INCONEL alloy 718 steel tube | UNS N07718 / W.Nr. 2.4668
INCONEL Alloy 718 Steel Tube
INCONEL alloy 718 is a high-strength, corrosion-resistant nickel-chromium material used at temperatures ranging from cryogenic to 1200°F (650°C). The alloy is particularly noted for its resistance to post-weld cracking, which is crucial in applications such as aerospace, chemical processing, and power generation.
Key Specifications
- UNS Number: N07718
- Werkstoff Number: 2.4668
- Form: Tubes
- Applications: Aerospace, gas turbines, nuclear reactors, pumps, tooling, and more
Chemical Composition
| Element | Percentage (%) |
|---|---|
| Nickel (Ni) | 50.0-55.0 |
| Chromium (Cr) | 17.0-21.0 |
| Iron (Fe) | Bal. (rem.) |
| Molybdenum (Mo) | 2.8-3.3 |
| Niobium (Nb) | 4.75-5.50 |
| Titanium (Ti) | 0.65-1.15 |
| Aluminum (Al) | 0.20-0.80 |
| Cobalt (Co) | ≤ 1.0 |
| Manganese (Mn) | ≤ 0.35 |
| Silicon (Si) | ≤ 0.35 |
| Carbon (C) | ≤ 0.08 |
| Phosphorus (P) | ≤ 0.015 |
| Sulfur (S) | ≤ 0.015 |
| Boron (B) | ≤ 0.006 |
| Copper (Cu) | ≤ 0.30 |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength (min) | 1375 MPa (200 ksi) |
| Yield Strength (0.2% offset) | 1034 MPa (150 ksi) |
| Elongation (min) | 12% |
| Hardness (max) | 330 HB |
| Melting Range | 1260-1340 °C (2300-2440 °F) |
Physical Properties
| Property | Value |
|---|---|
| Density | 8.19 g/cm³ (0.296 lb/in³) |
| Specific Heat Capacity | 435 J/kg·K |
| Thermal Conductivity | 11.4 W/m·K (at 100°C) |
| Electrical Resistivity | 1.25 µΩ·m (at 20°C) |
| Modulus of Elasticity | 211 GPa (30.6 x 10⁶ psi) |
Weight Chart
| Outer Diameter (OD) (mm) | Wall Thickness (mm) | Weight (kg/m) |
|---|---|---|
| 12.7 | 1.24 | 0.370 |
| 19.05 | 1.65 | 0.725 |
| 25.4 | 2.11 | 1.320 |
| 38.1 | 2.77 | 2.370 |
| 50.8 | 3.05 | 3.730 |
| 76.2 | 3.40 | 6.570 |
Pressure Rating
Pressure ratings are highly dependent on the specific dimensions and operating conditions. Below are indicative values for common sizes at room temperature:
| Tube Size (OD x Wall) (mm) | Pressure Rating (psi) |
|---|---|
| 12.7 x 1.24 | 3,200 |
| 19.05 x 1.65 | 2,500 |
| 25.4 x 2.11 | 2,000 |
| 38.1 x 2.77 | 1,600 |
| 50.8 x 3.05 | 1,400 |
| 76.2 x 3.40 | 1,200 |
Tolerances
| Dimensions | Tolerance Range |
|---|---|
| Outside Diameter (OD) | ±0.15 mm for OD ≤ 25.4 mm |
| ±0.20 mm for 25.4 mm < OD ≤ 38.1 mm | |
| ±0.30 mm for OD > 38.1 mm | |
| Wall Thickness | ±12% |
| Length | Up to 6.0 m ±6.0 mm |
| Ovality | 2% of OD for thin-wall tubes |
| Straightness | 1/8 inch in any 10-foot length |
Price List
The price of INCONEL alloy 718 steel tubes can vary based on factors such as size, wall thickness, and market conditions. Below is a general price range for some common sizes:
| Size (OD x Wall) (mm) | Price (USD per meter) |
|---|---|
| 12.7 x 1.24 | $100 – $150 |
| 19.05 x 1.65 | $150 – $200 |
| 25.4 x 2.11 | $200 – $250 |
| 38.1 x 2.77 | $250 – $300 |
| 50.8 x 3.05 | $300 – $350 |
| 76.2 x 3.40 | $350 – $400 |
Note: Prices are indicative and can fluctuate based on material costs, supplier, and order quantity.
Types of INCONEL Alloy 718 Tubes
INCONEL alloy 718 tubes can be supplied in various forms to suit specific application needs. These include:
- Seamless Tubes:
- Manufacturing Method: Extrusion or rotary piercing followed by cold drawing.
- Applications: High-pressure and high-temperature environments where superior mechanical properties are required.
- Welded Tubes:
- Manufacturing Method: Forming and welding of flat strips followed by heat treatment.
- Applications: Lower stress applications compared to seamless tubes but still offer excellent corrosion resistance.
- Heat Exchanger Tubes:
- Special Features: High resistance to corrosion and elevated temperatures.
- Applications: Used in heat exchangers for chemical processing, petrochemical, and nuclear power generation.
- Boiler Tubes:
- Special Features: High strength and corrosion resistance at high temperatures.
- Applications: Suitable for use in boilers and superheaters in power plants.
Heat Treatment
INCONEL alloy 718 tubes typically undergo the following heat treatments to achieve desired mechanical properties:
- Solution Annealing:
- Temperature: 1700-1850°F (925-1010°C)
- Purpose: Dissolves secondary phases and provides a homogeneous microstructure.
- Precipitation Hardening:
- Temperature: 1325°F (720°C) for 8 hours, furnace cool to 1150°F (620°C), hold for 8 hours, and air cool.
- Purpose: Enhances strength and hardness through precipitation of gamma prime (γ’) and gamma double prime (γ”) phases.
Applications
Due to its excellent mechanical properties, corrosion resistance, and ability to withstand extreme temperatures, INCONEL alloy 718 is extensively used in:
- Aerospace: Jet engines, rocket motors, spacecraft components
- Chemical Processing: Process equipment, heat exchangers, reactor vessels
- Power Generation: Gas turbines, nuclear reactors, steam generators
- Oil and Gas: Downhole tools, wellhead components, valves
- Marine: Submarine propulsion systems, marine fasteners
Conclusion
INCONEL alloy 718 steel tubes offer a combination of high strength, excellent corrosion resistance, and good fabricability, making them suitable for a wide range of demanding applications. Understanding their chemical composition, mechanical properties, and specific types can help in selecting the right tubes for your specific requirements. Whether for aerospace, power generation, or chemical processing, INCONEL alloy 718 provides reliable performance in challenging environments.
Alloy C276 is a highly versatile nickel-molybdenum-chromium alloy with excellent corrosion resistance in a wide range of severe environments. It is particularly known for its resistance to pitting, stress-corrosion cracking, and oxidizing atmospheres.
Alloy 400 is a nickel-copper alloy known for its excellent corrosion resistance and high strength across a wide temperature range. It is particularly effective in reducing and oxidizing environments and offers good mechanical properties at sub-zero temperatures.
Alloy 600, also known as Inconel 600, is a nickel-chromium alloy renowned for its exceptional resistance to high-temperature corrosion and oxidation.
INCONEL Alloy 625 (UNS N06625 / WNR 2.4856) is a highly versatile alloy widely used across various industries due to its exceptional mechanical properties, outstanding corrosion resistance, and excellent fabricability. It is particularly well-suited for high-stress and high-temperature applications in aerospace, marine, chemical processing, oil and gas, and power generation sectors.
Nickel 690 (UNS N06690 / WNR 2.4642) is a versatile alloy with excellent welding and fabrication characteristics. By adhering to best practices and understanding the specific requirements of this alloy, engineers and fabricators can ensure high-quality results in various industrial applications. Its robustness in resisting corrosion and maintaining mechanical integrity at high temperatures makes it a preferred choice for demanding environments.
Nickel Alloy 825 (UNS N08825 / WNR 2.4858) is a versatile alloy with excellent resistance to corrosion and high-temperature stability. Its favorable welding and fabrication characteristics make it a preferred choice for demanding industrial applications. By adhering to best practices and understanding the specific requirements of this alloy, engineers and fabricators can ensure high-quality results and reliable performance in various environments such as chemical processing, oil and gas, pollution control, and nuclear power.
