ASTM A193
Grade B8T
Bolt & Nut Manufacturer
What Is ASTM A193 Grade B8T
ASTM A193 is the standard specification for alloy and stainless steel bolting for high-temperature or high-pressure service, and Grade B8T is one of its stainless steel grades, based on Type 321 stainless steel (UNS S32100). What sets B8T apart from the more common Grade B8 (Type 304-based) is a single deliberate addition: titanium.
Chemical composition (wt%): Carbon ≤0.08 max, Manganese ≤2.00 max, Phosphorus ≤0.045 max, Sulfur ≤0.030 max, Silicon ≤1.00 max, Chromium 17.00–19.00, Nickel 9.00–12.00, and Titanium at a minimum of 5× the combined carbon-plus-nitrogen content, up to 0.70% maximum, with the balance Iron. That titanium addition preferentially combines with carbon to form titanium carbide, rather than allowing carbon to combine with chromium at the grain boundaries — the reaction responsible for sensitization in unstabilized grades.
Why this matters in service: when austenitic stainless steel is welded or held at elevated temperature for extended periods, unstabilized grades like B8 can develop chromium-depleted zones at grain boundaries, leaving the material vulnerable to intergranular corrosion. Because B8T’s carbon is already tied up as titanium carbide, this depletion doesn’t occur — which is precisely why B8T is specified for flange and piping fastening in refinery and petrochemical service that runs hot for the long term.
Where Grade B8T Genuinely Earns Its Cost
Sensitization Resistance
Titanium stabilization prevents chromium carbide precipitation at grain boundaries, protecting against intergranular corrosion after welding or sustained heat exposure.
Genuine High-Temperature Fitness
Where standard B8 can be a liability in continuous elevated-temperature service, B8T’s stabilized microstructure makes it a dependable choice for hot piping and flange fastening.
Class 1 and Class 2 Flexibility
Solution-annealed Class 1 for general corrosion-resistant duty, or strain-hardened Class 2 for higher strength where the service temperature allows it.
A Correctly Matched System
Supplied as a matched bolting system with ASTM A194 Grade 8T nuts, so the stud and nut share the same titanium-stabilized base metallurgy end to end.
Grade B8 vs B8M vs B8T — Which A193 Stainless Grade
ASTM A193 covers several stainless bolting grades, and buyers are usually choosing between the three that come up most often: B8 (unstabilized Type 304), B8M (Type 316, molybdenum-bearing), and B8T (Type 321, titanium-stabilized). Each is built for a different priority — general corrosion resistance, chloride and pitting resistance, or resistance to sensitization under welding and sustained heat. The comparison below is the one we walk through with buyers before quoting, so the grade selection matches the actual service condition rather than a generic “stainless bolt” assumption.
| Property | Grade B8 (Type 304) | Grade B8M (Type 316) | Grade B8T (Type 321) |
|---|---|---|---|
| Base UNS Designation | S30400 | S31600 | S32100 |
| Stabilizing Element | None | Molybdenum (pitting resistance) | Titanium (carbide stabilization) |
| Sensitization Resistance | Limited — carbide precipitation risk | Limited — same underlying risk | Strong — titanium ties up carbon |
| Chloride/Pitting Resistance | Moderate | Good — Mo addition | Moderate |
| Best Suited Service | General corrosion-resistant duty | Chloride-exposed process piping | High-temperature, weld-adjacent service |
| Relative Material Cost | Lowest | Moderate | Moderate-Higher |
Grade B8T Product Range
Stud Bolts
Full-thread and tap-end, ASTM A193 Grade B8T, Class 1 & 2
Hex Bolts
Full metric & imperial range in Grade B8T
Heavy Hex Nuts (A194 Gr.8T)
The matched nut counterpart to B8T stud bolts
Washers
Flat and spring washer profiles in matching grade
Threaded Rod / Continuous Thread Stud
Custom lengths for flange and process piping joints
Grade B8T Technical Specifications
Type 321 Base Alloy (wt%)
- Chromium (Cr) 17.00–19.00
- Nickel (Ni) 9.00–12.00
- Titanium (Ti) 5×(C+N) min, 0.70 max
- Carbon (C) 0.08 max
- Manganese (Mn) 2.00 max
- Iron (Fe) Balance
Class 1 vs Class 2 (min)
- Class 1 Tensile 515 MPa (75 ksi)
- Class 1 Yield 205 MPa (30 ksi)
- Class 2 Tensile 690 MPa (100 ksi)
- Class 2 Yield Size-dependent
- Condition Annealed / Strain-Hardened
- Elevated-Temp Fitness Excellent (Class 1)
Available Dimensions
- Metric Diameter M6 – M64
- Imperial Diameter 1/4″ – 4″
- Stud Length Custom to drawing
- Thread Type UNC / UNF / Metric
- Finish Passivated / As-machined
- Testing MTC / NABL on request
Application Areas
Wherever sustained high temperature and weld-adjacent service meet.
Refinery & Petrochemical Piping
and pipe joint fastening
Power Generation & Boiler Flanges
elevated-temperature fastening
Chemical Processing at Elevated Temp
fastening under sustained heat
Post-Weld / Heat-Affected Zone Service
where sensitization risk is highest
Food & Pharma Processing Equipment
fastening requiring corrosion life
Flange & Pipe Joint Fastening
process piping connections
General High-Temperature Industrial
continuous elevated-temp duty
Steam & Process Piping
flange and support fastening
Standard Export Documentation
Prepared as standard practice for every Grade B8T shipment.
Mill Test Certificate (MTC)
Heat number, chemical composition, and mechanical property verification for every lot.
Certificate of Conformance
Confirms the shipment matches the purchase order specification, grade, and class in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
Commercial Invoice & Packing List
Itemized value, Incoterm, and detailed carton/weight breakdown for customs clearance.
NABL Accredited Test Reports
Independent mechanical and chemical testing available on request for critical applications.
Bill of Lading
Ocean or air freight shipping document confirming carrier, mode, and consignee details.
Internationally Recognised Standards Coverage
Related Fastener Grades & Materials
Stainless Steel 316 Fasteners
General-purpose stainless bolting where chloride resistance matters more than sensitization risk.
View SS 316 →Super Duplex Fasteners
High strength and severe chloride resistance for demanding process environments.
View Super Duplex →Hastelloy B-3 Stud Bolts
Nickel-molybdenum alloy fastening for reducing acid and severe corrosion service.
View Hastelloy B-3 →Titanium Grade 2 Fasteners
Commercially pure titanium for corrosion-focused, non-magnetic fastening applications.
View Titanium Grade 2 →Sourcing Grade
B8T Fasteners?
Size · quantity · class · service temperature. Akbar Fasteners Pvt. Ltd. responds within 24 hours with pricing and mill test documentation.
Sales: +91 724 0000 733 · Support: +91 800 9315 333 · sales@akbarfasteners.in