified to ensure proper identification and traceability of the pipes. According to ASTM A335 standard, the marking requirements typically include the following information:

Manufacturer’s Name or Logo:
The manufacturer’s name or logo is usually stamped or printed on the pipe. This helps identify the source of the pipe and ensures accountability for its quality.

Pipe Grade and Size:
The grade of the pipe (e.g., P5, P9, P11, etc.) and its nominal size are commonly marked on the surface of the pipe. This information indicates the material composition and dimensions of the pipe.

Heat Number:
Each heat of steel used to produce the pipes is assigned a unique heat number during the manufacturing process. The heat number is typically stamped or marked on the pipe for traceability purposes.

ASTM A335 Specification:
The ASTM A335 specification number is often marked on the pipe to indicate compliance with the standard requirements for seamless ferritic alloy-steel pipe for high-temperature service.

Lot Number or Batch Number:
In addition to the heat number, pipes may also be marked with a lot number or batch number to further facilitate traceability and quality control.

Additional Markings:
Depending on the specific requirements of the purchaser or applicable regulations, additional markings may be required. These may include symbols indicating compliance with certain standards or specifications, country of origin, and special handling instructions.

It’s important to note that the specific marking requirements may vary depending on the contractual agreement between the buyer and the manufacturer, as well as any applicable regulations or industry standards. Compliance with marking requirements ensures that the pipes can be properly identified, tracked, and verified throughout their lifecycle, from manufacturing to installation and maintenance.




The types of alloy steel covered by the ASTM A335 – ASME SA335 specification are designed with a “P” prefix, from P5 to P92. Grades P11/P22 and P91/92 are typically found in power stations, whereas grades P5 and P9 are more common for application in the petrochemical industry. Grades P9, and P91 are, in the list, the more expensive (a P91 seamless pipe may cost approx 5€ per kg.).

Low-Alloy Steel


A335 Low-Alloy PipeUNS NumberYield Strength ksiTensile Strength ksiElongation %RockwellBrinell
P5K41545407030207 max
P12K11562326030174 max


  • Transverse/longitudinal: tension and flattening, hardness, bend tests- for material which has been heat-treated in batch furnaces, these tests shall be made on the 5% of the pipes from each heat lot number. For smaller lots, one pipe at a minimum has to be tested
  • ASTM A335 Gr. P91 shall have a hardness of 250 HB / 265 HV (25 HRC)
  • Hydro testing: shall be applied to every length of pipe
  • The non-destructive electric test is optional



A335 PipeOverUnder
NPS [DN]in.mmin.mm
1/8 to 1 1/2 / DN 6 to 401/64 (0.015)0.41/64 (0.015)0.4
Over 1 1/2 to 4 / DN 40 to 1001/32 (0.031)0.791/32 (0.031)0.79
Over 4 to 8 / DN 100 to 2001/16 (0.062)1.591/32 (0.031)0.79
Over 8 to 12 / DN 200 to 3003/32 (0.093)2.381/32 (0.031)0.79
Over 12 / > DN 300+/- 1% of the specified outside diameter


The tolerances in WT, in %, from specified are:

  • 1/8 to 2 1/2 [6 to 65] incl., all t/D ratios: over 20%, under 12.5%
  • Above 2 1/2 [65], t/D < or = 5%: over 22.5%, under 12.5%
  • Above 2 1/2 [65], t/D > 5%: over 15%, under 12.5%

t = Specified Wall Thickness; D = Specified Outside Diameter)


Chrome Moly Pipes: Werkstoff vs EN vs ASTM
Werkstoff /DINENASTM
1.541516Mo3A335 Grade P1
1.733513CrMo4-5A335 Grade P11, P12
1.738010CrMo9-10A335 Grade P22
1.7362X11CrMo5A335 Grade P5
  A335 Grade P9
1.4903X10CrMoVNb9-1A335 Grade P91


Pipe MillCountry  
Jiangu Chengde Steel Tube Co Ltd. LtdChina
Vallourec TubesGermany, France, & Brazil
TenarisItaly, Mexico, & Argentina
Sumitomo MetalJapan
Productos TubularesSpain
Tubos ReunidosSpain
Wyman GordonUSA
Michigan SeamlessUSA
Rockwell CollinsUSA

We recommend purchasing the ASTM A335 specification from the ASTM website or the IHS store to get a complete understanding of this topic.

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About the Author

Picture of Fabrizio S.

Fabrizio S.

Fabrizio is a seasoned professional in the international trading of materials for projects, including piping, steel, and metal commodities with a distinguished career spanning over two decades. He has become a pivotal figure in the industry, renowned for his expertise in bridging the gap between EPC contractors, end users, manufacturers, and stockists to facilitate the seamless delivery of complex piping product packages across the globe. Starting his journey with a strong academic background in business administration and international trade, Fabrizio quickly distinguished himself in the field through his adept negotiation skills, strategic vision, and unparalleled knowledge of the project materials market. His career trajectory has seen him collaborate with leading names in the construction, oil & gas, and petrochemical industries, earning a reputation for excellence in executing large-scale projects (EPC Contractors, Oil & Gas End Users). At the core of Fabrizio's success is his ability to understand the intricate needs of EPC contractors and end users, aligning these with the capabilities of manufacturers and stockists. He excels in orchestrating the entire supply chain process, from product specification and procurement to logistics and on-time delivery, ensuring that each project phase is executed flawlessly. Fabrizio's role involves intense coordination and communication, leveraging his extensive network within the industry to negotiate competitive prices, manage complex logistical challenges, and navigate the regulatory landscape of international trade. His strategic approach to package assembly and delivery has resulted in cost efficiencies, timely project execution, and high satisfaction levels among stakeholders. Beyond his professional achievements, Fabrizio is an active participant in industry forums and conferences, such as Adipec, Tube, and similar, where he shares insights on market trends, supply chain optimization, and the future of project materials trading. His contributions to the field are not only limited to his operational excellence but also include mentoring young professionals entering the trade. Fabrizio is one of the co-founders of Projectmaterials, a B2B marketplace targeting the above markets. https://www.linkedin.com/in/fvs20092023/

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20 Responses

  1. Dear sir
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  2. We urgently need 2 each of IP By-Pass Pipe Spool, Dia: 30 inch, Wall Thickness: 25 mm, Material: A-335 Gr P91, Length: 1000 mm (Seamless pipe) with bevels, Fluid-Steam, Pressure-10 Bar, Temperature-574°C, as per attached drawing, on or before 19th May, 2020.

    Delivery Terms : DDP Qatar/ CIF Doha Port/ Ex-Works(Provide Packing details with dimension)
    Also include all the following details when quoting.
    1. Packing charges
    2. Documentation charges.
    3. Datasheet.

  3. We need 2 each of IP By-Pass Pipe Spool,
    Dia: 30 inch, Wall Thickness: 25 mm,
    Material: A-335 Gr P91,
    Length: 1000 mm (Seamless pipe) with bevels, Fluid-Steam, Pressure-10 Bar, Temperature-574°C
    together with Data Sheet.
    Bid Closing date : 10th May, 2020.
    Delivery Terms: Ex- Works and CIF Doha, Qatar.


    ITEM 1: SPEC 610.00MM X 9.53MM (DIAM 24″) SCHED 20/STD (ASME B36.10): 12 METERS
    ITEM 2: SPEC 914.00MM X 9.53MM (DIAM 36″) SCHED 20/STD (ASME B36.10): 12 METERS

    IF NEEDED, CALL ME AT 281-989-7259.

  5. We are looking 15000 Kg Chrome Vanadium Molybdenum Seamless Tube. Pls advise your email ID to send more details

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