ASTM A193 GRADE B8A BOLTS — DATASHEET, DIMENSIONS & MECHANICAL PROPERTIES
Ananka Fasteners is a global leader in the manufacturing and supply of ASTM A193 Grade B8A Fasteners. Manufactured from high-purity AISI 304 austenitic stainless steel (UNS S30400), the "A" designation represents a critical metallurgical distinction: these fasteners undergo a strict carbide solution treatment (annealing) after all heading, machining, and thread rolling processes are complete.
This post-fabrication thermal processing ensures the complete eradication of any localized strain-hardening or residual stresses induced during manufacturing. The result is a fastener with maximum ductility, an ultra-low hardness cap (90 HRB max), and absolute immunity to stress-corrosion cracking (SCC), making B8A the premier choice for hydrogen sulfide (H2S) environments, NACE MR0175 compliance, and critical pressure vessel applications. All B8A components are certified with EN 10204 Type 3.1 Material Test Certificates (MTC).
■ Proprietary Datasheet Download
For lead piping engineers, NACE compliance auditors, and QA officers requiring documented proof of thermal cycle parameters and mechanical yield data for ASTM A193 B8A, our comprehensive technical datasheet is available via our secure portal.
ASTM A193 B8A — Complete Technical Yield & Thermal Datasheet
Contains empirical data for stress simulations, NACE MR0175 regulatory compliance audits, and precise heat-treatment parameters. Corporate credentials required.
⬇ ACCESS SECURE DATASHEET PORTAL■ Mill Test Certificate (MTC) Integration
Because the defining characteristic of a B8A fastener is invisible to the naked eye (its internal grain structure and stress profile), the EN 10204 3.1 Mill Test Certificate is the only legal verification of its integrity. Ananka Fasteners’ MTCs for B8A components explicitly detail:
- Post-Fabrication Verification: An explicit statement confirming that the carbide solution treatment was performed after threading and final machining.
- Hardness Testing Results: Empirical laboratory results proving the batch hardness is absolutely below 90 HRB.
- Chemical Spectrography & Traceability: Complete heat number linkage to the original 304 stainless steel melt.
- Mechanical Verification: Verified yield strength (30 ksi min) and tensile strength (75 ksi min) data from destructive batch testing.
■ Material Specifications (ASTM A193 B8A)
| Material Type | Austenitic Stainless Steel (Post-Fabrication Solution Annealed) |
|---|---|
| UNS Number | S30400 |
| Corresponding Nut Grade | ASTM A194 Grade 8A |
| Density | 8.00 g/cm³ (8,000 kg/m³) |
| Service Temperature Limit | Up to 815°C (1500°F) - Dependent on ASME Boiler & Pressure Vessel Codes |
| Magnetic Permeability | Strictly Non-Magnetic (Residual magnetism removed via final anneal) |
| Pitting Resistance (PREN) | 18.0 - 20.0 |
■ Dimensions of Heavy Hex Bolts (ASME B18.2.1)
Dimensional specifications for ASME B18.2.1 Heavy Hex Bolts. Heavy hex heads provide the expanded bearing footprint required to distribute high compressive loads across flanged joints without causing embedment or gasket failure.
| 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 | Mn (Max) | Si (Max) | P (Max) | S (Max) |
|---|---|---|---|---|---|---|---|
| B8A (S30400) | 0.08% | 18.0 - 20.0% | 8.0 - 11.0% | 2.00% | 1.00% | 0.045% | 0.030% |
■ Mechanical Properties
| Diameter Size Range | Tensile Strength (Min) | Yield Strength (0.2% Offset) | Elongation (in 4D) | Reduction of Area | Max Hardness |
|---|---|---|---|---|---|
| All Diameters | 75,000 psi (515 MPa) | 30,000 psi (205 MPa) | 30% Min | 50% Min | 90 HRB (192 HBW) |
*Notice the stringent 90 HRB maximum hardness limit. This is significantly lower than B8 Class 1 (96 HRB), legally ensuring that the threads have not retained any cold-working stresses.
■ Applicable Standards & Specifications
| Application Type | Bolts & Studs | Nuts | Grade Designation |
|---|---|---|---|
| Sour Gas / NACE Compliant | ASTM A193 | ASTM A194 | B8A / 8A |
| Cryogenic High-Stress | ASTM A320 | ASTM A194 | B8A / 8A |
| Heavy Flange Sealing | ASME B16.5 | ASME B18.2.2 | Heavy Hex Profile |
■ Engineering Clarification: B8 Class 1 vs. B8A
The distinction between A193 B8 Class 1 and A193 B8A is one of the most frequently misunderstood concepts in petrochemical piping design.
B8 Class 1 requires the raw steel bar to be carbide solution treated. However, after the bar is machined and the threads are rolled, the cold-working of the threads induces localized stress and slight magnetism, raising the thread surface hardness to a permitted 96 HRB.
B8A requires the fastener to be completely manufactured, threads and all, and then placed into the furnace for carbide solution treatment. This erases all manufacturing stress, capping the hardness at 90 HRB. Engineers mandate B8A specifically when the piping system operates in sour environments (H2S) where even microscopic residual stresses in the thread roots can act as initiation sites for catastrophic stress-corrosion cracking.
■ Fastener Types Available
| Fastener Category | Standard and Specialty Types Available | Primary Engineering Function |
|---|---|---|
| High-Integrity Studs | Fully Threaded Studs, Double-End Studs. | Connecting high-pressure flanges in refineries; completely stress-relieved for sour gas exposure. |
| Heavy Industrial Bolts | Heavy Hex Bolts, Hex Cap Screws. | Direct structural bolting where B8A ductility prevents brittle fracture under extreme shock loads. |
| Matched Nuts (A194 8A) | Heavy Hex Nuts. | Post-fabrication annealed nuts designed to thread perfectly onto B8A studs without galling. |
■ 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 a roster of 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 also hold the prestigious PED 2014/68/EU (Pressure Equipment Directive) certification issued by TÜV Rheinland.
- Furnace Capabilities: Our state-of-the-art continuous atmospheric heat treatment furnaces ensure perfect temperature uniformity during the critical 1900°F post-fabrication anneal required for B8A certification.
- 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 B8A compliant with NACE MR0175 / ISO 15156?
Yes, absolutely. NACE regulations severely limit the hardness of materials used in sour (hydrogen sulfide) gas environments to prevent sulfide stress cracking. The strict 90 HRB maximum hardness cap of B8A makes it fully NACE compliant for these aggressive applications. -
2. If B8A is so corrosion resistant, why isn't it used for everything?
The trade-off for eliminating residual stress is yield strength. Because the B8A is completely annealed, its yield strength is capped at 30,000 psi. In applications where ultra-high clamping force is required and SCC is not a risk, engineers will opt for B8 Class 2 (strain-hardened), which offers up to 100,000 psi yield strength. -
3. Can I test a bolt in the field to see if it is B8 or B8A?
Yes, with a simple magnet. A standard B8 Class 1 bolt will exhibit weak magnetism at the thread roots due to cold-working during thread rolling. A true B8A bolt will be completely non-magnetic everywhere, as the final annealing process removes all deformation-induced martensite.