A193 B8M Class 1 Stud Bolts
316 stainless bolting with molybdenum for chloride and pitting resistance — offshore, marine, chemical and coastal plant fasteners.
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 Grade B8M is the 316 stainless steel bolting grade. The 2 to 3 percent molybdenum in 316 sharply improves resistance to pitting and crevice corrosion in chloride environments, which is why B8M is specified for offshore platforms, coastal refineries, desalination and chemical plants where B8 would pit.
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What A193 B8M Class 1 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 1 — all diameters | 75 | 30 | 30 | 50 | 223 HBW / 96 HRB |
| Class 1A (B8MA) — 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, 2B and 2C properties are on the B8M Class 2 page.
Class 1: carbide solution treated. Class 1A (B8MA): solution treated in the finished condition, 192 HBW / 90 HRB max. Class 2: strain hardened, to 1½ in. Class 2B (B8M2): strain hardened to lower strength levels in size steps from 2 in. and under to 3 in. Class 2C (B8M3): strain hardened to 85 ksi with 60 % reduction of area, listed for 2 in. and under and for over 2 in.
Full A193 B8M Class 1 data sheet: chemistry, physical properties and standards →
Made to standard or to your drawing.
- Offshore platform and subsea topside bolting
- Seawater cooling and desalination flanges
- Chemical and pharmaceutical process piping
- Pulp and paper bleach plants
- Coastal and marine-atmosphere structures
- Sour service within NACE limits