A335 Pipe Specifications

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

Scope

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    
Grade Heat Treatment Type Normalizing Temperature Range F [C] Subcritical Annealing or Tempering
Temperature Range F [C]
P5 (b,c) Full or Isothermal Anneal, or
Normalize and Temper ***** 1250 [675]
Subcritical Anneal (P5c only) ***** 1325 – 1375 [715 – 745]
P9 Full or Isothermal Anneal, or
Normalize and Temper ***** 1250 [675]
P11 Full or Isothermal Anneal, or
Normalize and Temper ***** 1200 [650]
P22 Full or Isothermal Anneal, or
Normalize and Temper ***** 1250 [675]
P91 (type 1 and 2) Normalize and Temper, or 1900-1975 [1040 – 1080] 1350-1470 [730 – 800]
Quench and Temper 1900-1975 [1040 – 1080] 1350-1470 [730 – 800]

Chemical Requirements

Grade P5 P9 P11 P22 P91 (type 1) P91 type 1 shall also include the following: P91 (type 2) P91 type 2 shall also include the following P91 type 2 continued
Element UNS K41545 K90941 K11597 K21590 K91560 K91560
Carbon 0.15 max 0.15 max 0.05 – 0.15 0.05 – 0.15 0.08 – 0.12 V at 0.18 – 0.25 Heat: 0.08 – 0.12
Product: 0.07 – 0.13
V (heat) at 0.18 – 0.25
V (product) at 0.16 – 0.27
N / Al ration ≥ 4.0
Manganese 0.30 – 0.60 0.30 – 0.60 0.30 – 0.60 0.30 – 0.60 0.30 – 0.60 N at 0.030 – 0.070 0.30 – 0.50D N at 0.035 – 0.070D Sn at 0.01 maxD
Phosphorous, max 0.025 0.025 0.025 0.025 0.020 Ni at 0.40 max 0.20D Ni at 0.02 maxD Sb at 0.003 maxD
Sulfur, max 0.025 0.025 0.025 0.025 0.010 Al at 0.02 max 0.005D Al at 0.02 maxD As at 0.010 maxD
Silicon 0.50 max 0.25 – 1.00 0.50 – 1.00 0.50 max 0.20 -0.50 Cb at 0.06 – 0.10 0.20 – 0.40D Cb (heat) at 0.06 – 0.1
Cb (product) at 0.05 – 0.11
B at 0.001 maxD
Chromium 4.00 – 6.00 8.00 – 10.00 1.00 – 1.50 1.90 – 2.60 8.00 – 9.50 Ti at 0.01 max 8.00 – 9.50D Ti at 0.01 maxD W at 0.05 maxD
Molybdenum 0.45 -0.65 0.90 – 1.10 0.44 – 0.65 0.87 – 1.13 0.85 – 1.05 Zr at 0.01 max Heat: 0.85 – 1.05
Product: 0.80 – 1.05
Zr at 0.01 maxD Cu at 0.10 maxD
DApplies to both heat and product analyses.

Tensile Requirements

Seamless    
    P5 P9 P11 P22 P91 (1, 2) P91 type 1 and 2 shall have a hardness within the range of 190 to 250 [HBW] or 196 to 265 [HV] or 91 HRBW to 25 HRC.
Tensile Strength, min., psi
ksi 60 60 60 60 85
MPa 415 415 415 415 585
Yield Strength, min., psi
ksi 30 30 30 30 60
MPa 205 205 205 205 415

Permissible Variation in Wall Thickness

NPS [DN] Designator Tolerance, % from Specified
Over Under
1/8 to 2 1/2 [6 to 65] incl., all t/D ratios 20.0% 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 Thickness P5, P9, P11, P22   P91 (type 1 and 2)
in. mm Longitudinal Transverse   Longitudinal
5/16 (0.312) 8 30 20 20
9/32 (0.281) 7.2 28 19 19
1/4 (0.250) 6.4 27 18 18
7/32 (0.219) 5.6 26 17
3/16 (0.188) 4.8 24 16
5/32 (0.156) 4 22 15
7/8 (0.125) 3.2 21 14
3/32 (0.094) 2.4 20 13
1/18 (0.062) 1.6 18 12

Permissible Variations in Outside Diameter

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

NPS [DN] Designator Over Under
in. mm in. mm
1/8 to 1 1/2 [6 to 40], incl. 1/64 (0.015) 0.40 1/64 (0.015) 0.40
Over 1 1/2 to 4 [40 to 100], incl. 1/32 (0.031) 0.79 1/32 (0.031) 0.79
Over 4 to 8 [100 to 200], incl. 1/16 (0.062) 1.59 1/32 (0.031) 0.79
Over 8 to 12 [200 to 300], incl. 3/32 (0.093) 2.38 1/32 (0.031) 0.79
Over 12 [300] +/- 1% of the specified outside diameter

Mechanical Tests Specified

Transverse or Longitudinal Tension Test, Hardness Test, and Flattening 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.
Unless otherwise specified, the flattening test or bend test shall be chosen at the manufacturer’s option.

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)
Hydrostatic Nondestructive Marking
YES NO Test Pressure
NO YES NDE
NO NO NH
YES YES Test 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 (type 1 and 2)

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:

Quantity Feet, meters, or number of lengths
Name of material Seamless Alloy Steel Pipe
Grade P5, P9, P11, P22, P91 (type 1 or 2)
Manufacturer Hot-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
Length Specific or Random
End Finish

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