COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF ASTM A194 GRADE 9C NUTS
ASTM A194 Grade 9C specifies premium super-austenitic stainless steel nuts, widely recognized in the industry under the UNS N08367 designation (often referred to commercially as AL-6XN®). This ultra-high-performance alloy is heavily enriched with Chromium (20-22%), Nickel (23.5-25.5%), and Molybdenum (6-7%), while maintaining a strictly controlled low-carbon profile. This elite chemistry imparts extraordinary resistance to chloride-induced pitting, crevice corrosion, and stress corrosion cracking (SCC), making it a superior alternative to standard 300-series alloys in highly aggressive environments.
Standard Grade 9C fasteners are expertly machined from solution-treated bar stock. Because they do not undergo a post-machining anneal (unlike the "A" designated 9CA), they are permitted a higher maximum hardness limit (up to 32 HRC). This provides an exceptional balance of extremely high tensile strength and world-class chemical resistance, making them ideal for high-pressure, severe-corrosion piping systems where maximum mechanical yield is required.
■ Product Overview & Specifications
| Material Classification | Super Austenitic Stainless Steel (6% Moly Grade) |
|---|---|
| UNS Designation | N08367 |
| Microstructure | Fully Austenitic |
| Magnetic State | Non-Magnetic (May show slight magnetism from cold-working) |
| Density | ~8.06 g/cm³ (0.291 lb/in³) |
| Size Range | Metric: M6 to M100 | Imperial: 1/4" to 4" |
| Strengthening Method | Carbide Solution Treated Bar Stock |
■ Proprietary Datasheet Download (GATED)
ASTM A194 Grade 9C — Complete Technical Datasheet
Contains detailed proof load thresholds, dimensional tolerances for ASME B18.2.2 standard and heavy hex profiles, and critical high-temperature torque values.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
Material traceability is the backbone of safety in high-pressure 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, and proof load tests).
- EN 10204 Type 3.2: For critical commercial, offshore, or chemical applications, we facilitate third-party witness testing.
■ Chemical Composition
| Carbon (C) | Manganese (Mn) | Phosphorus (P) | Sulfur (S) | Silicon (Si) | Chromium (Cr) | Molybdenum (Mo) | Nickel (Ni) |
|---|---|---|---|---|---|---|---|
| 0.030 Max | 2.00 Max | 0.040 Max | 0.030 Max | 1.00 Max | 20.0 – 22.0 | 6.0 – 7.0 | 23.5 – 25.5 |
■ Mechanical Properties
| Mechanical Property | Grade 9C Limits |
|---|---|
| Hardness Limit (Rockwell) | 32 HRC Maximum |
| Proof Load | Dependent on Size |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASME Standard | SA194 Grade 9C |
| Common Trade Name | AL-6XN®, 6% Moly Nuts, UNS N08367 |
| European Equivalent | EN 1.4529 / X1NiCrMoCuN25-20-7 (Approximate) |
■ Applications & Industries
- Marine & Offshore: Seawater cooling systems, heat exchangers, and offshore platform structural fastening where chloride-induced pitting is a severe threat.
- Chemical Processing: Flue gas desulfurization (FGD) scrubbers, tall oil distillation columns, and aggressive acid processing lines.
- Desalination Plants: High-pressure reverse osmosis (RO) systems handling highly concentrated brine solutions.
■ Compatible Fastener Assemblies
| Internal Threads (A194 Gr 9C) | Mating Bolts (Equivalent Alloy) | Mating Studs (Equivalent Alloy) |
|---|---|---|
| Grade 9C Heavy Hex Nuts | UNS N08367 Heavy Hex Bolts | UNS N08367 Fully Threaded Studs |
■ Torque & Installation Guidelines
Due to the incredibly high alloy content and the fully austenitic nature of 9C, thread galling is a significant risk under high clamping loads. Premium, heavy-duty anti-seize lubrication (such as nickel or molybdenum-disulfide based pastes) is absolutely mandatory for installation.
| Nominal Diameter | Threads Per Inch (UNC) | Target Torque — Lubricated (ft-lbs) |
|---|---|---|
| 1/2" | 13 | 45 |
| 5/8" | 11 | 90 |
| 3/4" | 10 | 150 |
| 1" | 8 | 350 |
■ Frequently Asked Questions
1. What is the difference between Grade 9C and Grade 9CA?
Both utilize the identical UNS N08367 super-austenitic chemistry. A standard Grade 9C component may retain localized cold-work stresses from being machined, affording it a higher allowable hardness limit (up to 32 HRC). Grade 9CA is an alternate designation where the component is solution-annealed after all machining is completely finished, eliminating all stresses to guarantee a strictly non-magnetic state with a lower maximum hardness (90 HRB max).
2. Is Grade 9C a Duplex stainless steel?
No, it is a fully Super Austenitic stainless steel alloy. While its corrosion resistance is often compared to Super Duplex grades, its high Nickel (23.5-25.5%) fully austenitic microstructure gives it superior ductility and toughness across extreme temperature ranges, preventing the embrittlement issues that can occasionally affect duplex steels.
