A335 seamless ferritic Alloy Steel Pipe
Dec 03, 2025
ASTM A335 Seamless Ferritic Alloy Steel Pipe description
Scope of Application
This standard specifies the technical requirements for seamless ferritic alloy steel pipes with nominal wall thickness and thinnest wall thickness used in high-temperature services. It applies to forming operations such as bending, flanging, and welding, as well as high-temperature piping systems in boilers, pressure vessels, nuclear power, and petrochemical industries.
Material Classification
It covers various grades of ferritic alloy steel (such as P1, P2, P5, P9, P11, P12, P22, P91, P92, etc.), with a chromium content ≤10%, belonging to the category of medium-low alloy steel. Different grades are distinguished by chemical composition and heat treatment processes to meet specific high-temperature performance requirements.
Heat Treatment: Depending on the steel grade, full annealing, isothermal annealing, or normalizing and tempering treatment is required. For example, the tempering temperature after normalizing for P11 grade steel pipes needs to be ≥650°C, and for P91 grade+, it needs to be ≥730°C.
Dimensional tolerances: Outer diameter tolerance is controlled in sections according to pipe diameter (e.g., positive and negative tolerances are both 0.40mm when ≤48.3mm), and wall thickness tolerance is limited by proportion or fixed value (e.g., positive tolerance is 20% and negative tolerance is 12.5% when ≤73mm).
ASTM A335 Chrome Moly Pipe Specification
| Standard | ASTM A335/A335M (ASME SA335/SA335M) |
| Material | Alloy steel pipe |
| Manufacture | Seamless |
| Grade | P1, P2, P5, P5b, P5c, P9, P11, P12, P15, P21, P22, P23, P24, P36, P91 Type 1, P91 Type 2, P92, P93, P115, P122, P128, P911, P921 |
| Application | High-temperature service as well as bending, flanging (vanstoning), and similar welding operations as well as fusion welding |
ASTM A335/ A335M Chemical Composition %
Mechanical Properties: Tensile, Yield, Elongation & Hardness
Test and inspection
Hydrostatic Testing: Each steel pipe must undergo a hydrostatic test unless otherwise specified in the purchase order.
Non-destructive Testing: Ultrasonic testing (E213), eddy current testing (E309), or magnetic flux leakage testing (E570) may be used instead of the hydrostatic test, with the specific method specified by the buyer.
Surface Quality: Defects penetrating 12.5% of the wall thickness or violating the minimum wall thickness requirement are prohibited. Surface scratches must be ≤1.6mm or 5% of the nominal wall thickness.
Packaging and shipping
