ASTM B564 Inconel 600, 601, 625 (UNS N06625) • ASTM B637 Inconel 718 (UNS N07718), X-750 (UNS N07750) • Inconel 690, 783 • Nickel-Chromium Superalloy Flanges — All Types and Pressure Classes
BROWSE BY MATERIAL
Inconel is a family of nickel-chromium superalloys engineered for extreme performance — combining high-temperature strength, oxidation resistance, and corrosion resistance in environments that destroy conventional steels and stainless steels. Tesco Steel & Engineering manufactures Inconel flanges across the full grade range: from the corrosion-resistant workhorse Inconel 625 used in offshore and subsea applications, to the precipitation-hardened Inconel 718 found in aerospace gas turbines, to the high-temperature Inconel 601 used in furnaces operating beyond 1200°C.
Unlike stainless steels, Inconel alloys maintain significant yield strength at temperatures where stainless steels have largely lost structural integrity. Inconel 625, the most specified grade for piping flanges, is immune to chloride stress corrosion cracking (SCC) and has a Pitting Resistance Equivalent Number (PREN) of approximately 51 — higher than even super duplex stainless steel grades — making it the premium choice for the most aggressive seawater, sour gas, and chemical service conditions. All flanges are produced with full material traceability per EN 10204 3.1 or 3.2 and can be supplied with third-party inspection (Bureau Veritas, SGS, Lloyds, DNV).
Seven Inconel grades cover the full spectrum — from general-purpose corrosion resistance to aerospace-grade precipitation-hardened high-strength alloys and extreme-temperature furnace grades.
For furnace, heat treating, and high-temp oxidising service
The most specified grade for offshore, subsea, and chemical service
Precipitation-hardened; highest tensile strength
Nuclear steam generators and low-expansion gas turbine sealing
MAXIMUM CONTINUOUS SERVICE TEMPERATURE (°C) — OXIDISING ENVIRONMENT
Note: Inconel 718 retains good mechanical properties above 650°C but loses age-hardened strength — use Inconel X-750 or 625 for higher temperature applications.
| Grade | UNS | Ni | Cr | Mo | Fe | Nb | Al | Ti | Other |
|---|---|---|---|---|---|---|---|---|---|
| Inconel 600 | N06600 | ≥72.0 | 14.0–17.0 | — | 6.0–10.0 | — | — | — | Mn max 1.0, Si max 0.5 |
| Inconel 601 | N06601 | 58.0–63.0 | 21.0–25.0 | — | bal. | — | 1.0–1.7 | — | Cu max 1.0 |
| Inconel 625 | N06625 | ≥58.0 | 20.0–23.0 | 8.0–10.0 | max 5.0 | 3.15–4.15 | max 0.4 | max 0.4 | Co max 1.0 |
| Inconel 718 | N07718 | 50.0–55.0 | 17.0–21.0 | 2.8–3.3 | bal. | 4.75–5.50 | 0.2–0.8 | 0.65–1.15 | Co max 1.0 |
| Inconel X-750 | N07750 | ≥70.0 | 14.0–17.0 | — | 5.0–9.0 | 0.70–1.20 | 0.4–1.0 | 2.25–2.75 | Cu max 0.5 |
| Inconel 690 | N06690 | ≥58.0 | 27.0–31.0 | — | 7.0–11.0 | — | — | — | Mn max 0.5 |
| Inconel 783 | R30783 | 28.0–30.0 | 2.5–3.5 | — | 24.0–27.0 | 2.5–3.5 | 5.0–5.8 | — | Co 33–37% |
| Parameter | Inconel 625 | Inconel 600/601 | Inconel 718 |
|---|---|---|---|
| AWS Filler Wire | ERNiCrMo-3 (Alloy 625) | ERNiCr-3 (Alloy 82) | ERNiFeCr-2 (Alloy 718) |
| AWS Electrode | ENiCrMo-3 | ENiCrFe-3 (Alloy 182) | ENiFeCr-2 |
| Process | GTAW, SMAW, GMAW, SAW | GTAW, SMAW | GTAW preferred |
| Preheat | Not required | Not required | Not required |
| Max Interpass Temp | 175°C | 150°C | 150°C |
| PWHT | Not required | Not required | 720°C/8h + 620°C/8h for full strength |
| ASME P-Number | P43 Gr.1 | P45 (600) / P45 (601) | P43 Gr.4 |
| Notes | Excellent for dissimilar welds (CS to SS) | Avoid over-heating; use low heat input | Full strength requires double-aging cycle |
| ASME/ANSI B16.5 | WN, SO, SW, BL, TH, LJ, RTJ — Class 150 / 300 / 400 / 600 / 900 / 1500 / 2500 |
| ASME/ANSI B16.47 | WN, Blind [Series A & B] — Class 75 / 150 / 300 / 400 / 600 / 900 |
| ASME/ANSI B16.36 | Orifice flanges — WN, SO, TH — Class 300 / 600 / 900 / 1500 / 2500 |
| DIN Flanges | DIN 2527, 2566, 2573, 2576, 2631–2638, 2641, 2642, 2655, 2656, 2673 — PN6 to PN100 |
| BS 4504 / BS 1560 / BS 10 | WN, SO, Plate, Blank — PN 2.5 to PN 400 / Tables D, E, F, H |
| Face Types | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) |
| Size Range | NPS ½″ to 60″ |
🔬 Inconel 625 — Why It Is the Premier Offshore and Subsea Flange Material
With PREN ≈ 51, Inconel 625 outperforms super duplex stainless steel in pitting resistance. It is immune to chloride SCC, resistant to all concentrations of nitric acid, phosphoric acid, and seawater at all temperatures, and does not require PWHT — making field welding straightforward. It is the material of choice for subsea wellheads, risers, chemical injection lines, and flexible pipe end fittings in the offshore oil & gas industry.
Inconel 718 and X-750 flanges in jet engine exhaust manifolds, turbine casings, and afterburner sections. Inconel 625 for nacelle and engine mount brackets where corrosion resistance is critical.
Inconel 625 for subsea wellhead flanges, Christmas tree connections, chemical injection lines, flexible risers, and umbilical terminations — immune to seawater, H₂S, and CO₂ corrosion.
Inconel 625 and 690 for reactors, heat exchangers, and distillation columns handling nitric acid, sulfuric acid, phosphoric acid, and mixed acid systems where stainless steel fails.
Inconel 690 for pressurised water reactor (PWR) steam generator tube sheet flanges and nozzle connections. High Cr (27–31%) gives resistance to primary water stress corrosion cracking (PWSCC).
Inconel 600 and 601 for heat treating furnace flanges, radiant tube connections, and kiln headers at temperatures up to 1250°C. Inconel 601 specifically for aluminium-rich environments where Cr₂O₃ scale fails.
Inconel 625 for upstream sour gas pipelines, wellhead flanges, and production manifolds per NACE MR0175 / ISO 15156. Inconel 718 for high-pressure wellhead bolting under extreme load.
What are the ASTM standards and UNS numbers for Inconel flanges?
Inconel 600 (N06600), 601 (N06601), 625 (N06625), and 690 (N06690) are manufactured to ASTM B564 (nickel alloy forgings). Age-hardened Inconel 718 (N07718) and X-750 (N07750) are manufactured to ASTM B637. ASME boiler-code equivalents are SB564 and SB637. Inconel 783 (UNS R30783) is a cobalt-nickel alloy under ASTM B564.
Which Inconel grade is most commonly specified for flanges?
Inconel 625 (UNS N06625, ASTM B564) is the most widely used Inconel grade for piping flanges. Its Ni-Cr-Mo-Nb composition provides outstanding corrosion resistance without any heat treatment — it is used in the annealed condition, requires no PWHT after welding, and achieves PREN ≈ 51, making it the premium choice for offshore, subsea, chemical, and sour gas applications.
What is the difference between Inconel 625 and Inconel 718?
Inconel 625 is a solid-solution-strengthened alloy used primarily for its corrosion resistance (UTS ≥827 MPa, annealed). Inconel 718 is precipitation-hardened (aged at 720°C + 620°C) achieving UTS ≥1240 MPa — roughly 50% stronger — but requires complex heat treatment, careful welding, and is primarily chosen for aerospace structural applications rather than corrosion service.
What welding filler metal is used for Inconel 625 flanges?
ERNiCrMo-3 (AWS A5.14) bare wire — commercially Inconel Filler Metal 625 — is used for GTAW/GMAW. ENiCrMo-3 (AWS A5.11) covered electrode is used for SMAW. This same consumable is the standard choice for dissimilar metal welds joining Inconel 625 flanges to carbon steel or stainless steel piping. No preheat required; interpass temperature below 175°C.
What is the maximum service temperature for Inconel 625 flanges?
Inconel 625 is usable up to approximately 980°C in oxidising service. In the 425–650°C range, prolonged exposure can cause delta-phase precipitation reducing ductility — for high-strength applications in this range, Inconel 718 is preferred. For extreme temperatures above 1000°C, Inconel 601 (up to 1250°C) is the appropriate choice.
What is the difference between Inconel 600 and Inconel 601?
Inconel 600 (≥72% Ni, 14–17% Cr) offers good high-temperature oxidation resistance up to ~1100°C and is widely used in nuclear reactors (steam generator tubes) and heat treating furnaces. Inconel 601 adds ~1.4% aluminium, which forms a tenacious Al₂O₃-enriched oxide scale giving exceptional oxidation resistance up to 1250°C — making it the superior choice for the most extreme temperature furnace and industrial heating applications.
Does Inconel require post-weld heat treatment (PWHT)?
For Inconel 625, 600, and 601 — NO PWHT is required as standard practice. These solid-solution grades do not harden on cooling and are not susceptible to hydrogen cracking. Inconel 718 and X-750, however, require a double-aging cycle (720°C/8h then 620°C/8h for 718) after welding to restore full precipitation-hardened strength. Not performing the aging cycle after welding 718 leaves the weld in the soft solution-annealed condition.
What ASME P-Number is assigned to Inconel 625 flanges?
Inconel 625 (UNS N06625) = P-Number 43, Group 1. Inconel 718 (UNS N07718) = P-Number 43, Group 4. Inconel 600 (UNS N06600) = P-Number 45. These require separate WPS/PQR qualifications — a PQR for 625 (P43) does not qualify welding of 718 (P43, but different group). Always check the group number when specifying welding procedures for Inconel flanges.
Is Inconel 625 resistant to seawater and chloride corrosion?
Yes. Inconel 625 is immune to chloride stress corrosion cracking (SCC) and has outstanding pitting and crevice corrosion resistance in seawater at all temperatures. Its PREN ≈ 51 exceeds super duplex stainless steel (PREN ≈ 40–43), making it the premier material for subsea wellheads, offshore risers, seawater intake systems, naval applications, and desalination plant components in the most aggressive chloride environments.
What pressure classes are available for Inconel flanges?
ASTM B564/B637 Inconel flanges are available in ASME B16.5 pressure classes 150, 300, 400, 600, 900, 1500, and 2500 for NPS ½″ to 24″, and ASME B16.47 Series A & B for larger diameters. DIN pressure classes PN6 to PN100 are also available. Face types: RF, FF, RTJ. Tesco Steel manufactures all types — weld neck, blind, slip-on, socketweld, threaded, lap joint, and spectacle blind — from NPS ½″ to 60″ to order.
ASTM B564 / B637 • Inconel 600, 601, 625, 718, X-750, 690, 783 • All Types & Pressure Classes • Exported to 96 Countries
Inquiry Form WhatsAppCountries we export Inconel flanges to: USA, UK, Germany, France, Italy, Netherlands, Norway, Sweden, Denmark, Belgium, Spain, Finland, Poland, Russia, Czech Republic, Turkey, Saudi Arabia, UAE, Qatar, Kuwait, Bahrain, Oman, Iraq, Iran, Israel, Egypt, Libya, Algeria, Morocco, South Africa, Nigeria, Kenya, Angola, Tanzania, Canada, Mexico, Brazil, Argentina, Colombia, Venezuela, Australia, New Zealand, Singapore, Malaysia, Indonesia, Thailand, Philippines, Vietnam, South Korea, Japan, China, India and 40+ more destinations.
Major Exporting Hubs: Houston, Aberdeen, Dubai, Abu Dhabi, Al Khobar, Jubail, Doha, Kuwait City, Muscat, Singapore, Rotterdam, Oslo, Stavanger, Tokyo, Seoul, Perth, Melbourne, Lagos, Port Harcourt, Luanda.