Patriot Bolt machines Inconel 625 stud bolts from certified ASTM B446 round bar for flanges in seawater, subsea and aggressive chemical service. Alloy 625 (UNS N06625) is a nickel-chromium-molybdenum alloy strengthened with niobium, so it reaches 120 ksi minimum tensile strength without an aging treatment.
We make Inconel 625 studs to the specification on your purchase order or to your drawing. Every order ships with mill test reports traceable to the heat.
Inconel 625 Stud Bolts at a Glance
- Also called
- Alloy 625 · UNS N06625 · W.Nr. 2.4856
- Material specs
- ASTM B446 / ASME SB446 bar · NACE MR0175 / ISO 15156-3
- Strength
- 120 ksi min tensile, 60 ksi min yield (B446 Grade 1, annealed, to 4 in.)
- Corrosion
- Pitting and crevice resistant in seawater and chlorides
- Configurations
- Fully threaded, double-end and tap-end
Why Engineers Specify Inconel 625 Stud Bolts
Flange studs in seawater sit in tight crevices with little oxygen, which is where stainless steels pit. Inconel 625 has about 9% molybdenum and 21% chromium, giving it some of the best pitting and crevice resistance of any common bolting alloy.
- Seawater and subsea. Used for subsea flanges, risers and seawater systems.
- Acids. Resists a wide range of oxidizing and reducing acids.
- No aging required. Strength comes from solid-solution strengthening, so there is no age-hardening step to control.
- Sour service. Listed in NACE MR0175 / ISO 15156-3, within the limits that standard sets.
Inconel 625 Stud Bolt Specifications
ASTM B446 covers Alloy 625 rod and bar in two grades. Grade 1 (annealed) is the usual choice for bolting.
| ASTM B446 grade | Size | Tensile, min | Yield (0.2%), min | Elongation, min |
|---|---|---|---|---|
| Grade 1, annealed | To 4 in. | 120 ksi | 60 ksi | 30% |
| Grade 1, annealed | Over 4 to 10 in. | 110 ksi | 50 ksi | 25% |
| Grade 2, solution annealed | All | 100 ksi | 40 ksi | 30% |
Grade 2 is meant for high-temperature creep service and has lower strength. Annealed 625 is weaker than B7, so confirm the stud size and preload with your engineer.
Inconel 625 Chemical Composition
| Element | Weight % |
|---|---|
| Nickel | 58.0 min |
| Chromium | 20.0–23.0 |
| Molybdenum | 8.0–10.0 |
| Niobium + tantalum | 3.15–4.15 |
| Iron | 5.0 max |
| Cobalt | 1.0 max |
| Aluminum | 0.40 max |
| Titanium | 0.40 max |
| Carbon | 0.10 max |
| Manganese | 0.50 max |
Typical limits for UNS N06625. The mill test report for your heat is the controlling document.
Stud Configurations
- Fully threaded studs, threaded end to end, for flange bolting where grip length varies.
- Double-end studs, threaded on both ends with an unthreaded center.
- Tap-end studs, with one end made to thread into a tapped hole.
625 can gall. Use a compatible thread lubricant or anti-seize.
Applications and Industries
- Subsea and offshore: Manifold, riser and seawater flange studs. See Oil & Gas.
- Chemical and refining: Acid and chloride service. See Petrochemical & Refining.
- Marine and aerospace: Hardware exposed to salt spray and high temperature. See Aerospace.
Certification and Traceability
Patriot Bolt is ISO 9001:2015 certified. Each Inconel 625 order includes mill test reports traceable to the heat, along with a certificate of conformance to the specification on your purchase order.
Compare Inconel 625 with other bolting grades in our Fastener Materials Matrix.
Inconel 625 Stud Bolt FAQ
Why choose 625 over 316 stainless studs?
316 stainless can pit and crack in warm seawater and chloride service. 625 resists both and has twice the minimum yield strength of annealed 316.
Is Inconel 625 or 718 better for studs?
718 is much stronger. 625 is chosen when pitting and crevice corrosion resistance is the main concern.
Which ASTM B446 grade should I order?
Grade 1 (annealed) is the usual choice for bolting. Grade 2 is for high-temperature creep service.
Do you make matching nuts?
Yes. We also machine Inconel 625 nuts.
Request a Quote
Send us the stud configuration, diameter, length, thread, specification and quantity, or upload your drawing. Our team will confirm the material and lead time. Call (281) 581-0176 or request a quote.
Also in Inconel 625: Socket head cap screws · Hex head cap screws · Inconel heavy hex nuts · All stud bolts