A335 Pipe Specifications

NPS 1/4″ – 24″
Schedules 40 through 160, STD, XH and XXH


This specification covers nominal wall and minimum wall seamless ferritic alloy-steel pipe intended for high-temperature service. ASTM A335 pipe ordered to this specification shall be suitable for fusion welding, bending, flanging (vanstoning), and similar forming operations.

Material & Manufacture

Pipe may be either hot finished or cold drawn with the finishing heat treatment noted below.

Heat Treatment Requirements

P5, P9, P11, and P22  
GradeHeat Treatment TypeNormalizing Temperature Range F [C]Subcritical Annealing or Tempering
Temperature Range F [C]
P5 (b,c)Full or Isothermal Anneal
Normalize and Temper*****1250 [675]
Subcritical Anneal (P5c only)*****1325 – 1375 [715 – 745]
P9Full or Isothermal Anneal
Normalize and Temper*****1250 [675]
P11Full or Isothermal Anneal
Normalize and Temper*****1200 [650]
P22Full or Isothermal Anneal
Normalize and Temper*****1250 [675]
P91Normalize and Temper1900-1975 [1040 – 1080]1350-1470 [730 – 800]
Quench and Temper1900-1975 [1040 – 1080]1350-1470 [730 – 800]

Chemical Requirements

GradeP-5P-9P-11P-22P-91P-91 shall also include the following:
ElementUNS DesignationK41545S50400K11597K21590K91560
Carbon0.15 max0.15 max0.05 – 0.150.05 – 0.150.08 – 0.12V at 0.18 – 0.25
Manganese0.30 – 0.600.30 – 0.600.30 – 0.600.30 – 0.600.30 – 0.60N at 0.030 – 0.070
Phosphorous, max0.0250.0250.0250.0250.020Ni at 0.40 max
Sulfur, max0.0250.0250.0250.0250.010Al at 0.02 max
Silicon0.50 max0.25 – 1.000.50 – 1.000.50 max0.20 -0.50Cb at 0.06 – 0.10
Chromium4.00 – 6.008.00 – 10.001.00 – 1.501.90 – 2.608.00 – 9.50Ti at 0.01 max
Molybdenum0.45 -0.650.90 – 1.100.44 – 0.650.87 – 1.130.85 – 1.05Zr at 0.01 max

Tensile Requirements

  P-5P-9P-11P-22P-91P91 shall not have a hardness not exceeding 250 HB/265 HV [25HRC].
Tensile Strength, min., psi
Yield Strength, min., psi

Permissible Variation in Wall Thickness

NPS [DN] DesignatorTolerance, % from Specified
1/8 to 2 1/2 [6 to 65] incl., all t/D ratios20.0%12.5%
Above 2 1/2 [65], t/D < or = 5%22.5%12.5%
Above 2 1/2 [65], t/D > 5%15.0%12.5%
(t = Specified Wall Thickness; D = Specified Outside Diameter)

Elongation Requirements

Calculated Minimum Elongation Values
Elongation in 2 in. or 50 mm, min %
Wall ThicknessP5, P9, P11, P22 P91
in.mmLongitudinalTransverse Longitudinal
5/16 (0.312)8302020
9/32 (0.281)7.2281919
1/4 (0.250)6.4271818
7/32 (0.219)5.62617
3/16 (0.188)4.82416
5/32 (0.156)42215
7/8 (0.125)3.22114
3/32 (0.094)2.42013
1/18 (0.062)1.61812

Permissible Variations in Outside Diameter

Outside Diameter at any point shall not vary from standard specified more than:

NPS [DN] DesignatorOverUnder
1/8 to 1 1/2 [6 to 40], incl.1/64 (0.015)0.401/64 (0.015)0.40
Over 1 1/2 to 4 [40 to 100], incl.1/32 (0.031)0.791/32 (0.031)0.79
Over 4 to 8 [100 to 200], incl.1/16 (0.062)1.591/32 (0.031)0.79
Over 8 to 12 [200 to 300], incl.3/32 (0.093)2.381/32 (0.031)0.79
Over 12 [300]+/- 1% of the specified outside diameter

Mechanical Tests Specified

Transverse or Longitudinal Tension Test and Flattening Test, Hardness Test, or Bend Test
For material heat treated in a batch-type furnace, tests shall be made on 5% of the pipe from each treated lot. For small lots, at least one pipe shall be tested.
For material heat treated by the continuous process, tests shall be made on a sufficient number of pipe to constitute 5% of the lot, but in no case less than 2 pipe.
Notes for Hardness Test:P91 shall not have a hardness not exceeding 250 HB/265 HV [25HRC].
Notes for Bend Test:For pipe whose diameter exceeds NPS 25 and whose diameter to wall thickness ratio is 7.0 or less shall be subjected to the bend test instead of the flattening test.
Other pipe whose diameter equals or exceeds NPS 10 may be given the bend test in place of the flattening test subject to the approval of the purchaser.
The bend test specimens shall be bent at room temperature through 180 without cracking on the outside of the bent portion.
The inside diameter of the bend shall be 1 inch [25 mm].
Hydrostatic TestEach length of pipe shall be Hydro tested, at option of manufacture, nondestructive electric testing can be used.

See our full list of pipe testing services.

Required Markings on Each Length

(On Tags attached to each Bundle in case of Bundled Pipe) Markings will adhere to prescribed specifications in A 999/A999M and be: Rolled, Stamped, or Stenciled (Mfrs. Option)

In addition, markings will include:
Length of pipe
Marking to indicate the test method(s)
YESNOTest Pressure
YESYESTest Pressure/NDE
Schedule Number
Heat Number or Manufacturer’s number by which heat can be identified
An Additional Symbol “S” if the pipe conforms to any Supplementary Requirements
S1 – Product Analysis
S2 – Transverse Tension Test
S3 – Flattening Test
S4 – Metal Structure and Etching Tests
S5 – Photomicrographs
S6 – Photomicrographs for Individual Pieces
S7 – Alternative Heat Treatment – Grade P91
Pipe that has been weld repaired shall be marked “WR”.

Reference Documents

  • ASTM A999/A 999M Specification for General requirements for Alloy and Stainless Steel Pipe.
  • ASTM E 213 Practice for Ultrasonic Examination of metal Pipe and Tubing
  • ASTM E 309 Practice for Eddy-Current Examination of Steel Tubular Products Using Magnetic Saturation
  • ASTM E 381 Method of Macroetch testing Steel Bars, Billets, Blooms, and Forgings
  • ASTM E 570 Practice for Flux Leakage Examination of Ferromagnetic Steel Tubular Products
  • ASME B26.10M Welded and Seamless Wrought Steel Pipe

Ordering Information

Orders for material under this specification should include the following, as required, to describe the desired material adequately:

QuantityFeet, meters, or number of lengths
Name of materialSeamless Alloy Steel Pipe
GradeP5, P9, P11, P22, P91
ManufacturerHot-finished or cold-drawn
Size using one of the following:
NPS and Schedule Number
Outside Diameter and Nominal Wall Thickness
Outside Diameter and Minimum Wall Thickness
Inside Diameter and Nominal Wall Thickness
Inside Diameter and Minimum Wall Thickness
LengthSpecific or Random
End Finish

Click here to request a quote for A 335 pipe.