ASTM A194 Grade 8S (Nitronic 60)
Nitronic 60 heavy hex nut — the anti-galling nut for stainless studs, assembled dry without seizing; 80 ksi proof load.
What A194 8S is.
ASTM A194 Grade 8S is the Nitronic 60 nut. Its silicon-manganese austenitic chemistry resists galling against 304, 316, Nitronic 50 and other stainless studs, which is why it is specified wherever stainless joints must be assembled dry or taken apart repeatedly.
Grade 8SA is the same nut solution treated after finishing. We machine both from certified S21800 bar.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.10 |
| Manganese | Mn | 7.0 | 9.0 |
| Phosphorus | P | — | 0.060 |
| Sulfur | S | — | 0.030 |
| Silicon | Si | 3.5 | 4.5 |
| Chromium | Cr | 16.0 | 18.0 |
| Nickel | Ni | 8.0 | 9.0 |
| Nitrogen | N | 0.08 | 0.18 |
Values per ASTM A194/A194M-24, Tables 1, 2 and 3 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Nut style and size (in.) | Proof load stress (ksi) | Hardness, min | Hardness, max |
|---|---|---|---|
| Heavy hex, all sizes | 80 | 183 HBW / 88 HRB | 271 HBW / 25 HRC |
| Hex (finished pattern), all sizes | 75 | 183 HBW / 88 HRB | 271 HBW / 25 HRC |
| Grade 8SA (solution treated in the finished condition), all sizes | 80 heavy hex · 75 hex | 183 HBW / 88 HRB | 271 HBW / 25 HRC |
Values per ASTM A194/A194M-24, Tables 1, 2 and 3 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Jam nuts: 46 % of the tabulated proof load.
Specifications that apply.
How A194 8S ships from Houston.
- Heavy hex nuts (the default for pressure bolting)
- Finished hex nuts
- Jam nuts
- Custom and special nuts to drawing
A194 8S fasteners we make.
Every item is manufactured to your drawing or standard in A194 8S, imperial or metric, with an EN 10204 3.1 certificate.
What is ASTM A194 Grade 8S?
Grade 8S is the Nitronic 60 nut in A194. The alloy's 4 percent silicon and 8 percent manganese change how the surface work-hardens so that it does not cold-weld to another stainless surface under thread pressure. In practice a Grade 8S nut can be run onto a dry stainless stud, torqued and removed without the seizing that ruins ordinary stainless fasteners. It is machined from solution-annealed bar, non-magnetic and comparable to 316 in general corrosion resistance.
Testing, certification and marking
- Hardness tested per lot; proof-load tested on request or where the specification requires it
- Grade symbol 8S, or 8SB on nuts machined from bar (ASTM A194 Table 7), and manufacturer's identification on one face of every nut
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
- Oversize tapping for coated studs and PTFE / zinc / hot-dip galvanized finishes available
Recent A194 8S jobs.
ASTM A193 Grade B8S (Nitronic 60)
Nitronic 60 bolting — the anti-galling stainless: 95 ksi, non-magnetic, and threads that will not seize against other stainless steels.
ASTM A193 / ASME SA-193ASTM A193 Grade B8R (Nitronic 50 / XM-19)
Nitronic 50 bolting — twice the yield strength of 316 with better seawater corrosion resistance and no loss of ductility, non-magnetic even after cold work.
ASTM A194 / ASME SA-194ASTM A194 Grade 8M (316 Stainless)
316 stainless heavy hex nut for B8M studs — molybdenum-bearing for chloride and marine service, 80 ksi proof load.