For engineers in aerospace propulsion and high-pressure chemical engineering, GH4169 cold-drawn tubes are critical yet extremely difficult to manufacture. Due to their exceptionally high work hardening rate, standard cold-drawing processes often lead to three serious industrial challenges:
Residual stress cracking: Improper reduction rate control can cause microscopic internal stresses, leading to spontaneous cracking of the tube during storage or use.
Wall thickness eccentricity: Poor concentricity creates "weak points" that can fail under high-pressure hydraulic loads.
Surface scratches: Insufficient lubrication or annealing can result in rough inner/outer diameters, accelerating high-temperature oxidation.
At Gnee Steel, we eliminate these risks. Our optimized process guidelines ensure that every seamless tube meets the structural integrity and precision requirements of your mission-critical systems.
Click to view today's standard operating procedure for GH4169 precision tubing processing
GH4169 (718 Alloy) Cold-Drawn Tube Precision and Surface Finishing Guide
GH4169 (718 Alloy) Cold-Drawn Tube Precision and Surface Finishing Guide
GH4169 (Inconel 718) is a precipitation-hardening nickel-based superalloy tube that requires special processing methods during cold drawing to control its high work hardening rate and maintain high precision and surface quality. Cold-drawn GH4169 tubes are widely used in critical fields such as aerospace and high-temperature applications, where surface stability and dimensional accuracy (e.g., outer diameter/inner diameter tolerances within ±0.015 mm to ±0.03 mm) are paramount.
How does Inconel 718 perform at high temperatures?
Inconel 718 is a precipitation-hardening nickel-based alloy designed to exhibit extremely high yield strength, tensile strength, and creep rupture strength at temperatures up to 1300°F (700°C). Inconel 718 has a slow age-hardening response, therefore, spontaneous hardening does not occur during heating and cooling, annealing, or welding.
GH4169 Tube Accuracy and Dimensional Tolerances
Cold-drawn GH4169 tubes offer excellent dimensional control, particularly suitable for small-diameter, thin-walled tubes.
Dimensional Accuracy: Precision cold drawing processes produce tubes with outer diameter (OD) and wall thickness tolerances meeting or falling below ASTM A519 standards.
Outer/Inner Diameter Tolerances: For precision applications (e.g., DIN/EN standards), outer diameter tolerances for small-diameter tubes can be maintained at ±0.05 mm or less.
Wall Thickness: Wall thickness tolerances are typically within 10%–12.5% of the nominal thickness.
Straightness: Cold-drawn tubes often exhibit localized straightness deviations, with a maximum deviation of 1 mm per meter of length.
Manufacturing stage: Using a multi-stage cold drawing process combined with intermediate annealing (performed in argon at 850°C–1000°C), extremely small dimensions can be achieved, such as 2mm outer diameter x 0.08mm wall thickness.
Contact us to customize GH4169 products to fit your project dimensions
GH4169 Tube Surface Treatment Guidelines
GH4169 has a high work hardening tendency, making surface treatment challenging but crucial for performance.
A. Surface Conditions and Treatments
Solution Annealing and Pickling: After cold drawing, the tubes are typically annealed to restore ductility and pickled to remove oxides.
Surface Treatments: Available surface treatments include bright, polished, and ground. Special surface treatments such as HL (brushed) or 4K/8K (mirror finish) are available for specific applications.
Polishing: Abrasive polishing compounds are used to remove defects and improve corrosion resistance.
Laser Polishing: Continuous wave fiber laser polishing can reduce surface roughness (Ra) by more than 80% and improve microhardness.
B. Surface Roughness (Ra) Control
Cold drawing allows for surface roughness Ra of 20 to 30 inches on both the outer and inner diameters.
For critical applications, polishing techniques are employed (using sandpaper ranging from 600# to 2500# in sequence).
C. Improving Fatigue Life through Surface Integrity
Axial Polishing: Axial surface polishing (TCPA) significantly improves fatigue life compared to circumferential polishing (up to 134%).
Grinding: Cubic boron nitride grinding generates significant residual compressive stress (up to -930 MPa), thereby improving fatigue resistance.
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1. Inconel 718 Pipe Equivalent Material
The equivalent designation for Inconel 718 pipe is UNS N07718. It is also known as Werkstoff Nr. 2.4668 and JIS NCF 718. The table below explains these and other globally equivalent designations.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| Inconel 718 | N07718 | - | GH4169 | NCF718 | - | 2.4668 | - |
2. Manufacturing and Dimensions of GH4169 Precision Tubes
| Parameter | Standard Capability | Our "Aerospace Grade" | Commercial Advantage |
| OD Tolerance | ± 0.15 mm | h8, h9, h10, h11 | Ready for automated assembly. |
| Concentricity | ≤ 10% deviation | ≤ 5% deviation | Uniform High-Pressure safety. |
| Surface Finish (Ra) | ≤ 0.8 μm | ≤ 0.4 μm (BA Finish) | Mirror finish; reduces friction. |
| Straightness | ≤ 1.5 mm/m | ≤ 0.5 mm/m | Optimized for high-speed CNC. |
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3. Chemical composition (wt%) of GH4169 seamless steel tube
| Element | Content (%) | Standard Requirement | Function |
|---|---|---|---|
| Nickel (Ni) | 50.0 – 55.0 | 50.0 – 55.0 | Matrix element; provides high-temperature stability and corrosion resistance |
| Chromium (Cr) | 17.0 – 21.0 | 17.0 – 21.0 | Oxidation and corrosion resistance |
| Iron (Fe) | Balance (~18-20) | Balance | Fe-Ni-Cr base alloy |
| Niobium (Nb) | 4.75 – 5.50 | 4.75 – 5.50 | Core strengthening element – forms γ″ phase (Ni₃Nb) |
| Molybdenum (Mo) | 2.80 – 3.30 | 2.80 – 3.30 | Solid-solution strengthening; enhances pitting and creep resistance |
| Titanium (Ti) | 0.65 – 1.15 | 0.65 – 1.15 | Forms γ′ strengthening phase (Ni₃(Al,Ti)) |
| Aluminum (Al) | 0.20 – 0.80 | 0.20 – 0.80 | Forms γ′ strengthening phase |
| Carbon (C) | ≤ 0.08 | ≤ 0.08 | Low carbon for weldability and toughness |
| Manganese (Mn) | ≤ 0.35 | ≤ 0.35 | Deoxidizer |
| Silicon (Si) | ≤ 0.35 | ≤ 0.35 | Deoxidizer |
| Phosphorus (P) | ≤ 0.015 | ≤ 0.015 | Ensures toughness |
| Sulfur (S) | ≤ 0.015 | ≤ 0.015 | Ensures hot workability |
| Boron (B) | 0.002 – 0.006 | 0.002 – 0.006 | Grain boundary strengthener |
| Cobalt (Co) | ≤ 1.00 | ≤ 1.00 | Residual element |
| Copper (Cu) | ≤ 0.30 | ≤ 0.30 | Residual element |
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4. GH4169 Precision Tube: Mechanical Properties at 650°C (1200°F)
| Mechanical Performance at 650°C (1200°F) | Value |
|---|---|
| Yield Strength (0.2% Offset) | ≥ 850 MPa |
| Tensile Strength | ≥ 1000 MPa |
| Elongation (δ5) | ≥ 15% |
| Industrial Durability | Tested for 100+ hours stress-rupture life at 690 MPa |
5. 100% Certified Testing & Documentation
EN 10204 3.1 and EN 10204 3.2 Material Test Certificates (MTC)
Raw Materials Certificate
100% PMI
Heat Treatment Charts
Third-Party Inspection Report
Surface roughness and size measurement
Manufacturer Test Certificate (Impact Testing, Flattening, Flare, Bend, Hardness, Intergranular, Pitting Corrosion, Grain size, ET, UT, HT)
Laboratory Test Certificate from the Government-Approved Lab
6. Why choose to source GH4169 precision tubes from Gnee Alloy?
✅️Direct Factory Pricing: Eliminate the 15-20% markup from trading companies.
✅️Wholesale Inventory: We maintain an active stock of standard Sch 40 and Sch 80 sizes for Fast Global Shipping.
✅️Custom Fabrication: We offer precision cutting, centerless grinding, and specialized end-forming to match your CAD blueprints.
Gnee Alloy GH4169 Pipe certificate
Contact us now to get the latest export price for GH4169 in 2026
FAQ
Q1: Is GH4169 tubing equivalent to Inconel 718 for high-pressure fuel lines?
A: Yes. GH4169 is the technical equivalent of Inconel 718 (UNS N07718). Our material is globally interchangeable and meets all international aerospace certification requirements.
Q2: How do you prevent internal oxidation (scale) during annealing?
A: We utilize Vacuum Bright Annealing (BA). By heating the tubes in a high-vacuum or pure hydrogen atmosphere, we prevent oxygen from touching the surface, ensuring a mirror-bright internal diameter (ID).
Q3: Can you provide tubes for sour gas (H2S) service?
A: Absolutely. Our GH4169 is processed to meet the hardness and microstructural requirements of NACE MR0175, making it ideal for deep-sea oil and gas instrumentation.
Q4: Do you offer bulk discounts for long-term supply contracts?
A: Yes. As a Tier-1 Manufacturer, we offer tiered Wholesale Pricing and dedicated inventory reserves for our long-term aerospace and energy partners.