What is ASTM A335 pipe?

We also call ASTM A335 pipe as ASME S/A335 Chrome-Moly pipe, it is a type of seamless pipe could be used in high temperature environments of 540 – 750 °C.

The A335 pipes are generally called chrome moly pipe as they have a high level of Chromium and Molybdenum presence in it. While Molybdenum increases the overall strength, resistance, elasticity, hardenability and overall quality, moly ensures that the material is more resistant to softening, restrains the growth of grains and lessens the chances of embrittlement. It is the single additive that is responsible for the increase in high temperature resistance and it also improves the corrosion resistance to steel.

A335 Alloy Steel Pipe Grades

A335 steel pipe is often chromium molybdenum pipe due to the chemical composition of molybdenum (Mo) and chromium (Cr ). Pipe ordered to this specification must be suitable for bending, flanging and similar forming operations, and for fushion welding.

Molybdenum increases the strength of steel, as well as yield strength, wear resistance, impact qualities, and hardness. It increases softening strength, strengthens grain growth, and makes chrome steel less susceptible to embrittlement. Increases creep resistance at high temperature. It also improves the corrosion resistance of steel and inhibits pitting formation.

Chromium (chromium) is the essential component of stainless steel. Any steel with chromium of 12% or more is considered stainless. Chromium is virtually irreplaceable in resistance to oxidation at elevated temperatures. Chromium raises tension, performance and hardness at room temperature.

The chromium molybdenum composition of steel alloy steel tube is ideal for use in power plants, refineries, petrochemical plants and oil field services where fluids and gases are transported at extremely high temperatures and pressures.

A335 P5, P9, P11, P22, P91 Pipe Chemical Composition

Grade UNS C Mn ASTM A335 P S Si Cr Mo Others
ASTM A335 P1 K11522 0.10-0.20 0.30-0.80 0.025 0.025 0.10-0.50 0.44-0.65
ASTM A335 P2 K11547 0.10-0.20 0.30-0.61 0.025 0.025 0.10-0.30 0.50-0.81 0.44-0.65
ASTM A335 P5 K41545 0.15 0.30-0.60 0.025 0.025 0.50 4.00-6.00 0.45-0.65
ASTM A335 P5b K51545 0.15 0.30-0.60 0.025 0.025 1.00-2.00 4.00-6.00 0.45-0.65
ASTM A335 P5c K41245 0.12 0.30-0.60 0.025 0.025 0.50 4.00-6.00 0.45-0.65 *A
ASTM A335 P9 S50400 0.15 0.30-0.60 0.025 0.025 0.25-1.00 8.00-10.00 0.90-1.10
ASTM A335 P11 K11597 0.05-0.15 0.30-0.60 0.025 0.025 0.50-1.00 1.00-1.50 0.44-0.65
ASTM A335 P12 K11562 0.05-0.15 0.30-0.61 0025 0.025 ≤0.50 0.80-1.25 0.44-0.65
ASTM A335 P15 K11578 0.05-0.15 0.30-0.60 0.025 0.025 1.15-1.65 0.44-0.65
ASTM A335 P21 K31545 0.05-0.15 0.30-0.60 0.025 0.025 0.50 2.65-3.35 0.80-1.06
ASTM A335 P22 K21590 0.05-0.15 0.30-0.60 0.025 0.025 0.50 1.90-2.60 0.87-1.13
ASTM A335 P23 K41650 0.04-0.10 0.10-0.60 0.030 0.010 0.50 1.90-2.60 0.05-0.30 *B
ASTM A335 P36 K21001 0.10-0.17 0.80-1.20 0.030 0.025 0.25-0.50 0.30 0.25-0.50 *C
ASTM A335 P91 K91560 0.08-0.12 0.30-0.60 0.020 0.010 0.20-0.50 8.00-9.50 0.85-1.05 *D
ASTM A335 P92 K92460 0.07-0.13 0.30-0.60 0.020 0.010 0.50 8.50-9.50 0.30-0.60 *E
ASTM A335 P122 K92930 0.07-0.14 0.70 0.020 0.010 0.50 10.00-11.50 0.25-0.60 *F
ASTM A335 P911 K91061 0.09-0.13 0.30-0.60 0.020 0.010 0.10-0.50 8.50-9.50 0.90-1.10 *G

*The UNS designation is established in accordance with Practice E527, and SAE J 1086 – Practice for numbering metals and alloys.
*All values are the maximum unless a range is furnished.
*A – 4 times of Carbon≤Titanium≤0.70% or Columbium:8 times of Carbon~10 times of Carbon.
*B – V:0.20-0.30, Cb:0.02-0.08, B: 0.0010-0.006, N:≤0.0015, Al:≤0.030, W:1.45-1.75, Ni:≤0.40, Ti: 0.005-0.060, Ti/N:≥3.5.
*C – Ni:1.00-1.30, Cu:0.50-0.80, Cb:0.015-0.045, V:≤0.02, N:≤0.02, Al:≤0.050.
*D – V:0.18-0.25, N:0.030-0.070, Ni:≤0.40, Al:≤0.02, Cb:0.06-0.10, Ti:≤0.01, Zr:≤0.01.
*E – V:0.15-0.25, N:0.03-0.07, Ni:≤0.40, Al:≤0.02, Cb:0.04-0.09, W:1.5-2.0, B:0.001-0.006, Ti:≤0.01, Zr:≤0.01.
*F – V:0.15-0.30, W:1.30-2.50, Cu:0.30-1.70, Cb:0.04-0.10, B:0.0005-0.005, N:0.040-0.1, Ni:≤0.5, Al:≤0.02, (Ti&Zr):≤0.01.
*G – V:0.18-0.25, Ni:≤0.40, Cb:0.060-0.10, B:0.0003-0.006, N:0.04-0.09, Al:≤0.02, W:0.90-1.10, Ti:≤0.01, Zr:≤0.01.

ASTM A335 Pipe Mechanical Properties

ASTM A335 Grade Tensile Strength Yield Strength Elongation % Hardness(HB)
ksi MPa ksi MPa Longitudinal Transverse
ASTM A335 P1 55 380 30 205 30 20
ASTM A335 P2 55 380 30 205 30 20
ASTM A335 P5 60 415 30 205 30 20
ASTM A335 P5b 60 415 30 205 30 20
ASTM A335 P5c 60 415 30 205 30 20
ASTM A335 P9 60 415 30 205 30 20
ASTM A335 P11 60 415 30 205 30 20
ASTM A335 P12 60 415 32 220 30 20
ASTM A335 P15 60 415 30 205 30 20
ASTM A335 P21 60 415 30 205 30 20
ASTM A335 P22 60 415 30 205 30 20
ASTM A335 P23 74 510 58 400 20
ASTM A335 P91 85 585 60 415 20 ≤250
ASTM A335 P92 90 620 64 440 20 ≤250
ASTM A335 P122 90 620 58 400 20 ≤250
ASTM A335 P911 90 620 64 400 20

*All values are minimum unless otherwise specified.
*The specimen for elongation test shall be in the gauge length of 2 inches or 50 mm(or 4D).

Heat Treatment and Delivery Conditions

ASTM A335 pipes may be either hot finished or cold drawn with finishing treatment listed below:

  1. Pipes of all grades of ASTM A335 except P5c, P23, P91, P92, P122, and P911 shall be reheated, and furnished in the full-annealed, isothermal annealed, or normalized and tempered condition, the minimum tempering temperature  for grades P5, P5b, P9, P21, and P22 shall be 1250°F (675°C), the minimum tempering temperature for grades P1, P2, P11, P12, and P15 shall be 1200°F (650°C). It is recommended that the temperature for tempering should be at least 100°F (50°C) above the intended service temperature; consequently, the purchaser should advise the manufacturer if the service temperature is to be over 1100°F (600°C).
  2. ASTM A335 Pipe of Grades P1, P2, and P12, either hot finished or cold drawn, may be given a final heat treatment at 1200°F (650°C) to 1300°F (705°C) instead of heat treatments above-mentioned.
  3. Pipe of grade P5c shall be given a final heat treatment in the range from 1325°F (715°C) to 1375°F (745°C).
  4. ASTM A335 grades P92 & P911 shall be normalized at 1900°F (1040°C) minimum and tempered at 1350°F (730°C) minimum as a final heat treatment.
  5. Grade P122 shall be normalized at 1900°F (1040°C) minimum, and tempered at 1350°F (730°C) minimum as a final heat treatment.
  6. Grade P23 shall be normalized at 1900°F (1040°C) minimum with air cooling or accelerated cooling and tempered at 1350°F (730°C) minimum as a final heat treatment.
  7. ASTM A335 P91 shall be normalized at 1900°F (1040°C) minimum, and tempered at 1350°F (730°C) minimum as a final heat treatment. Alternatively, liquid quenching and tempering is allowed for thicknesses above 3 inch when mutually agreed upon between the manufacturer and the purchaser. In this case the pipe shall be quenched from 1900°F (1040°C) minimum and tempered at 1350°F (730°C) minimum as final heat treatment.

Tests and Examinations

  1. Unless an alternative nondestructive electric test is selected or otherwise specified by the purchaser, hydrostatic test shall be performed for each length of ASTM A335 pipe.
  2. Mechanical Tests: pipes of all grades of ASTM A335 shall take transverse or longitudinal tension test and flattening test, hardness test, or bend test. The test will be made on 5% of the pipe from each heat number.
  3. The nondestructive test (NDT) shall be performed in accordance with Practice E 213, Practice E 309, or Practice E 570. These NDT methods includes: Ultrasonic Examination, which shall be performed to detect both longitudinally and transversely oriented discontinuities; Eddy Current Examination, which has the capability to detect significant discontinuities especially of short abrupt type; Flux Leakage Examination, which is capable of detecting the presence and location of significant longitudinally and transversely oriented discontinuities.

Equivalent Alternatives

The alternative to certain grade of ASTM A335 can be found in ASTM A426 and ASTM A369. ASTM A426 is the standard specification for centrifugally cast ferritic alloy steel pipe for high-temperature service. ASTM A369 is the standard specification for carbon and ferritic alloy steel forged or bored pipe for high-temperature service. Both of them specify relatively equivalent grades of Cr-Mo alloy steel pipe. The main difference between ASTM A335, ASTM A426, and ASTM A369 is the manufacture of the pipe: ASTM A335 – hot rolled or cold drawn; ASTM A426 – centrifugal casting; ASTM A369: forging.

Other standards related to the seamless Cr-Mo alloy steel pipe include: ASTM A213 – standard specification for seamless ferritic and austenitic alloy steel boiler, superheater, and heat exchanger tubes; ASTM A199 – standard specification for seamless cold drawn intermediate alloy steel heat exchanger and condenser tubes; ASTM A200 – standard specification for seamless intermediate alloy steel tubes for refinery service.

SA335 Gr P9 Seamless Pipe

    Referred standards ASTM

    a. ASTM A999/ A999M, Standard specification for common requirements for stainless and alloy steel pipe
    b. ASTM A92, Hardness test methods for steel materials
    c. E213, Instructions and practice for ultra sonic testing of steel pipe and tube
    d. E309 Eddy-Current Examniation methods for steel pipe products
    e, E381, Inspection methods for steel bars, beams, profiles, billets and forgings.
    f, E527, Numbering metals and alloys practices
    g, E570, Instructions for flux leakage examniation of ferromagnetic steel pipe products

    Nominal Pipe Size

    ASME B36.10M dimensions standard for welded and seamless steel pipe

    Raw steel material that used for the production

    Pipe material shall be either hot finished or cold drawn with the related heat treatment required for different grades. For Grade P2 and P12 the steel should be manufactured by coarsegrain melting procedures.

    A335 is a grade of ferritic alloy steel alloy tube. It has excellent physical properties including very good strength, weldability and resistance to corrosion. It is most commonly used in the area of petrochemical applications such as oil and gas pipelines, where its resistance to sour service environments such as high temperatures and pressures is particularly important.

    It is well suited for welding and forming operations as it has excellent machinability and weldability properties. Its great strength makes it suitable for high pressure operating conditions, and its corrosion resistance makes it suitable for sour service environments. Its properties also make it ideal for uses in elevated temperature applications such as boilers and heat exchangers.

    The main benefit of A335 is its strength and resistance to higher pressures and temperatures. Its strength can be further enhanced by heat treatment and cold working, allowing it to be used in even more extreme conditions. Its weldability makes it easy to join with other parts, and its resistance to corrosion means that it is suitable for use in areas with high concentrations of sour gases and gasses containing corrosive elements.

    Although A335 has many benefits, it also has some drawbacks. Its cost and difficulty of fabrication are higher than other steel alloys, making it more expensive for certain applications. A335 is also particularly sensitive to weld cracking and can suffer from certain types of cracking upon prolonged service. Proper weld preparation and attention to detail is needed to ensure weld integrity when working with A335.

    ASTM A335 Seamless Pipes

    How to order an ASTM A335 Pipe

    When asking for a quote, it will be very helpful if the client can provide detailed information:

    1.  Name of material: seamless alloy steel pipe.
    2. Specific grades.
    3. Manufacture: hot rolled or cold drawn.
    4. Size: NPS+Schedule Number; O.D+Nominal W.T; O.D+Minimum W.T; I.D+ Nominal W.T; I.D+Minimum W.T.
    5. Length(fixed or random) and Quantity.
    6. End Finish(butt welding ends or plain ends).

    An example: ASTM A335 Gr. P11 SMLS Pipe, 12″ SCH80, Length=6 m, cold drawn, BW ends, 225 pieces.

    Related ASTM A335 pipes

    How to choose the right p-grades of A335 steel pipe?

    ASTM A335 / ASME SA335, covers moly chrome seamless tubes intended for high temperature service. It is commonly used in petrochemical and power generation industries, including refineries, power plants, petrochemical plants, hydrocrackers, coking plants, high and very high temperature lines, reheating lines, distillation, oil services, etc.

    Sometimes referred to as “Grade P” pipes, there are more than 16 degrees, with the most commonly used P-Grades being P5, P9, P11, P22 and P91. The most commonly used P-grades in refineries are P5, P9. The most commonly used in the power generation industry and petrochemical plants are P11, P22 and P91. So do you know how to select the right P grades?

    According to the A335 standard, the selection will depend on the design, service conditions, mechanical properties and high temperature characteristics. Each grade recognized according to the specification may have different requirements for a wide variety of options, as the operating environment and fluids running through the line can cover pressure, corrosion, and temperature variations. In addition, differences in chemical composition between different grades affect their physical properties.

    In general, when choosing a P-grade material, some of the questions below should know:

    • Physical properties of strength;
    • Upper temperature limits;
    • Allowable stress;
    • Thermal fatigue and number of operating cycles;
    • Number and configuration of loops and curves;
    • Creep resistance compatibility;
    • Hardness measurements;
    • Manufacturing time and costs;
    • Weight considerations including pipe supports;
    • Preheating temperatures and post-welding heat treatment temperatures;

    The selection of parts to be welded, welding procedures, welding quality assurance and weld filler materials.

    Other significant variables include water or steam temperature, pH, oxygen content of the fluid, steam quality, flow velocity, quality of the oxide layer on the inner surface of the pipe.