Project Description
Inconel 625 (UNS N06625 / W. Nr. 2.4856 / NiCr22Mo9Nb) is a precipitation-hardenable nickel-chromium-molybdenum-niobium superalloy that delivers outstanding strength, toughness, and corrosion resistance without any heat treatment beyond annealing. Its niobium addition (3.15–4.15%) stiffens the alloy matrix through solid-solution hardening, while the combined chromium-molybdenum content provides broad-spectrum corrosion resistance — from seawater and chloride pitting to H₂S SCC and mineral acids. These properties make Inconel 625 bar the most widely specified nickel alloy in offshore and deepwater oil & gas infrastructure worldwide, covering subsea systems, wellhead equipment, flexible risers, and sour-service pressure vessels. SHUNFU METAL produces N06625 bar from VIM-cast heats with optional ESR or VAR remelting, ensuring homogeneous Nb distribution, controlled grain size, and full material traceability from melt to finished bar.
Inconel 625 / N06625 — Introduction
Alloy 625 is designated in two grades under ASTM B446: Grade 1 (annealed, optimized for corrosion resistance) and Grade 2 (solution-annealed at higher temperature, optimized for creep and rupture resistance above 600 °C). Both grades share the same chemistry but differ in heat treatment, giving engineers flexibility to select the right condition for their service environment. The alloy’s high molybdenum content (8–10%) provides exceptional resistance to pitting and crevice corrosion in chloride-rich environments; niobium and tantalum together provide solid-solution strengthening that elevates room-temperature yield strength above 414 MPa in the annealed condition — without any aging treatment.
Inconel 625 is qualified to NACE MR0175 / ISO 15156-3 for sour-service applications, and is listed under ASME Section VIII Div. 1 Code Case 2332 for pressure vessel use. SHUNFU METAL tests every lot for PREN compliance, verifies chemistry by OES, and can supply EN 10204 3.1 or third-party witnessed 3.2 MTR with every shipment.
Equivalent Grades & Applicable Standards
| Standard Body | Designation / Grade | Specification / Form |
|---|---|---|
| ASTM | N06625 | B446 (bar & rod), B443 (plate/sheet), B444 (tube), B564 (forgings) |
| ASME | N06625 | SB-446 (bar), SB-443 (plate), SB-444 (tube), SB-564 (forgings) |
| AMS | — | AMS 5666 (bar, rod, wire & forgings), AMS 5599 (sheet, strip & plate) |
| EN / DIN | NiCr22Mo9Nb / 2.4856 | EN ISO 9723 (bar), DIN 17744, DIN 17752 (bar), EN 10095 |
| BS | NA 21 | BS 3076 (bar) |
| ISO | NiCr22Mo9Nb | ISO 15156-3 (NACE sour service), ISO 9723 (bar & rod) |
| GOST | ХН75МБ / ЭИ602 | GOST 5632 (heat-resistant & corrosion-resistant alloys) |
| JIS | NCF 625 | JIS G 4901 (bar), JIS G 4902 (plate), JIS G 3464 (tube) |
| NACE / API | N06625 | NACE MR0175 / ISO 15156-3 (sour well service); API 6A (wellhead) |
Oil & Gas Applications of Inconel 625 Bar
Inconel 625’s unique combination of NACE-qualified sour-service resistance, high strength, and unlimited seawater corrosion immunity makes it the preferred bar stock material for these critical components across all segments of the oil & gas industry:
- Subsea connector mandrels
- Flexible riser end fittings
- Umbilical termination bars
- Subsea tree valve stems
- Wellhead hanger mandrels
- Sour-service valve bodies
- BOP bonnet bolting
- Tubing head adapters
- Seawater lift pump shafts
- Mooring chain connecting pins
- Riser clamp bolts & studs
- Platform flare tip rings
- HPHT downhole tool housings
- Sour gas injection mandrels
- Packer slip elements
- CRA-cladding weld overlay bars
N06625 Bar — Supply Dimensions
SHUNFU METAL stocks and produces Inconel 625 bar in four production forms. All bars are 100% ultrasonically tested per ASTM E2375; MTR per EN 10204 3.1 supplied as standard with every order.
| Product Form | Section Profile | Size Range | Standard Length |
|---|---|---|---|
| Hot-Rolled Round Bar | Round | Ø 6 mm – Ø 200 mm | 3 m – 6 m (cut-to-length available) |
| Hot-Rolled Flat Bar | Flat / Square | Thickness 6–150 mm × Width 20–400 mm | 2 m – 6 m |
| Forged Round Bar | Round | Ø 80 mm – Ø 1,000 mm | 0.5 m – 4 m (custom billet & ingot) |
| Forged Flat Bar / Block | Flat / Block | Thickness 50–700 mm × Width up to 1,500 mm | Custom / as-ordered |
Surface conditions: as-forged/rolled (black), turned/peeled, centerless-ground, or polished. Custom profiles (hex, ring, disc, custom cross-section) available. Tolerances per ASTM B446 or customer drawing. Grade 1 or Grade 2 condition supplied to specification.
Inconel 625 Chemical Composition
Composition limits per ASTM B446 for UNS N06625 bar & rod. SHUNFU METAL verifies each heat via OES and issues a full chemical certificate. Mo and Nb+Ta are highlighted as the primary corrosion- and strength-controlling elements.
| Ni | Cr | Mo | Nb+Ta | Fe | Al | Ti | C | Mn | Si | S |
|---|---|---|---|---|---|---|---|---|---|---|
| Bal. (≥58.0) |
20.0–23.0 | 8.0–10.0 | 3.15–4.15 | ≤ 5.0 | ≤ 0.4 | ≤ 0.4 | ≤ 0.10 | ≤ 0.5 | ≤ 0.5 | ≤ 0.015 |
| All values in weight %. Mo (highlighted) drives pitting/crevice corrosion resistance; Nb+Ta (highlighted) provide solid-solution strengthening and stabilize the matrix against sensitization. | ||||||||||
PREN = %Cr + 3.3×%Mo + 16×%N. Inconel 625 typically achieves PREN ≥ 51, placing it among the most pitting-resistant commercial alloys available in bar form. SHUNFU METAL reports PREN on each heat certificate.
Mechanical Properties of N06625 Bar
Typical and minimum values per ASTM B446 and AMS 5666. SHUNFU METAL performs tensile testing per ASTM E8 and hardness per ASTM E18 / E10 on production bar ends for every lot. Grade 1 (annealed) and Grade 2 (solution-annealed at higher temperature) are both available.
| Condition | Tensile Strength MPa (ksi) |
0.2% Yield Strength MPa (ksi) |
Elongation % (min) |
Hardness HRB (typ.) |
|---|---|---|---|---|
| Grade 1 — Annealed (Hot-Finished) | ≥ 827 (120) · typ. 862–965 (125–140) | ≥ 414 (60) · typ. 448–517 (65–75) | ≥ 30 | 85–95 |
| Grade 2 — Solution-Annealed (Hot-Finished) | ≥ 758 (110) · typ. 827–896 (120–130) | ≥ 345 (50) · typ. 380–448 (55–65) | ≥ 30 | 80–92 |
| Grade 1 — Annealed (Cold-Drawn) | ≥ 896 (130) · typ. 965–1,070 (140–155) | ≥ 517 (75) · typ. 586–655 (85–95) | ≥ 25 | 92–100 |
| As-Forged / Solution-Annealed (Grade 2) | typ. 793–930 (115–135) | typ. 379–483 (55–70) | ≥ 30 | 82–95 |
Grade 1 annealing: 871–1,010 °C (1,600–1,850 °F). Grade 2 solution anneal: 1,093–1,204 °C (2,000–2,200 °F), followed by rapid water quench or forced-air cool. Physical properties: density 8.44 g/cm³; melting range 1,290–1,350 °C; modulus of elasticity 205 GPa at 20 °C. SHUNFU METAL performs all heat treatment under controlled atmosphere to prevent surface contamination.