ASTM A335 is the specification covering minimal and nominal wall requirements for seamless ferritic alloy-steel pipe for use in high temperature service. Piping under this specification contains more alloying elements like Chromium, Nickel and Molybdenum than carbon steel pipes. The presence of these substances makes A335 pipes apt for projects that require tolerance to extremely high or low temperatures (cryogenic).

ASTM A335 pipes are also called low-alloy pipes because the amount of alloying elements in these piping is typically below 5%. These elements im[prove the properties of the steel piping in the following ways.

Welder working in manufacturing production plant. Welding method MIG. Source: Shutterstock

 Alloying Elements Used in ASTM A335 Power Alloy PIpes


Commonly called “moly” in the industry; this element is one of the most crucial additions to alloy steel production. Molybdenum improves steel toughness and hardenability. Between 0.2% and 5%, it also helps control grain growth in steel pipes, making them more resistant to brittleness. 


As one of the most important elements used in alloy steel pies, chromium display different benefits according to the percentage of substance used. For example, in low-alloy steels, only about 0.5% to 2% of chromium is used. This amount helps improve the steel’s hardness, yield, and tensile strength at room temperature.

At the same time, when 4% to 18% of the element is added to the steel, it helps resist corrosion by preventing oxidation at high temperatures.


In lower quantities, it helps eliminate excess oxygen from molten steel. When combined with phosphorus and sulfur, manganese reduces the pipe brittleness. In higher percentages, manganese improves hardenability by affecting the transformation points. 


This element decreases the oxygen content in the material to improve the hardenability of steel. In lower quantities, silicon improves pipe strength while it enhances the steel’s magnetic properties in larger amounts. 


This element helps improve the machinability of steel because of its free-machining properties. 


The carbon content in ASTM A335 pipes varies from 0.05% to 1%. This element is often used in steel pipes because it targets steel hardness. Carbon is known to improve the strength of piping by reconfiguring the crystal lattice of the steel.


Even adding 0.17% phosphorous to steel can improve its yield and tensile strength by 62 MPa. This substance improves the machinability of the piping when added to the site. Phosphorus is also beneficial as additive as it can help enhance the corrosion resistance of steel piping.

General Properties of ASTM A335 Pipes 

These pipes also exhibit high tensile strength and corrosion resistance, making them withstand high amounts of pressure. These properties make ASTM A 335 pipes well suited for several forming and fusion welding operations, including flanging and bending.  These pipes also have a general NPS of between ¼ to 24 and cover schedules 40 through 160, XXH, XH, and STD.

Some important applications for ASTM A335 pipes include;

  • ASTM A335 Pipes Used in Power Plants, Downstream Oil and Gas: Grades P11, P22, P91
  • ASTM A335 Pipes Used in Refineries: Grade P5, P9

Relevant Specifications for ASTM A 335 Power Alloy PIpes

  • ASTM E 570: Provides guidelines for practice testing of Flux Leakage of Ferromagnetic Steel Tubular Products
  • ASTM A 999/A 999M: General Standard Requirements of Stainlessless Steel and Alloy PIpes
  • ASTM E 527: Practice for Numbering Alloys and Metals
  • ASTM E 381: Macrotech Test Methods for Testing Steel Bars, Blooms, billets, and Forgings 
  • ASTM E 213: Ultrasonic Test Practice for Metal Tubing and Pipe
  • ASTM E 309: Eddy-Current Test Practice for Steel Tubular Products with Magnetic Saturation 
  • ASTM A 450/A 450 M: General Specification Requirements for Austenitic Alloy, Carbon, and Ferritic Alloy Steel Tubes

Important Characteristics of ASTM A 335 Pipes

  • Pipes under this specification can be cold drawn or hot rolled
  • The pipe ends can be plain ended or beveled.
  • All ASTM A 355 pipes undergo quality and strength testing, including- longitudinal/transverse tests, flattening, bending, and hardness tests.
  • ASTM A 355 typically covers low-alloy pipes, i.e. pipes with less than 5% alloying elements.
  • All pipes under this specification are hydro tested. Meanwhile, the non-destructive electric examination is usually conducted on the client’s demands
  • The grades under ASTM A 335 specs have varied uses, with P22/P92 being used in power plants and P9/P5 pipes being popular in petrochemical projects.

Chemical Properties of ASTM A 336 Pipes

 Element  Grade P5 Grade P9 Grade P11 Grade P22 P91 Type 1
 Molybdenum 0.45 to 0.65 0.90 to 1.10 0.44 to 0.65 0.87 to 1.13 0.85 to 1.05
 Chromium 4.0 to 6.0 8.0 to 10.0 1.0 to 1.50  1.90 to 2.60 8.0 to 9.50
 Sulfur (Max %) 0.025 0.025 0.025 0.025 0.010
 Phosphorous (Max %) 0.025 0.025 0.025 0.024 0.020
 Manganese 0.30 to 0.60 0.30 to 0.60 0.30 to 0.60 0.30 to 0.60 0.30 to 0.60

 0.15 (max) 0.15 (max) 0.05 to 0.15 0.5 to 0.15 0.08 to 0.12
 Silicon 0.05 (max) 0.25 to 1.00 0.50 to 1.0 0.50 (max) 0.20 to 0.50

Tensile Properties of ASTM A 335 Pipes

   Tensile Strength (Minimum) Yield Strength  (Minimum)
 P5 415 MPa 205 MPa
 P9 415 MPa 205 MPa
 P11 415 MPa 205 MPa
 P22 415 MPa 205 MPa
 P91 585 MPa 415 Mpa

How to Order ASTM A 335 Power Alloy Pipes Correctly?

All orders for ASTM A 335 pipe must include the following details.

  • Quantity (Number of lengths, feet, or meters)
  • Type of Material (seamless power alloy steel)
  • ASTM A 335 Grade
  • Manufacturing Details (cold drawn or hot finished)
  • Sizing Details-Specifying 
  • Schedule (SCH) Number or Nominal Pipe Size (NPS)
  • Nominal Wall Thickness or Outside Diameter (OD)
  • Minimum Wall Thickness or Outside Diameter
  • Nominal Wall Thickness or Outside Diameter
  • Minimal Wall Thickness or Inside Diameter
  •  Pipe Length-Single Random Length (SRL), Double Random Length (DRL), or Specific/Customized
  • End Finish Type (As per Specification ASTM A 999/ A 999M)
  • Optional Testing Requirements
  • Test Reports (if required)
  • Special Designations