ASTM A193 Grade B8 Stud Bolts
Stud bolts and threaded rod in ASTM A193 Grade B8 — AISI 304 austenitic stainless, 75 ksi minimum tensile with no diameter restrictions, Brinell hardness max 96 in the collected grade chart. The corrosion-resistant sibling of B7 for stainless piping systems, paired with A194 8 nuts.
Last updated: 2026-11
Specifications
B8 is what happens when a flanged joint needs the B7 stud pattern but cannot tolerate rust: the same continuous-thread or double-end stud format, rolled from AISI 304 austenitic stainless instead of quenched-and-tempered alloy steel. The collected grade chart lists it with no diameter restrictions and a 75 ksi minimum tensile across the range, Brinell hardness maxing at 96 — the soft, ductile profile typical of the solution-annealed austenitic grades. That softness is the design trade: B8 gives up the 125-ksi strength of B7 in exchange for base-metal corrosion resistance and cryogenic toughness, which is why it appears on chemical, food-grade and low-temperature piping where the medium or the environment would eat a coated carbon stud. Where the line carries corrosive media specifically, step to the molybdenum-alloyed B8M; where higher strength is the constraint, the strain-hardened B8 classes (per the B8M3 page in this series) recover yield at the cost of the annealed ductility.
| Standard | ASTM A193 Grade B8 (material; also listed under A320 low-temperature use in the collected chart); stud dimensions per ASME B18.31.2 |
|---|---|
| Material | AISI 304 austenitic stainless steel (UNS S30400 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) |
| Strength vs B7 | 75 ksi tensile against B7's 125 ksi — the corrosion-for-toughness trade of the annealed stainless grade |
| Nut pairing | ASTM A194 Grade 8 nuts (the 304 pairing; see the A194 series for grade selection) |
| Typical applications | Stainless piping systems, chemical and food-grade plants, low-temperature service where coated carbon steel is not wanted |
Materials
- AISI 304 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 B8 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
When does a spec call for B8 instead of B7 studs?
When corrosion protection would have to be a coating system, and the operator would rather not maintain one. B7 studs depend entirely on galvanizing or fluoropolymer coatings in wet or corrosive service; B8 is stainless through the section, so scratches and wear do not create rust points. The price is strength — 75 ksi minimum tensile against B7's 125 ksi — and a much lower hardness ceiling, so the joint design must accept the lower bolt capacity. High-temperature or corrosive hydrocarbon service typically jumps to B8M (316-based) for the molybdenum pitting resistance instead.
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