A/SA335 Pipe Specifications

ASTM A335 / ASME SA335 is a standard specification for seamless
ferritic alloy-steel pipe intended for high-temperature service.

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APP stocks a full range of A/SA335 pipe in:

    • Grades P5, P9, P11, P22 & P91
    • NPS ¼” to 24” OD
    • Schedules 20 through XXH
    • See A691 for sizes above 24″OD

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Key Characteristics

  • Seamless construction — no weld seam, giving uniform strength around the circumference
  • High-temperature strength — retains mechanical properties at elevated temperatures where carbon steel would fail
  • Oxidation and creep resistance — resists scaling and slow deformation under sustained stress at heat
  • Pressure-bearing capability — designed specifically for pressurized systems
  • Weldable — though proper preheat and post-weld heat treatment (PWHT) are required

Primary Applications & Industries

  • Power Generation The dominant user of A335 pipe. Used extensively in coal, gas, and nuclear power plants for main steam lines, reheat lines, headers, and superheater/reheater tubing — anywhere steam is at high pressure and temperature.
  • Petroleum Refining & Petrochemicals Used in process piping that handles hot hydrocarbons, hydrogen service, and high-pressure process streams. P5 and P9 grades see use in hydrogen-rich, sulfur-bearing environments due to their resistance to hydrogen attack (per Nelson curves).
  • Chemical Processing High-temperature reactor feed and effluent lines, heat exchanger connections, and piping in catalytic cracking units.
  • Boilers & Pressure Vessels As the ASME SA335 designation implies, extensively used in boiler construction for steam distribution and connecting pressure vessels where the ASME code is the governing standard.
  • Pulp & Paper Industry Recovery boilers and high-pressure steam distribution within mills.
  • Heat Exchangers Connecting and manifold piping where elevated temperatures are sustained.

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 Full or Isothermal Anneal, or ***** 1250 [675]
Normalize and Temper ***** 1250 [675]
Subcritical Anneal (P5c only) ***** 1325 – 1375 [715 – 745]
P9 Full or Isothermal Anneal, or ***** 1250 [675]
Normalize and Temper ***** 1250 [675]
P11 Full or Isothermal Anneal, or ***** 1200 [650]
Normalize and Temper ***** 1200 [650]
P22 Full or Isothermal Anneal, or ***** 1250 [675]
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 0.010 maxD
Phosphorous, max 0.025 0.025 0.025 0.025 0.020 Ni at 0.40 max 0.020D Ni at 0.20 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 0.020 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 – 0.10
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

 

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* This information is provided for quick references. Always consult applicable ASME, ASTM and Manufacture’s standards.