A335 / SA335 P11 Chrome Moly Pipe
Dec 04, 2025
What is P11 Material
P11 Alloy Steel Pipe (A335 Grade P11) is a seamless ferritic alloy steel pipe compliant with the ASTM A335/A335M-2018 standard, classified as a high-temperature service alloy steel seamless pipe. It is primarily used in petroleum extraction, natural gas transmission, and thermal power generation, featuring 100% recyclability that aligns with national energy conservation strategies.
The pipe material contains elements such as carbon (C), manganese (Mn), and chromium (Cr). Chromium enhances carbide stability, although its elevated-temperature strength declines above 550°C. Production processes include:
Hot-rolling (piercing, rolling, etc.)
Cold-drawing (requiring annealing, acid cleaning, etc.)
A335 / SA335 P11 Chrome Moly Pipe specification
P11 Pipe Chemical Requirements
| Carbon | 0.05% - 0.15% |
| Manganese | 0.30% - 0.60% |
| Phosphorus, max | 0.025% |
| Sulfur, max | 0.025% |
| Silicon | 0.50% - 1.00% |
| Chromium | 1.00% - 1.50% |
| Molybdenum | 0.44% - 0.65% |
P11 Pipe Specification
| Tensile Strength, min, PSI, (MPa) | Yield Strength, min, (MPa) |
| 60,000 (415) | 30,000 (205) |
Dimension Tolerances
Tolerance in wall thickness:
|
NPS [DN] Designator |
Tolerance % on Wall Thickness |
|
|---|---|---|
|
Over (+) |
Under (-) |
|
|
1/8 to 2 1/2 [6 to 65] for all t/D ratios |
20.0 |
12.5 |
|
Above 2 1/2'' [65], t/D ≤ 5% |
22.5 |
12.5 |
|
Above 2 1/2 [65], t/D > 5% |
15.0 |
12.5 |
|
t = Wall Thickness; D = Outer Diameter |
||
Permissible variations for Outer Diameter:
|
NPS [DN] Designator |
Over (+) |
Under (-) |
||
|---|---|---|---|---|
|
in. |
mm |
in. |
mm |
|
|
1/8 to 1 1/2 [6 to 40] |
1/16 (0.015) |
0.40 |
1/16 (0.015) |
0.40 |
|
Over 1 1/2 to 4 [40 to 100] |
1/32 (0.031) |
0.79 |
1/32 (0.031) |
0.79 |
|
Over 4 to 8 [100 to 200] |
1/16 (0.062) |
1.59 |
1/32 (0.031) |
0.79 |
|
Over 8 to 12 [200 to 300] |
3/32 (0.093) |
2.38 |
1/32 (0.031) |
0.79 |
|
Over 12 [300] |
+/- 1% of the specified outside diameter |
|||
Manufacturing Processes
Hot-Rolling (Seamless Pipe)
Round billet → Heating → Piercing → Three-roll skew rolling, continuous rolling, or extrusion → Tube stripping → Sizing (or reducing) → Cooling → Blank pipe → Straightening → Hydrostatic testing (or NDT) → Marking → Storage.
Cold-Drawing (Rolling) (Seamless Pipe)
Round billet → Heating → Piercing → Pointing → Annealing → Acid cleaning → Oiling (copper plating) → Multi-pass cold drawing (cold rolling) → Blank pipe → Heat treatment → Straightening → Hydrostatic testing (NDT) → Marking → Storage.
Test and inspection
Packaging and shipping
