COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF ASTM A194 GRADE 9CA NUTS
ASTM A194 Grade 9CA 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 aggressive environments.
What distinguishes Grade 9CA is the critical "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. This vital thermal process eliminates any residual cold-work stresses, ensuring a fully softened, strictly non-magnetic state (60-90 HRB). This structural restoration maximizes the alloy's resistance to Stress Corrosion Cracking in highly aggressive chemical and marine applications.
■ Product Overview & Specifications
| Material Classification | Super Austenitic Stainless Steel (6% Moly Grade - Annealed) |
|---|---|
| UNS Designation | N08367 |
| Microstructure | Fully Austenitic (Post-Annealed) |
| Magnetic State | Strictly Non-Magnetic (Annealed post-machining) |
| Density | ~8.06 g/cm³ (0.291 lb/in³) |
| Size Range | Metric: M6 to M100 | Imperial: 1/4" to 4" |
| Strengthening Method | Full Solution Annealing After Machining |
■ Proprietary Datasheet Download (GATED)
ASTM A194 Grade 9CA — 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
Because Grade 9CA 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 9CA (Annealed) Limits |
|---|---|
| Hardness Limit (Rockwell) | 60 - 90 HRB Maximum |
| Proof Load | Dependent on Size |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASME Standard | SA194 Grade 9CA |
| Common Trade Name | AL-6XN® (Annealed), 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 stress corrosion cracking 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 9CA) | Mating Bolts (Equivalent Alloy) | Mating Studs (Equivalent Alloy) |
|---|---|---|
| Grade 9CA 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 9CA, 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 does the "A" stand for in Grade 9CA?
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. Why is max hardness capped for 9CA?
Because the "A" specification is designed to eliminate stress through annealing, the hardness is restricted between 60 and 90 HRB. If a nut measures harder than this, it indicates residual cold-work stress remains from the manufacturing process, and it would fail the 9CA specification.
3. Is Grade 9CA 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.