A335 P91 High Temperature Seamless Pipe
A335 P91 high-temperature ferritic alloy steel pipe is a heat-resistant alloy steel pipe used in high-temperature and high-pressure applications, belonging to the P91 grade material in the American ASTM A335 standard. This alloy pipe is mainly composed of alloying elements such as chromium, molybdenum, vanadium, and niobium, possessing excellent high-temperature strength, oxidation resistance, and creep resistance. It is widely used in high-temperature and high-pressure pipeline systems in thermal power generation, nuclear power, petrochemical, and energy fields, such as key components like boiler superheaters, reheaters, and steam pipelines.
A335 P91 alloy pipe is a seamless ferritic alloy steel pipe for high-temperature applications in the American ASTM A335/A335M standard, corresponding to 10Cr9Mo1VNbN (i.e., P91) in Chinese GB5310, X10CrMoVNb9-1 in European EN 10216-2, and STBA26 in Japanese JIS G3467. Its chemical composition is basically the same: C 0.08–0.12%, Cr 8.0–9.5%, Mo 0.85–1.05%, V 0.18–0.25%, Nb 0.06–0.10%, N 0.03–0.07%.
Regarding mechanical properties, ASTM requires a tensile strength ≥585MPa and a yield strength ≥415MPa at room temperature; GB5310 has similar requirements and additionally specifies high-temperature performance at 600℃.
Despite the different standard systems, A335 P91 is highly versatile in supercritical power plant projects worldwide. The materials from different countries are highly mutually recognized in terms of composition and performance, with only slight differences in inspection items (such as impact test temperature) and delivery details.
GNEE Group is a leading manufacturer and supplier of A335 P91 chromium-molybdenum alloy pipes. We are equipped with the latest eddy current testing and hydrostatic testing equipment to ensure the quality of every pipe. Material certificates are provided with each pipe upon delivery. Contact us for high-quality A335 P91 high-temperature and high-pressure alloy pipes for your power plants, oil refineries, and chemical plants.
A335 P91 Low Alloy Seamless Round Pipes specification
| Specifications | ASTM A 335 / ASME SA 335 |
| Size | 1/8"NB TO 30"NB IN |
| Schedule | SCH20, SCH30, SCH40, STD, SCH80, XS, SCH60, SCH80, SCH120, SCH140, SCH160, XXS, UPTO 4″ WALL THICK |
| Length | Single Random, Double Random & Required Length, Custom Size – 12 Meter lengths |
| Form | Round, Square, Rectangular, Hydraulic Etc. |
| Type | Seamless |
P91 seamless ferritic alloy-steel pipe Chemical Composition
| Grade | C % | Mn % | P % | S % | Si % | Cr % | Mo % |
|---|---|---|---|---|---|---|---|
| P91 | 0.08-0.12 | 0.30-0.60 | 0.020 max | 0.010 max | 0.20 -0.50 | 8.00 - 9.50 | 0.85 - 1.05 |
P91 Chrome Moly Alloy Seamless Pipe Mechanical Properties
| Grade | Tensile Strength, MPa | Yield Strength, MPa | Elongation, % |
|---|---|---|---|
| P91 | 585 min | 415 min | 20 min |
A335 P91 Chrome Moly Alloy Seamless Pipe Manufacturing Process and Dimensional Specifications
Manufactured using hot rolling or cold drawing processes, with an outer diameter range of 10.3-1219 mm and a wall thickness of 2.0-120 mm. Hot-rolled tubes require a piercing → continuous rolling → sizing → straightening process, while cold-drawn tubes require multiple diameter reduction passes. Key process control points include:
- Hot deformation temperature range: 900-1150℃, final rolling temperature: not lower than 850℃
- Cold deformation per pass: ≤20%, total deformation: ≤60%
- Finished products must undergo 100% eddy current testing or ultrasonic testing, with a defect detection sensitivity of 0.5 mm.
For special requirements, internal shot peening (Sa2.5 grade) or pickling passivation can be performed, with a surface roughness Ra≤12.5μm. According to ASME B36.10M standard, common specifications such as Φ323.9×36mm and Φ457×50mm are typically 6-12.5m in length.
A335 P91 Seamless Ferritic Alloy Steel Pipe Weldability Analysis
1. A335P91 steel has a martensitic microstructure and is typically supplied in a normalized + tempered state. As a high-alloy steel, it has poor weldability and is prone to cold cracking, weld joint embrittlement, and softening in the HAZ region. Strict adherence to the process specifications is essential to obtain satisfactory weld joints.
2. Strict control of welding and heat treatment temperatures, using lower welding parameters, is crucial to ensuring complete root penetration of the weld.
3. A moderate preheating temperature, ideally controlled within the range of 150℃~200℃, is beneficial for the flow of molten iron in the weld pool and overcomes the problem of incomplete fusion and penetration at the weld root caused by the difficulty in wire feeding in high-Cr alloy steels.
A335 P91 seamless ferritic alloy-steel pipe Main Application Areas
Power Industry
Core Applications: Manufacturing high-temperature superheaters and reheaters for subcritical and supercritical boilers, as well as high-temperature headers and steam pipes with wall temperatures ≤600℃.
Advantages: At 550-650℃, its allowable stress can be twice that of traditional steels (such as T9 and 2.25Cr-1Mo steel), and under the same conditions, the pipe wall thickness can be reduced by 40%, significantly reducing material costs and equipment weight. For example, in a 600MW supercritical boiler, after P91 steel pipes replaced traditional 12Cr1MoV steel, the superheater tube wall thickness was reduced from 35mm to 21mm, and the thermal efficiency was improved by approximately 2%.
Petrochemical Industry
Core Applications: Used in furnace tubes, high-temperature and high-pressure reactors, heat exchangers, and transmission pipelines in petroleum cracking units.
Advantages: Its high chromium (8.0%-9.5%) and molybdenum (0.85%-1.05%) content endows the steel with excellent resistance to hydrogen sulfide corrosion and high-temperature oxidation, enabling long-term stable operation in sulfur-containing media. For example, in hydrocracking units, P91 steel pipes, replacing TP304 stainless steel, extend service life to over 10 years and reduce maintenance costs by 50%.
Aerospace Applications
Core Applications: Manufacturing high-temperature components such as aero-engine combustion chambers and turbine blades.
Advantages: Under extreme high-temperature (>650℃) and high-pressure environments, P91 steel pipes exhibit significantly superior creep strength and creep resistance compared to ordinary alloy steels, meeting the dual requirements of lightweight and high reliability for aero-engine materials.
Other Industrial Applications
Machinery and Instrumentation: Used in manufacturing high-precision mechanical parts, such as high-temperature and high-pressure valves and pump bodies. Its high strength and corrosion resistance ensure long-term stable operation of equipment.
Environmental Engineering: In flue gas desulfurization and denitrification units, P91 steel pipes can withstand acidic media corrosion, extending equipment service life.
A335 P91 Chrome Moly Alloy Seamless Pipe Factory
A335 P91 High-Temperature Alloy Steel Pipes Packaging and shipping
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