ASTM A193 GRADE B8CLN & B8CLNA BOLTS — DATASHEET, DIMENSIONS & MECHANICAL PROPERTIES
Ananka Fasteners is a premier global manufacturer and supplier of ASTM A193 Grade B8CLN and B8CLNA Fasteners. Forged from ultra-premium AISI 347LN austenitic stainless steel (UNS S34751), these highly specialized fasteners represent the absolute pinnacle of high-temperature welding metallurgy. They are engineered to solve the most complex structural challenges in extreme thermal environments.
This alloy combines three elite chemical strategies: Niobium (Columbium) stabilization ("C") to guarantee high-temperature creep strength, an ultra-low Carbon limit ("L" ≤ 0.030%) to ensure total immunity to weld-decay and sensitization, and a precise Nitrogen charge ("N") to restore and elevate the yield strength lost by removing the carbon. While Grade B8CLN undergoes standard carbide solution treatment, the B8CLNA designation demands strict post-fabrication annealing to eradicate all residual stresses and cap the hardness at 90 HRB for severe NACE MR0175 compliance. All B8CLN/B8CLNA components are strictly supported by EN 10204 Type 3.1 Material Test Certificates (MTC).
■ Proprietary Datasheet Download
For lead welding metallurgists, thermal dynamics engineers, and NACE compliance auditors requiring empirical high-temperature creep resistance data, weld-decay profiles, and interstitial nitrogen stress models for ASTM A193 B8CLN/B8CLNA, the complete technical datasheet must be accessed.
ASTM A193 B8CLN / B8CLNA — Complete Technical Yield & Weldability Datasheet
Contains empirical data for stress simulations, ASTM A262 intergranular corrosion test results, and high-temperature creep thresholds. Corporate credentials required.
⬇ ACCESS SECURE DATASHEET PORTAL■ Mill Test Certificate (MTC) Integration
Because the defining characteristics of B8CLN/B8CLNA rely on an extremely complex balance of elemental suppressants (Carbon) and enhancers (Nitrogen + Niobium), the EN 10204 3.1 Mill Test Certificate (MTC) is the absolute proof of component integrity. Ananka Fasteners’ MTCs for B8CLN explicitly guarantee:
- Triple-Chemistry Verification: Empirical spectrography proving the Carbon is strictly capped ≤ 0.030%, Niobium is ≥ 10x Carbon, and Nitrogen falls within the critical 0.10% to 0.16% structural window.
- Mechanical Baseline Proof: Destructive test verification proving the nitrogen compensation successfully hit the 30 ksi minimum yield threshold without cold-working.
- Post-Fabrication Verification (B8CLNA): An explicit statement confirming that carbide solution treatment was performed after all machining and threading.
- Hardness Limit Proof (B8CLNA): Guaranteed laboratory results proving the batch hardness is fully capped below 90 HRB for severe NACE MR0175 compliance.
■ Material Specifications (ASTM A193 B8CLN / B8CLNA)
| Material Type | Low-Carbon, Nitrogen-Strengthened, Niobium-Stabilized Austenitic Stainless Steel |
|---|---|
| UNS Number | S34751 |
| Corresponding Nut Grade | ASTM A194 Grade 8CLN (for B8CLN) / Grade 8CLNA (for B8CLNA) |
| Density | 8.00 g/cm³ (8,000 kg/m³) |
| Strengthening Mechanism | Interstitial Solid Solution Strengthening (Nitrogen offsets Carbon loss) |
| Magnetic Permeability | Non-Magnetic (B8CLNA) | Weakly Magnetic at thread roots (B8CLN Class 1) |
| Pitting Resistance (PREN) | 18.0 - 20.0 |
■ 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 massive compressive loads across heavily welded flanged joints in critical thermal infrastructure.
| 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 A193)
| Grade | C (Max) | Cr | Ni | Nb (Niobium) + Ta | N (Nitrogen) | Mn (Max) | Si (Max) |
|---|---|---|---|---|---|---|---|
| B8CLN / B8CLNA (S34751) | 0.030% | 17.0 - 19.0% | 9.0 - 13.0% | 10x (C%) Min - 1.00% Max | 0.10 - 0.16% | 2.00% | 1.00% |
■ Mechanical Properties
| Grade / Class | Tensile Strength (Min) | Yield Strength (0.2% Offset) | Elongation | Reduction of Area | Max Hardness |
|---|---|---|---|---|---|
| B8CLN (Class 1) | 75,000 psi (515 MPa) | 30,000 psi (205 MPa) | 30% Min | 50% Min | 96 HRB (223 HBW) |
| B8CLNA (Class 1A) | 75,000 psi (515 MPa) | 30,000 psi (205 MPa) | 30% Min | 50% Min | 90 HRB (192 HBW) |
*Unlike Grade B8N (which uses Nitrogen to push yield strength to 35 ksi), the Nitrogen in B8CLN is primarily utilized to restore the baseline yield firmly to 30 ksi, compensating for the severe physical weakening effect of the ultra-low carbon chemistry necessary for safe, heavy welding.
■ Applicable Standards & Specifications
| Application Type | Bolts & Studs | Nuts | Grade Designation |
|---|---|---|---|
| High-Temp Heavy Weldments | ASTM A193 | ASTM A194 | B8CLN / 8CLN |
| NACE / Welded Thermal Systems | ASTM A193 | ASTM A194 | B8CLNA / 8CLNA |
| Cryogenic Aviation Assemblies | ASTM A320 | ASTM A194 | B8CLN / 8CLN |
■ The Engineering Synthesis: Solving the High-Temp Weld Trilemma
Thermal structural engineers face a complex "Trilemma" when specifying fasteners that must be permanently welded to extremely hot pressure vessels: they need Niobium stabilization (for creep resistance), high yield strength, and total immunity to weld-decay.
Standard B8C (347) has the creep strength and yield, but can still suffer mild sensitization in very heavy multi-pass welds. B8CL (347L) solves the weld-decay issue with low carbon, but physically weakens the bolt, often failing strict ASME flange pressure tests due to inadequate yield strength. B8T (321) relies on Titanium, which burns off across a welding arc, losing its stabilization.
Grade B8CLN is the ultimate solution. It utilizes Niobium (which transfers smoothly across a welding arc), retains pristine weldability via the "L" grade (zero sensitization), and uses Nitrogen solid-solution strengthening to ensure the fastener maintains the robust 30 ksi yield limit. This allows engineers to safely arc-weld studs directly into high-temperature catalytic crackers without requiring post-weld heat treatment.
■ Fastener Types Available
| Fastener Category | Standard and Specialty Types Available | Primary Engineering Function |
|---|---|---|
| Thermal Weld Studs | Weld Studs, Tap End Studs, Fully Threaded Spool Rods. | Designed to be permanently arc-welded into extreme high-temperature refining housings. |
| Heavy Industrial Fasteners | Heavy Hex Bolts, Hex Cap Screws, U-Bolts. | High-torque structural fastening for aerospace exhaust and heat exchangers requiring absolute sensitization immunity. |
| Matched Nuts (A194) | Heavy Hex Nuts (Grade 8CLN / 8CLNA). | Strictly matched chemistry prevents galvanic corrosion and unequal thermal expansion across the flanged joint. |
■ 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.
- Exotic Alloy Mastery: Our deep expertise in highly engineered welding and thermal alloys extends far beyond 347LN; we actively forge and machine superalloys including Inconel 718, Nimonic, Hastelloy C276, and Titanium Grade 5.
- 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 specialized fasteners globally.
■ Engineering FAQs
-
1. Is ASTM A193 B8CLNA compliant with NACE MR0175 for sour gas?
Yes, flawlessly. The "A" designation guarantees a post-fabrication solution anneal, capping the hardness at a maximum of 90 HRB and removing all cold-working stress. Combined with the low-carbon chemistry and Niobium stabilization, this makes B8CLNA exceptionally resistant to sulfide stress cracking (SSC) in high-temperature H2S environments. -
2. Why is Niobium (B8CLN) better for welding than Titanium (B8T)?
Titanium is highly reactive and tends to volatilize (burn off) when exposed to the intense heat of an electric welding arc, leaving the heat-affected zone unstabilized. Niobium (Columbium) is vastly more stable and transfers across the welding arc cleanly, guaranteeing the entire weldment remains fully stabilized against carbide precipitation. -
3. Does the addition of Nitrogen make the weld brittle?
No. In austenitic stainless steels like 347LN, Nitrogen acts as a powerful austenite stabilizer. It actually refines the grain structure in the heat-affected zone during welding, improving both the mechanical toughness and localized corrosion resistance of the weldment.