ASTM A335 Grade P91 is also commonly known as ASME SA335 Grade P91 Pipes. These pipes are ferritic chrome-moly alloy steel pipes that are majorly used for high-temperature applications. The UNS designation for this grade P91 is K91560.
ASTM A335 Grade P91 Seamless Pipe
ASTM A335 P91 Pipe
P91 Alloy Steel Seamless Pipe
The major constituents and Molybdenum (Moly) and Chromium (Chrome). These elements provide the pipe with specific properties such as enhanced corrosion resistance and an overall increase in strength, creep resistance and wear resistance. P91 pipes contain other alloys in minimal quantities such as aluminium, columbium, nickel, nitrogen, titanium, vanadium and zirconium in the composition. The pipes are based on the A335 standard but when forged or bored these pipes can also come under the A369 standard. These pipes have minimum yield strength of 415 MPA and a minimum tensile strength of 585 MPA. The elongation limit of these pipes ranges from 20% to 30%. ASTM A335 GR. P91 pipes get its enhanced creep strength and durability due to the heat treatment process, in which the metal is normalized at 1500 Deg. C, air cooled at 200 Deg. C and then tempered by heat at 760 Deg. C.
All of these properties make the P91 pipes ideal for use in industrial plants, factories and refineries where these pipes can be used to carry fluids and gasses such as water, oil and steam at extremely high temperatures. Due to their high wear resistance, these pipes last longer and thus are extremely economically viable. These pipes can be used at continuously high temperatures of about 650°C.
N-Pipe Solutions Inc. is a major supplier of Low Alloy steel Seamless pipes from India. We provide high-quality pipes to clients throughout the world. Pipes are stock in NPS/NB dimension as per ASME B36.10 in various thicknesses as per clients requirements. All pipes supplied by us are duly inspected by our in-house quality control department before being supplied to the client. All pipes are available with complete traceability and mill test certificate as per EN 10204 3.1.
We provide the best competitive prices to our clients backed by quality service.
This specification covers nominal wall and minimum wall seamless ferritic alloy-steel pipe intended for high-temperature service. Pipe ordered to this specification shall be suitable for bending, flanging (vanstoning), and similar forming operations, and for fusion welding. Selection will depend upon design, service conditions, mechanical properties, and high-temperature characteristics.
2.1 ASTM Standards:
A999/A999M Specification for General Requirements for Alloy and Stainless Steel Pipe
E92 Test Methods for Vickers Hardness and Knoop Hardness of Metallic Materials
E213 Practice for Ultrasonic Testing of Metal Pipe and Tubing
E309 Practice for Eddy-Current Examination of Steel Tubular Products Using Magnetic Saturation
E381 Method of Macroetch Testing Steel Bars, Billets, Blooms, and Forgings
E527 Practice for Numbering Metals and Alloys in the Unified Numbering System (UNS)
E570 Practice for Flux Leakage Examination of Ferromagnetic Steel Tubular Products
2.2 ASME Standard:
B36.10M Welded and Seamless Wrought Steel Pipe
Orders for material under this specification should include the following, as required, to describe the desired material adequately:
Material furnished to this specification shall conform to the applicable requirements of the current edition of Specification A999/A999M, unless otherwise provided herein
All pipes shall be reheated for heat treatment and heat-treated by the requirements of Table 2.
TABLE 2 Heat Treatment Requirements A
|Grade||Heat Treat Type||Normalizing Temperature, min or range °F [°C]||Cooling Media||Subcritical Annealing or Tempering Temperature, min or range °F [°C]|
|P91 Type 1||normalize and temper or||1900–1975 [1040–1080]||--||1350–1470 [730–800]C|
|P91 Type 2||quench and temper||1900–1975 [1040–1080]||--||1350–1470 [730–800|
A Where ellipses (--) appear in this table there is no requirement.
|Grade||UNS Designation A||Carbon||Manganese||Phosphorus, max||Sulfur, max||Silicon||Chromium||Molybdenum||Others|
|P91 Type 1||K21590||0.08-0.12||0.30–0.60||0.020||0.010||0.20-0.50||8.00-9.50||0.85-1.05||V 0.18–0.25
Ni 0.40 max
Al 0.02 max
Ti 0.01 max
Zr 0.01 max
|P91 Type 2||K21590||0.08-0.12 0.07-0.13||0.30–0.50D||0.020D||0.005D||0.20-0.40D||8.00-9.50D||0.85-1.05 0.80-1.05||V Heat 0.18–0.25
Ni 0.20 maxD
Al 0.020 maxD
N/Al ratio $4.0
Ti 0.01 maxD
Zr 0.01 maxD
Sn 0.010 maxD
Sb 0.003 maxD
As 0.010 maxD
B 0.001 maxD
W 0.05 maxD
Cu 0.10 maxD
A New designation established in accordance with Practice E527 and SAE J1086, Practice for Numbering Metals and Alloys (UNS).
D Applies to both heat and product analyses.
|Grade||Tensile strength, min:||Yield strength, min:||Elongation Requirements|
|P91 Type 1 and Type 2||85||585||60||415||20|
1) For pipe ordered to NPS [DN] or outside diameter, variations in outside diameter shall not exceed those specified in Table 6.
2) For pipe ordered to inside diameter, the inside diameter shall not vary more than +/- 1 % from the specified inside diameter.
|NPC [DN] Designator||Over||Under|
|1/2 to 1 1/2 [6 to 40],incl.||1/64 (0.015)||0.40||1/64 (0.015)||0.40|
|Over 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 (0.031)||0.79||1/16 (0.031)||0.79|
|Over 8 to 12 [200 to 300],incl.||3/32 (0.031)||0.79||1/32 (0.031)||0.79|
|Over 12 ||± 1% of specified outside diameter|
In addition to the implicit limitation of wall thickness for pipe imposed by the limitation on weight in Specification A999/A999M, the wall thickness for pipe at any point shall be within the tolerances specified in Table 7. The minimum wall thickness and outside diameter for inspection for compliance with this requirement for pipe ordered by NPS [DN] and schedule number is shown in ASME B36.10M.
|NPS [DN] Designator||Tolerance, % form Specified|
|1/8 to 2 1/2 [6 to 65] incl., all t/D ratios A||20.0||12.5|
|Above 2 1/2, t/D<=5%A||22.5||12.5|
|Above 2 1/2, t/D>5%A||15.0||12.5|
A t= Specified Wall Thikness; D=Specified Outer Diameter.
The pipes need to be Hydro tested as per ASTM A530.
Transverse or Longitudinal Tension Test, Hardness Test, and Flattening or Bend Test
Certification and test reports, as described in Section 25 of Specification A999/A999M, are required.
16.1 In addition to the marking prescribed in Specification A999/A999M, the marking shall include the length, the schedule number, if the pipe is ordered to a schedule number, and the heat number or manufacturer’s number by which the heat can be identified. An additional symbol “S”, if the pipe conforms to any of the Supplementary Requirements S1 to S6, The marking may be by stenciling, stamping, or rolling at manufacture’s option.
Furthermore, the marking designated in below table to indicate the test method(s) shall be included.
|Marking to indicate the test method(s)|
NDE can be any of the following: Ultrasonic / Flux Leakage / Eddy Current