Inconel 625 flanges are forged from Alloy 625 (UNS N06625) to ASTM B564 / ASME SB564, a nickel-chromium-molybdenum alloy strengthened by niobium. With about 21% chromium, 9% molybdenum and more than 58% nickel, it resists pitting and crevice corrosion in seawater, handles many acids and sour gas, and keeps high strength from cryogenic temperatures up to around 980 °C in oxidising atmospheres.
Raaj Fittings forges and machines Alloy 625 flanges in-house at our two plants in India, in all common flange types from ½" upwards and in Class 150 to 2500, for offshore, chemical, refinery and power projects across the Middle East, Europe and the Americas.
| Material specification | ASTM B564 / ASME SB564 UNS N06625, Grade 1 (annealed) or Grade 2 (solution annealed) |
|---|---|
| Dimensional standards | ASME B16.5, ASME B16.47 Series A and B, EN 1092-1, DIN, BS 4504, JIS B2220 |
| Pressure class | ASME Class 150, 300, 600, 900, 1500 and 2500; PN 6 to PN 400 |
| Facing | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), Male & Female, Tongue & Groove |
| Certification | EN 10204 3.1 mill test certificate as standard; EN 10204 3.2 on request |
| Element, % | UNS N06625 |
|---|---|
| Nickel (Ni) | 58.0 min |
| Chromium (Cr) | 20.0 – 23.0 |
| Molybdenum (Mo) | 8.0 – 10.0 |
| Niobium + tantalum (Nb + Ta) | 3.15 – 4.15 |
| Iron (Fe) | 5.0 max |
| Carbon (C) | 0.10 max |
| Manganese (Mn) | 0.50 max |
| Silicon (Si) | 0.50 max |
| Phosphorus (P) | 0.015 max |
| Sulphur (S) | 0.015 max |
| Aluminium (Al) | 0.40 max |
| Titanium (Ti) | 0.40 max |
| Cobalt (Co) | 1.0 max |
| Property (min.), annealed | UNS N06625 |
|---|---|
| Tensile strength | 827 MPa (120 ksi) |
| Yield strength (0.2% offset) | 414 MPa (60 ksi) |
| Elongation | 30% |
| Grade | UNS | Werkstoff Nr. | EN / DIN designation | Common names |
|---|---|---|---|---|
| Alloy 625 | N06625 | 2.4856 | NiCr22Mo9Nb | Inconel® 625 |
Where the service is less severe, Incoloy 825, duplex or super duplex flanges may be more economical; for strongly reducing acids, Hastelloy C276 is often chosen.
Every heat is PMI-verified and its chemistry and mechanical properties are confirmed against the material specification before the flanges are released. Each piece is marked with grade, size, rating and heat number for traceability to its EN 10204 3.1 mill test certificate. EN 10204 3.2 certification and inspection by the buyer's nominated third-party agency are available on request, as are PED 2014/68/EU compliance for European projects and IBR certification for Indian boiler applications.
Alloy 625 flanges are forged to ASTM B564 / ASME SB564, UNS N06625, and dimensioned to ASME B16.5, B16.47 or the required EN, DIN, BS or JIS standard.
Grade 1 is annealed and is used up to about 595 °C, where it has the higher strength. Grade 2 is solution annealed for creep and rupture strength in service above that temperature.
Alloy 625 has a higher pitting resistance than super duplex and is effectively immune to crevice corrosion in ambient seawater, so it is used where crevices, warm water or sour conditions make duplex marginal. It costs considerably more, so super duplex is often chosen for less severe service.
Inconel is a trademark of Special Metals Corporation. Flanges are supplied to the ASTM specification for UNS N06625, often called Alloy 625, which has the same chemistry.