ASTM A335 P5 Pipe Specification

ASTM A335 P5 / ASME SA335 P5 pipe is a seamless chrome-moly alloy steel pipe designed for high-temperature and corrosive service environments. With a chemical composition containing 4.00%–6.00% chromium and 0.45%–0.65% molybdenum, this grade delivers excellent resistance to oxidation, improved creep strength, and long-term structural stability under elevated temperatures. Known as P5 grade chrome-moly pipe, it is widely used in boilers, heat exchangers, power plants, and petrochemical systems where consistent performance and durability are required.

In welded pipe applications, the corresponding standard is ASTM A691 5CR, produced from ASTM A387 Grade 5 alloy steel plates. This ensures compatibility across both seamless and welded product forms, offering engineers reliable choices depending on project requirements. By combining mechanical strength, corrosion resistance, and weldability, ASTM A335 P5 pipe remains a key material in critical high-temperature piping systems worldwide.

Key Element of Chrome and Moly for P5 Pipe

As we know ASTM A335 / ASME SA335 named chrome moly pipe because they have a high level of Cr and Mo, these two are key elements for Alloy Pipe. Chromium will increase oxidation resistance and provides high-temperature strength, along with the better tensile & yield strength with proper hardness at room temperature.

Molybdenum increases the overall strength, resistance, hardenability, elasticity, and whole quality, Moly  make material more resistant to softening, restrains the growth of grains and reduce the chances of brittle.

ASTM A335 P5 mechanical properties same with Grade P9, P11, P22, Minimum tensile strength 415MPa, minimum yield strength 205Mpa. Those grades are popular used in different industries.

ASTM A335 P5/ASTM A234 WP5/ASTM 387 Grade 5/ASTM A691 5CR/ASTM A182 F5

ASTM A335 P5 material is highly versatile, with properties that make it suitable for bending, flanging (vanstoning), fusion welding, and machining, depending on project requirements. This flexibility allows P5 pipes to be fabricated into a wide range of pipe fittings and components such as elbows, bends, tees, reducers, caps, and flanges, as well as other equipment used for high-temperature fluid transmission systems.

Since product forms vary across the piping industry, the ASTM A335 P5 specification corresponds to several related standards, each governing a different product category:

• ASTM A234 WP5 – standard for seamless and welded pipe fittings (e.g., elbows, tees, reducers, caps).

• ASTM A182 F5 – standard for forged flanges and fittings.

• ASTM A387 Grade 5 – standard for chrome-moly alloy steel plates used in pressure vessels and welded structures.

• ASTM A691 5CR – equivalent standard for welded chrome-moly alloy steel pipe, manufactured from ASTM A387 Grade 5 steel plates.

In summary, ASTM A335 specifies seamless chrome-moly alloy steel pipes, while ASTM A691 covers welded chrome-moly pipes. Together, these standards ensure full material compatibility across seamless pipes, welded pipes, pipe fittings, flanges, and plates, supporting reliable construction of high-temperature piping systems.

Ferritc Steel

Ferritc steel are defined as low and intermediate alloy steel where the Chrome content up to 10%. When Chrome content more than 12%, it will be classified to stainless steel.

ASTM A335 P5 Chemical Composition

Mechanical Properties

Elongation

For wall thickness 5/16 in [8mm] and over:
Elongation in 2 in or 50mm or 4D minimum%: Longitudinal 30% and Transverse 20%.
Elongation smaller 2 in or 50mm or 4D minimum%: Longitudinal 22% and Transverse 14%.

For strip tests a deduction of each 0.8mm below 8mm shall be calculated as below:
8mm, Longitudinal 30%, Transverse 20%;
7.2mm, 28% & 19%;
6.4mm, 27% & 18%;
5.6mm, 26% & 18%.

Tests

Tensile tests: Transverse and Longitudinal
Flattening test of ASTM A999/A999M
Hardness test not exceeding 250 HBW/265 HV30 [25HRC]
Bend Test shall be carried as per ASTM A370
Hydrostatic Test is required, depending on the buyer’s decision both Hydrostatic test and a nondestructive test could be carried out.

Heat Treatment

ASTM A335 P5 shall be heat treated with full or isothermal anneal or normalize and temper or subcritical anneal, temperature 675℃.

ASTM A335 P9 Dimension Tolerances

Outside diameter for 6mm to 40mm, vary +/-0.40mm.
For OD 40 to 100mm, +/-0.79mm.
OD 100 to 200mm, +1.59/-0.79mm.
OD 200 to 300, +2.38/-0.79mm.
Over 300mm 12 inch, +/-1% from specified OD in the PO.
(In case of ordered on inside diameter, shall not vary more than 1% from specified ID.

Wall Thickness Tolerance

DN6 to 65, +20%/-12.5%
Abover DN65 t/D ≤5%A, +22.5%/-12.5%
Abover DN65 t/D ＞5%A, +22.5%/-12.5%

At= Specified Wall Thickness; D = Specified Outer Diameter

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