COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF ASTM A194 GRADE 8CLNA NUTS
ASTM A194 Grade 8CLNA specifies an exceptionally advanced, high-performance austenitic stainless steel nut, corresponding to AISI Type 347LN. This highly specialized grade combines three distinct metallurgical advantages: Columbium (Niobium) stabilization, an ultra-low carbon profile (0.005% - 0.020%), and Nitrogen strengthening to provide unparalleled resistance to sensitization and intergranular corrosion.
What sets Grade 8CLNA apart is the crucial "A" designation. This mandates that the fasteners undergo a final Carbide Solution Treatment (full annealing) after all forging, machining, and thread-tapping operations are completed. This vital thermal process eliminates any residual cold-work stresses introduced during manufacturing, ensuring a fully softened, strictly non-magnetic state (60-90 HRB). This restoration of the matrix maximizes resistance to Stress Corrosion Cracking (SCC) in highly aggressive applications, making it the ultimate choice for heavy welded assemblies and extreme thermal cycling.
■ Product Overview & Specifications
| Material Classification | Columbium-Stabilized, Nitrogen-Strengthened Austenitic Stainless Steel (Type 347LN - Annealed) |
|---|---|
| UNS Designation | S34751 |
| Microstructure | Austenitic (Low-Carbon, Stabilized, Nitrogen-Strengthened, 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 8CLNA — 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 B8CLNA assemblies.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
Material traceability is the backbone of safety in high-pressure and high-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, offshore, or high-temperature petrochemical applications, we facilitate third-party witness testing.
■ Chemical Composition
The highly precise chemistry of Grade 8CLNA provides unparalleled metallurgical stability. The stringent 0.020% maximum carbon limit ensures absolute resistance to intergranular corrosion, while Chromium and Nickel provide an impenetrable baseline austenitic matrix for extreme operational environments.
| Carbon (C) | Manganese (Mn) | Chromium (Cr) | Nickel (Ni) | Phosphorus (P) | Sulfur (S) | Silicon (Si) |
|---|---|---|---|---|---|---|
| 0.005 – 0.020 | 2.00 Max | 17.0 – 19.0 | 9.0 – 13.0 | 0.045 Max | 0.030 Max | 1.00 Max |
■ Mechanical Properties
Because Grade 8CLNA 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 8CLNA (Annealed) Limits |
|---|---|
| Hardness Limit (Rockwell) | 60 - 90 HRB Maximum |
| Proof Load | Dependent on Size |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASME Standard | SA194 Grade 8CLNA |
| Common Trade Name | Type 347LN Stainless Nuts (Annealed), Columbium-Stabilized Low-Carbon |
| European Equivalent | EN 1.4546 / X5CrNiNb18-10 (Approximate mapping for 347 family) |
■ Applications & Industries
- Heavy Welded Assemblies: Structural joints where massive welding operations take place, requiring absolute immunity to heat-affected zone (HAZ) sensitization.
- Petrochemical Refining: Fasteners for high-temperature distillation columns and aggressive flare stack systems where standard 300-series steel degrades.
- Aerospace & Power Generation: Radiant superheaters, engine manifolds, and boiler tubes operating continuously in high-temperature, severe oxidation environments.
■ Compatible Fastener Assemblies
| Internal Threads (A194 Gr 8CLNA) | Mating Bolts (A193 Gr B8CLNA) | Mating Studs (A193 Gr B8CLNA) |
|---|---|---|
| Grade 8CLNA Heavy Hex Nuts | ASTM A193 Grade B8CLNA Hex Bolts | A193 Grade B8CLNA Fully Threaded Studs |
■ Torque & Installation Guidelines
Due to the fully softened and high-nickel austenitic nature of 8CLNA, thread galling is a prominent risk under high clamping loads—especially in high-temperature service applications. Premium, high-temperature anti-seize lubrication (such as nickel-based paste) is absolutely mandatory for installation.
| 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 8CLNA?
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 8CLNA compare to Grade 8CLN?
While both share the exact same chemical composition (Columbium stabilized, ultra-low carbon, and Nitrogen strengthened), Grade 8CLN may retain residual stress and slight magnetism from the manufacturing process. Grade 8CLNA guarantees that these stresses are 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.
