ASTM A193 Grade B8M Stud Bolts
Stud bolts and threaded rod in ASTM A193 Grade B8M — AISI 316 molybdenum-alloyed austenitic stainless, 75 ksi minimum tensile with no diameter restrictions, Brinell hardness max 96 in the collected grade chart. The chloride-resistant stud grade for chemical, offshore and coastal piping, paired with A194 8M nuts.
Last updated: 2026-11
Specifications
B8M is the 316-family member of the A193 stud grades: the same austenitic stainless construction as B8 with 2–3% molybdenum added to the alloy, which is what lifts pitting and crevice resistance in chloride-bearing service. The collected grade chart lists it identically to B8 in the strength columns — 75 ksi minimum tensile, no diameter restrictions, Brinell max 96 — so the selection between the two is made by the medium, not the mechanicals: chlorides, coastal atmosphere, or process streams with pitting risk specify B8M, clean dry service can stay with B8. Like all annealed A193 stainless studs it trades strength for toughness and corrosion resistance, clamping with A194 8M heavy hex nuts; where the joint needs more yield than the annealed grade gives, the strain-hardened B8M classes (see the B8M3 page) are the structured way up without leaving the 316 metallurgy.
| Standard | ASTM A193 Grade B8M (material; also listed under A320 low-temperature use in the collected chart); stud dimensions per ASME B18.31.2 |
|---|---|
| Material | AISI 316 molybdenum-alloyed austenitic stainless steel (UNS S31600 material family) |
| Tensile strength, min | 75 ksi — no diameter restrictions in the collected chart ("all included, no restrictions") |
| Hardness | Brinell max 96 (collected chart; no hardness minimum listed for this grade) |
| Alloy difference vs B8 | Molybdenum addition (2–3% in the 316 chemistry) for chloride pitting and crevice resistance — same 75 ksi chart strength |
| Nut pairing | ASTM A194 Grade 8M nuts (the 316 pairing) |
| Typical applications | Chemical process piping, offshore and coastal installations, chloride-bearing or pitting-prone service |
Materials
- AISI 316 molybdenum-alloyed austenitic stainless steel
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 B8M Stud 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 quantity is 1,000–10,000 pieces depending on size. Stock items run 3–7 days. High-strength and custom parts run 15–25 days. Quantities or variants outside the standard range are confirmed at 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
B8 or B8M — how much chloride exposure justifies the molybdenum upgrade?
Treat it as a medium question, not a strength question — the collected chart lists both grades at the same 75 ksi minimum tensile. Any repeated chloride contact (seawater splash, de-icing salt, brine streams, coastal fog) is the regime where plain 304 develops pitting and crevice attack and the 316 molybdenum addition earns its price. For internals of dry, clean service there is no mechanical reason to pay for B8M. And where a B8M joint is strength-limited rather than corrosion-limited, the strain-hardened Class 1/2/2B/2C sub-grades recover yield within the same 316 metallurgy — that is the B8M3 selection, covered on its own page.
Related knowledge
- What Bolt Property Classes 8.8, 10.9 and 12.9 Encode — and When High Strength Stops Being the Right Choice
- Bolt Grade Selection: ISO 898-1 8.8/10.9/12.9 vs ASTM A307 and A325
- 8.8 vs 10.9 vs 12.9 Bolts: Strength, Hardness and Cost — What the Evidence Settles
- Calculating Bolt Preload and Clamp Force: Torque, Friction and Tightening Method
- How to Determine Tightening Torque and Choose a Tightening Method for a Bolted Joint
- Fastener Failure Modes: Which Fatigue, Creep and SCC Controls the Evidence Supports
- Hydrogen Embrittlement in High-Strength Bolts: Which Grades Need Controls, Which Coatings and Baking Schedules Are Acceptable, and What to Require Before the RFQ
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