COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF ASTM A194 GRADE 8LNA NUTS
ASTM A194 Grade 8LNA specifies premium austenitic stainless steel nuts manufactured from AISI Type 304LN. This advanced alloy is engineered with an exceptionally low carbon profile (Max 0.030%) to prevent sensitization (chromium carbide precipitation) during high-temperature service or heavy welding processes.
What sets Grade 8LNA apart is the crucial "A" designation, which mandates that the fasteners undergo a final Carbide Solution Treatment (full annealing) after all forging, machining, and thread-tapping operations are completed. To compensate for the mechanical yield strength that is naturally lost when reducing carbon levels, Grade 8LNA utilizes the intentional metallurgical addition of Nitrogen. Nitrogen acts as a powerful solid-solution strengthening agent, while the post-machining annealing ensures a fully softened, strictly non-magnetic state (60-90 HRB) that drastically minimizes susceptibility to Stress Corrosion Cracking (SCC) and maintains extraordinary toughness in severe cryogenic applications.
■ Product Overview & Specifications
| Material Classification | Nitrogen-Strengthened Austenitic Stainless Steel (Type 304LN - Annealed) |
|---|---|
| UNS Designation | S30453 |
| Microstructure | Austenitic (Low-Carbon, Nitrogen-Stabilized, Post-Annealed) |
| Magnetic State | Strictly Non-Magnetic (Annealed post-machining) |
| Density | ~8.00 g/cm³ (0.289 lb/in³) |
| Size Range | Metric: M6 to M100 | Imperial: 1/4" to 4" |
| Strengthening Method | Nitrogen Strengthening & Full Solution Annealing After Machining |
■ Proprietary Datasheet Download (GATED)
ASTM A194 Grade 8LNA — Complete Technical Datasheet
Contains detailed proof load thresholds, dimensional tolerances for ASME B18.2.2 standard and heavy hex profiles, and precise galling-prevention torque values for A193 B8LNA assemblies.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
Material traceability is the backbone of safety in high-pressure and extreme-temperature environments. Every lot shipped by Ananka is accompanied by fully authenticated documentation mapping back to raw steel mill certificates.
- EN 10204 Type 3.1: Issued by our independent quality department, providing specific heat-traceable test results (actual chemical analysis, mechanical test results, hardness limits, and proof load tests).
- EN 10204 Type 3.2: For critical aerospace, cryogenic, or high-temperature petrochemical applications, we facilitate third-party witness testing.
■ Chemical Composition
The stringent 0.030% maximum carbon limit ensures absolute resistance to intergranular corrosion. The Chromium (18.0 - 20.0%) and Nickel (8.0 - 11.0%) provide an impenetrable baseline austenitic matrix for extreme operational environments.
| Carbon (C) | Manganese (Mn) | Chromium (Cr) | Nickel (Ni) | Phosphorus (P) | Sulfur (S) | Silicon (Si) |
|---|---|---|---|---|---|---|
| 0.030 Max | 2.00 Max | 18.0 – 20.0 | 8.0 – 11.0 | 0.045 Max | 0.030 Max | 1.00 Max |
■ Mechanical Properties
Because Grade 8LNA is explicitly annealed after all machining to remove localized cold-work hardening, ASTM tightly controls the hardness range to guarantee the matrix remains fully softened and stress-free.
| Mechanical Property | Grade 8LNA (Annealed) Limits |
|---|---|
| Hardness Limit (Rockwell) | 60 - 90 HRB Maximum |
| Proof Load | Dependent on Size |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASME Standard | SA194 Grade 8LNA |
| Common Trade Name | Type 304LN Stainless Nuts (Annealed), Nitrogen-Strengthened 18-8 |
| European Equivalent | EN 1.4311 / X2CrNiN18-10 |
■ Applications & Industries
- Cryogenic Engineering: LNG (Liquefied Natural Gas) terminals and liquid oxygen systems where Nitrogen alloying maintains incredibly high toughness and prevents embrittlement at sub-zero temperatures.
- Heavy Welded Assemblies: Structural joints where massive welding operations take place, requiring absolute immunity to heat-affected zone (HAZ) sensitization.
- Chemical Processing: Pressure vessels and transfer lines handling aggressive chemicals where low carbon is required and internal stresses must be eliminated to prevent SCC.
■ Compatible Fastener Assemblies
| Internal Threads (A194 Gr 8LNA) | Mating Bolts (A193 Gr B8LNA) | Mating Studs (A193 Gr B8LNA) |
|---|---|---|
| Grade 8LNA Heavy Hex Nuts | ASTM A193 Grade B8LNA Hex Bolts | A193 Grade B8LNA Fully Threaded Studs |
■ Torque & Installation Guidelines
Due to the fully softened austenitic nature of 8LNA, severe thread galling is a prominent risk under high clamping loads. Premium high-performance anti-seize lubrication is absolutely mandatory for safe installation and future unbolting.
| Nominal Diameter | Threads Per Inch (UNC) | Target Torque — Lubricated (ft-lbs) |
|---|---|---|
| 1/2" | 13 | 30 |
| 5/8" | 11 | 60 |
| 3/4" | 10 | 100 |
| 1" | 8 | 250 |
■ Frequently Asked Questions
1. What does the "A" stand for in Grade 8LNA?
The "A" indicates that the component has been Annealed after all manufacturing and machining processes are complete. This removes all internal cold-work stresses generated during machining, ensuring the part is fully softened and strictly non-magnetic to maximize resistance against Stress Corrosion Cracking.
2. How does Grade 8LNA compare to Grade 8LN?
While both share the exact same chemical composition (Low carbon and Nitrogen strengthened), Grade 8LN may retain residual stress and slight magnetism from the manufacturing process. Grade 8LNA guarantees that these stresses are completely removed through post-machining full solution annealing.
3. Why is the hardness specifically capped at 90 HRB?
Because the "A" specification is designed to eliminate internal stress through annealing, the hardness is restricted between 60 and 90 HRB. If a nut measures harder than 90 HRB, it strongly indicates that residual cold-work stress remains from the machining or threading process, meaning the part is not fully annealed and fails the specification.
