ASTM A335/A335M Pipe Specification

ASTM A335/A335M - Specification for Seamless Ferritic Alloy Steel Pipes for High Temperature Service

‌ASTM A335‌/A335M (also known as ASME SA-335/SA-335M) is a standard for seamless ferritic alloy steel pipes for high temperature service developed by the American Society for Testing and Materials (ASTM). This standard is applicable to high temperature and high pressure environments in industries such as petroleum, chemical industry, power station boilers, and power systems, such as boilers, steam pipes, etc., and covers a variety of material grades, such as P1, P5, P11, P22, P91, etc.

Scope of application:
This standard applies to seamless alloy steel pipes used in high temperature environments. These steel pipes are usually used in high temperature and high pressure equipment such as boilers, superheaters, pressure pipes, and chemical pipes.

ASTM A335 steel pipes must have processing properties such as bending, flanging, and welding.

Standard content:
The ASTM A335 standard specifies in detail the size, shape, chemical composition requirements and corresponding test methods of ferritic alloy steel pipes. The standard applies to seamless ferritic alloy steel pipes with an outer diameter of 21.3-762mm, requiring strict chemical composition control and high temperature performance (creep resistance, oxidation resistance) and mechanical indicators (tensile strength ≥ 415-585 MPa). In addition, the standard also specifies the manufacturing process (such as normalizing + tempering heat treatment), dimensional tolerances and optional supplementary testing (such as ultrasonic, hardness testing, etc.)

ASTM A335 standard product features:

1. Specification range
Outer diameter range: 21.3mm-762mm

Wall thickness range: 2.0mm-130mm

Common specifications:

OD (mm)	WT (mm)	Applicable grades (such as P11/P22/P91)
21.3	2.0	P11、P22
114.3	8.0	P11、P91
323.9	12.0	P22、P91
508.0	14.0	P91、P92
711.0	25.0	P92

Non-standard specifications: Some manufacturers can customize special sizes, such as large-diameter thick-walled pipes (such as 711×25mm).
Length: Usually 6m, 12m fixed length, can also be customized according to customer needs. A high-temperature piping system that can meet different size requirements.

2. Material and brand
ASTM A335/A335M standard covers a variety of ferritic alloy steel materials (low/medium alloy steel with chromium content ≤10%), such as P1, P2, P5, P5B, P5C, P9, P11, P12, P21, P22, P23, P36, P91 (Type1, Type2), P92, etc.

3. Chemical composition

ASTM A335 contains multiple grades, and the content of chromium (Cr) and molybdenum (Mo) of different grades determines its temperature resistance and corrosion resistance.

Grade	Cr (%)	Mo (%)	Typical Application
P11	1.00~1.50	0.44~0.65	Petrochemical boiler tubes
P22	1.90~2.60	0.87~1.13	High-pressure steam pipelines
P91	8.00~9.50	0.85~1.05	Supercritical power station pipelines
P92	8.50~9.50	0.30~0.60	Ultra-supercritical boilers

Note: High alloy grades such as P91/P92 have stronger creep resistance and oxidation resistance due to the presence of tungsten (W), boron (B) and other elements.

4. Mechanical performance requirements

Grade	Tensile strength (MPa)	Yield strength (MPa)	Elongation (%)	Maximum operating temperature
P11	≥415	≥205	≥30	≤550℃
P22	≥415	≥205	≥30	≤600℃
P91	≥585	≥415	≥20	≤650℃
P92	≥620	≥440	≥20	≤625℃

Key performance:
High temperature endurance strength (e.g. P91 is twice as strong as traditional steel at 550℃).
Oxidation resistance (chromium forms a dense oxide film).

5. Manufacturing process and testing requirements

Production method:
The production method of ASTM A335 steel pipe includes hot rolling, cold drawing and hot expansion, etc., and it is delivered after heat treatment such as normalizing + tempering (e.g. P91 requires 1040℃ normalizing + 730℃ tempering) to ensure the mechanical properties and high temperature characteristics of the steel pipe.

Testing items:
Non-destructive testing (UT ultrasonic, RT radiographic testing).
Hydraulic pressure test (to ensure pressure bearing capacity).
Supplementary requirements (such as grain size, hardness test, etc.).

Typical application areas:

Seamless steel pipes under ASTM A335/A335M standards are widely used in various high-temperature and high-pressure equipment, such as:

1. Boilers and superheaters: used to manufacture high-temperature and high-pressure pipes and equipment to ensure the effective transfer of heat energy and the stable operation of equipment. Such as supercritical boiler superheaters, main steam pipes (P91/P92).

2. Chemical and petroleum industries: In the process of chemical and petroleum processing, it is necessary to transport high-temperature and high-pressure media such as steam, oil and gas, etc. These steel pipes can withstand the corrosion of these media and the impact of high temperature and high pressure. Such as cracking furnace tubes, high-temperature reactors (P11/P22).

3. Natural gas industry: In the process of natural gas transportation and storage, a high-temperature and high-pressure pipeline system is required to ensure the safe transportation and storage of natural gas.
4. Nuclear energy/aerospace: high-temperature components (P92).

Comparison of A335 pipes with other standards:

ASTM A106: Carbon steel seamless pipe (≤450℃), chromium-free molybdenum alloy, low temperature resistance.
API 5L: Oil and gas pipeline, focusing on pressure resistance, not for high temperature.
ASTM A213: Austenitic alloy steel pipe for boiler, containing nickel-chromium stainless steel (such as TP304).

Notes:
1. Ordering instructions: When ordering seamless steel pipes under the ASTM A335/A335M standard, it is necessary to specify the quantity, material, specification, manufacturing method, end processing, selection requirements, test report and other detailed information of the steel pipe.
2. Standard update: With the continuous advancement of technology and the continuous improvement of standards, the ASTM A335/A335M standard will also be updated and revised. Users should pay attention to the latest version of the standard when selecting.

Latest version:
As of 2025, the latest version of ASTM A335 is ASTM A335/A335M-24b, which was released on October 15, 2024. This version adds material grades such as P92, optimizes the alloy ratio to improve high temperature performance, and is suitable for extreme environments such as supercritical boilers (≤625℃). The standard adopts the SI/English dual unit system and is cited by international standards such as ASME to ensure the safety and reliability of pipelines under high temperature and high pressure.

Conclusion:

ASTM A335/A335M is the core standard for high temperature and high pressure seamless alloy steel pipes. The seamless steel pipes under this standard have excellent high temperature resistance, corrosion resistance and mechanical properties. Through strict composition control, heat treatment process and testing requirements, it ensures its reliability in extreme environments and is widely used in various high temperature and high pressure equipment. High-end materials such as P91/P92 have become the first choice in supercritical power generation, chemical industry and other fields.

Read more: Different types of boiler tubes and their role in energy or Suggestions for selecting boiler tube materials