Seamless Inconel 625 Pipe (UNS N06625 / 2.4856) – High-Performance Nickel Alloy Pipe for Extreme Environments
On this page: Overview · Chemistry · International Standards · Key Advantages · Technical Specifications · Applications · Quality & Certification · FAQ
Overview of Inconel 625 Seamless Pipe
Seamless Inconel 625 Pipe, also known as Alloy 625 Pipe,UNS N06625 Pipe, or EN 2.4856 Nickel Alloy Pipe, is a high-performance nickel-chromium-molybdenum superalloy designed for applications requiring exceptional corrosion resistance, high strength, and reliability under extreme conditions.
Manufactured from a solid billet through hot extrusion and cold drawing, seamless manufacture eliminates the longitudinal manufacturing weld seam; pressure capability, fatigue life and service life still depend on dimensions, material condition, inspection acceptance criteria, the design code and operating conditions.
Because of its outstanding performance, Inconel 625 seamless pipes are widely used in aerospace, oil & gas, marine engineering, chemical processing, and nuclear power industries.
The alloy’s strength comes from solid-solution strengthening through molybdenum and niobium additions, which significantly enhance mechanical properties without the need for precipitation hardening.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| N06625 | Inconel 625 | 2.4856 | NiCr22Mo9Nb | NCF625 | NS3306 / NS336 (legacy) |
Grade correspondence does not make ASTM, ASME, EN, JIS and GB delivery requirements interchangeable. Confirm chemistry, heat treatment, mechanical properties, dimensions, testing and certification against the purchase specification. See the grade designation index.
Chemical Composition and Material Characteristics
Chemical Composition
Inconel 625 is primarily composed of nickel, chromium, molybdenum, and niobium, providing excellent resistance to aggressive environments.
Typical chemical composition includes:
- Nickel (Ni): ≥ 58%
- Chromium (Cr): 20 – 23%
- Molybdenum (Mo): 8 – 10%
- Niobium + Tantalum (Nb + Ta): 3.15 – 4.15%
Material Characteristics
These elements provide:
- Excellent oxidation resistance
- Outstanding pitting and crevice corrosion resistance
- Superior chloride stress corrosion cracking resistance
- Excellent high-temperature strength and fatigue resistance
International Standards and Specifications
Our Inconel 625 seamless pipes and tubes comply with major international standards to ensure reliability and compatibility in critical industrial systems.
Product Type | ASTM Standard | ASME Standard |
|---|---|---|
Seamless Pipe & Tube | ASTM B444, ASTM B829 | ASME SB444 |
Welded Pipe | ASTM B705, ASTM B775 | ASME SB705 |
Welded Tube | ASTM B704, ASTM B751 | ASME SB704 |
ASTM B444 Inconel 625 Pipe Grades
ASTM B444 specifies two grades with different heat-treatment conditions:
- Grade 1 (Annealed) – annealed condition for general corrosion service
- Grade 2 (Solution annealed) – solution-annealed condition; creep-rupture and fatigue performance should be confirmed against the ordered revision and service conditions
These standards ensure consistent performance in high-pressure and high-temperature systems.
Key Performance Advantages of Inconel 625 Seamless Pipes
Outstanding Corrosion Resistance
Inconel 625 offers exceptional resistance to:
- Chloride stress corrosion cracking (SCC)
- Pitting corrosion
- Crevice corrosion
- Oxidizing and reducing acids
This makes the alloy highly suitable for marine environments and offshore oil production systems.
High Temperature Strength
The alloy retains useful strength at elevated temperatures; long-term design values depend on stress and environment — see the ordered specification for allowable values, making it ideal for high-temperature industrial systems.
Excellent Oxidation Resistance
Inconel 625 forms a stable protective oxide layer, preventing scaling and degradation in high-temperature oxidizing environments.
Superior Fabricability and Weldability
Despite its high strength, Alloy 625 seamless pipes exhibit excellent weldability and formability, allowing fabrication of complex piping systems.
Technical Specifications of Seamless Inconel 625 Pipes
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for Inconel 625.
Chemical Composition
The composition of Inconel 625 is carefully balanced to achieve its superior corrosion resistance and high strength.
| C | Mn | Si | P | S | Cr | Nb + Ta | Co | Mo | Fe | Al | Ti | Ni |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ≤0.100 | ≤0.500 | ≤0.500 | ≤0.015 | ≤0.015 | 20.000 – 23.000 | 3.150 – 4.150 | ≤ 1.000 | 8.000 – 10.000 | ≤ 5.000 | ≤ 0.400 | ≤ 0.400 | 58.0 min |
Source: ASTM B444-23, Table 2 (chemical requirements, UNS N06625). Chromium 20.0 min – 23.0 max and molybdenum 8.0 min – 10.0 max are given as ranges; nickel is a 58.0 % minimum (not a balance), while iron is limited to 5.0 % max. Niobium and columbium are interchangeable names for the same element.
Mechanical Properties (Specification Limits)
Inconel 625 is specifically designed to maintain its strength in high-stress, corrosive environments.
| Grade (ASTM B444) | Heat Treatment | Tensile (min) | Yield, 0.2% (min) | Elongation in 50 mm (min) |
|---|---|---|---|---|
| Grade 1 | Annealed | 827 MPa (120 ksi) | 414 MPa (60 ksi) | 30 % |
| Grade 2 | Solution annealed | 690 MPa (100 ksi) | 276 MPa (40 ksi) | 30 % |
Room-temperature minimum tensile properties for UNS N06625, based on ASTM B444-23, Table 1, subject to its scope and footnotes; elongation in 50 mm (2 in.). Inch-pound values govern in this edition; SI values are conversions. Table 1 tensile values apply to straight lengths; smaller sizes and hot-finished material are subject to the Table 1 footnotes. Hardness ≤ 200 HBW is not an ASTM B444 acceptance requirement — specify it in the order if required. State the required grade and specification edition in the purchase order.
Physical Properties (Reference)
These physical properties highlight the material’s ability to perform reliably under a wide range of conditions.
| Density | Melting Point | Thermal Expansion | Thermal Conductivity | Modulus of Elasticity | Electrical Resistivity |
|---|---|---|---|---|---|
| 8.44 g/cm³ | 1290 – 1350 °C approx | 12.8 μm/(m·°C) (20–100 °C) | 9.8 W/(m·K) (20 °C) | 207 GPa | 1.29 × 10⁻⁶ Ω·m (20 °C) |
Size Tolerance Chart (mm)
Cold-Finished Pipes and Tubes:
| Specified/Calculated Nominal OD (Inches) | Permissible Variation (Inches) | Specified/Calculated Nominal OD (mm) | Permissible Variation (mm) |
|---|---|---|---|
| 0.500 to 5⁄8, excl. | ±0.005 | 12.7 to 15.8, excl. | ±0.127 |
| 5⁄8 to 1 1⁄2, incl. | ±0.0075 | 15.8 to 38.1, incl. | ±0.190 |
| Over 1 1⁄2 to 3 1⁄2, incl. | ±0.010 | Over 38.1 to 88.9, incl. | ±0.254 |
| Over 3 1⁄2 to 4 1⁄2, incl. | ±0.015 | Over 88.9 to 114.3, incl. | ±0.381 |
| Over 4 1⁄2 to 6, incl. | ±0.020 | Over 114.3 to 152.4, incl. | ±0.508 |
| Over 6 to 6 5⁄8, incl. | ±0.025 | Over 152.4 to 168.3, incl. | ±0.635 |
| Specified/Calculated Nominal OD (Inches) | Permissible Variation (Inches) | Specified/Calculated Nominal OD (mm) | Permissible Variation (mm) |
|---|---|---|---|
| 2 1⁄2 to 5 1⁄2, excl. | ±0.031 | 63.5 to 139.7, excl. | ±0.787 |
| 5 1⁄2 to 9 1⁄4, incl. | ±0.047 | 139.7 to 234.9, incl. | ±1.19 |
| Condition | Specified/Calculated Nominal OD (Inches) | Permissible Variation (Wall Thickness) |
|---|---|---|
| Cold-Finished | 0.500 to 5⁄8, excl. | ±15.0% |
| 5⁄8 to 4 1⁄2, incl. | ±10.0% | |
| Over 4 1⁄2 to 6 5⁄8, incl. | ±12.5% | |
| Hot-Finished | 2 1⁄2 to 9 1⁄4, incl. | ±12.5% |
Common Industrial Applications
Because of its exceptional performance, Alloy 625 seamless pipes are widely used in mission-critical industries.
Oil and Gas Industry
Common applications include:
- Sour gas production tubing
- Subsea pipelines
- Flare stacks
- Downhole completion equipment
Chemical Processing Industry
Inconel 625 piping is used for handling aggressive chemicals such as:
- Phosphoric acid
- Organic acids
- Chloride-containing process fluids
Marine and Offshore Engineering
The alloy’s excellent seawater corrosion resistance makes it suitable for:
- Seawater cooling systems
- Submarine propulsion components
- Offshore platforms
Aerospace Engineering
In aerospace systems, Inconel 625 pipes are used for:
- Aircraft engine exhaust systems
- Fuel delivery systems
- High-temperature bellows and ducts
Nuclear Power Systems
Typical nuclear applications include:
- Reactor core components
- Control rod assemblies
- Heat exchanger tubing
Quality Assurance and Certification
Material Test Certificate (MTC)
Standard documentation includes an EN 10204 3.1 Material Test Certificate (MTC) with heat-number traceability, chemical composition and mechanical test results as required by the ordered specification.
Third-Party Inspection
Third-party inspection (TPI) or EN 10204 3.2 documentation must be agreed before order placement.
FAQ
What is Inconel 625 pipe used for?
Inconel 625 pipes are used in high-temperature and corrosive environments, including aerospace, offshore oil platforms, chemical plants, and nuclear facilities.
What is the difference between Inconel 625 and stainless steel?
Compared with stainless steel, Inconel 625 offers significantly higher corrosion resistance and better high-temperature strength, especially in aggressive chemical and marine environments.
What standards apply to Inconel 625 seamless pipes?
The most common standards include ASTM B444, ASTM B829, and ASME SB444.
Why choose seamless Inconel 625 pipes instead of welded pipes?
Seamless manufacture avoids a longitudinal production weld. Pressure capability, dimensional accuracy and service reliability depend on the specified material condition, dimensions, inspection requirements, fabrication and applicable design code.
Need tubing specified by actual outside diameter and wall thickness? See our Inconel 625 seamless tube range.
Why Choose Our Inconel 625 Seamless Pipes?
As a professional supplier of high-nickel alloy pipes, we provide:
Certified Material
Fully certified UNS N06625 / Alloy 625 pipes.
Complete Documentation
Complete EN 10204 3.1 MTR documentation.
Inspection & Traceability
Strict quality inspection and traceability.
Custom Sizes & Support
Custom sizes and technical support for demanding projects.
Contact our engineering team today for technical consultation or a customized quotation.
Ready to Request a Quotation?
Send the NPS and schedule (or actual OD and wall), quantity, length, end finish and the inspection items you need as acceptance criteria — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.
