ASTM A193 Grade B8M3 (Class 2C) Studs and Bolts
Strain-hardened 316 stainless studs and bolts to ASTM A193 Grade B8M3 Class 2C — 85,000 psi (585 MPa) minimum tensile strength, 60% minimum reduction of area, and the full ASTM A193 composition table, quoted from the collected datasheet.
Last updated: 2026-11
Specifications
B8M3 (Class 2C) is the high-ductility variant of strain-hardened 316 stainless within ASTM A193: the collected datasheet tabulates the full composition (C 0.08% max, Cr 16.0–18.0%, Ni 10.0–14.0%, Mo 2.00–3.00%, Mn 2.00% max, Si 1.00% max, P/S 0.045%/0.030% max) and the Class 2C mechanical properties — 85,000 psi (585 MPa) minimum tensile, 65,000 psi (450 MPa) yield at 2" and under, 30% minimum elongation, a strict 60% minimum reduction of area and 35 HRC (321 HBW) maximum hardness. The datasheet's engineering note: B8M2 (Class 2B) pushes higher yield (75 ksi small diameters) with only 40% RA for static flanged joints, while B8M3 trades yield (65 ksi) for the mandated 60% RA and 30% elongation that let the fastener plastically absorb shock in seismic, offshore and thermal-cycling service.
| Designation | ASTM A193 Grade B8M3, Class 2C (strain-hardened 316 stainless, S31600) |
|---|---|
| Chemical composition (per ASTM A193) | C 0.08% max | Cr 16.0–18.0% | Ni 10.0–14.0% | Mo 2.00–3.00% | Mn 2.00% max | Si 1.00% max | P 0.045% max / S 0.030% max (collected datasheet table, verbatim) |
| Tensile strength (min) | 85,000 psi (585 MPa), all diameters (collected Class 2C table) |
| Yield strength, 0.2% offset | 65,000 psi (450 MPa) for 2" and under (M48); 60,000 psi (415 MPa) over 2" (collected table, verbatim) |
| Elongation in 4D | 30% min (collected table) |
| Reduction of area | 60% min — the defining Class 2C requirement, vs 35–45% (Class 2) and 40% (Class 2B) in the collected comparison |
| Max hardness | 35 HRC (321 HBW) (collected table) |
| Metallurgical note | The M3 designation mandates a specific degree of mechanical deformation after solution annealing to reach the 60% reduction-of-area window |
| Standards pairing | Dynamic load / high-vibration: ASTM A193 bolts & studs with ASTM A194 nuts (grade 8M); cryogenic high-impact: ASTM A320 with ASTM A194 (8M); pressure-vessel flanges: ASME B16.5 / ASME B18.2.2 heavy hex series (collected datasheet table) |
| Sour-service note | Generally not NACE MR0175 compliant — the 22 HRC austenitic limit excludes strain-hardened B8M3 (up to 35 HRC); see the annealed B8M page for the strict-NACE variant |
| MOQ / lead time | Not owner-confirmed for this family — confirmed at quotation |
Materials
- ASTM A193 B8M3 (Class 2C) strain-hardened 316 stainless steel (S31600)
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (ASTM A193 Grade B8M3 (Class 2C) Studs and Bolts) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantities and lead times for this family are confirmed at quotation — send your sizes, grades and quantities on the RFQ and the quote will carry a firm schedule. Sample availability is confirmed with the quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
B8M2 (Class 2B) or B8M3 (Class 2C) for my flanged joint?
The collected datasheet's comparison: B8M2 pushes higher yield strength (75 ksi for small diameters) but guarantees only 40% reduction of area — for static flanged joints wanting maximum steady clamping force. B8M3 sacrifices yield (65 ksi) but mandates 60% RA with 30% elongation, for dynamic environments — seismic refinery zones, offshore wave impact, extreme thermal cycling — where the fastener must plastically stretch and absorb energy rather than snap.
Is B8M3 compliant with NACE MR0175 for sour gas?
Generally no, per the collected datasheet FAQ: NACE MR0175 restricts austenitic stainless hardness to 22 HRC to prevent sulfide stress cracking, while strain-hardened B8M3 permits up to 35 HRC. For strict NACE compliance the datasheet points to fully annealed B8M Class 1 / Class 1A — see our ASTM A193 B8M page.
What should an RFQ for B8M3 studs state?
State the grade and class (ASTM A193 B8M3 Class 2C), stud type (fully threaded, double-end, tap-end) and diameter series, the matched nut grade (ASTM A194 8M per the collected pairing table), and the service case (dynamic load, cryogenic, ASME B16.5 flange). Commercial terms are confirmed at quotation.
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support