High-temperature & Corrosion-resistant
Astm a335 p91 alloy steel seamless pipe offers exceptional creep strength and corrosion resistance, ideal for boiler pipeline protection in power plants and petrochemical industries.
High-temperature & Corrosion-resistant
Astm a335 p91 alloy steel seamless pipe offers exceptional creep strength and corrosion resistance, ideal for boiler pipeline protection in power plants and petrochemical industries.
ASTM A335 P91 Pipe is a seamless ferritic alloy steel pipe engineered for high-temperature and high-pressure service, offering outstanding corrosion resistance and creep resistance. Conforming to the ASTM A335/ASME SA335 specification and designated as UNS K91560, this Chrome Moly Pipe is crafted with a composition of 8.00-9.50% chromium, 0.85-1.05% molybdenum, and enhanced with vanadium, niobium, and nitrogen, making it a creep strength enhanced ferritic (CSEF) steel. It is ideal for boiler pipeline protection in supercritical and ultra-supercritical power plants, petrochemical industries, and other industrial piping systems requiring durability under extreme conditions.
The ASTM A335 P91 Pipe is manufactured through hot-rolling or cold-drawing processes, followed by specific heat treatment: normalizing at 1040-1080°C and tempering at 730-800°C to achieve a martensitic microstructure with superior mechanical properties. The addition of vanadium (0.18-0.25%), niobium (0.06-0.10%), and nitrogen (0.03-0.07%) enhances creep strength and high-temperature performance, making it suitable for applications up to 650°C. The pipe is designed for bending, flanging, and fusion welding, requiring preheating (200°C) and post-weld heat treatment (PWHT at 730-760°C) to prevent cracking, especially for thicker walls. Available in sizes from 1/2” to 24” (DN15 to DN600), with wall thicknesses from SCH 40 to SCH XXS, and lengths up to 16 meters, it meets diverse project requirements.
The Seamless Alloy Pipes undergo rigorous testing, including tensile, flattening, hardness, and hydrostatic tests, to ensure compliance with ASTM A335 standards. With a minimum tensile strength of 585 MPa, yield strength of 415 MPa, and elongation of 20%, the pipe offers robust resistance to high temperatures and pressures. Its corrosion resistance is enhanced by high chromium content, making it ideal for handling corrosive fluids and gases in petrochemical applications, while its creep resistance supports long-term performance in high-pressure steam lines. Surface treatments like oil-dip, varnish, or 3LPE/FBE coatings enhance durability, and plain or beveled ends facilitate easy installation.
Compared to grades like P22 or P11, the ASTM A335 P91 Pipe is optimized for supercritical and ultra-supercritical boiler systems due to its superior creep strength, allowing for thinner walls and improved thermal efficiency. Its resistance to hydrogen sulfide corrosion and stress cracking makes it suitable for oil and gas pipelines, while its robustness supports applications in reheat lines, heat exchangers, and high-pressure boiler components. The pipe’s compatibility with ASTM A234 WP91 fittings ensures seamless integration into complex piping systems, making it a preferred choice for engineers seeking reliable industrial piping solutions.
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.08–0.12 |
| Manganese (Mn) | 0.30–0.60 |
| Phosphorus (P) | ≤0.02 |
| Sulfur (S) | ≤0.01 |
| Silicon (Si) | 0.20–0.50 |
| Chromium (Cr) | 8.00–9.50 |
| Molybdenum (Mo) | 0.85–1.05 |
| Vanadium (V) | 0.18–0.25 |
| Niobium (Nb) | 0.06–0.10 |
| Nitrogen (N) | 0.03–0.07 |
| Property | Value |
|---|---|
| Tensile Strength (MPa) | 585 min |
| Yield Strength (MPa) | 415 min |
| Elongation (%) | 20 min |
| Hardness (HBW) | ≤250 |
| Grade | UNS Designation | Chemical Composition % | |||||||
|---|---|---|---|---|---|---|---|---|---|
| P91 Type 1 | K91560 | C | Mn | P | S | Si | Ni | Cr | Mo |
| 0.08-0.12 | 0.30-0.60 | 0.020 | 0.010 | 0.20-0.50 | 0.40 max | 8.00-9.50 | 0.85-1.05 | ||
| V | N | Al | Cb | Ti | Zr | Sn | Sb | ||
| 0.18-0.25 | 0.030-0.070 | 0.02 max | 0.06-010 | 0.01 max | 0.01 max | _ | _ | ||
| P91 Type 2 | K91560 | C | Mn | P | S | Si | Ni | Cr | Mo |
| 0.08-0.12 | 0.30-0.50 | 0.020 | 0.005 | 0.20-0.40 | 0.40 max | 8.00-9.50 | 0.85-1.05 | ||
| V | N | Al | Cb | Ti | Zr | Sn | Sb | ||
| 0.18-0.25 | 0.035-0.070 | 0.02 max | 0.06-0.10 | 0.01 max | 0.01 max | 0.010 max | 0.003 max | ||
ASTM A335 P91 Type 1 & Type 2 have subtle differences mainly in elements Mn, S, Si, N, Sn and Sb content, and Type 2 has stricter requirements on element content than Type 1. P91 type 1 and 2 shall have a hardness within the range of 190 to 250 [HBW] or 196 to 265 [HV] or 91 HRBW to 25 HRC.
P91 (9Cr-1Mo-V-Nb) is a high-performance ferritic alloy steel designed for high-temperature service in power plants and petrochemical systems.
Maintains mechanical performance up to 600°C, allowing reduced wall thickness in steam piping and headers.
Withstands aggressive thermal and chemical environments, supporting advanced boiler design.
Offers up to 10× longer fatigue life compared to conventional steels, reducing shutdowns and failures.
Requires controlled heat treatment to maintain tempered martensitic structure and creep strength.
Chromium, molybdenum, vanadium, and niobium enhance strength, oxidation resistance, and weldability.
Widely used in superheaters, reheaters, HRSGs, and headers with compatible welding consumables.
P91 alloy steel has become the industry standard for high-efficiency power plant systems. It delivers exceptional performance in demanding thermal environments and is essential for systems operating under high pressure and temperature conditions.
ASTM A335 chrome moly pipes are widely used in various industries due to their excellent mechanical properties and resistance to high temperatures.
Used in high-temperature and high-pressure boiler tubes, superheaters, and reheaters for efficient energy conversion.
Applied in refineries and petrochemical plants to transport high-temperature hydrocarbons.
Used in facilities handling corrosive and high-temperature fluids during various chemical reactions.
Employed in nuclear power plants for critical piping systems resistant to extreme heat and pressure.
Used in furnaces and heat exchangers due to excellent resistance to high temperature and thermal fatigue.
Applied in high-pressure steam systems in industries like pulp and paper where thermal durability is essential.
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