A193 B8M Class 2 Stud Bolts
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.
Threaded rod inserted through the holes of mating flanges, paired with heavy hex nuts. Available in every diameter and length, imperial and metric, for flanged connections in critical service. Supplied bare or coated, with full material traceability.
ASTM A193 B8M Class 2 is 316 stainless bar that has been carbide solution treated and then strain hardened. The cold work lifts the tensile strength from 75 ksi to 110 ksi in ¾ in. and under, stepping down by size to 90 ksi at 1½ in. A193 adds two large-diameter classes for 316: Class 2B (marked B8M2) to 3 in. and Class 2C (marked B8M3) at 85 ksi with high ductility, listed for 2 in. and under and for over 2 in.
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What A193 B8M Class 2 must meet.
| 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 | 110 | 95 | 15 | 45 | 321 HBW / 35 HRC |
| Class 2 — over ¾ to 1 | 100 | 80 | 20 | 45 | 321 HBW / 35 HRC |
| Class 2 — over 1 to 1¼ | 95 | 65 | 25 | 45 | 321 HBW / 35 HRC |
| Class 2 — over 1¼ to 1½ | 90 | 50 | 30 | 45 | 321 HBW / 35 HRC |
| Class 2B (B8M2) — 2 and under | 95 | 75 | 25 | 40 | 321 HBW / 35 HRC |
| Class 2B (B8M2) — over 2 to 2½ | 90 | 65 | 30 | 40 | 321 HBW / 35 HRC |
| Class 2B (B8M2) — over 2½ to 3 | 80 | 55 | 30 | 40 | 321 HBW / 35 HRC |
| Class 2C (B8M3) — 2 and under | 85 | 65 | 30 | 60 | 321 HBW / 35 HRC |
| Class 2C (B8M3) — over 2 | 85 | 60 | 30 | 60 | 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.; Class 2B is listed in size steps to 3 in. and Class 2C for 2 in. and under and over 2 in. Strain-hardened austenitic steel may not show uniform properties through the section, particularly over ¾ in. diameter.
Carbide solution treated, then strain hardened by cold reduction of the bar before machining. Class 2B (B8M2) and Class 2C (B8M3) are strain hardened to lower strength levels so that large diameters keep usable ductility. Full-size testing of headed Class 2 components after strain hardening is permitted by the specification.
Full A193 B8M Class 2 data sheet: chemistry, physical properties and standards →
Made to standard or to your drawing.
- Offshore platform and subsea flange bolting
- Seawater cooling and desalination piping
- Chemical process units with chlorides
- Coastal refinery and terminal piping
- Pulp and paper bleach plant
- Pharmaceutical and food equipment with high bolt loads