For engineers in the aerospace, energy, and petrochemical industries, the biggest challenge in welding GH4169 steel pipe lies in the integrity of the weld and heat-affected zone (HAZ). During welding, extremely high temperatures can lead to:
Heat-affected zone softening: The strengthening phase dissolves, resulting in a significantly lower strength in the weld area compared to the base metal.
Strain-aging cracking: Residual stresses from welding can cause spontaneous cracking during the cooling phase or initial high-temperature service.
Pressure burst risk: Under high-pressure cycling, insufficiently strong welds are highly susceptible to bursting accidents.
At Gnee Steel, we are committed to eliminating these risks. Our ASME SB168 GH4169 welded steel pipe is not simply manufactured; it undergoes a proprietary double-aging process to ensure the weld area achieves the same structural integrity as the base metal.
Get a quote for GH4169 heat-treated pipes now
ASME SB168 GH4169 Heat Treatment Process for Welded Steel Pipes
ASME SB168 GH4169 Heat Treatment Process for Welded Steel Pipes
ASME SB168 GH4169 (Inconel 718) welded pipe requires a two-stage aging heat treatment to optimize high-temperature strength and restore the toughness of the heat-affected zone (HAZ). The standard treatment method is as follows: first, aging at 720°C for 8 hours, then furnace cooling to 620°C and holding at that temperature for 8 hours, and finally air cooling.
What is GH4169 equivalent to?
Inconel 718
GH4169 (equivalent to the American brand Inconel 718) is a precipitation-hardening nickel-based superalloy widely used in the aerospace industry due to its excellent mechanical properties (Lu et al., 2014).
1. GH4169 Pipe Technical Specifications and Scope of Supply
| Feature | Specification Details | Industrial Advantage |
| Standard | ASME SB168 / ASTM B168 | International pressure vessel compliance. |
| Designation | GH4169 / UNS N07718 | Direct global equivalency to Alloy 718. |
| Outside Diameter | 150mm to 1200mm | Ideal for heavy-duty exhaust & ducting. |
| Wall Thickness | 2.0mm to 30.0mm | High-pressure rated structural support. |
| Surface Finish | Pickled, Polished, or BA | Ready for precision aerospace assembly. |
2. ASME SB168 GH4169 Pipe Chemical Composition (by weight)
| Element | Content (%) | Standard Requirement | Function |
|---|---|---|---|
| Nickel (Ni) | 50.0 – 55.0 | 50.0 – 55.0 | Matrix element; provides corrosion resistance and high-temperature stability |
| 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 | Primary γ″ strengthening element – critical for strength after heat treatment |
| 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 |
| 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 |
Click to download the GH4169 alloy PDF file now
3. Physical properties of GH4169 welded pipe (after heat treatment)
| Property | Value | |
|---|---|---|
| Density | 8.19 g/cm³ | |
| Melting Range | 1260 – 1336°C | |
| Thermal Conductivity (20°C) | 11.4 W/m·K | |
| Thermal Conductivity (500°C) | ~16.0 W/m·K | |
| Coefficient of Thermal Expansion (20-100°C) | 13.0 × 10⁻⁶/°C | |
| Coefficient of Thermal Expansion (20-600°C) | ~14.5 × 10⁻⁶/°C | |
| Specific Heat (20°C) | 435 J/kg·K | |
| Modulus of Elasticity (20°C) | ~200 GPa | |
| Poisson's Ratio | 0.29 – 0.30 | |
| Magnetic Permeability | ~1.005 (slightly magnetic) |
4. GH4169 pipe double aging heat treatment process
| Process Stage | Temperature Range | Duration | Metallurgical Purpose |
| Solution Anneal | 940°C - 1010°C | 1 - 2 Hours | Relieves weld stress & dissolves brittle phases. |
| Primary Aging | 718°C (1325°F) | 8 Hours | Controlled precipitation of
γ′′γ′′ (Gamma Double Prime). |
| Secondary Aging | 621°C (1150°F) | 8 Hours | Final matrix stabilization for peak yield strength. |
This process ensures that the hardness of the entire pipe is uniformly 36-44 HRC, maximizing its industrial durability and fatigue life.
5. GH4169 pipe quality assurance
As a Tier-1 Manufacturer, we understand that "good enough" is not an option for high-pressure service. We provide total Zero-Leakage certainty through rigorous NDT testing:
100% Radiographic Testing (RT): Every inch of the weld seam is X-ray inspected to ensure zero porosity, slag inclusions, or lack of fusion.
Hydrostatic Pressure Testing: Every pipe is tested up to 200 Bar (2900 PSI) to verify its safety under extreme operating loads.
Dye Penetrant Inspection (FPI): Scans for microscopic surface stress cracks that traditional inspections might miss.
MTC 3.1 Traceability: Full EN 10204 compliance documenting the exact chemical heat analysis and heat treatment chart.
Why choose Gnee Alloy?
✅️Cost-effective Solution: Our heat-treated welded pipes offer comparable performance to seamless tubes at a significant cost saving for large diameters.
✅️Direct Factory Pricing: Eliminate trading markups and buy directly from the original superalloy processor.
✅️Custom Fabrication: We offer precision cutting, beveling, and specialized bending services to match your assembly drawings.
✅️Global Fast Shipping: Optimized logistics to minimize lead times for international maintenance and production runs.
Gnee Steel GH4169(inconel 718) Certificate
📦 Packaging and Shipping
All Nickel Based Alloy products are packaged using the following methods:
Wooden pallets or crates
Moisture-proof packaging
Labels with furnace number, standard, and size labels
Shipped worldwide by sea, air, or express
Gnee Steel GH4169 Product Packing
Contact us for the latest export price quote for GH4169 Alloy
FAQ
Q1: Is ASME SB168 material suitable for nuclear reactor internals?
A: Yes. When produced with high-purity VIM+VAR base material and 100% RT-tested welds, our SB168 GH4169 pipes meet the rigorous safety and durability standards required for nuclear structural members.
Q2: How does the double-aging process prevent strain-age cracking?
A: By precisely controlling the precipitation rate of the γ′′ phases during the 16-hour cycle, we allow the metal to stress-relieve in a controlled manner, preventing the spontaneous "embrittlement" that leads to cracks in poorly treated welds.
Q3: Can you provide non-standard custom wall thicknesses?
A: Absolutely. Our fabrication shop can roll and weld GH4169 plates into specialized wall thicknesses and non-standard diameters to meet your exact thermal engineering calculations.
Q4: Do you offer bulk discounts for petrochemical refinery overhauls?
A: Yes. As a Reliable Supplier for major energy programs, we provide attractive tiered pricing for high-volume procurement and long-term MRO contracts.
