Inconel 625 (UNS N06625)
The corrosion all-rounder — 120 ksi in the annealed condition, resistant to seawater, sour gas, acids and oxidation to 1800 °F, and the F468 nickel fastener grade Ni 625.
What Inconel 625 is.
Inconel 625 is a nickel-chromium alloy with 9 percent molybdenum and 3.5 percent niobium. The molybdenum and niobium strengthen it in solution to 120 ksi without ageing and give it outstanding resistance to pitting, crevice corrosion and stress-corrosion cracking in seawater, sour gas and a wide range of acids, plus oxidation resistance to about 1800 °F.
ASTM B446 covers the bar in Grade 1 (annealed) and Grade 2 (solution annealed); ASTM F468 covers 625 fasteners as Ni 625. We machine 625 studs, bolts, nuts and components from certified B446 bar.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Nickel | Ni | 58.0 | — |
| Chromium | Cr | 20.0 | 23.0 |
| Molybdenum | Mo | 8.0 | 10.0 |
| Niobium + tantalum | Nb+Ta | 3.15 | 4.15 |
| Iron | Fe | — | 5.0 |
| Cobalt | Co | — | 1.0 |
| Aluminum | Al | — | 0.40 |
| Titanium | Ti | — | 0.40 |
| Carbon | C | — | 0.10 |
| Manganese | Mn | — | 0.50 |
| Silicon | Si | — | 0.50 |
| Phosphorus | P | — | 0.015 |
| Sulfur | S | — | 0.015 |
Values per ASTM B446-19 Table 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Condition and size | Tensile strength, min (ksi) | Yield strength 0.2%, min (ksi) | Elongation, min (%) |
|---|---|---|---|
| Grade 1 (annealed) — up to 4 in. | 120 | 60 | 30 |
| Grade 1 (annealed) — over 4 to 10 in. | 110 | 50 | 25 |
| Grade 2 (solution annealed) — all sizes | 100 | 40 | 30 |
Values per ASTM B446-19 Table 1 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Grade 1 annealed at 1600 °F minimum; Grade 2 solution annealed at 2000 °F minimum (an 1800 °F stabilizing anneal is optional), the grade normally chosen for service above about 1100 °F.
| Nominal diameter (in.) | Hardness | Full-size tensile (ksi) | Full-size yield, min (ksi) | Machined tensile, min (ksi) | Machined yield, min (ksi) | Elongation in 4D, min (%) |
|---|---|---|---|---|---|---|
| All sizes | 85 HRB – 35 HRC | 120 min | 60 | 120 | 60 | 30 |
Values per ASTM F468-23 Table 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Full-size tensile range and yield; machined-specimen minimums in the last three columns.
| Nut style | Hardness, min | Proof stress, min (ksi) |
|---|---|---|
| Hex and hex flange | 85 HRB – 35 HRC | 60 (Gr 1) · 120 (Gr 2) |
| Heavy hex, large hex flange and thick | 85 HRB – 35 HRC | 65 (Gr 1) · 130 (Gr 2) |
Values per ASTM F467-24 Table 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Specifications that apply.
How Inconel 625 ships from Houston.
- Full-thread studs and stud bolts
- Hex and heavy hex bolts
- Socket head cap screws
- Hex nuts in the same alloy
- Threaded rod
- Machined components from certified bar
Inconel 625 fasteners we make.
Every item is manufactured to your drawing or standard in Inconel 625, imperial or metric, with an EN 10204 3.1 certificate.
What is Inconel 625?
Alloy 625 gets its strength from molybdenum and niobium dissolved in the nickel-chromium matrix, so it needs no heat treatment and its properties are stable across the whole temperature range from cryogenic to about 1800 °F. The same alloying makes it one of the most corrosion-resistant engineering alloys available: it resists pitting and crevice attack in seawater, sulfide stress cracking in sour gas, and a wide range of oxidising and reducing acids. F468 lists it as Ni 625 for fasteners, with a 120 ksi tensile and 60 ksi yield minimum; F467 offers Grade 1 (60 ksi proof) and Grade 2 (120 ksi proof) nuts.
Testing, certification and marking
- Tensile and hardness tested per lot on the finished product
- Grade or alloy marking F468AC on bolts and F467AC / F467AD on nuts and manufacturer's identification on every piece
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
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The general-purpose nickel-chromium alloy — oxidation resistant to 2000 °F, immune to chloride stress-corrosion cracking, for furnace, heat-treat and nuclear hardware.
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