COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF ASTM A194 GRADE 8MLN NUTS
ASTM A194 Grade 8MLN specifies premium austenitic stainless steel nuts manufactured from AISI Type 316LN. 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, combined with intentional additions of Molybdenum and Nitrogen.
The molybdenum (2.00% - 3.00%) significantly enhances resistance to chloride pitting and crevice corrosion compared to standard 304 stainless. To compensate for the mechanical yield strength that is naturally lost when reducing carbon levels, Grade 8MLN utilizes Nitrogen as a powerful solid-solution strengthening agent. This stabilizes the austenitic matrix, ensuring the material maintains exceptional tensile strength and toughness across a wide array of aggressive environments, including severe cryogenic applications.
■ Product Overview & Specifications
| Material Classification | Nitrogen-Strengthened Austenitic Stainless Steel (Type 316LN) |
|---|---|
| UNS Designation | S31653 |
| Microstructure | Austenitic (Low-Carbon, Nitrogen-Stabilized) |
| 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 |
■ Proprietary Datasheet Download (GATED)
ASTM A194 Grade 8MLN — 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 B8MLN assemblies.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
Material traceability is the backbone of safety in high-pressure and critical 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
| Carbon (C) | Manganese (Mn) | Chromium (Cr) | Nickel (Ni) | Molybdenum (Mo) | Phosphorus (P) | Sulfur (S) | Silicon (Si) |
|---|---|---|---|---|---|---|---|
| 0.030 Max | 2.00 Max | 16.0 – 18.0 | 10.0 – 13.0 | 2.00 – 3.00 | 0.045 Max | 0.030 Max | 1.00 Max |
■ Mechanical Properties
| Mechanical Property | Grade 8MLN Limits |
|---|---|
| Hardness Limit (Rockwell) | 32 HRC Maximum |
| Proof Load | Dependent on Size |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASME Standard | SA194 Grade 8MLN |
| Common Trade Name | Type 316LN Stainless Nuts, Nitrogen-Strengthened 316L |
| European Equivalent | EN 1.4406 / X2CrNiMoN17-11-2 |
■ Applications & Industries
- Marine & Coastal Engineering: Structural fastening and piping systems exposed directly to seawater and severe salt-spray environments where pitting resistance is vital.
- 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.
- Petrochemical Processing: Pressure vessels and transfer lines handling aggressive organic acids and moderately high concentrations of chlorides.
■ Compatible Fastener Assemblies
| Internal Threads (A194 Gr 8MLN) | Mating Bolts (A193 Gr B8MLN) | Mating Studs (A193 Gr B8MLN) |
|---|---|---|
| Grade 8MLN Heavy Hex Nuts | ASTM A193 Grade B8MLN Hex Bolts | A193 Grade B8MLN Fully Threaded Studs |
■ Torque & Installation Guidelines
Due to the fully austenitic nature of 8MLN, severe thread galling is a major 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 "MLN" designation mean?
The letters indicate the precise metallurgical profile of the nut: M indicates the presence of Molybdenum (for pitting resistance). L indicates Low Carbon (capped at 0.030% to prevent sensitization). N indicates a precise Nitrogen addition, which powerfully strengthens the steel matrix from within to compensate for the lower carbon content.
2. How is Grade 8MLN different from standard Grade 8M (Type 316)?
Standard Grade 8M (Type 316) has a higher allowable carbon limit, making it susceptible to chromium carbide precipitation if exposed to high temperatures during welding. Grade 8MLN lowers the carbon to solve this problem, but adds Nitrogen so the nut retains the high mechanical yield strength required for heavy pressure piping systems.
3. Why specify Grade 8MLN for Cryogenics?
Unlike standard carbon steel which becomes brittle and shatters at ultra-low temperatures, austenitic stainless steels remain ductile. The addition of Nitrogen in Type 316LN (Grade 8MLN) specifically enhances microstructural stability, ensuring the fasteners maintain immense impact toughness in environments like liquid nitrogen (-320°F) or LNG processing.
