ASTM A193 / A320 SPECIALTY AUSTENITIC BOLTS (B8C, B8T, B8F, B8P, B8LN, B8MLN) — DATASHEET & PROPERTIES
Ananka Fasteners is a premier global manufacturer and supplier of ASTM A320 Specialty Austenitic Fasteners. While standard A320 Grade B8 (304) and B8M (316) handle the majority of cryogenic and Liquefied Natural Gas (LNG) applications, advanced aerospace, nuclear, and chemical synthesis networks often demand fasteners that combine certified sub-zero impact toughness with highly specialized metallurgical traits.
This comprehensive datasheet covers the elite specialty grades within the A320 (and A193) specifications: B8C (Niobium Stabilized), B8T (Titanium Stabilized), B8F (Free-Machining), B8P (High-Nickel/Non-Magnetic), B8LN (Nitrogen Strengthened 304), and B8MLN (Nitrogen Strengthened 316). Supplied in the Class 1 (fully annealed) condition, these fasteners guarantee maximum ductility and Charpy V-Notch impact absorption at temperatures plunging to -320°F (-196°C). All components are strictly supported by EN 10204 Type 3.1 Material Test Certificates (MTC) verifying their specific micro-alloying and sub-zero capabilities.
■ Proprietary Datasheet Download
For lead cryogenic engineers, LNG plant designers, and aerospace metallurgists requiring empirical Charpy V-Notch impact data and sub-zero stress-strain curves for the A320 specialty austenitic series, the complete technical datasheet must be accessed.
ASTM A320 Specialty Austenitic Series — Complete Technical Yield & Cryogenic Datasheet
Contains empirical data for stress simulations, -320°F impact toughness tables, and magnetic permeability (μ) curves. Corporate credentials required.
⬇ ACCESS SECURE DATASHEET PORTAL■ Mill Test Certificate (MTC) Integration
Because the elite performance of the A320 specialty series relies on hyper-specific alloying and certified impact resistance, the EN 10204 3.1 Mill Test Certificate (MTC) is the absolute, legally binding proof of component integrity. Ananka Fasteners’ MTCs for B8 specialty grades explicitly guarantee:
- Cryogenic Impact Verification: Documented Charpy V-Notch (CVN) destructive testing results proving the batch absorbed the required kinetic energy at sub-zero temperatures.
- Precise Alloy Spectrography: Verification of the specific stabilizers (Titanium, Niobium) or strengtheners (Nitrogen) mandated by the exact requested sub-grade.
- Thermal Processing Data: Verification that proper carbide solution treatment was performed to ensure total austenitization before deployment.
- Complete Traceability: Heat number documentation linking the finished bolt back to the primary super-alloy melt.
■ Material Specifications (Specialty Grades)
| B8C (UNS S34700) | 347 Stainless. Niobium (Columbium) stabilized. Prevents sensitization in cryogenic systems that also endure high-heat purges. |
|---|---|
| B8T (UNS S32100) | 321 Stainless. Titanium stabilized. High-temperature oxidation resistance combined with sub-zero toughness. |
| B8F (UNS S30300) | 303 Stainless. Sulfur/Selenium alloyed for extreme machinability. Note: Lower impact toughness than other grades. |
| B8P (UNS S30500) | 305 Stainless. High-Nickel content ensures the lattice remains absolutely non-magnetic, even at -320°F (-196°C). |
| B8LN (UNS S30453) | 304LN Stainless. Ultra-low carbon for weldability, Nitrogen-charged to restore yield strength. |
| B8MLN (UNS S31653) | 316LN Stainless. Adds 2-3% Moly to the B8LN formula for aggressive marine/offshore cryogenic environments. |
■ Dimensions of Heavy Hex Bolts (ASME B18.2.1)
Standard dimensional specifications for ASME B18.2.1 Heavy Hex Bolts. The heavy hex profile provides the expanded bearing footprint necessary to securely distribute compressive loads across heavily insulated flanged joints in cryogenic piping networks.
| Nominal Size (in) | Threads per Inch (TPI) | Width Across Flats (Max) | Head Height (Max) | Width Across Corners (Min) |
|---|---|---|---|---|
| 1/2" | 13 | 0.875" | 0.344" | 0.969" |
| 5/8" | 11 | 1.062" | 0.422" | 1.175" |
| 3/4" | 10 | 1.250" | 0.500" | 1.383" |
| 7/8" | 9 | 1.438" | 0.578" | 1.589" |
| 1" | 8 | 1.625" | 0.656" | 1.796" |
| 1-1/8" | 8 (UN) | 1.812" | 0.734" | 2.002" |
| 1-1/4" | 8 (UN) | 2.000" | 0.812" | 2.209" |
| 1-1/2" | 8 (UN) | 2.375" | 0.969" | 2.622" |
| 2" | 8 (UN) | 3.125" | 1.281" | 3.449" |
■ Chemical Composition (per ASTM A320 / A193)
| Grade | C (Max) | Cr | Ni | Mo | Key Stabilizing / Alloying Element |
|---|---|---|---|---|---|
| B8C (347) | 0.08% | 17.0 - 19.0% | 9.0 - 13.0% | - | Niobium (Nb): 10x Carbon Content |
| B8T (321) | 0.08% | 17.0 - 19.0% | 9.0 - 12.0% | - | Titanium (Ti): 5x Carbon Content |
| B8F (303) | 0.15% | 17.0 - 19.0% | 8.0 - 10.0% | - | Sulfur/Selenium: 0.15% Min |
| B8P (305) | 0.12% | 17.0 - 19.0% | 10.5 - 13.0% | - | High Nickel: Drives magnetic transparency |
| B8LN (304LN) | 0.03% | 18.0 - 20.0% | 8.0 - 11.0% | - | Nitrogen (N): 0.10 - 0.16% |
| B8MLN (316LN) | 0.03% | 16.0 - 18.0% | 10.0 - 14.0% | 2.0 - 3.0% | Nitrogen (N): 0.10 - 0.16% |
■ Mechanical Properties (Class 1)
| Grade / Specification | Tensile Strength (Min) | Yield Strength (0.2% Offset) | Elongation | Reduction of Area | Max Hardness |
|---|---|---|---|---|---|
| All Grades Listed (Class 1) | 75,000 psi (515 MPa) | 30,000 psi (205 MPa) | 30% Min | 50% Min | 96 HRB (223 HBW) |
*To ensure absolute ductility at cryogenic temperatures, ASTM A320 fasteners are strictly utilized in their Class 1 (fully annealed) state. Strain-hardening (Class 2) introduces internal stress that compromises Charpy impact toughness and is generally avoided for sub-zero liquid containment.
■ Applicable Standards & Specifications
| Application Type | Bolts & Studs | Nuts | Primary Advantage |
|---|---|---|---|
| LNG / Liquid Oxygen Storage | ASTM A320 | ASTM A194 | Extreme Sub-Zero Impact Toughness |
| Aerospace / High Thermal Cycle | ASTM A320 (B8C/B8T) | ASTM A194 (8C/8T) | Resists sensitization during hot-gas purges |
| Offshore Welded Cryo-Spools | ASTM A320 (B8MLN) | ASTM A194 (8MLN) | Weldable, chloride-resistant, high-yield |
■ The Engineering Nuance: Why Use Specialized Alloys in the Cold?
Engineers often ask why standard A320 B8 (304 SS) isn't sufficient for all cryogenic applications. The answer lies in the dynamic realities of industrial systems:
- Thermal Cycling (B8C / B8T): LNG vaporizers and aerospace engines often cycle between -320°F liquid exposure and +1000°F steam or exhaust gas purges. Standard 304 will sensitize and corrode under these massive thermal swings. Niobium (B8C) and Titanium (B8T) stabilize the alloy for this exact abuse.
- Marine Welding (B8MLN): If a cryogenic pipeline is located on an offshore floating platform (FLNG) and requires welded components, it needs ultra-low carbon (for welding), Moly (for saltwater), and Nitrogen (to restore the yield strength lost to the low carbon). B8MLN solves all three perfectly.
- Magnetic Transparency (B8P): MRI machines and advanced radar systems require liquid helium cooling (-452°F). Standard B8 becomes slightly magnetic under extreme cold and stress. B8P's high nickel content locks the austenite lattice, keeping it entirely non-magnetic.
■ Fastener Types Available
| Fastener Category | Standard and Specialty Types Available | Primary Engineering Function |
|---|---|---|
| Cryogenic Flange Studs | Fully Threaded Stud Bolts, Double-End Studs, Weld Studs. | Provides guaranteed tensioning for ASME B16.5 flanges on highly specialized cryogenic pipelines. |
| Precision Intricate Bolts | Custom CNC Turned Screws, Socket Head Cap Screws (B8F). | B8F (303 SS) allows for the rapid machining of intricate, non-welded instrument housings. |
| Matched Nuts (A194) | Heavy Hex Nuts (Grades 8C, 8T, 8P, 8LN, 8MLN). | Guarantees the entire joint assembly meets identical cryogenic impact and chemical thresholds. |
■ Commercial Supply Chain Dynamics: Why Choose Ananka
The global industrial fastener market requires manufacturing entities capable of blending hyper-scale production volume with microscopic precision. Ananka Fasteners exemplifies the apex of modern industrial hardware manufacturing, servicing over 240 high-value corporate clients spanning more than 40 countries.
- Stringent Global Certification: Ananka operates under an integrated management system certified to ISO 9001:2015, ISO 14001:2015, and ISO 45001:2018. We hold the prestigious PED 2014/68/EU certification for explosive, high-pressure environments.
- Sub-Zero Testing Infrastructure: We maintain advanced, in-house cryogenic testing facilities to perform mandatory Charpy impact testing on specialized A320 batches, ensuring rapid turnaround.
- Customization and Capacity: Utilizing a strict 6-step in-house quality check protocol, we possess the agile manufacturing capacity to rapidly prototype, forge, anneal, test, and ship highly exotic cryogenic fasteners globally.
■ Engineering FAQs
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1. Does ASTM A320 explicitly require impact testing for all austenitic grades?
Technically, ASTM A320 exempts standard austenitic stainless steels (like 304 and 316) from impact testing down to -320°F. However, for specialized grades or when required by stringent corporate offshore/LNG specifications, mandatory Charpy testing is enforced. We execute impact testing whenever dictated by client specification. -
2. Why is ASTM A320 B8F (303 SS) risky for cryogenic pressure vessels?
Grade B8F relies on Sulfur or Selenium to break up metal chips during rapid CNC machining. These chemical "inclusions" act as massive stress concentrators. While it makes the bolt easy to manufacture, it destroys the metal's impact toughness. It should never be used in pressure-containing or heavy-shock cryogenic systems, which is why it is often heavily restricted by engineers despite existing in the specification. -
3. Is NACE MR0175 compliance possible with these specialty A320 grades?
Yes. By specifying the "A" suffix (e.g., B8CA, B8MLNA), the fasteners are guaranteed to undergo post-fabrication solution annealing. This removes all cold-working stress and caps the hardness below the NACE threshold, making them safe for cryogenic sour-gas (H2S) exposure.