ASTM A194 Grade 8T (321 Stainless)
321 stainless heavy hex nut for B8T studs — titanium stabilised for hot, cyclic and welded 321 equipment.
What A194 8T is.
ASTM A194 Grade 8T is the Type 321 nut for A193 and A320 Grade B8T studs. Titanium stabilisation protects it from sensitisation in hot service, and it carries the standard Grade 8 family proof load of 80 ksi and 126 to 300 HBW hardness.
Grade 8TA is the same nut solution treated after finishing. We machine both from certified 321 bar.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.08 |
| Manganese | Mn | — | 2.00 |
| Phosphorus | P | — | 0.045 |
| Sulfur | S | — | 0.030 |
| Silicon | Si | — | 1.00 |
| Chromium | Cr | 17.0 | 19.0 |
| Nickel | Ni | 9.0 | 12.0 |
| Titanium | Ti | 5 × (C+N) | 0.70 |
| Nitrogen | N | — | 0.10 |
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 | 126 HBW / 60 HRB | 300 HBW / 32 HRC |
| Hex (finished pattern), all sizes | 75 | 126 HBW / 60 HRB | 300 HBW / 32 HRC |
| Grade 8TA (solution treated in the finished condition), all sizes | 80 heavy hex · 75 hex | 126 HBW / 60 HRB | 192 HBW / 90 HRB |
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. Strain-hardened Grade 8 nuts (S1) are proof tested to 125 / 115 / 105 / 100 ksi heavy hex by size and hardness limits do not apply.
Specifications that apply.
How A194 8T ships from Houston.
- Heavy hex nuts (the default for pressure bolting)
- Finished hex nuts
- Jam nuts
- Custom and special nuts to drawing
A194 8T fasteners we make.
Every item is manufactured to your drawing or standard in A194 8T, imperial or metric, with an EN 10204 3.1 certificate.
What is ASTM A194 Grade 8T?
Grade 8T is the 321 member of the A194 Grade 8 family. Titanium at five times the carbon-plus-nitrogen content stabilises the steel against sensitisation, making it the right nut for 321 equipment that is welded or runs hot. Mechanically it is identical to Grade 8: machined from solution-annealed bar, 80 ksi proof load, non-magnetic.
Testing, certification and marking
- Hardness tested per lot; proof-load tested on request or where the specification requires it
- Grade symbol 8T, or 8TB 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
ASTM A193 Grade B8T Class 1 (321 Stainless)
321 stainless bolting stabilised with titanium — the match for 321 piping and vessels in hot, cyclic and welded service.
ASTM A194 / ASME SA-194ASTM A194 Grade 8C (347 Stainless)
347 stainless heavy hex nut for B8C studs — stabilised against sensitisation for hot hydrogen, refinery and welded stainless service.
ASTM A194 / ASME SA-194ASTM A194 Grade 8 (304 Stainless)
304 stainless heavy hex nut for A193 and A320 B8 studs — solution treated, 80 ksi proof load, corrosion resistant from cryogenic to 1500 °F.