Product Overview
ASTM A335 P91 Alloy Steel Seamless Pipe
Jiangsu Cunrui Metal Products Co., Ltd.
ASTM A335 P91 is a seamless ferritic alloy steel pipe designed for high-temperature and high-pressure service. It belongs to the chromium-molybdenum alloy family, featuring 8.0–9.5% chromium and 0.85–1.05% molybdenum, with controlled additions of vanadium, niobium, and nitrogen. This composition delivers exceptional creep strength, oxidation resistance, and thermal stability, making it the material of choice for critical power generation and petrochemical applications.
P91 offers a higher allowable stress at elevated temperatures compared to traditional low‑alloy grades like P22. For a given pressure and temperature, a P91 pipe can be designed with thinner walls, reducing overall weight, material cost, and welding time. Its tempered martensitic microstructure, stabilized by fine vanadium‑niobium carbonitride precipitates, ensures reliable performance under long-term high‑temperature exposure. The material also features lower thermal expansion than austenitic stainless steels, which minimizes thermal fatigue during plant startup and shutdown cycles
- Standard Compliance: ASTM A335 / ASME SA335
- Material Type: Seamless Ferritic Alloy Steel
- UNS Designation: K91560
- Equivalent Grades: ASME SA335 P91, ASTM A213 T91, EN 10216‑2 X10CrMoVNb9‑1 (1.4903), DIN 17175 X10CrMoVNb9‑1, BS 3604‑2 Gr. 91, GB 5310 10Cr9Mo1VNb
Chemical Composition
comparison of product parameters
| Element | P91 Type 1 (wt%) | P91 Type 2 (wt%) |
| Carbon (C) | 0.08 – 0.12 | 0.08 – 0.12 |
| Manganese (Mn) | 0.30 – 0.60 | 0.30 – 0.50 |
| Phosphorus (P) | 0.020 max | 0.020 max |
| Sulfur (S) | 0.010 max | 0.005 max |
| Silicon (Si) | 0.20 – 0.50 | 0.20 – 0.40 |
| Chromium (Cr) | 8.00 – 9.50 | 8.00 – 9.50 |
| Molybdenum (Mo) | 0.85 – 1.05 | 0.85 – 1.05 |
| Vanadium (V) | 0.18 – 0.25 | 0.18 – 0.25 |
| Niobium (Nb) | 0.06 – 0.10 | 0.06 – 0.10 |
| Nitrogen (N) | 0.030 – 0.070 | 0.030 – 0.070 |
| Nickel (Ni) | 0.40 max | 0.40 max |
| Aluminum (Al) | 0.040 max | 0.040 max |
Mechanical Properties
| Property | Value |
| Tensile Strength, min | 585 MPa (85 ksi) |
| Yield Strength (0.2% offset), min | 415 MPa (60 ksi) |
| Elongation (2″ or 50mm gage), min | 20% |
| Hardness (HBW), max | 250 HB |
| Impact Energy (Charpy V‑notch), min | 35 J |
Values based on ASTM A335/A335M specification requirements
Heat Treatment
ASTM A335 P91 seamless pipes are supplied in the heat‑treated condition, typically normalized and tempered, to achieve the required martensitic microstructure and mechanical properties.
| Heat Treatment | Temperature | Cooling Media |
| Normalizing | 1040 – 1080°C (1900 – 1975°F) | Air |
| Tempering | 730 – 800°C (1350 – 1470°F) minimum | Air |
Optionally, quenching and tempering may be used instead of normalizing and tempering.
Product Traits & Competitive Edges
Properties & Merits
Superior Creep Strength
Resists long‑term deformation under high temperature and pressure, enabling thinner‑wall designs that cut cost and weight.
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Excellent Oxidation & Corrosion Resistance
8.00–9.50% Cr forms a protective oxide layer, ideal for steam and sour service environments.
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Stable High‑Temperature Performance
Maintains mechanical integrity during frequent thermal cycles, reducing shutdown risks.
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Optimized Thermal Properties
Higher thermal conductivity and lower expansion than austenitic steels, minimizing thermal stress.
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Cost‑Effective Alternative
Higher thermal conductivity and lower expansion than austenitic steels, minimizing thermal stress.
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About Jiangsu Cunrui Metal Products Co., Ltd
Reliable Manufacturer with 20+ Years of Expertise
Founded in 2006 and headquartered in Wuxi, Jiangsu, we are a professional manufacturer and exporter with a self‑owned factory, total investment of CNY 180 million, and annual sales exceeding CNY 2 billionJiangsu Cunrui Metal Products Co., Ltd.. Our 100+‑strong team includes 18 dedicated engineers for R&D and quality control, ensuring technical precision and consistent product qualityJiangsu Cunrui Metal Products Co., Ltd..
Applications
Power generation plants (coal‑fired and gas‑fired) – main steam lines, hot reheat lines, superheater tubes, reheater tubes, boiler headers, and manifolds
Petrochemical and refinery industries – high‑temperature process piping, hydrocrackers, catalytic crackers, and heating furnace piping-5-27
Nuclear power – high‑temperature systems where creep strength is critical.
Why Choose Cunrui?
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Competitive & Transparent Pricing: Direct sourcing from major mills combined with efficient in‑house processing eliminates unnecessary intermediaries, allowing us to offer factory‑direct pricing that is consistently fair and transparent.
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Comprehensive Quality Assurance: Our strict quality control system covers every stage-from raw material inspection to in‑process checks and final product testing. All products undergo chemical composition verification, mechanical property testing, dimensional inspection, and non‑destructive testing as required.
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Full Certification Package: We provide complete Mill Test Certificates (MTC) compliant with EN 10204 Type 3.1 or 3.2, including heat‑traceable chemical analysis, tensile and hardness test results, heat treatment records, and NDT reports. Third‑party inspection services (TÜV, SGS, BV, Lloyd's Register) are available upon request-49-87
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Third‑Party Transshipment Available: For clients concerned about tariff or customs complexities, we can arrange compliant third‑country transshipment routing through logistics partners experienced in optimizing duty exposure.
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Extensive Qualification & Industry Approvals: Our products are backed by ISO 9001:2015 quality management certification, and all pipes are manufactured and tested strictly in accordance with ASTM and ASME standards, with optional CE marking for European market compliance. Each shipment is accompanied by full traceable documentation.
Ready to Order?
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