NCF625 seamless pipe is a nickel-chromium-molybdenum-niobium alloy pipe designated as UNS N06625 (W.Nr.2.4856, DIN NiCr22Mo9Nb) under JIS G4901 in Japan, and commonly known by the trade name Inconel 625. It is a solid-solution strengthened alloy supplied in seamless tubular form conforming to ASTM B444 (seamless pipe and tube) and ASTM B829 (general requirements). NCF625 seamless pipe combines outstanding pitting and crevice corrosion resistance with high tensile strength from -196°C to 650°C, making it a top choice for oil & gas, chemical processing, marine, and nuclear industries.
Inconel 625 (NCF625) Seamless Pipe – Actual Marking
Request NCF625 Seamless Pipe Price List & Mill Test Certificate
Sourcing reliable NCF625 / UNS N06625 seamless pipe with verified material traceability is critical for high-temperature and corrosion-resistant projects. Below you can view our official mill test certificate to check chemical composition and mechanical properties.
What is NCF625 Nickel-Alloy Base Metallurgy?
The metallurgy of NCF625 is built on a face-centered cubic (FCC) nickel matrix with three principal alloying additions: chromium (20.0–23.0%), molybdenum (8.0–10.0%), and niobium (3.15–4.15%). Unlike precipitation-hardened alloys such as Inconel 718, NCF625 derives its strength primarily through solid-solution strengthening and the formation of metastable Ni&sub3;Nb carbide phases at grain boundaries - not from gamma-prime or gamma-double-prime precipitation.
Each element plays a distinct role:
- Nickel (≥58%) - provides the FCC matrix, stabilizing the alloy against stress-corrosion cracking and chloride-induced pitting.
- Chromium (20–23%) - forms a tenacious Cr&sub2;O&sub3; passive film, granting oxidation resistance up to 980°C and resistance to oxidizing acid media.
- Molybdenum (8–10%) - enhances resistance to reducing acids (H&sub2;SO&sub4;, H&sub3;PO&sub4;) and chloride pitting; raises the PREN (Pitting Resistance Equivalent Number) to approximately 47.5.
- Niobium (3.15–4.15%) - combines with carbon to form MC-type carbides, stabilizing against sensitization and intergranular corrosion during welding and elevated-temperature service.
- Iron (≤5.0%) - controlled to a maximum limit; excessive Fe reduces high-temperature stability and promotes phase instability.
The absence of a precipitation-hardening heat treatment means NCF625 is supplied in the solution-annealed condition (1093°C / 2000°F, air cool or water quench) and requires no post-weld aging. This simplifies fabrication and reduces total project lead time compared to Inconel 718 or Rene 41.
NCF625 Seamless Pipe Chemical Composition per ASTM Standard
The NCF625 chemical composition is governed by ASTM B444 for seamless pipe and tube, with identical element ranges as ASTM B446 (bar) and B443 (plate). The table below lists each element, its specification range per ASTM B444, and its metallurgical function:
| Element | ASTM B444 Range (%) | Function |
|---|---|---|
| Nickel (Ni) | ≥58.0 | Base matrix; stabilizes FCC structure |
| Chromium (Cr) | 20.0–23.0 | Passive oxide film; oxidation resistance |
| Molybdenum (Mo) | 8.0–10.0 | Pitting & crevice corrosion resistance |
| Niobium+Tantalum (Nb+Ta) | 3.15–4.15 | Carbide stabilization; sensitization prevention |
| Iron (Fe) | ≤5.0 | Controlled residual; phase stability |
| Cobalt (Co) | ≤1.0 | Impurity control (nuclear purity grade ≤0.05%) |
| Carbon (C) | ≤0.10 | Low carbon for weldability |
| Manganese (Mn) | ≤0.50 | Deoxidizer; hot-workability |
| Silicon (Si) | ≤0.50 | Deoxidizer; limited to prevent embrittlement |
| Phosphorus (P) | ≤0.015 | Strict impurity; prevents hot cracking |
| Sulfur (S) | ≤0.015 | Strict impurity; prevents hot shortness |
| Aluminum (Al) | ≤0.40 | Oxidation aid; controlled excess prevented |
| Titanium (Ti) | ≤0.40 | Minor; carbon getter |
NCF625 Seamless Pipe Typical Mechanical Properties
ASTM B444 specifies two delivery conditions for NCF625 seamless pipe. Grade 1 (cold-worked / strain-hardened) provides higher tensile strength for high-pressure service, while Grade 2 (solution-annealed) offers maximum ductility and optimal corrosion performance. Typical mechanical and physical properties are summarized below:
| Property | Grade 1 (Cold-Worked) | Grade 2 (Solution Annealed) |
|---|---|---|
| Tensile Strength, min | 827 MPa (120 ksi) | 655 MPa (95 ksi) |
| Yield Strength (0.2%), min | 415 MPa (60 ksi) | 310 MPa (45 ksi) |
| Elongation in 50 mm, min | 30% | 30% |
| Hardness (typical) | 25–35 HRC | ≤20 HRC (~95 HRB) |
| Density | 8.44 g/cm³ | |
| Melting Range | 1290–1350°C | |
| Elastic Modulus (RT) | 207.8 GPa | |
| Thermal Conductivity (RT) | 9.8 W/m·K | |
| Coefficient of Thermal Expansion (20–100°C) | 12.8 µm/m·K | |
| Delivery Condition | Cold-worked (strain-hardened) | Solution annealed at 1093°C, air/water cool |
NCF625 Seamless Pipe Key Corrosion & High-Temperature Performance
The exceptional corrosion resistance of NCF625 stems from its high Cr, Mo, and Nb content working synergistically with the nickel matrix. The PREN (Pitting Resistance Equivalent Number) is approximately 47.5, significantly higher than 316L stainless steel (PREN ~24) and comparable to Hastelloy C-276 (PREN ~48). The following table uses a 5-star rating system to quantify performance across critical service environments:
| Corrosion / Temperature Environment | Rating | Notes |
|---|---|---|
| Chloride pitting (seawater, 3.5% NaCl) | ★★★★★ | No pitting up to 35°C; CPT >90°C |
| Crevice corrosion (saltwater gaskets/flanges) | ★★★★★ | CCT >75°C in ASTM G48 Method D |
| Stress corrosion cracking (Cl− + H&sub2;O, >60°C) | ★★★★★ | Immune in U-bend tests per ASTM G36 |
| Sulfuric acid (10–40%, <80°C) | ★★★★★ | Corrosion rate <0.1 mm/yr at 40%, 80°C |
| Hydrochloric acid (dilute, <3%, RT) | ★★★★☆ | Good at low concentration; limited at >5% |
| Hydrofluoric acid (dilute, RT) | ★★★☆☆ | Moderate; prefer Monel 400 or Hastelloy C-2000 |
| Sour gas (H&sub2;S, CO&sub2;, Cl−) per NACE MR0175 | ★★★★★ | Qualified for sour service up to 232°C |
| Oxidation resistance (air, continuous) | ★★★★★ | Scaling limit 980°C; safe continuous service ≤650°C |
| Caustic soda (NaOH, 10–70%) | ★★★★☆ | Good; prefer Ni-200 for >300°C concentrated |
| High-sulfur flue gas (>540°C) | ★★☆☆☆ | Sulfidation risk above 540°C; use Inconel 617 |
Best-suited conditions: chloride-bearing brines, mixed oxidizing/reducing acids, sour gas with H&sub2;S/CO&sub2;, FGD scrubber environments, and cryogenic-to-650°C structural service. Not recommended: concentrated HCl (>5%), high-sulfur flue gas above 540°C, or strongly reducing acid media at elevated temperature - Hastelloy C-276 or B-2 are better choices for these niches.
Get NCF625 Pipe Corrosion Data Sheet & COT Report
NCF625 Seamless Pipe Manufacturing & NDT Inspection Requirements
NCF625 seamless pipe is manufactured by a hot-cold extrusion and pilgering or cold-drawing route from a centrifugally cast or forged hollow billet. The complete production flow and mandatory inspection items per ASTM B444 are as follows:
- 1. Melting & Refining: Vacuum Induction Melting (VIM) followed by Electroslag Remelting (ESR) to achieve ultralow impurity levels (S, P ≤0.015%). Air-melted + ESR route is acceptable for non-nuclear grades.
- 2. Hot Extrusion: Billet heated to 1150–1200°C, extruded through a die and mandrel to form the hollow. Hot working must finish above 950°C to avoid edge cracking.
- 3. Cold Pilger / Cold Draw: Multiple passes reduce OD and wall to specified dimensions (e.g., 6–324 mm OD, 0.5–30 mm WT). Inter-pass annealing at 1093°C is required to restore ductility.
- 4. Solution Annealing: Final heat treatment at 1093°C (2000°F) ±14°C for 1–2 hours depending on section thickness, followed by water quench or rapid air cool to prevent carbide precipitation.
- 5. Straightening & Cutting: Rotary straightened to L/1000; ends square-cut or beveled for welding.
Mandatory non-destructive testing (NDT) per ASTM B444 and general requirements ASTM B829:
| NDT Method | Standard | Detectable Defects |
|---|---|---|
| Eddy Current Testing (ET) | ASTM E426 / E571 | Surface & near-surface cracks, pits |
| Ultrasonic Testing (UT) | ASTM E213 / E524 | Longitudinal & transverse wall defects |
| Hydrostatic Test | ASTM E1003 | Through-wall leaks, pressure integrity |
| PMI (Positive Material ID) | ASTM E1621 | Verify alloy grade & Mo/Nb content on-site |
| OES Spectrometry | ASTM E3047 | Full chemical composition heat-lot verification |
| Dimensional Inspection | ASME B36.19M / B36.10M | OD, WT, length, ovality tolerances |
Main Applications of NCF625 Seamless Pipe
NCF625 seamless pipe is specified across industries where a combination of strength, chloride pitting resistance, and sour-gas qualification is required. Key application sectors include:
- Oil & Gas Upstream: Downhole production tubing, subsea flowlines and risers, umbilical tubing, and topside gas processing lines requiring NACE MR0175 / ISO 15156 sour-service qualification.
- Chemical & Petrochemical: Heat exchanger tube bundles handling H&sub2;SO&sub4;, H&sub3;PO&sub4;, and organic acids; reactor cooling coils; high-pressure hydrogen transfer lines.
- Marine Engineering: Seawater cooling pipelines on offshore platforms, submarine exhaust risers, and desalination plant evaporator tubing where chloride pitting is the primary failure mode.
- Power Generation: Flue gas desulfurization (FGD) absorber outlet dampers and reheater tubing in coal-fired plants; nuclear steam generator tubing in high-purity water loops.
- Aerospace: Fluid conveyance lines for fuel and hydraulic systems; exhaust ducting where oxidation resistance to 980°C and thermal fatigue tolerance are required.
- Pharmaceutical & Fine Chemical: High-purity fluid transfer tubing electropolished to Ra ≤0.4 µm for bioprocessing skids.
When to use NCF625 seamless pipe:
- Chloride-containing aqueous environments at temperatures from -196°C to 650°C where pitting, crevice, or stress-corrosion cracking is a risk.
- Sour oil & gas service (H&sub2;S + CO&sub2; + Cl−) up to 232°C per NACE MR0175.
- Seawater cooling systems where 316L or duplex 2205 has failed or is projected to fail within the design life.
- Mixed oxidizing/reducing acid environments in the chemical industry where no single acid concentration dominates.
- Applications requiring high strength without post-weld precipitation hardening (faster fabrication cycle than Inconel 718).
When NOT to use NCF625 seamless pipe:
- Strongly reducing acid media (e.g., concentrated HCl >5% or HF at elevated temperature) - Hastelloy C-276 or B-2 is more appropriate.
- Load-bearing structural service above 650°C - precipitation-hardened Inconel 718 or solid-solution Inconel 617 provides superior creep-rupture strength.
- High-sulfur flue gas environments above 540°C - sulfidation attack accelerates; Inconel 617 or RA85H is preferred.
- When project cost is the dominant constraint and corrosion severity is mild - super-duplex 2507 or 6% Mo austenitic (e.g., 254SMO) may suffice at a fraction of the cost.
NCF625 Seamless Pipe Common Welding & Fabrication Tips
NCF625 exhibits excellent weldability for all conventional arc-welding processes - GTAW (TIG), GMAW (MIG), SMAW, and SAW - as well as electron beam and friction welding. The low carbon content (≤0.10%) and niobium stabilization prevent sensitization, so no post-weld heat treatment is required. Key fabrication guidelines:
- Welding consumables: Use matching ERNiCrMo-3 (AWS A5.14) filler wire for TIG/MIG, or ENiCrMo-3 (AWS A5.11) covered electrodes for SMAW. For dissimilar joints to carbon steel or stainless, ERNiCrMo-3 remains the preferred over-alloyed filler.
- No preheat: Preheating is not required and should be avoided; the interpass temperature must be kept below 150°C to prevent hot-cracking and carbide coarsening.
- Joint preparation: A 60–70° V-groove with 1–2 mm root face and 2–3 mm root gap is recommended for full-penetration single-side welds in pipe sizes up to 6" schedule 40S.
- Purging: For root pass protection, maintain a pure argon purge (O&sub2; <0.03%) on the ID side during GTAW root welding; flow rate 5–10 L/min until the root is 3 mm thick minimum.
- Cold bending: Minimum bend radius is 3×OD for annealed pipe; cold-worked Grade 1 pipe should not be bent below 5×OD without intermediate stress relief.
- Machining: NCF625 work-hardens rapidly; use sharp positive-rake carbide tooling, low surface speed (30–45 m/min), and generous lubrication to avoid galling and built-up edge.
- Pickling & passivation: Post-weld, remove heat tint with 20–25% HNO&sub3; + 3–5% HF solution at 40°C for 15–30 minutes, then neutralize and rinse thoroughly.
Contact GNEE Alloy for NCF625 Seamless Pipe Quote & TDS
Why Choose US as Your Supplier Partner?
GNEE Alloy is a specialized Nickel Based Alloy manufacturer and exporter with 20 years of production experience and a proven export record to over 40 countries. Our NCF625 seamless pipe supply capability includes:
- Stock Inventory: Standard sizes of NCF625 / Inconel 625 seamless pipe (1/4" to 12") are available for immediate dispatch from our Tianjin and Shanghai warehouses.
- Full NDT Capability: In-house ET, UT, hydrostatic, PMI, and OES spectrometry facilities; every pipe shipped with a complete NDT report per ASTM B444 / B829.
- Material Certification: EN 10204 3.1 / 3.2 certificates with third-party inspection by SGS, BV, or TÜV available on request.
- Custom Processing: Cutting to length, beveling, bending, flaring, electropolishing, and U-bending for heat exchanger bundles.
- Export Packaging: Seaworthy wooden cases with plastic end caps, rust-inhibitor VCI paper, and desiccant; FCL or LCL shipment by sea, air, or rail per customer preference.
- 24-Hour Technical Support: Our metallurgical engineers provide material selection guidance, welding procedure specifications (WPS), and corrosion-data consultation within 24 hours of inquiry.
For a full NCF625 seamless pipe price list, stock list, or technical data sheet, contact GNEE Alloy today. Factory-direct pricing, no middleman markup, full EN 10204 certification, and worldwide shipping.
GNEE Offers Comprehensive Testing Services
Packaging & Shipping
FAQ
Q1: What is NCF625 equivalent to?
NCF625 is the Japanese JIS G4901 designation for the same alloy registered as UNS N06625, W.Nr.2.4856, DIN NiCr22Mo9Nb, and commercially known as Inconel 625. All equivalents share identical chemical composition and mechanical property ranges.
Q2: What ASTM standard covers NCF625 seamless pipe?
ASTM B444 is the primary standard for NCF625 (UNS N06625) seamless pipe and tube. General delivery requirements (dimensions, tolerances, NDT) are specified in ASTM B829. Welded pipe is covered separately under ASTM B704/B705.
Q3: What temperature can NCF625 seamless pipe withstand?
NCF625 seamless pipe is rated for continuous structural service from -196°C to 650°C. It resists oxidation in air up to 980°C, but load-bearing capacity and creep-rupture strength degrade above 650°C; for structural service above this limit, Inconel 718 or 617 is recommended.
Q4: Is NCF625 pipe weldable without post-weld heat treatment?
Yes. NCF625 is a solid-solution strengthened alloy with low carbon and niobium stabilization, making it resistant to sensitization and intergranular corrosion after welding. No preheat, no post-weld solution treatment, and no aging is required.
Q5: What is the pitting resistance of NCF625 compared to 316L and Hastelloy C-276?
The PREN of NCF625 is approximately 47.5, compared to ~24 for 316L stainless and ~48 for Hastelloy C-276. NCF625's critical pitting temperature (CPT) in ASTM G150 exceeds 90°C, far higher than 316L's ~20°C, placing it in the top tier of chloride-pitting-resistant alloys.
Q6: Can NCF625 seamless pipe be used in sour gas (H&sub2;S) service?
Yes. NCF625 (UNS N06625) is listed in NACE MR0175 / ISO 15156 as qualified material for sour service in oil & gas production up to 232°C, covering environments containing H&sub2;S, CO&sub2;, and chloride brines. This makes it a standard choice for downhole tubing and subsea flowlines.
Q7: What sizes are available for NCF625 seamless pipe?
GNEE Alloy supplies NCF625 seamless pipe from 6 mm (1/8") to 324 mm (12") OD, with wall thicknesses from 0.5 mm to 30 mm. Lengths are available in random (4–7 m), fixed, or cut-to-size. Non-standard sizes can be produced to order with a minimum MOQ.
