ASTM A335 P91 Alloy Steel Seamless Pipes and Tubes

ASTM A335  P91 Alloy Steel Seamless Pipes and Tubes

ASTM A335 P91 Alloy Steel Seamless Pipes and Tubes

ASTM A335 / A 335M, ASME SA335 P11, P12, P22, P91 is the standard applicable to seamless ferritic alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes.


ASTM A335 /A335M ASME SA335 pipes shall be made by the seamless process and shall be either hot-finished or cold drawn with the finishing treatment.
ASTM A335 /A335M 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.
Standard: ASTM A335/A335M, ASME SA335
Description Name: ASTM A335 / ASME SA335 P11 Seamless pipes, ASTM A335 / ASME SA335 P12 Seamless pipes, ASTM A335 / ASME SA335 P22 Seamless pipes, ASTM A335 / ASME SA335 P91 Seamless pipes, ASTM A335 P11 Seamless pipes, ASTM A335 / ASME SA335 P12 Seamless alloy pipes, ASTM A335 P22 Superheater pipes, ASTM A335 P91 Superheater pipes, ASTM A335 P91 Superheater pipes, ASTM A335 P11 boiler pipes, ASTM A335 P12 boiler pipes, ASTM A335 P22 boiler pipes, ASTM A335 P91 boiler pipes, ASTM A335 / ASME SA335 P22 Seamless pipes, ASTM A335 / ASME SA335 P12 Seamless alloy pipes, Seamless superheater pipes, Boiler pipes, Alloy steel pipe, High Pressure boiler pipe, High Temperature pipe.
Size: 50.8 to 860 mm
Wall Thickness: 2.77 to 100mm
Shape: Round
Length: Single random length/ Double random length or as customer’s actual request
Grade: P11, P12, P22, P91

Referenced Documents

ASTM A 999/A999M specification for general requirements for alloy and stainless-steel pipe
E92 Test method for Vickers 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 macro etch testing steel bars, billets, blooms, and forgings

Chemical Composition

Chemical Components (%)
Grade C Mn P S Si Cr Mo V Nb N Al others
P11 0.05-0.15 0.30-0.60 ≤0.025 ≤0.025 0.50-1.00 1.0-1.50 0.44-0.65 / / / / /
P12 0.05-0.15 0.30-0.61 ≤0.025 ≤0.025 ≤0.50 0.80-1.25 0.45-0.65 / / / / /
P22 0.05-0.15 0.30-0.60 ≤0.025 ≤0.025 ≤0.50 1.90-2.60 0.87-1.13 / / / / /
P91 0.08-0.12 0.30-0.60 ≤0.020 ≤0.010 0.20-0.50 8.0-9.50 0.85-1.05 0.18-0.25 0.030-0.070 ≤0.40 ≤0.02

Cb 0.06-0.10

Ti 0.01max

Zr 0.01max

Heat Treatment Requirements

Grade UNS


Heat Treat Type Austenitizing/ Solutioning

Temperature, min or range °F [°C]

Subcritical Annealing or Tempering

Temperature, Min or range °F [°C]

P11 K11597 full or isothermal anneal normalize and temper 1200 [650]
P12 K11562 full or isothermal anneal normalize and temper subcritical anneal

1200 [650]

1200-1300 [650 to 705]

P22 K21590 full or isothermal anneal normalize and temper 1250 [675]
P91 K91560 normalize and temper

quench and temper





Tensile Requirements and Hardness:

Mechanical Properties
Grade Tensile Yield Elongation Hardness
Strength (Mpa) Strength (Mpa) (%)
P11 P12 ≥415 ≥220 ≥30 ≤89HRB
P22 ≥415 ≥200 ≥30 ≤89HRB
P91 ≥585 ≥415 ≥20 91HRB-25HRC

Flattening Test—One flattening test shall be made on specimens from each end of one finished tube, not the one used for the flaring test, from each lot

Flaring Test—One flaring test shall be made on specimens from each end of one finished tube, not the one used for the flattening test, from each lot

Hydrostatic or Nondestructive Electric Test—Each tube shall be subjected to the nondestructive electric test or the hydrostatic test. The type of test to be used shall be at the option of the manufacturer, unless otherwise specified in the purchase order.

Materials and Manufacture

  • The Tubes shall be made by the seamless process and shall be either hot-finished or cold finished, as specified.
  • Heat Treatment—Ferritic Alloy and Ferritic Stainless Steels—The ferritic alloy and ferritic stainless steels shall be reheated for heat treatment in accordance with the requirements of Standard. Heat treatment shall be carried out separately and in addition to heating for hot forming.

A / N+T

N+T / Q+T



  • Mill test certificates will be issued according to EN10204.3
  • All tubes shall be supplied as per applicable ASTM A335 /A335M Specification.

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