Product Description
AL-6XN (UNS N08367) is a premium super-austenitic stainless steel designed for extreme corrosion resistance in aggressive environments. This low carbon, high purity, nitrogen-bearing alloy offers superior performance compared to conventional austenitic stainless steels. With its high content of nickel (24%), chromium (20.5%), molybdenum (6.2%), and nitrogen (0.22%), AL-6XN alloy delivers outstanding resistance to pitting, crevice corrosion, and stress corrosion cracking.
Originally developed for seawater applications, AL-6XN alloy has proven its exceptional performance in a broad range of corrosive environments. The high molybdenum and nitrogen content creates a robust barrier against localized corrosion, while the high nickel content provides excellent resistance to chloride stress-corrosion cracking. Unlike standard austenitic stainless steels, AL-6XN alloy maintains its structural integrity and corrosion resistance even in the most challenging conditions.
FUSHUN METAL supplies premium quality AL-6XN alloy in various product forms, combining excellent corrosion resistance with superior mechanical properties, formability, and weldability. This versatile material offers a cost-effective alternative to more expensive nickel-based alloys in applications where extreme corrosion resistance is essential for long-term performance.
Applications
AL-6XN alloy is specifically engineered for environments where conventional stainless steels would fail due to aggressive corrosion. Its exceptional performance makes it the material of choice for numerous demanding applications across various industries:
- Chemical Processing: Tanks, vessels, piping, heat exchangers, and other equipment handling corrosive chemicals, particularly those containing chlorides
- Offshore Oil & Gas: Process systems, piping, and equipment for platforms exposed to seawater and crude oil
- Marine Applications: Condensers, heat exchangers, piping systems, and components exposed to seawater
- Pulp & Paper: Filter washers, vats, press rolls, and equipment in chlorine dioxide bleaching plants
- Power Generation: Flue gas desulfurization systems, reheaters, service water piping, and condenser tubing
- Desalination: Equipment, pumps, and piping handling high-chloride brine solutions
- Pharmaceutical & Food Processing: Process vessels and piping where product purity is essential
- Environmental Systems: Air pollution control equipment and wastewater treatment systems
The exceptional corrosion resistance of AL-6XN alloy makes it particularly valuable in applications exposed to seawater, chloride-containing process streams, oxidizing acids, and mixed acid environments. Its high strength and excellent fabricability enable cost-effective solutions for the most demanding service conditions.
Standards
AL-6XN alloy (UNS N08367) is covered by numerous standards and specifications from major international organizations:
American Society for Testing and Materials (ASTM):
- ASTM A240/A240M – Plate, Sheet, and Strip
- ASTM A479/A479M – Bars and Shapes
- ASTM A312/A312M – Seamless and Welded Pipe
- ASTM A358/A358M, A409/A409M – Welded Pipe
- ASTM A813/A813M, A814/A814M – Welded Pipe
- ASTM A249/A249M, A269/A269M, A270/A270M – Welded and Seamless Tube
- ASTM A688/A688M, A676/A676M – Welded Tube
- ASTM B690 – Seamless Pipe and Tube
- ASTM B472 – Billets and Bars for Reforging
- ASTM B691 – Rod, Bar, and Wire
- ASTM B804 – Pipe Welded with Filler
- ASTM B366 – Wrought Nickel Alloy Welding Fittings
- ASTM B462 – Pipe Flanges, Fittings, and Valves
- ASTM B564 – Nickel Alloy Forgings
- ASTM B834 – Powder Metal Product
American Society of Mechanical Engineers (ASME):
- ASME Boiler and Pressure Vessel Code – Section II, Part D (UNS N08367)
- ASME Section III (Nuclear) and Section VIII Division 1 (Unfired Pressure Vessel)
- ASME Code for Pressure Piping, Sections B31.1 (Power Piping) and B31.3 (Process Piping)
- ASME SA-240, SA-358, SA-409, SA-813, SA-814, SA-312, SA-249, SA-688, SB-462, SB-366, SB-564, SB-804
Additional Standards and Approvals:
- NACE MR0175 – Approved for use in contact with hydrogen sulfide-containing petroleum and natural gas
- Norsok standard M-DP-001 – Approved for use on Norwegian offshore oil platforms
- U.S. Food and Drug Administration (FDA) – Approved for food contact applications
- National Sanitation Foundation (NSF) – Approved for food and water applications
Material Designation and Chemical Composition
AL-6XN alloy is known under the following designations:
| Designation System | Designation |
|---|---|
| UNS | N08367 |
| ASTM | AL-6XN |
| Cast Form | CN-3MN (UNS J94651) |
The typical chemical composition of AL-6XN alloy is as follows:
| Element | Typical (Weight %) | Specification Range (Weight %) |
|---|---|---|
| Carbon (C) | 0.02 | 0.03 max. |
| Manganese (Mn) | 0.40 | 2.00 max. |
| Phosphorus (P) | 0.020 | 0.040 max. |
| Sulfur (S) | 0.001 | 0.030 max. |
| Silicon (Si) | 0.40 | 1.00 max. |
| Chromium (Cr) | 20.5 | 20.00-22.00 |
| Nickel (Ni) | 24.0 | 23.50-25.50 |
| Molybdenum (Mo) | 6.2 | 6.00-7.00 |
| Nitrogen (N) | 0.22 | 0.18-0.25 |
| Copper (Cu) | 0.2 | 0.75 max. |
| Iron (Fe) | Balance | Balance |
The high levels of chromium, nickel, molybdenum, and nitrogen in AL-6XN alloy contribute to its exceptional Pitting Resistance Equivalent Number (PREN = % Cr + 3.3% Mo + 30% N) of approximately 47.6, significantly higher than conventional stainless steels.
Physical and Mechanical Properties
AL-6XN alloy offers an exceptional combination of high strength and excellent corrosion resistance, making it suitable for a wide range of demanding applications.
Physical Properties
| Property | Value |
|---|---|
| Density | 8.06 g/cm³ (0.291 lb/in³) |
| Melting Range | 2410-2550°F (1320-1400°C) |
| Modulus of Elasticity | 28.3 × 10⁶ psi (195 GPa) |
| Shear Modulus | 10.8 × 10⁶ psi (74 GPa) |
| Poisson’s Ratio | 0.31 |
| Thermal Conductivity (68-212°F) | 7.5 Btu/hr•ft•°F (14.1 W/m•K) |
| Coefficient of Thermal Expansion (68-212°F) | 7.9 × 10⁻⁶/°F (14.2 × 10⁻⁶/°C) |
| Specific Heat Capacity | 0.11 Btu/lb•°F (500 J/kg•K) |
| Electrical Resistivity | 535 Ohm•circ mil/ft (89.0 μΩ•cm) |
| Magnetic Permeability (Annealed) | 1.0028 |
| Scaling Temperature | 1885°F (1030°C) |
Mechanical Properties
| Property | Typical Value |
|---|---|
| Yield Strength (0.2% Offset) | 57 ksi (393 MPa) |
| Ultimate Tensile Strength | 112 ksi (770 MPa) |
| Elongation in 2″ (51 mm) | 44% |
| Hardness | 89 HRB |
AL-6XN alloy maintains excellent strength at elevated temperatures and demonstrates exceptional toughness at cryogenic temperatures. The ASME maximum allowable design stress for AL-6XN alloy is 26.2 ksi (180.6 MPa) at 200°F (93°C), which is significantly higher than that of many other austenitic stainless steels.
Corrosion Resistance
AL-6XN alloy exhibits outstanding resistance to various corrosive environments:
- Pitting and Crevice Corrosion: With a Pitting Resistance Equivalent Number (PREN) of approximately 47.6, AL-6XN alloy offers superior resistance to pitting and crevice corrosion in chloride-containing environments.
- Critical Crevice Corrosion Temperature (CCCT): Typically 110°F (43°C) in ferric chloride solution (ASTM G-48B), which is significantly higher than conventional stainless steels.
- Seawater Resistance: Excellent resistance to crevice corrosion in natural seawater, even during extended periods of stagnation or with chlorination.
- Stress Corrosion Cracking: High resistance to chloride stress corrosion cracking due to the high nickel content.
- Acid Resistance: Good resistance to a variety of acids, including sulfuric, phosphoric, and mixed acids.
- Microbially Influenced Corrosion (MIC): Superior resistance to MIC compared to conventional stainless steels.
Heat Treatment
AL-6XN alloy is supplied in the fully annealed condition. For proper annealing after fabrication:
- Heat treat above 2025°F (1110°C)
- Cool rapidly to prevent precipitation of secondary phases
- Never heat above 2350°F (1290°C) to avoid incipient melting
- Avoid furnace cooling
- Remove all oxides completely after heat treatment
The high nitrogen content in AL-6XN alloy significantly retards the formation of sigma phase, enhancing the alloy’s metallurgical stability compared to non-nitrogen bearing high-molybdenum stainless steels.
Available Dimensions
FUSHUN METAL supplies AL-6XN alloy in a wide range of product forms and dimensions to meet diverse application requirements:
Plate, Sheet and Strip
| Product Form | Thickness | Width | Length |
|---|---|---|---|
| Plate | 0.1875″ to 6.0″ (4.75 mm to 152 mm) | Up to 120″ (3048 mm) | Up to 480″ (12192 mm) |
| Sheet | 0.015″ to 0.1874″ (0.38 mm to 4.74 mm) | Up to 60″ (1524 mm) | Up to 240″ (6096 mm) |
| Strip | 0.005″ to 0.1874″ (0.13 mm to 4.74 mm) | Up to 36″ (914 mm) | Coil form |
Bar and Rod Products
| Product Form | Diameter/Size | Length |
|---|---|---|
| Round Bar | 0.25″ to 12.0″ (6.35 mm to 305 mm) | Up to 240″ (6096 mm) |
| Square Bar | 0.5″ to 8.0″ (12.7 mm to 203 mm) | Up to 240″ (6096 mm) |
| Hexagonal Bar | 0.5″ to 4.0″ (12.7 mm to 102 mm) | Up to 240″ (6096 mm) |
| Flat Bar | 0.125″ to 8.0″ (3.18 mm to 203 mm) thick | Up to 240″ (6096 mm) |
| Rod and Wire | 0.03″ to 0.5″ (0.76 mm to 12.7 mm) | Coil form or straight lengths |
Pipe and Tube Products
| Product Form | Outside Diameter | Wall Thickness | Length |
|---|---|---|---|
| Seamless Pipe | 0.5″ to 14″ (12.7 mm to 356 mm) | Schedule 5S to XXS | Up to 480″ (12192 mm) |
| Welded Pipe | 0.5″ to 36″ (12.7 mm to 914 mm) | Schedule 5S to XXS | Up to 480″ (12192 mm) |
| Seamless Tube | 0.125″ to 5″ (3.18 mm to 127 mm) | 0.015″ to 0.5″ (0.38 mm to 12.7 mm) | Up to 480″ (12192 mm) |
| Welded Tube | 0.25″ to 24″ (6.35 mm to 610 mm) | 0.015″ to 0.5″ (0.38 mm to 12.7 mm) | Up to 480″ (12192 mm) |
Additional product forms available include forgings, fittings, flanges, and custom fabrications. FUSHUN METAL can supply AL-6XN alloy in special sizes and forms to meet specific customer requirements.
Fabrication Information
AL-6XN alloy offers excellent fabrication properties, making it suitable for various manufacturing processes:
Forming
AL-6XN alloy can be readily formed using conventional methods:
- Hot Forming: Recommended temperature range 1830-2300°F (1000-1260°C), followed by annealing above 2025°F (1110°C) and rapid cooling.
- Warm Forming: Recommended for operations like dishing and flanging at temperatures up to 600°F (315°C).
- Cold Forming: Excellent cold formability for bending, drawing, and pressing operations. Additional pressure is required compared to standard 300 series stainless steels due to higher strength.
- Tube Forming: Can be bent to a minimum bend radius of two times the tube outside diameter, with tighter radii possible using proper techniques.
Welding
AL-6XN alloy is readily weldable using standard stainless steel welding techniques:
- Recommended Processes: Gas Tungsten Arc Welding (GTAW), Gas Metal Arc Welding (GMAW), Shielded Metal Arc Welding (SMAW), Flux Cored Arc Welding (FCAW), and Submerged Arc Welding (SAW).
- Filler Metals: Overmatched composition filler metals containing at least 9% molybdenum are recommended to compensate for chemical segregation in the weld. Common choices include Alloy 625, Alloy 22, and Alloy 276.
- Shielding Gas: Inert gas mixtures are recommended for GTAW. Adding 3-5% nitrogen to the shielding gas enhances corrosion resistance of autogenous welds.
- Interpass Temperature: Should not exceed 200°F (95°C).
- Post-Weld Cleaning: All heat tint and oxides should be removed after welding to maintain optimal corrosion resistance.
Machining
AL-6XN alloy can be machined using standard techniques with the following considerations:
- Higher strength and work hardening rate require reduced cutting speeds compared to 304 or 316L stainless steels.
- Sharp tools, rigid setups, and sufficient cooling are essential for successful machining.
- Feed rates should be high enough to ensure the tool cutting edge gets under the work-hardened zone.
- Lubricants such as sulfur-chlorinated petroleum oil are recommended.
Surface Finishing
Proper surface finishing is critical for maintaining the corrosion resistance of AL-6XN alloy:
- Descaling: Can be done by mechanical methods (blasting, grinding) or chemical treatments.
- Pickling: Typically performed using nitric plus hydrofluoric acid solutions at elevated temperatures.
- Passivation: Performed using nitric acid solutions to remove surface contaminants and enhance passive film formation.
- Removing Iron Contamination: Essential for maintaining corrosion resistance, can be done using nitric acid cleaning or commercial stainless cleaners.
Why Choose FUSHUN METAL for AL-6XN Alloy
When you need the exceptional corrosion resistance and mechanical properties of AL-6XN alloy for your challenging applications, FUSHUN METAL stands as your premier supplier for several compelling reasons:
Comprehensive Quality Assurance
At FUSHUN METAL, we implement rigorous quality control at every stage of production. Our AL-6XN alloy products undergo comprehensive testing to ensure they meet or exceed all applicable ASTM and ASME specifications. Each shipment includes full traceability and material certification, giving you complete confidence in the integrity and performance of your materials.
Complete Product Range
We offer one of the most extensive ranges of AL-6XN alloy products available, including plate, sheet, strip, bar, tube, pipe, and custom fabrications. This variety allows you to source all your super-austenitic stainless steel requirements from a single, reliable supplier, streamlining your procurement process and ensuring consistency across your projects.
Technical Expertise and Support
Our team of metallurgical experts possesses in-depth knowledge of AL-6XN alloy’s properties, fabrication requirements, and performance characteristics. We provide comprehensive technical support to help you select the optimal material specifications for your application, recommend appropriate fabrication techniques, and troubleshoot any challenges that may arise during manufacturing or in service.
Global Supply Capabilities
With our extensive global supply network, FUSHUN METAL can deliver AL-6XN alloy products to customers worldwide with competitive lead times. Our logistics expertise ensures your materials arrive when and where you need them, supporting your project schedules and operational requirements.
Competitive Value
We understand that AL-6XN alloy represents a significant investment in your project’s long-term performance. FUSHUN METAL offers competitive pricing while maintaining the highest quality standards, providing excellent value for this premium corrosion-resistant material. Our expertise in life-cycle cost analysis can help demonstrate how AL-6XN alloy delivers superior long-term economics compared to less resistant materials that require frequent replacement.
For your next project requiring the exceptional properties of AL-6XN alloy, we invite you to contact our team to discuss your specific requirements. Our experts are ready to help you select the optimal product specifications, provide technical guidance, and deliver premium quality materials that will perform reliably in even the most demanding environments.
