ASTM A335 P5 alloy steel seamless pipe

ASTM A335 P5 alloy steel seamless pipe, also known as chromium-molybdenum steel P5 pipe or 5Cr-0.5Mo steel pipe, is a high-quality seamless ferritic alloy steel pipe.

ASTM A335 is a standard for high-temperature chromium-molybdenum (Cr-Mo) alloy steel seamless pipe developed by the American Society for Testing and Materials (ASTM). It is suitable for boilers, heat exchangers, and high-pressure piping systems serving high-temperature conditions.

P5 is a sub-grade (corresponding to UNS grade K41545), indicating that the main alloying elements are 5% chromium (Cr) and 0.5% molybdenum (Mo), possessing excellent high-temperature strength and oxidation resistance.

ASTM A335 P5 Chemical Composition

The chemical composition of ASTM A335 P5 is tightly controlled to provide the required combination of high-temperature strength, oxidation resistance, and fabrication performance.

Element	ASTM A335 P5 Requirement, wt.%	Main Function
Carbon (C)	≤ 0.15	Contributes to strength and hardness
Manganese (Mn)	0.30–0.60	Improves strength and hardenability
Silicon (Si)	≤ 0.50	Deoxidation and oxidation resistance
Chromium (Cr)	4.00–6.00	Improves oxidation and corrosion resistance
Molybdenum (Mo)	0.45–0.65	Improves high-temperature strength and creep resistance
Phosphorus (P)	≤ 0.025	Controlled to limit embrittlement
Sulfur (S)	≤ 0.025	Controlled to maintain material quality

This composition combination imparts the following to the material:

High-temperature stability: Long-term service temperature can reach above 540°C, suitable for thermal equipment;
Creep resistance: Molybdenum and chromium synergistically strengthen grain boundaries, reducing the risk of high-temperature deformation;
Corrosion resistance: Chromium forms a dense oxide film, resisting corrosion from flue gas and media.

Mechanical Properties of ASTM A335 P5 Pipe

Property	Value
Tensile Strength, min	60,000 psi (415 MPa)
Yield Strength, min	30,000 psi (205 MPa)
Elongation (Longitudinal), min	30%
Elongation (Transverse), min	20%
Hardness, max	250 HB / 265 HV

ASTM A335 P5 pipe maintains excellent strength and creep resistance above 600°C, making it ideal for high-temperature steam, supercritical pressure, and hot oil pipelines.

Manufacturing Process and Specifications

Production Method: Primarily uses hot rolling or hot expansion processes (depending on wall thickness requirements), delivered in a heat-treated state (normalizing + tempering) to ensure a uniform ferrite microstructure.

Size Coverage:
Outer Diameter: 21.3–762mm (covering mainstream industrial piping specifications);
Wall Thickness: 2.0–130mm (meeting different pressure rating requirements);
Length: Standard length 12m, custom lengths also available.

Surface and Connections: Mostly black pipe (uncoated), round cross-section, welded connections possible.

Core Application Areas

Energy Industry: High-temperature and high-pressure steam pipelines in thermal power plants, boiler superheater tubes, etc.;
Oil and Gas Industry: High-temperature pipe sections in petroleum cracking units and natural gas transmission pipelines;
Chemical Equipment: High-temperature reactor pipes, heat exchanger tube bundles, etc.

FAQ About ASTM A335 P5 Seamless Pipe

1. What is ASTM A335 P5 pipe?

ASTM A335 P5 is a seamless ferritic chromium-molybdenum alloy-steel pipe designed for high-temperature service. P5 corresponds to UNS K41545 and contains 4.00–6.00% chromium and 0.45–0.65% molybdenum.

2. Is ASTM A335 P5 a seamless pipe?

Yes. ASTM A335 is a specification for seamless ferritic alloy-steel pipe for high-temperature service.

3. What is the chemical composition of P5 steel?

ASTM A335 P5 contains up to 0.15% carbon, 0.30–0.60% manganese, up to 0.50% silicon, 4.00–6.00% chromium and 0.45–0.65% molybdenum, with phosphorus and sulfur limited to 0.025% maximum each.

4. What is the difference between ASTM A335 P5 and P9?

Both are Cr-Mo alloy-steel grades for high-temperature service, but P9 contains significantly more chromium and molybdenum than P5. P5 contains 4.00–6.00% Cr and 0.45–0.65% Mo, while P9 contains 8.00–10.00% Cr and 0.90–1.10% Mo.

5. What is ASTM A335 P5 used for?

ASTM A335 P5 is commonly used for high-temperature piping in power plants, refineries, petrochemical plants, boilers, heat exchangers and other industrial process systems.

Read more：Standards for boiler pipes or ASTM A335 seamless ferritic alloy steel pipe for high temperature use