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In high-pressure hydraulic systems, sour-gas injection lines, and high-temperature process circuits, tubular components must withstand extreme hoop stress, corrosive media, and thermal cycling without creeping or cracking. Seamless Inconel 718 (UNS N07718 / W.Nr. 2.4668 / GH4169) is the precipitation-hardenable nickel superalloy of choice for these critical lines. Unlike solution-strengthened alloys (e.g., Inconel 600/625), Alloy 718 achieves yield strengths exceeding 1035 MPa after aging while retaining good weldability—essential for instrument tubing, pressure transmitter lines, and high-temperature process piping. Shanghai COCESS Special Alloys Co., Ltd supplies seamless Inconel 718 tubing and pipe in strict accordance with ASTM B983 / B829 and AMS 5589 / 5590, offering full traceability and optional NACE MR0175 compliance for oil & gas and aerospace applications.
Inconel 718 is strengthened by the precipitation of coherent γ" (Ni₃Nb) during a two-step aging heat treatment. Seamless tubes are typically supplied in the solution-annealed condition to allow bending, swaging, and welding prior to final age hardening.
Chemical Composition (Weight %, per ASTM B983 / AMS 5589):
Nickel (Ni): 50.00 – 55.00 % (Balance)
Chromium (Cr): 17.00 – 21.00 % (Oxidation & general corrosion)
Iron (Fe): 16.00 – 20.00 % (Austenite stabilizer)
Niobium + Tantalum (Nb+Ta): 4.75 – 5.50 % (Primary γ" (Ni₃Nb) strengthener)
Molybdenum (Mo): 2.80 – 3.30 % (Solid-solution strengthening, pitting resistance)
Titanium (Ti): 0.65 – 1.15 %
Aluminum (Al): 0.20 – 0.80 %
Carbon (C): ≤ 0.08 %
Sulfur (S): ≤ 0.015 % (Tightly controlled for surface integrity & hot workability)
Cobalt (Co): ≤ 1.00 %
Boron (B): ≤ 0.006 %
Tubing is commonly shipped in the solution-annealed (soft) condition and aged by the end-user after installation or bending.
Tensile Strength (Rm): ≥ 1275 MPa (185 ksi); typical 1300 – 1380 MPa
Yield Strength (Rp0.2): ≥ 1035 MPa (150 ksi); typical 1100 – 1170 MPa
Elongation (A5): ≥ 12 – 15 %
Hardness: 331 – 401 HB (34 – 44 HRC) in fully aged condition
Density: 8.24 g/cm³ (0.297 lb/in³)
Service Temperature: –253 °C to 650 °C continuous; short excursions to 700 °C depending on stress.
Pressure Rating Advantage: Due to its high yield strength, allowable design stress for Inconel 718 tubing is significantly higher than for 300-series stainless steels or Alloy 600/625, allowing smaller OD or thinner walls for equivalent pressure containment.
Shanghai COCESS stocks and produces seamless Inconel 718 in the following typical ranges (custom sizes on request):
|
Product Form |
Standard |
Outside Diameter (OD) |
Wall Thickness (WT) |
Condition |
|---|---|---|---|---|
|
Seamless Instrument / Precision Tube |
ASTM B829, AMS 5589 |
3.0 – 50.0 mm (1/8" – 2") |
0.5 – 5.0 mm |
Solution Annealed, Bright / Pickled |
|
Seamless Process / Boiler Tube |
ASTM B983, AMS 5590 |
6.0 – 219.0 mm |
1.0 – 20.0 mm |
Solution Annealed, Pickled |
|
Small-Diameter Coiled Tubing |
Per Customer Spec |
3.18 – 12.7 mm (1/4" – 1/2") |
0.5 – 2.0 mm |
Solution Annealed, Level Wound or Spooled |
|
Cut-to-Length / Bent Pre-forms |
Per Drawing |
As above |
As above |
Deburred ends, stress-relieved if specified |
Lengths: Standard 3–6 m random or fixed; coiled tubing in continuous lengths up to several hundred meters.
Surface Finish: Bright annealed (BA) for instrument tubing; pickled / descaled for process tubing.
Dimensional Tolerances: OD and WT per ASTM B829 / B983 or to customer tighter spec (e.g., ±0.05 mm OD for instrument lines).
Aerospace & Defense: Hydraulic and fuel system tubing, pneumatic lines, instrument sensing lines (pressure/temp probes), and rocket engine propellant feed lines (LOX/LH₂ compatible).
Oil & Gas / Subsea: Chemical injection lines (CIL), downhole control lines in sour (H₂S/CO₂) wells—NACE MR0175 / ISO 15156 compliant—and subsea umbilical tubing.
Power Generation: High-pressure sampling lines in gas turbines, nuclear auxiliary system tubing.
High-Performance Testing Labs: Autoclave tubing, high-pressure gas transfer lines.
Every shipment from Shanghai COCESS Special Alloys Co., Ltd includes:
EN 10204 3.1 Mill Test Report: Full heat analysis, mechanical test results, and heat treatment record.
Dimensional Inspection: OD, WT, ovality, and straightness checked per order requirements.
Non-Destructive Testing (Optional): Eddy Current Testing (ECT per ASTM E426), Ultrasonic Testing (UT), Hydrostatic / Pneumatic Pressure Test.
End Preparation: Square cut, chamfered, or capped; coil ends taped/tagged.
Third-Party Witness: SGS, TÜV, DNV, BV available upon request.
For current Inconel 718 seamless tube and pipe stock, size availability, or a project quotation—including instrument tubing, process pipe, or coiled control line—please contact Shanghai COCESS Special Alloys Co., Ltd. Our technical team can advise on bend radii, allowable stress values, and post-bend aging practices to ensure reliable performance in your system.
Website: https://en.cocessalloys.com
Email: sales@cocessalloys.com
