UNS N08825 825 nickel alloy welded pipe

UNS N08825, also known as Alloy 825, is a nickel-iron-chromium alloy with significant additions of molybdenum, copper, and titanium. Pipes made from this alloy, especially welded pipes, are highly valued for their exceptional corrosion resistance, mechanical properties, and ability to withstand extreme environments, including high temperatures and aggressive chemical exposure.

Key Properties of UNS N08825 Alloy Welded Pipe

- Chemical Composition:

Nickel (38-46%): Provides excellent resistance to stress corrosion cracking.

Iron (Balance): Acts as the base metal.

Chromium (19.5-23.5%): Enhances resistance to oxidation and pitting.

Molybdenum (2.5-3.5%): Improves resistance to crevice corrosion.

Copper (1.5-3.0%): Enhances performance in sulfuric and phosphoric acid environments.

Titanium (0.6-1.2%): Stabilizes the alloy, preventing intergranular corrosion.

- Corrosion Resistance:

Excellent resistance to oxidizing and reducing acids, such as sulfuric acid, phosphoric acid, and nitric acid.

High resistance to pitting, crevice corrosion, and stress corrosion cracking in chloride-rich environments.

Outstanding performance in chemical processing, marine, and acidic media.

- Thermal Stability:

Operates effectively in a wide temperature range, typically up to 540°C (1000°F).

Retains mechanical properties even at elevated temperatures.

- Weldability:

Alloy 825 pipes are readily weldable using standard techniques like GTAW (TIG), GMAW (MIG), and SMAW (Stick Welding).

Requires proper welding procedures to avoid heat-affected zone (HAZ) corrosion.

- Mechanical Properties:

Tensile Strength: 550 MPa (min)

Yield Strength: 220 MPa (min)

Elongation: 30% (min)

Applications of UNS N08825 Welded Pipes

- Chemical Processing:

Transporting sulfuric, phosphoric, and nitric acids in industrial plants.

Piping for reactors and evaporators.

- Oil and Gas Industry:

Used in sour gas environments due to resistance to hydrogen sulfide stress cracking.

Heat exchangers and pipelines for offshore and marine applications.

- Marine Environments:

Resistant to seawater corrosion, ideal for desalination plants, marine piping, and heat exchangers.

- Power Generation:

Used in nuclear and thermal power plants for condenser tubing and other critical components.

- Pollution Control Systems:

Flue gas scrubbers and effluent treatment systems.

- Food and Pharmaceutical Industries:

Piping for hygienic and corrosion-resistant fluid transport systems.

Advantages of UNS N08825 Welded Pipes

Superior Corrosion Resistance:

Handles a wide range of chemical exposures and extreme environments.

Good Fabricability:

Easily formed and welded without significant loss in corrosion resistance.

Versatility:

Suitable for both high-temperature and cryogenic applications.

Cost-Effective:

Compared to solid nickel alloys, Alloy 825 offers a good balance of performance and cost.

Standards and Specifications

ASTM B705: Standard specification for nickel alloy welded pipes.

ASME SB705: Pressure vessel applications for UNS N08825 welded pipes.

DIN 2.4858: Equivalent German standard.

ISO 15156-3: Suitable for sour gas environments in the oil and gas industry.

Summary

UNS N08825 welded pipes are a reliable choice for industries demanding high corrosion resistance, mechanical strength, and versatility. They are particularly suitable for chemical processing, marine, and high-temperature applications, thanks to their ability to perform under aggressive environmental conditions while maintaining structural integrity.