ASTM A193 GRADE B8N & B8NA BOLTS — DATASHEET, DIMENSIONS & MECHANICAL PROPERTIES

Ananka Fasteners is a premier global manufacturer and supplier of ASTM A193 Grade B8N and B8NA Fasteners. Forged from AISI 304N austenitic stainless steel (UNS S30451), these fasteners utilize a critical metallurgical mechanism known as interstitial solid solution strengthening. By meticulously alloying the standard 304 matrix with Nitrogen, the material achieves a significantly higher baseline yield and tensile strength without sacrificing ductility, fracture toughness, or requiring destructive cold-working.

While Grade B8N undergoes standard carbide solution treatment, the B8NA designation strictly mandates post-fabrication annealing. This final thermal cycle eliminates all residual stresses induced during thread rolling, legally capping the hardness at 90 HRB. This ensures B8NA fasteners are fully immune to stress-corrosion cracking (SCC) while still delivering the elevated strength characteristics provided by the nitrogen charge. All our B8N/B8NA studs, heavy hex bolts, and threaded rods are strictly supported by EN 10204 Type 3.1 Material Test Certificates (MTC).

For lead piping engineers, cryogenic specialists, and NACE compliance auditors requiring empirical nitrogen solid-solution yield curves and impact toughness data for ASTM A193 B8N/B8NA, the complete technical datasheet is available via our secure portal.

Because the defining characteristic of B8N/B8NA is a precise gaseous alloy addition, the EN 10204 3.1 Mill Test Certificate (MTC) is the essential, legally binding proof of component integrity. Ananka Fasteners’ MTCs for B8N explicitly guarantee:

• Nitrogen Verification: Empirical spectrography proving the Nitrogen concentration falls strictly within the critical 0.10% to 0.16% performance window.
• Elevated Mechanical Proof: Destructive test verification proving the batch meets the elevated 35 ksi minimum yield and 80 ksi minimum tensile requirements.
• Post-Fabrication Verification (B8NA): An explicit statement confirming that carbide solution treatment was performed after all threading, ensuring absolute stress relief.
• Hardness Limit Proof (B8NA): Guaranteed laboratory results proving the batch hardness is fully capped below 90 HRB for severe service compliance.

Standard dimensional specifications for ASME B18.2.1 Heavy Hex Bolts. The heavy hex profile provides the expanded bearing footprint necessary to distribute the elevated compressive loads generated by nitrogen-strengthened fastening systems.

*Notice the mechanical advantage: Standard B8 (304) yields at 30,000 psi and 75,000 psi tensile. The addition of nitrogen in B8N elevates the yield to 35,000 psi and tensile to 80,000 psi, all while remaining in the fully annealed, highly ductile Class 1 state.

When a piping engineer needs higher yield strength than standard B8 Class 1 (30 ksi) can provide, they generally have two choices: cold-working or chemistry.

The Cold-Working Route (Class 2): Strain-hardening a 304 bolt pushes the yield strength to 100 ksi. However, this process dramatically reduces the fastener's ductility, introduces internal stress, and renders the bolt non-compliant for highly corrosive sour gas (H2S) environments due to a high hardness profile.

The Chemistry Route (B8N/B8NA): By utilizing Nitrogen strengthening, engineers achieve an immediate 16% increase in baseline yield strength (to 35 ksi) without inducing a single pound of mechanical stress. The bolt retains pristine ductility, absolute structural stability, and, in the case of B8NA, fully complies with the strict 90 HRB hardness caps mandated by NACE MR0175 for sour service.

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 molecularly strengthened alloys extends far beyond 304N; we actively forge and machine superalloys including Inconel 718, Nimonic, Hastelloy C276, Monel, 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.

• 1. Is ASTM A193 B8NA compliant with NACE MR0175 for sour gas?
  Yes, absolutely. The "A" designation signifies post-fabrication annealing. Because the final thermal cycle removes all residual thread-rolling stress and strictly caps the hardness at 90 HRB, B8NA is fully compliant with NACE restrictions for deployment in H2S (sour gas) environments, while still offering higher yield strength than standard B8A.
• 2. Does the addition of Nitrogen negatively impact corrosion resistance?
  Quite the opposite. Nitrogen actually acts synergistically with Chromium and Molybdenum to actively improve localized pitting and crevice corrosion resistance. This is why Nitrogen is heavily utilized in advanced duplex and super-austenitic marine alloys.
• 3. Is B8N suitable for cryogenic temperatures?
  Yes. Nitrogen-strengthened austenitic steels retain incredible toughness at sub-zero temperatures. Because it remains fully austenitic without the reliance on strain-hardening, it will not undergo a brittle fracture transition, making it ideal for LNG storage and processing facilities.