ASTM A335 P12 (ASME SA335 P12) is a seamless alloy steel pipe designed for high-temperature service.
P12 main alloying elements are 0.08–1.25% chromium and 0.44–0.65% molybdenum, classifying it as a Cr-Mo alloy steel.
This material offers excellent high-temperature strength, heat resistance, and oxidation resistance, and is commonly used in boilers, superheaters, heat exchangers, and pressure vessel piping.
P12 pipes are also commonly used for bending, flanging (vanstoning), and similar forming operations, as well as for fusion welding.
When conducting chemical composition testing for P12, it shall be carried out in accordance with ASTM A999. The chemical composition requirements are as follows:
| Grade | Composition, % | ||||||
| C | Mn | P | S | Si | Cr | Mo | |
| P12 | 0.05 - 0.15 | 0.30 - 0.61 | 0.025 max | 0.025 max | 0.50 max | 0.08 - 1.25 | 0.44 - 0.65 |
Chromium significantly enhances the high-temperature resistance of steel pipes and improves their stability during long-term high-temperature service. Molybdenum increases high-temperature strength and creep resistance.
| Grade | ASTM A335 P12 | |
| Tensile strength, min, ksi [MPa] | 60 [415] | |
| Yield strength, min, ksi [MPa] | 32 [220] | |
| Elongation in 2 in. or 50 mm (or 4D), min, % | Longitudinal | Transverse |
| Basic minimum elongation for wall 5/16 in [8 mm] and over in thickness, strip tests, and for all small sizes tested in full section | 30 | 20 |
| When standard round 2 in or 50 mm gage length or proportionally smaller size specimen with the gage length equal to 4D (4 times the diameter) is used | 22 | 14 |
| For strip tests a deduction for each 1/32 in [0.8 mm] decrease in wall thickness below 5/16 in. [8 mm] from the basic minimum elongation of the following percentage points shall be made | 1.50 | 1.00 |
Manufacturer and Condition
ASTM A335 P12 steel pipes shall be made by the seamless process and shall be either hot finished or cold drawn, as specified.
Heat Treatment
All P12 pipe shall be reheated for heat treatment and heat treated in accordance with the requirements of the table.
| Grade | Heat Treat Type | Subcritical Annealing or Tempering Temperature |
| ASTM A335 P12 | full or isothermal anneal | — |
| normalize and temper | 1200 ℉ [650 ℃] | |
| subcritical anneal | 1200 ~ 1300 ℉ [650 ~ 705 ℃] |
Each length of pipe with an outside diameter greater than 10 in. [250 mm] and a wall thickness less than or equal to 0.75 in. [19 mm] shall be subjected to a hydrostatic test.
Alternatively, nondestructive testing in accordance with ASTM E213, E309, and E570 may be used.
Regardless of the testing method chosen, it shall be indicated on the pipe marking, with the marking requirements as follows:
| Ultrasonic | Flux Leakage | Eddy Current | Hydrostatic | Marking |
| No | No | No | Yes | Test Pressurer |
| Yes | No | No | No | UT |
| No | Yes | No | No | FL |
| No | No | Yes | No | EC |
| Yes | Yes | No | No | UT / FL |
| Yes | No | Yes | No | UT / EC |
| No | No | No | No | NH |
| Yes | No | No | Yes | UT / Test Pressurer |
| No | Yes | No | Yes | FL / Test Pressurer |
| No | No | Yes | Yes | EC / Test Pressurer |
Dimension Tolerance
For pipes ordered to NPS [DN] or outside diameter, variations in outside diameter shall not exceed those specified in the blow table.
| NPS [DN] Designator | Permissible Variations | |
| in. | mm | |
| 1/8 to 1 1/2 [6 to 40], inch. | ±1/64 [0.015] | ±0.40 |
| Over 1 1/2 to 4 [40 to 100], inch. | ±1/32 [0.031] | ±0.79 |
| Over 4 to 8 [100 to 200], inch. | -1/32 - +1/16 [-0.031 - +0.062] | -0.79 - +1.59 |
| Over 8 to 12 [200 to 300], inch. | -1/32 - +3/32 [-0.031 - 0.093] | -0.79 - +2.38 |
| Over 12 [300] | ±1 % of specified outside diameter | |
For pipes ordered to inside diameter, the inside diameter shall not vary more than ±1 % from the specified inside diameter.
Wall Thickness Tolerance
In addition to the implicit limitation of wall thickness for pipe imposed by limitation on weight in ASTM A999, the wall thickness for pipe at point shall be within the tolerances in the blow table.
| NPS [DN] Designator | Tolerance, % form Specified |
| 1/8 to 2 1/2 [6 to 65] incl. all t/D ratios | -12.5 - +20.0 |
| Above 2 1/2 [65], t/D ≤ 5% | -12.5 - +22.5 |
| Above 2 1/2, t/D ＞ 5% | -12.5 - +15.0 |
t = Specified Wall Thickness; D = Specified Outside Diameter.
| ASME | ASTM | EN | GB | JIS |
| ASME SA335 P12 | ASTM A213 T12 | EN 10216-2 13CrMo4-5 | GB/T 5310 15CrMoG | JIS G 3462 STBA22 |
Material: ASTM A335 P12 seamless steel pipes and fittings;
Size: 1/8" to 24", or customized according to your requirements;
Length: Random length or cut to order;
Packaging: Black coating, beveled ends, pipe end protectors, wooden crates, etc.
Support: IBR certification, TPI inspection, MTC, cutting, processing, and customization;
MOQ: 1 m;
Payment Terms: T/T or L/C;
Price: Contact us for the latest P12 steel pipe prices.
