ASTM A335 Grade P11 Seamless Pipes

The ferritic alloy-steel seamless pipes made of ASTM A335/ ASME SA-335 Grade P11 are widely used in high-temperature service. In particular, ASTM A335 P11 seamless pipes are mainly intended for the cold-reheat piping system of the coal-fired power plant. The pipe may be ordered to NPS, outside diameter, or inside diameter, and shall be furnished with scale-free surface. It has a nominal chemical composition of 1.25Cr-0.5Mo-Si and UNS designation number of K11597 with P number of 4.

Chemical Composition Requirements

Element	Composition, %
C	0.05–0.15
Mn	0.30–0.60
P	≤0.025
S	≤0.025
Si	0.50–1.00
Cr	1.00–1.50
Mo	0.44–0.65

*Chemical requirements for ASTM A335 Gr. P11 based on product analysis.

Mechanical Properties

Tensile Strength MPa [ksi], min.	Yield Strength MPa [ksi], min.
415 [60]	205 [30]

*Tensile requirements for ASTM A335 Gr. P11.

Items	Longitudinal	Transverse
*EL1	30	20
*EL2	22	14

*Elongation requirements for ASTM A335 Gr.P11.
*EL₁: basic minimum elongation in 2″ or 50 mm, %, for wall thickness ≥ 8 mm, strip tests, and for all small sizes tested in full section.
*EL₂: elongation in 2″ [50 mm], %, when standard round 2″ gauge length or proportionally smaller size specimen with the gauge length equal to 4D is used.
*For strip tests a deduction of 1.50 and 1.00 (for longitudinal and transverse, respectively) for each 0.8 mm decrease in wall thickness below 8 mm from the basic minimum elongation shall be made.

Manufacture & Heat Treatment

The ASTM A335 Gr. P11 seamless pipe shall be either hot rolled or cold drawn. It may be furnished in full or isothermal annealing condition, or normalized and tempered condition. When normalizing + tempering heat treatment is adopted, the tempering temperature shall be no less than 650°C [1200°F].

Dimensional Tolerances

For ASTM A335/ ASME SA-335 Grade P11 pipes order to inside diameter, the inside diameter shall not vary more than ±1% from the specified inside diameter. For pipes ordered to NPS [DN] or outside diameter, the permissible variations (tolerances) in outside diameter are presented in the table below.

Size	Over inch mm	Under inch mm
1/8"≤NPS≤1.5"	1/64 0.40	1/64 0.40
1.5"	1/32 0.79	1/32 0.79
4"	1/16 1.59	1/32 0.79
8"	3/32 2.38	1/32 0.79
NPS>12"	±1% of O.D.

The length tolerance is usually specified by the purchaser. The lower tolerance for wall thickness is 12.5%. The upper tolerance for wall thickness is 20.0% for 1/8″≤NPS≤2.5″. For NPS > 2.5″, when t/D ≤ 5%, the upper tolerance for wall thickness is 22.5%; when t/D > 5%, the upper tolerance for wall thickness is 15.0%.

Testing

PMI chemical analysis, ultrasonic test, hydrostatic test, eddy current test, tension test, flattening test, etching test, bend test.