ASTM A193 Grade B8 Class 2 (304 Strain Hardened)
304 stainless bolting cold worked after solution treatment — 125 ksi tensile in ¾ in. and under, with strength stepping down by diameter to 1½ in.
What A193 B8 Class 2 is.
ASTM A193 B8 Class 2 is the strain-hardened version of the 304 stainless grade. The bar is carbide solution treated and then cold drawn or reduced, which raises the tensile strength from the 75 ksi of Class 1 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.; Class 2B carries the strain-hardened idea to 3 in. at lower strength levels.
Class 2 is specified where a 304 joint needs bolt strength close to alloy steel without giving up corrosion resistance. We supply B8 Class 2 studs, bolts and cap screws from strain-hardened certified bar, marked B8SH, and match them with A194 Grade 8 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 | 18.0 | 20.0 |
| Nickel | Ni | 8.0 | 11.0 |
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 |
| Class 2B — 2 and under | 95 | 75 | 25 | 40 | 321 HBW / 35 HRC |
| Class 2B — over 2 to 2½ | 90 | 65 | 30 | 40 | 321 HBW / 35 HRC |
| Class 2B — over 2½ to 3 | 80 | 55 | 30 | 40 | 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. and Class 2B to 3 in. Strain-hardened austenitic steel may not show uniform properties through the section, particularly over ¾ in. diameter.
Specifications that apply.
How A193 B8 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 B8 Class 2 fasteners we make.
Every item is manufactured to your drawing or standard in A193 B8 Class 2, imperial or metric, with an EN 10204 3.1 certificate.
What is ASTM A193 B8 Class 2?
Class 2 is the same 304 stainless steel as B8 Class 1, put through a cold-working step after the solution anneal. Reducing the bar through a die stretches and tangles the crystal structure, and the metal becomes stronger and harder in proportion to the reduction. Austenitic stainless responds strongly to this: a modest reduction takes the yield strength from 30 ksi to 100 ksi. The trade is ductility and uniformity, which is why the specification allows lower strength as the diameter grows and does not certify Class 2 above 1½ in.
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.
- Class 2B: 95 ksi tensile at 2 in. and under, 90 ksi over 2 to 2½ in. and 80 ksi over 2½ to 3 in., for joints that need more than Class 1 without the full Class 2 cold work.
Temperature limits
Strain hardening is undone by heat. Above about 800 °F the cold-worked structure begins to recover and the added strength is lost, so Class 2 is not the right grade for high-temperature flanges; use Class 1, or B8C and B8T for stabilized service. At low temperature the strain-hardened material is used under ASTM A320 Class 2, with impact testing by agreement.
Testing, certification and marking
- Tensile and hardness tested per lot on the finished product
- Grade symbol B8SH and manufacturer's identification on every piece
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
- Hardness checked on the finished product; 321 HBW / 35 HRC maximum
- PMI verification and intergranular corrosion testing (ASTM A262) arranged on request
Recent A193 B8 Class 2 jobs.
ASTM A193 Grade B8 Class 1 (304 Stainless)
304 stainless bolting — Class 1 for corrosion resistance and cryogenic-to-1500 °F service, Class 2 strain hardened to 125 ksi for strength.
ASTM A193 / ASME SA-193ASTM A193 Grade B8M Class 2 (316 Strain Hardened)
316 stainless bolting cold worked after solution treatment — 110 ksi tensile in ¾ in. and under, with B8M2 and B8M3 classes for diameters to 3 in. and beyond.
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.