Tesco Steel & Engineering manufactures Inconel 690 flanges (UNS N06690 / W.Nr. 2.4642) — the high-chromium nickel-chromium-iron alloy with ~60% Ni, ~29% Cr and ~9.5% Fe. Its very high chromium (about double that of Alloy 600) gives outstanding resistance to stress-corrosion cracking in high-temperature water — the reason it replaced Alloy 600 in nuclear steam-generator tubing — plus excellent resistance to oxidizing acids (nitric, mixed nitric-HF) and to high-temperature oxidizing and sulphidizing gases. Available in weld neck, slip-on, blind, socket-weld, threaded, lap-joint, spectacle and orifice types to ASTM B564 / ASME B16.5. Class 150 to 2500, NPS 1/2″ to 24″, PN6 to PN400. ISO 9001:2015 certified. Made in India.
Inconel 690 (UNS N06690) Nuclear-Grade Flanges
Inconel 690 Weld Neck & Blind Flanges
Tesco Steel & Engineering manufactures Inconel 690 flanges in all types from weld neck to orifice, Class 150 to 2500 — supplied with EN 10204 3.1 / 3.2 certification, PMI and third-party inspection on request. Explore the wider Inconel flange range, the base Inconel 600 flanges and high-strength Inconel 625 flanges, and the flange dimension charts.
| Inconel 690 flanges are available in the following specifications: | |
|---|---|
| Material Grade | Inconel 690 / UNS N06690 / W.Nr. 2.4642 (NiCr29Fe) |
| Alloy Type | High-chromium nickel-chromium-iron alloy (Ni-Cr-Fe), non-age-hardenable |
| Size | 1/2″ NB to 24″ NB (DN 15 to DN 600); larger to ASME B16.47 |
| Class / Rating | 150#, 300#, 600#, 900#, 1500#, 2500# · 3000#, 6000#, 9000# (socket-weld / threaded) |
| Pressure Ratings | PN 6 – PN 400 (PN6, 10, 16, 25, 40, 64, 100, 160, 250, 320, 400) |
| Material Standards | ASTM B564, ASME SB564, AMS 5781; EN designation 2.4642 |
| Dimensional Standards | ASME B16.5, ASME B16.47 (Series A & B), MSS SP-44, DIN EN 1092-1 |
| Flange Types | Weld Neck (WNRF), Slip-On (SORF), Blind, Socket Weld (SWRF), Lap Joint, Threaded / Screwed, Spectacle Blind, Long Weld Neck, Orifice, Plate |
| Flange Faces | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), Tongue & Groove (T&G) |
| Weld Filler | ERNiCrFe-7 / ERNiCrFe-7A (Filler Metal 52 / 52M), ENiCrFe-7 |
| Testing | PMI, hydrostatic, UT, MT/PT per spec; EN 10204 3.1 / 3.2 |
Inconel 690 is a high-nickel alloy with about 29% chromium — roughly double that of Alloy 600. This very high chromium is the source of its outstanding stress-corrosion-cracking resistance in high-temperature water and its resistance to oxidizing acids and hot gases.
| Element | Inconel 690 (UNS N06690) |
|---|---|
| Nickel (Ni) | 58.0% min (~60%) |
| Chromium (Cr) | 27.0 – 31.0% (~29%) |
| Iron (Fe) | 7.0 – 11.0% (~9.5%) |
| Carbon (C) | 0.05% max |
| Manganese (Mn) | 0.5% max |
| Copper (Cu) | 0.5% max |
| Silicon (Si) | 0.5% max |
| Sulphur (S) | 0.015% max |
| Mechanical Property (annealed, typical) | Inconel 690 |
|---|---|
| Tensile Strength | 590 – 760 MPa (85–110 ksi) |
| Yield Strength 0.2% | 240 – 415 MPa (35–60 ksi) |
| Elongation | 35 – 45% |
| Max Service Temperature | ~1090 °C (oxidizing) |
| Density | 8.19 g/cm³ |
| Melting Range | 1343 – 1377 °C |
| Standard | Inconel 690 Designation |
|---|---|
| UNS (USA) | N06690 |
| Werkstoff (Germany) | 2.4642 |
| EN designation | NiCr29Fe |
| ASTM / ASME | B564 / SB564 (forgings); B166, B167, B168 (other forms) |
| AMS | 5781 |
| Common names | Inconel 690, Alloy 690, Nickel Alloy 690 |
Inconel 690 Weld Neck Flange (WNRF)
Inconel 690 Slip-On Flange (SORF)
Inconel 690 Blind Flange
| Flange Type | Description & Inconel-690-Specific Use |
|---|---|
| Weld Neck (WNRF) | Tapered hub butt-welded to pipe for high-integrity nuclear, oxidizing-acid and high-temperature service; weld with ERNiCrFe-7 (FM 52) filler. |
| Slip-On (SORF) | Fillet-welded over the pipe; used in oxidizing-acid and high-temperature piping at moderate pressure. |
| Blind | Seals pipe ends and vessel nozzles in nuclear, reprocessing and acid systems. |
| Socket Weld (SWRF) | Small-bore (1/2″–2″) instrument and branch connections. |
| Lap Joint (LJRF) | Used with an Inconel 690 stub end where frequent dismantling is required; economizes on alloy in the backing ring. |
| Threaded (TRFF) | Internal NPT/BSP threads for non-welded low-pressure connections. |
| Spectacle Blind / Long Weld Neck / Orifice | Isolation spades, nozzle/long-neck and flow-metering flanges in Inconel 690 for nuclear and oxidizing duty. |
| Property | 690 (N06690) | 600 (N06600) | 625 (N06625) |
|---|---|---|---|
| Type | Ni-Cr-Fe (high-Cr) | Ni-Cr-Fe | Ni-Cr-Mo-Nb |
| Chromium | ~29% | ~15.5% | ~21.5% |
| High-temp-water SCC resistance | Excellent (nuclear) | Moderate (PWSCC prone) | Good |
| Oxidizing-acid resistance | Excellent | Good | Excellent |
| Strength | Moderate | Moderate | Very high |
| Typical role | Nuclear steam generators, oxidizing acids | General nickel alloy, chloride/HT | Seawater, sour-service, high strength |
~29% chromium gives outstanding resistance to primary-water and caustic stress-corrosion cracking — the standard for PWR steam-generator tubing.
Excellent in nitric and mixed nitric-hydrofluoric acids — ideal for nuclear reprocessing and acid service.
Resists high-temperature oxidizing and sulphidizing atmospheres for furnace and process duty.
Non-age-hardenable and readily welded with high-chromium FM 52 filler — no PWHT needed for strength.
| Industry | Typical Application |
|---|---|
| Nuclear Power | PWR steam-generator tubing, reactor and primary-circuit flanged components |
| Nuclear Reprocessing | Hot-nitric and mixed-acid reprocessing and waste-vitrification flanges |
| Chemical Processing | Oxidizing-acid (nitric, mixed) reactor and piping flanges |
| Heat Treatment / Furnaces | High-temperature oxidizing and sulphidizing atmosphere flanged connections |
| Petrochemical | High-temperature oxidizing process flanges |
| Pollution Control | Acidic and oxidizing flue-gas flanged connections |
Made from certified Alloy 690 with PMI verification of the ~29% chromium — full chemistry confirmed on the MTC.
Manufactured to ASTM B564 / ASME B16.5 in the annealed condition for optimum SCC and corrosion resistance.
WNRF, SORF, blind, socket-weld, threaded, lap-joint, spectacle, LWN, orifice and plate — in RF, FF, RTJ and T&G.
EN 10204 3.1 / 3.2 MTC, heat/lot traceability, hydrostatic and third-party inspection on request.
Inconel 690 flange prices reflect the high nickel and very high chromium content plus forging and machining — it is a premium nuclear-grade alloy for high-temperature-water and oxidizing-acid service. Tesco Steel & Engineering offers competitive ex-works pricing from Mumbai with full export documentation and material traceability. Click Ask for Quote or message us on WhatsApp at +91 92233 66922 with flange type, size (NB), pressure class, quantity and documentation requirements.
Q1. What is an Inconel 690 flange?
An Inconel 690 flange is a pipe flange made from the high-chromium nickel-chromium-iron alloy UNS N06690 (W.Nr. 2.4642) — about 60% nickel, 29% chromium and 9.5% iron. Its very high chromium gives outstanding resistance to stress-corrosion cracking in high-temperature water, oxidizing acids and high-temperature oxidizing gases. It was developed as the nuclear-grade upgrade of Alloy 600. Flanges are forged to ASTM B564 and machined to ASME B16.5 / B16.47 dimensions.
Q2. What is the chemical composition of Inconel 690?
Inconel 690 (UNS N06690) nominal composition: nickel 58% minimum (~60%), chromium 27–31% (~29%), iron 7–11% (~9.5%), with carbon 0.05% max, manganese 0.5% max, copper 0.5% max, silicon 0.5% max and sulphur 0.015% max. The very high chromium content (about double that of Alloy 600) is the key to its corrosion and SCC resistance.
Q3. Why does Inconel 690 have such high chromium?
Inconel 690 contains about 29% chromium — roughly double the ~15.5% in Alloy 600. This high chromium dramatically improves resistance to stress-corrosion cracking in high-temperature water and to oxidizing acids and hot oxidizing/sulphidizing gases. It is the reason Alloy 690 replaced Alloy 600 as the standard material for pressurized-water-reactor (PWR) steam-generator tubing, where primary-water stress-corrosion cracking (PWSCC) was a problem.
Q4. Why is Inconel 690 used in nuclear power?
Inconel 690 is the standard material for PWR steam-generator tubing and many reactor components because its high chromium gives outstanding resistance to primary-water and caustic stress-corrosion cracking at the high temperatures of the reactor coolant circuit. It is also used in nuclear reprocessing and waste-vitrification equipment for its resistance to hot nitric and mixed acids.
Q5. What is the difference between Inconel 690 and 600?
Both are Ni-Cr-Fe alloys, but Inconel 690 has about 29% chromium versus ~15.5% in Alloy 600. The higher chromium gives 690 far better resistance to stress-corrosion cracking in high-temperature water, to oxidizing acids (nitric, mixed nitric-HF) and to high-temperature oxidizing/sulphidizing atmospheres. Alloy 600 keeps an edge in some reducing and chloride conditions and at the very highest temperatures, but 690 is preferred for nuclear and oxidizing-acid service.
Q6. What standards apply to Inconel 690 flanges?
Inconel 690 flanges are forged to ASTM B564 (UNS N06690) and machined to ASME B16.5 (1/2 inch to 24 inch) or ASME B16.47 / MSS SP-44 for larger sizes, with EN 1092-1 for PN-rated flanges. The European designation is W.Nr. 2.4642 / NiCr29Fe. Material is supplied with EN 10204 3.1 / 3.2 certification.
Q7. Can Inconel 690 flanges be welded?
Yes. Inconel 690 has good weldability by GTAW (TIG), GMAW and SMAW using matching high-chromium filler such as ERNiCrFe-7 / ERNiCrFe-7A (Filler Metal 52/52M) and ENiCrFe-7. It is non-age-hardenable, so no post-weld heat treatment is generally required; clean joints and controlled heat input give sound, SCC-resistant welds, which is important for nuclear service.
Q8. What media does Inconel 690 resist?
Inconel 690 resists high-temperature water and caustic stress-corrosion cracking, oxidizing acids including nitric and mixed nitric-hydrofluoric, hot sulphuric and many process acids, and high-temperature oxidizing and sulphidizing gases. The high chromium makes it especially strong in oxidizing conditions, complementing the molybdenum-bearing alloys used in reducing conditions.
Q9. What are the mechanical properties of Inconel 690?
Typical Inconel 690 properties in the annealed condition: tensile strength about 590–760 MPa (85–110 ksi), yield strength about 240–415 MPa (35–60 ksi), elongation about 35–45%, density 8.19 g/cm³. It combines good strength with excellent ductility, toughness and corrosion resistance.
Q10. Are Inconel 690 flanges supplied with material test certificates?
Yes. Every Inconel 690 flange is supplied with EN 10204 3.1 (or 3.2) mill test certificates confirming chemistry, mechanical properties and heat/lot traceability, with PMI, hydrostatic testing and third-party inspection on request. Tesco Steel & Engineering is an ISO 9001:2015 certified manufacturer and exporter from Mumbai, India.