COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF ASTM A194 GRADE 8CLN NUTS
ASTM A194 Grade 8CLN 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.
The addition of Columbium acts as a stabilizing agent to prevent chromium carbide precipitation (sensitization) during exposure to severe high-temperature ranges (800°F to 1500°F). By strictly capping the carbon at a maximum of 0.020%, the risk of intergranular corrosion during heavy welding or long-term thermal cycling is virtually eliminated. To counteract the natural loss of yield strength associated with low carbon levels, Nitrogen is intentionally alloyed into the matrix, acting as a powerful solid-solution strengthener that ensures these components maintain immense structural integrity in high-pressure piping assemblies.
■ Product Overview & Specifications
| Material Classification | Columbium-Stabilized, Nitrogen-Strengthened Austenitic Stainless Steel (Type 347LN) |
|---|---|
| UNS Designation | S34751 |
| Microstructure | Austenitic (Low-Carbon, Stabilized, Nitrogen-Strengthened) |
| Magnetic State | Non-Magnetic (May exhibit slight magnetism from cold-working) |
| Density | ~8.00 g/cm³ (0.289 lb/in³) |
| Size Range | Metric: M6 to M100 | Imperial: 1/4" to 4" |
| Strengthening Method | Nitrogen Solid-Solution Strengthening & Columbium Stabilization |
■ Proprietary Datasheet Download (GATED)
ASTM A194 Grade 8CLN — 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 B8CLN 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 8CLN 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
| Mechanical Property | Grade 8CLN Limits |
|---|---|
| Hardness Limit (Rockwell) | 32 HRC Maximum |
| Proof Load | Dependent on Size |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASME Standard | SA194 Grade 8CLN |
| Common Trade Name | Type 347LN Stainless Nuts, Columbium-Stabilized Low-Carbon |
| European Equivalent | EN 1.4546 / X5CrNiNb18-10 (Approximate mapping for 347 family) |
■ Applications & Industries
- Petrochemical Refining: Fasteners for Fluid Catalytic Cracking (FCC) units, 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.
- Heavy Welded Assemblies: Structural joints where massive welding operations take place, requiring absolute immunity to heat-affected zone (HAZ) sensitization.
■ Compatible Fastener Assemblies
| Internal Threads (A194 Gr 8CLN) | Mating Bolts (A193 Gr B8CLN) | Mating Studs (A193 Gr B8CLN) |
|---|---|---|
| Grade 8CLN Heavy Hex Nuts | ASTM A193 Grade B8CLN Hex Bolts | A193 Grade B8CLN Fully Threaded Studs |
■ Torque & Installation Guidelines
Due to the high-nickel austenitic nature of 8CLN, 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 "CLN" designation mean?
This nomenclature breaks down the three critical metallurgical advantages of the alloy: C stands for Columbium (Niobium) stabilization, which prevents carbide precipitation at high temperatures. L stands for extremely Low Carbon (capped at 0.020%) for superior weldability. N represents Nitrogen addition, which recovers the mechanical yield strength that is naturally reduced when carbon is minimized.
2. How does Grade 8CLN compare to Grade 8C?
Grade 8C (Type 347) relies solely on Columbium/Niobium stabilization and has a standard carbon limit. Grade 8CLN (Type 347LN) utilizes that same Columbium stabilization but drastically lowers the carbon to 0.020% max for even greater security against intergranular corrosion, while adding Nitrogen to ensure it meets the same high-tensile pressure bolting standards.
3. Is Grade 8CLN suitable for sub-zero cryogenic environments?
Yes. Like all nitrogen-alloyed austenitic stainless steels, Grade 8CLN retains extraordinary ductility and impact toughness at cryogenic temperatures without becoming brittle, making it an excellent dual-use alloy for both extreme heat and extreme cold.
