Stainless Steel, Duplex & Nickel Alloy Fasteners
Pressure bolting is a matched set: stud grade, nut grade, length and lubricant. Choose the material for the flange and service, then the stud and nut grades. We supply stud bolts, hex bolts, heavy hex nuts and washers with EN 10204 3.1 certificates.
- ASME B18.2.1
- ASME B18.2.2
- ASME B18.31.2
- DIN 931 / 933 / 934 (legacy)
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is flange bolting?
Flange bolting is usually a fully threaded stud bolt with two heavy hex nuts. Stud material comes from ASTM A193 (B7, B8, B8M) for high-temperature service or A320 (L7) for low temperature, and nuts from ASTM A194 (2H, 8, 8M). Duplex studs can be ordered to ASTM A1082, and Alloy 625, C276, Monel 400 and K-500 bolts, cap screws and studs to ASTM F468 (0.250–1.500 in.) with nuts to ASTM F467, and Alloy 718 bolting to ASTM A1014, where specified; for alloys where no finished fastener specification is asserted — such as Alloy 825 and 904L — bolts, studs and nuts may be machined from bar of the same alloy, where applicable, with finished requirements to the purchase specification or project drawing.
How to order fasteners: checklist
- Stud diameter, thread (UNC / 8UN / metric) and length
- Stud and nut grades — e.g. ASTM A193 B7 / A194 2H
- Number of nuts per stud (normally two)
- Coating — plain, zinc, hot-dip galvanised, PTFE / Xylan
- Sour service — B7M / 2HM to NACE MR0175
- Certificate — EN 10204 3.1
Fasteners by Material Family and Grade
Each fastener page sits under its grade. Open it for the bar standard, nut pairing and coatings.
Types of Fasteners
Stud and Nut Pairings
Use the nut grade the bolting specification pairs with the stud. Mixing grades is a common inspection reject.
| Service | Stud | Nut |
|---|---|---|
| Carbon steel flanges, general | ASTM A193 B7 | ASTM A194 2H |
| Sour service (hardness-limited) | ASTM A193 B7M | ASTM A194 2HM |
| Low temperature | ASTM A320 L7 | ASTM A194 Gr 7L (impact-tested) |
| High temperature (Cr-Mo-V) | ASTM A193 B16 | ASTM A194 Gr 4 or 7 |
| Stainless 304 | ASTM A193 B8 (Class 1 or 2) | ASTM A194 8 |
| Stainless 316 | ASTM A193 B8M (Class 1 or 2) | ASTM A194 8M |
| Nickel alloy, corrosive | Alloy 625 / 718 / K-500 to project spec | Same alloy |
Torque, Stud Length and Coatings
Torque T = K × F × d — K, the nut factor, depends mostly on the lubricant (about 0.2 dry, much lower with anti-seize). Stud length covers two flange thicknesses, the gasket, two nuts and thread projection; ASME B16.5 tabulates lengths by size, class and facing. Coatings — PTFE/fluoropolymer, zinc-nickel or hot-dip galvanising (with oversize-tapped nuts) — protect carbon-steel bolting; electroplated high-strength bolts must be baked against hydrogen embrittlement.
Stainless and nickel-alloy threads gall: always use anti-seize and tighten steadily.
How Bolting Standards Fit Together
Fasteners Grades & Material Standards
| Grade | Material standard | Best for |
|---|---|---|
| Inconel 825 | May be machined from ASTM B425 bar (UNS N08825), where applicable; finished fastener requirements are to the purchase specification or project drawing | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking and sour gas |
| SS 904L | May be machined from ASTM A479 bar (UNS N08904), where applicable; finished fastener requirements are to the purchase specification or project drawing | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
| SS 304 | ASTM A193 B8 · A194 8 | General corrosion resistance, food, water and architectural work |
| SS 304L | ASTM A193 B8 · A194 8 | Welded tanks, piping and vessels in general corrosive service |
| SS 310 / 310S | May be machined from ASTM A276 / A479 bar (UNS S31008), where applicable; finished fastener requirements are to the purchase specification or project drawing | Furnaces, burners and heat treatment at high temperature |
| SS 316 / 316L | ASTM A193 B8M · A194 8M | Chloride-bearing process fluids, marine air and pharmaceutical service |
| SS 321 | ASTM A193 B8T | High-temperature service between 425 and 815 °C |
| SS 347 | ASTM A193 B8C | Welded high-temperature piping in refineries and power plants |
| Duplex 2205 | ASTM A1082 (S32205) where specified for applicable duplex bolts, studs, cap screws and nuts; for other types, material may be supplied to ASTM A276 / A479 bar where applicable, subject to the purchase specification | Strength with chloride resistance at a stainless-steel budget |
| Super Duplex 2507 | ASTM A1082 (S32750) where specified for applicable duplex bolts, studs, cap screws and nuts; for other types, material may be supplied to ASTM A276 / A479 bar where applicable, subject to the purchase specification | Seawater and high-chloride service where strength also matters |
| Inconel 600 | May be machined from ASTM B166 bar (UNS N06600), where applicable; finished fastener requirements are to the purchase specification or project drawing | High-temperature oxidation, caustic and nuclear service |
| Inconel 625 | ASTM F468 (N06625) where specified for applicable bolts, hex cap screws, socket-head cap screws and studs (0.250–1.500 in.), and ASTM F467 for applicable nuts (0.250–1.500 in.); for other types, material may be supplied to ASTM B446 bar where applicable, subject to the purchase specification | Seawater, high strength and high temperature in one alloy |
| Inconel 718 | ASTM A1014 (UNS N07718) where specified for applicable bolts and studs — product-type scope pending current standard text; for other types, material may be supplied to ASTM B637 bar where applicable, subject to the purchase specification or project drawing | Very high strength at temperatures up to about 650 °C |
| Incoloy 800 / 800H / 800HT | May be machined from ASTM B408 bar (UNS N08800), where applicable; finished fastener requirements are to the purchase specification or project drawing | Furnaces, petrochemical heaters and high-temperature piping |
| Hastelloy C276 | ASTM F468 (N10276) where specified for applicable bolts, hex cap screws, socket-head cap screws and studs (0.250–1.500 in.), and ASTM F467 for applicable nuts (0.250–1.500 in.); for other types, material may be supplied to ASTM B574 bar where applicable, subject to the purchase specification | The most aggressive mixed acids, wet chlorine and hypochlorite |
| Hastelloy C22 | May be machined from ASTM B574 bar (UNS N06022), where applicable; finished fastener requirements are to the purchase specification or project drawing | Mixed oxidising and reducing acids, and weld overlays |
| Monel 400 | ASTM F468 (N04400) where specified for applicable bolts, hex cap screws, socket-head cap screws and studs (0.250–1.500 in.), and ASTM F467 for applicable nuts (0.250–1.500 in.); for other types, material may be supplied to ASTM B164 bar where applicable, subject to the purchase specification | Seawater, hydrofluoric acid and marine service |
| Monel K500 | ASTM F468 (N05500) where specified for applicable bolts, hex cap screws, socket-head cap screws and studs (0.250–1.500 in.), and ASTM F467 for applicable nuts (0.250–1.500 in.); for other types, material may be supplied to ASTM B865 bar where applicable, subject to the purchase specification | High-strength pump shafts, bolting and springs in seawater |
Dimensional standards
Guides, tools & standards for fasteners
Fasteners for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiFasteners — questions buyers ask
What nut goes with A193 B7?
ASTM A194 2H heavy hex nuts (2HM with B7M for sour service).
What is the difference between B8 Class 1 and Class 2?
Class 1 is carbide solution treated; Class 2 is strain hardened for higher strength. State the class on the order.
How is stud bolt length calculated?
Two flange thicknesses + gasket + two heavy-hex-nut heights + thread projection; ASME B16.5 gives lengths by size, class and facing.
Why do stainless bolts seize?
Stainless and nickel-alloy threads gall under load. Use anti-seize on threads and nut faces and tighten at moderate speed.