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.
What A193 B8T Class 1 is.
ASTM A193 Grade B8T is bolting made from Type 321, the titanium-stabilised 18-8 stainless. Like 347 it resists sensitisation in the 800 to 1500 °F range, so it keeps its corrosion resistance after welding and through long hot service where plain 304 would not.
B8T is specified wherever the pressure equipment is 321: refinery furnace tubes and headers, expansion bellows, exhaust systems and aerospace ground hardware. Class 1 is solution treated; Class 2 is strain hardened. We machine it from certified 321 bar and pair it with ASTM A194 Grade 8T nuts.
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 A193/A193M-24, Tables 1 and 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Nominal diameter (in.) | Tensile strength, min (ksi) | Yield strength 0.2% offset, min (ksi) | Elongation in 4D, min (%) | Reduction of area, min (%) | Hardness, max |
|---|---|---|---|---|---|
| Class 1 — all diameters | 75 | 30 | 30 | 50 | 223 HBW / 96 HRB |
| Class 1A (B8TA) — all diameters | 75 | 30 | 30 | 50 | 192 HBW / 90 HRB |
Values per ASTM A193/A193M-24, Tables 1 and 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Class 1 sizes ¾ in. and smaller may be 241 HBW / 100 HRB. Strain-hardened Class 2 properties are on the B8T Class 2 page.
Specifications that apply.
How A193 B8T Class 1 ships from Houston.
- Full-thread studs and stud bolts
- Double-end and tap-end studs
- Hex and heavy hex bolts
- Socket head cap screws
- Threaded rod (cut and rolled thread)
- Machined components from certified bar
A193 B8T Class 1 fasteners we make.
Every item is manufactured to your drawing or standard in A193 B8T Class 1, imperial or metric, with an EN 10204 3.1 certificate.
What is ASTM A193 B8T?
B8T is the Type 321 grade in A193. Titanium at five times the carbon-plus-nitrogen content forms stable titanium carbides so that chromium is not pulled out of solution when the steel is heated into the sensitising range. The base 18-8 chemistry is otherwise the same as 304, and so are the two classes: Class 1 solution treated at 75 ksi, Class 2 strain hardened up to 125 ksi in ¾ inch and under.
When to choose 321 over 304 or 347
Choose a stabilised grade whenever the bolting will be welded, sit for long periods between 800 and 1500 °F, or bolt equipment that is itself 321 or 347. Between the two stabilised grades, follow the equipment material. Titanium-stabilised 321 has slightly lower creep strength than 347 but is more readily available in some bar sizes, and the two are accepted interchangeably by most piping specifications.
Nuts and galling
Use ASTM A194 Grade 8T nuts with B8T studs. Lubricate or coat austenitic threads before assembly; galling will otherwise seize the joint before it reaches torque.
Testing, certification and marking
- Tensile and hardness tested per heat-treat lot on the finished product
- Grade symbol B8T and manufacturer's identification on every piece
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
- Intergranular corrosion testing (ASTM A262) and PMI arranged on request
Recent A193 B8T Class 1 jobs.
ASTM A193 Grade B8T Class 2 (321 Strain Hardened)
Titanium-stabilized 321 bolting cold worked to 125 ksi tensile in ¾ in. and under — a stronger stabilized bolt for welded stainless equipment at moderate temperature.
ASTM A194 / ASME SA-194ASTM A194 Grade 8T (321 Stainless)
321 stainless heavy hex nut for B8T studs — titanium stabilised for hot, cyclic and welded 321 equipment.
ASTM A193 / ASME SA-193ASTM A193 Grade B8C Class 1 (347 Stainless)
347 stainless bolting stabilised with niobium against sensitisation — for hot hydrogen, refinery and welded stainless service between 800 and 1500 °F.