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.
What A193 B8T Class 2 is.
ASTM A193 B8T Class 2 is the strain-hardened version of the 321 grade. The bar is carbide solution treated and then cold reduced, which raises the tensile strength from the annealed minimum to 125 ksi in ¾ in. and smaller sizes. Because cold work cannot penetrate a large section evenly, the specification steps the required strength down by diameter and stops at 1½ in.
We supply B8T Class 2 studs, bolts and cap screws from strain-hardened certified bar, marked B8TSH, and match them with ASTM A194 8T nuts. The chemistry, corrosion resistance and companion nut are identical to B8T Class 1; only the condition and strength differ.
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 2 — ¾ and under | 125 | 100 | 12 | 35 | 321 HBW / 35 HRC |
| Class 2 — over ¾ to 1 | 115 | 80 | 15 | 35 | 321 HBW / 35 HRC |
| Class 2 — over 1 to 1¼ | 105 | 65 | 20 | 35 | 321 HBW / 35 HRC |
| Class 2 — over 1¼ to 1½ | 100 | 50 | 28 | 45 | 321 HBW / 35 HRC |
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 2 is limited to 1½ in. Strain-hardened austenitic steel may not show uniform properties through the section, particularly over ¾ in. diameter.
Specifications that apply.
How A193 B8T Class 2 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 2 fasteners we make.
Every item is manufactured to your drawing or standard in A193 B8T Class 2, imperial or metric, with an EN 10204 3.1 certificate.
What is ASTM A193 B8T Class 2?
B8T Class 2 is 321 stainless steel, solution treated and then strain hardened, with the same size-stepped strength table as B8 Class 2. Titanium ties up carbon so the alloy resists intergranular attack after welding, and that protection survives cold work. Like every strain-hardened austenitic grade it gives its strength back above about 800 °F, so Class 2 belongs on moderate-temperature joints; the hot end of 321 service is Class 1 territory.
Why the strength drops with size
- ¾ in. and under: 125 ksi tensile, 100 ksi yield. Cold work reaches the core of a small bar.
- Over ¾ to 1 in.: 115 ksi tensile, 80 ksi yield.
- Over 1 to 1¼ in.: 105 ksi tensile, 65 ksi yield.
- Over 1¼ to 1½ in.: 100 ksi tensile, 50 ksi yield. The largest size certified as Class 2 for this grade.
Class 2 or Class 1?
Specify Class 2 when the joint needs bolt strength close to alloy steel and runs below about 800 °F. Specify Class 1 for hot service, for large diameters, for sour service to NACE MR0175 / ISO 15156 where cold-worked austenitic bolting is restricted, and wherever the design only needs the annealed strength. Both classes share one chemistry, so the corrosion performance is the same.
Testing, certification and marking
- Tensile and hardness tested per lot on the finished product
- Grade symbol B8TSH and manufacturer's identification on every piece
- Hardness checked on the finished product; 321 HBW / 35 HRC maximum
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness 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 A193 / ASME SA-193ASTM A193 Grade B8C Class 2 (347 Strain Hardened)
Niobium-stabilized 347 bolting cold worked to 125 ksi tensile in ¾ in. and under — strength for moderate-temperature joints that must not sensitize.
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.