What is AL6XN?
AL-6XN (UNS designation N08367) is a type of weldable stainless steel that consists of an alloy of nickel (24%), chromium (22%) and molybdenum (6.3%) with other trace elements such as nitrogen.
The high nickel and molybdenum content in AL-6XN alloy gives it strong resistance to chloride stress-corrosion cracking. Molybdenum also help prevent pitting in chloride environments. The alloy's strength is increased and pitting resistance is further enhanced by, the nitrogen addition, which frequently permits the use of lighter, thinner section.
AL-6XN ALLOY ADVANTAGES
Corrosion Resistance:
Corrosion in the forms of pitting, crevice and stress corrosion cracking in other stainless steel is often better managed with AL-6XN alloy. In both hot and cold environments, this alloy resists corrosion from a variety of acids and salt solutions (sodium chloride).
Cost-Benefit:
While the initial cost may be higher the alloy's durability and low maintenance make it a more economical choice over time.
High Resistance to Pitting and Crevice Corrosion:
With its high molybdenum and nitrogen content AL-6XN prevents small, localized forms of corrosion like pitting, and crevice attacks even in chloride-rich environments.
Great Strength:
AL-6XN has greater strength than standard 300 series stainless steels. This allows it to be used in thinner sections without sacrificing performance or durability.
Versatile Product Availability:
AL-6XN comes in a number of shapes and sizes such as sheets, plates, pipes, tubes, bars, and fitting. It is ideal for a variety of application in various industries, due to its broad range of product forms.
Applications of AL6XN Stainless Steel
Flue Gas Desulfurization (FGD) Equipment:
AL-6XN is ideal for FGD systems in power plants because it resists the corrosive gases and acidic byproducts produced during flue gas treatment.
Reverse Osmosis Desalination Equipment and Pumps:
Its excellent resistance to saltwater corrosion makes AL-6XN perfect for use in desalination systems and high-pressure pumps.
Chemical Process Tanks and Pipelines:
AL-6XN is appropriate for tanks and pipelines in chemical processing facilities because it can withstand harsh chemicals and high temperatures.
Seawater Heat Exchangers:
The alloy performs well in seawater environments, resisting pitting and crevice corrosion in heat exchanger systems.
Tall Oil Distillation Columns and Packing:
AL-6XN is used in tall oil refining due to its resistance to acidic and corrosive process fluids, improving equipment lifespan.
Offshore Oil and Gas Production Equipment:
Its strength and corrosion resistance make it reliable for harsh offshore environment exposed to saltwater and high pressure.
Pulp and Pipelines:
AL-6XN ensures durability and lowers maintenance in paper manufacturing facilities by resisting the strong chemicals used in pulp bleaching.
Salt Dryers:
The alloy is suitable for salt drying equipment, as it can handle high chloride exposure without corroding or breaking down.
FORGING
Hot forging of AL-6XN is done by using standard forging methods. It can heat uniformly to its optimum temperature range (typically about 1200°C to 950°C) and then be forged. After forging, it needs to be quickly cooled to maintain corrosion resistance.
COLD FORMING
AL-6XN presents good cold formability and it can be bent, or shaped at room temperature. However, due to the high strength, more force will be required in comparison to conventional stainless steels. Proper tools and equipment should be used to avoid cracking or stress.
MACHINING
AL-6XN is machinable, but its high strength makes it more challenging than 300 series stainless steels. To get better results and prevent tool wear, or work hardening use sharp tools, modest cutting speeds and lots of coolant.
Chemical Compositions of AL6XN Stainless Steel
| Ni | Cr | Mo | Mn | Cu | Si | C | N | S | P | Fe | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| MIN | 23.5 | 20.0 | 6.0 | - | - | - | - | 0.18 | - | - | - |
| MAX | 25.5 | 22.0 | 7.0 | 2.0 | 0.75 | 1.0 | 0.03 | 0.25 | 0.03 | 0.04 | bal |
Nickel (Ni) – 23.5% to 25.5%:
Nickel increases corrosion resistance, especially in acidic and chloride-rich environments. It also enhances ductility and weldability.
Chromium (Cr) – 20.0% to 22.0%:
Chromium is essential for corrosion resistance by forming a passive oxide layer. It also contributes to strength and oxidation resistance.
Molybdenum (Mo) – 6.0% to 7.0%:
Molybdenum increases overall strength and resistance to pitting and crevice corrosion especially in chloride conditions.
Manganese (Mn) – up to 2.0%:
Manganese improves hot-working properties and helps remove oxygen and sulfur during steelmaking, which also increases toughness.
Copper (Cu)Up to 0.75%:
Copper improves corrosion performance overall and increases resistance to specific acids, such as sulfuric acid.
Silicon (Si) – up to 1.0%:
Silicon increases oxidation resistance and helps in the steelmaking process by removing oxygen.
Carbon (C) – 0.03% max:
A low carbon content helps prevent carbide precipitation during welding, which could lead to intergranular corrosion.
Nitrogen (N) – 0.18% to 0.25%:
Nitrogen improves pitting resistance and adds strength to the alloy without reducing ductility.
Sulfur (S) – 0.03% max:
Sulfur is usually kept low as it can lead to poor corrosion resistance and hot cracking during welding.
Phosphorus (P) – 0.04% max:
Like sulfur, phosphorus must be controlled because it can negatively affect toughness and weldability.
Mechanical Properties of AL6XN Stainless Steel
| Mechanical Properties | |
|---|---|
| Minimum Specified Properties, ASME SB-688 Plate | |
| Ultimate Tensile Strength, ksi | 95 |
| 0.2% Yield Strength, ksi | 45 |
| Elongation, % | 30 |
| Hardness MAX, HRC | 30.5 |
Ultimate Tensile Strength – 95 ksi:
The material's maximum tensile strength, or the highest stress can withstand before breaking when stretched. An alloy with a strength of 95 ksi is robust and long-lasting under tension.
0.2% Yield Strength – 45 ksi:
This is the stress level at which the material starts to deform permanently. At 45 ksi, AL-6XN offers good strength for structural applications.
Elongation – 30%:
This shows the material's ductility, or ability to stretch without breaking. A 30% elongation means it can absorb stress and deform without cracking.
Hardness (Max) – 30.5 HRC:
Hardness measures resistance to surface wear and indentation. A maximum of 30.5 HRC indicates moderate hardness, making the alloy machinable yet tough.
Physical properties of AL6XN Stainless Steel
| Temperature, °F | 70 | 200 | 300 | 400 | 600 | 700 | 800 |
|---|---|---|---|---|---|---|---|
| Coefficient of Thermal Expansion, in/in/°F × 10⁻⁶ |
6.7 | 7.9 | 8.3 | 8.4 | 8.6 | 8.7 | 8.8 |
| Thermal Conductivity BTU•in/ft²•hr•°F |
6.7 | 7.5 | 8.1 | 8.7 | 10.0 | 10.6 | 11.2 |
| Modulus of Elasticity Dynamic, psi × 10⁶ |
28.3 | 27.4 | 26.1 | 24.8 | 24.0 | 23.8 | 23.4 |
Density (0.291 lb/in³):
The alloy has a moderate weight, helping in applications where strength-to-weight ratio is important.
Melting Range (2410–2540°F):
AL-6XN can withstand very high temperatures before melting, making it suitable for high-heat applications.
Electrical Resistivity (535 Ohm-circ mil/ft at 68°F):
It has a relatively high resistivity, meaning it doesn't conduct electricity easily, typical for stainless steels.
Coefficient of Thermal Expansion:
The expansion rate increases with temperature. At 70°F it's 7.0, and at 800°F it's 8.8. This helps engineers plan for dimensional changes during heating.
Thermal Conductivity:
Increases with temperature, starting from 6.7 at 70°F to 11.2 at 800°F. It means the alloy gets better at conducting heat as it heats up.
Modulus of Elasticity (Dynamic):
Measures stiffness it decreases from 28.3 × 10⁶ psi at 70°F to 23.4 × 10⁶ psi at 800°F. The alloy becomes more flexible at higher temperatures.
AL6XN Stainless Steel Products
AL6XN Plates
AL6XN Sheets
AL6XN Coils
AL6XN Bars
AL6XN Pipes
AL6XN Fittings
