ASTM A335 is the standard specification for seamless ferritic alloy steel pipe intended for high-temperature service.
Specified Standard Edition: ASTM A335
Standard Title: Standard Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service
The specification covers both nominal-wall and minimum-wall seamless alloy steel pipe.
ASTM A335 pipes are required to be suitable for bending, flanging and similar forming operations, as well as fusion welding.
Material selection depends on the design, service conditions, required mechanical properties and high-temperature characteristics.
ASTM A335 covers multiple ferritic alloy steel grades. Commonly specified grades include:
P5 / P9 / P11 / P22 / P91 / P92
| Grade | Material Description & Typical Service |
|---|---|
| P5 / P9 | Higher-chromium alloy grades used in high-temperature process and refinery piping where the applicable material specification requires these grades |
| P11 | Cr-Mo alloy steel commonly specified for high-temperature pressure piping and steam service |
| P22 | Higher Cr-Mo alloy steel widely used for elevated-temperature steam and process piping |
| P91 | Modified 9Cr-1Mo-V-Nb steel developed for high-temperature service requiring higher strength than conventional Cr-Mo grades |
| P92 | Advanced 9Cr-class creep-strength-enhanced ferritic steel used in demanding high-temperature power and steam applications |
Other ASTM A335 grades can be reviewed according to the project specification.
The required grade should be selected according to the applicable piping design code, design temperature, design pressure, service medium and project material specification.
ASTM A335 defines separate chemical-composition requirements for each grade.
| Grade | Principal Alloy System |
|---|---|
| P5 | Approximately 5Cr-Mo alloy system |
| P9 | Approximately 9Cr-Mo alloy system |
| P11 | Cr-Mo alloy steel |
| P22 | Approximately 2¼Cr-1Mo alloy system |
| P91 | Modified 9Cr-1Mo steel with controlled V, Nb and N additions |
| P92 | Modified 9Cr steel with Mo-W-V-Nb alloying additions |
Because ASTM A335 includes multiple alloy systems, chemical composition should be verified against the exact ordered grade rather than applying one composition range to the complete A335 product family.
Mechanical-property requirements are grade-specific. ASTM A335 specifies requirements including:
Different grades have different strength and hardness requirements.
P11, P22 and the higher-strength P91/P92 grades should therefore be treated as separate materials during engineering selection, purchasing and fabrication.
The required mechanical properties are verified against the exact ASTM A335 grade and applicable wall thickness.
Heat treatment is a critical requirement for ASTM A335 alloy steel pipe and varies by grade.
Depending on the specified grade, applicable heat-treatment routes include:
Higher-alloy and creep-strength-enhanced grades such as P91 and P92 require tightly controlled grade-specific heat treatment.
The required delivery condition should be confirmed from the ordered ASTM A335 grade and project specification rather than applying one common heat treatment to all A335 materials.
Each length of ASTM A335 pipe is subject to hydrostatic testing in accordance with the applicable specification requirements.
Where project specifications impose additional pressure-test requirements, these should be stated at the enquiry and order stage.
ASTM A335 requires each pipe to be examined by a nondestructive examination method in accordance with the applicable requirements.
The available examination method depends on pipe dimensions, specification requirements and the applicable referenced practice.
Project requirements for the following should be identified during the RFQ stage where applicable:
Applicable mechanical tests include:
Test requirements depend on pipe dimensions and the applicable ASTM A335 provisions.
ASTM A335 includes optional supplementary requirements that may be specified by the purchaser. These provide additional testing or quality requirements beyond the base specification.
Where supplementary requirements are required, the applicable designation and required test frequency should be stated in the purchase order.
This is particularly important for power-generation, critical steam piping and project-controlled pressure-piping applications.
ASTM A335 is a material specification rather than a single fixed-dimensional product standard.
Pipe dimensions are commonly ordered using either of the following formats:
| Ordering Method | Required Dimensions |
|---|---|
| Nominal Pipe Size | NPS + Schedule |
| Specified Dimensions | Outside Diameter + Wall Thickness |
The purchase order should clearly identify whether nominal-wall or minimum-wall pipe is required.
Dimensional requirements and tolerances should follow the applicable ASTM general requirements and project specification.
ASTM A335 and ASTM A213 can include similar Cr-Mo and high-temperature alloy systems, but they cover different product forms and applications.
| Comparison | ASTM A335 | ASTM A213 |
|---|---|---|
| Product Form | Seamless ferritic alloy steel pipe | Seamless ferritic and austenitic alloy steel tubes |
| Primary Service | High-temperature service | Boiler, superheater and heat exchanger service |
| Typical Grade Designations | P11 / P22 / P91 | T11 / T22 / T91 |
The specifications should not be treated as interchangeable solely because the alloy systems appear similar.
| Parameter | Capability |
|---|---|
| Product Form | Seamless Alloy Steel Pipe |
| Typical Grades | P5 / P9 / P11 / P22 / P91 / P92 |
| Manufacturing | Cold Drawn / Cold Rolled |
| Outside Diameter | 6–114 mm |
| Wall Thickness | 0.8–25 mm |
| Length | Up to 40 m |
| Heat Treatment | Grade-Specific |
| Inspection | Hydrostatic / UT / ET as specified |
| Documentation | MTC / EN 10204 / TPI as required |
| Third-Party Inspection | Available upon request |
| Custom Sizes | Subject to grade and technical review |
| MOQ | According to grade, dimensions and production requirements |
ASTM A335 standard requirements and FYN manufacturing capability are stated separately.
Actual grade availability and manufacturable dimensions are confirmed according to the required grade, outside diameter, wall thickness, length, heat treatment, inspection and quantity.
ASTM A335 seamless alloy steel pipe is primarily used in high-temperature pressure piping systems.
P11, P22, P91 and P92 are among the alloy grades used in steam piping systems where the selected material meets the applicable design conditions and piping code.
For high-temperature pressure piping connecting boilers, superheaters, reheaters, headers and associated steam-system equipment.
For high-temperature steam transfer outside the heat-transfer tube sections where ASTM A335 pipe is specified by the piping design.
P5, P9 and other Cr-Mo grades are used in high-temperature process piping where the project material specification requires ASTM A335 alloy steel pipe.
For high-temperature pressure piping carrying steam or process fluids under conditions compatible with the selected A335 grade.
Available documentation can include:
Documentation requirements should be specified during the RFQ stage.
Typical export packing includes:
End preparation can be reviewed according to the piping fabrication requirement.
Long-length pipes may require special packing and transportation arrangements.
Production lead time depends on grade, dimensions, quantity, heat treatment and inspection requirements.
For quotation, please specify:
ASTM A335/A335M + Grade + NPS / OD + Schedule / Wall Thickness + Length + Quantity
| Required Information | Details |
|---|---|
| Standard | ASTM A335/A335M |
| Grade | P5 / P9 / P11 / P22 / P91 / P92 or other specified grade |
| Pipe Size | NPS or outside diameter |
| Wall Thickness | Schedule or specified wall thickness |
| Wall Basis | Nominal wall or minimum wall |
| Length | Required pipe length |
| Quantity | Required order quantity |
| Heat Treatment | Required condition, if specified |
| Testing | Hydrostatic / NDE requirements |
| Supplementary Requirements | Applicable designation and test frequency, if required |
| Material Designation | ASTM or ASME designation required by the project |
| End Preparation | Required end preparation |
| Documentation | Inspection documentation requirements |
| Third-Party Inspection | If required |
| Delivery | Delivery destination |
For project enquiries, send your piping material specification, MTO, drawing or technical specification for technical review.
For an accurate quotation, please send your required grade, NPS or outside diameter, schedule or wall thickness, length and quantity.
For power-generation and high-temperature piping projects, please also provide the applicable piping material specification, supplementary requirements, NDE requirements and inspection documentation requirements.
For P91 / P92 projects, include the complete material and heat-treatment requirements from the project specification for technical review.
