UNS C46400, universally recognized as "Naval Brass," is a specialized, high-strength copper alloy engineered specifically for relentless survival in aggressive marine environments. Fundamentally a 60/40 Copper-Zinc alloy, its defining metallurgical characteristic is the precise, deliberate addition of ~1% Tin (Sn). This critical Tin inclusion acts as a powerful defensive shield against dezincification—a destructive form of galvanic corrosion where seawater leaches the zinc out of standard brasses, leaving behind a brittle, porous copper shell.
Because C46400 features a dual-phase (alpha-beta) crystalline microstructure, it provides significantly higher tensile strength and rigidity than single-phase alloys like Cartridge Brass. This combination of structural stiffness, phenomenal hot-forging capabilities, and heavy-duty saltwater corrosion resistance makes Naval Brass fasteners the premier, cost-effective choice for heavy marine architecture, underwater turnbuckles, propeller shaft bolting, and coastal desalination plants.
| Material Classification | Tin-Alloyed Alpha-Beta Brass (Naval Brass) |
|---|---|
| UNS Designation | C46400 |
| Microstructure | Dual-Phase (Alpha-Beta) Solid Solution |
| Magnetic State | Completely Non-Magnetic |
| Density | 8.41 g/cm³ (0.304 lb/in³) |
| Size Range | Metric: M6 to M64 | Imperial: 1/4" to 2-1/2" |
| Primary Attribute | Extreme Resistance to Seawater Dezincification |
Contains detailed hot-forging dimensional tolerances for large-diameter marine bolts, specific galvanic compatibility charts for submerged seawater joints, and maritime certification compliance testing methods.
⬇ DOWNLOAD DATASHEETIn heavy marine engineering, material failure at depth is catastrophic. The exact percentage of Tin must be verified to ensure anti-corrosive properties, and Lead must be minimized for structural integrity. Ananka provides total maritime traceability.
The formulation of C46400 is relatively simple but highly effective. By capping trace impurities like Lead (to maintain impact toughness) and Iron, and relying entirely on the 1% Tin shield, it thrives in stagnant, polluted, or fast-flowing seawater where standard 70/30 or free-machining brasses would rapidly disintegrate.
| Copper (Cu) | Tin (Sn) | Lead (Pb) | Iron (Fe) | Zinc (Zn) |
|---|---|---|---|---|
| 59.0 – 62.0 | 0.50 – 1.00 | 0.20 Max | 0.10 Max | Balance (~39.0) |
| Mechanical Property | Typical Limits (Half-Hard / Hot Forged) |
|---|---|
| Tensile Strength | 55,000 - 75,000 psi (380 - 515 MPa) |
| Yield Strength | 25,000 - 45,000 psi (170 - 310 MPa) |
| Elongation (in 2 inches) | 20% - 35% |
| Hardness (Rockwell B) | 55 - 75 HRB |
| Standard / System | Designation |
|---|---|
| ASTM Specifications | ASTM B21 (Rod, Bar, and Shapes), ASTM F467 / F468 |
| Common Trade Names | Naval Brass, Alloy 464, Uninhibited Naval Brass |
| European Equivalent | EN CW712R / CuZn38Sn1 (DIN 2.0530) |
| Military / Marine Std | MIL-B-4612 / SAE J461 |
| Mating Bolts/Studs | Internal Threads (Nuts) | Washers |
|---|---|---|
| C46400 Hot Forged Heavy Hex Bolts | C46400 Heavy Hex Nuts | C46400 or Silicon Bronze Flat Washers |
While C46400 Naval Brass is significantly stronger and more rigid than pure copper or single-phase brasses, it still acts as a "soft" metal compared to Grade 8 steel or B8M stainless. Fasteners must be torqued carefully, and the use of marine-grade anti-seize is recommended to prevent thread galling during underwater assembly.
| Nominal Diameter | Threads Per Inch (UNC) | Max Target Torque (in-lbs) | Max Target Torque (ft-lbs) |
|---|---|---|---|
| 1/4" | 20 | 65 - 75 | ~ 5.5 |
| 3/8" | 16 | 180 - 200 | ~ 16 |
| 1/2" | 13 | 360 - 400 | ~ 32 |
| 3/4" | 10 | 1200 - 1440 | ~ 100 - 120 |
Standard brasses like C36000 lack the protective Tin addition. If placed in an electrolyte like seawater, a galvanic reaction occurs between the Copper and the Zinc within the alloy itself. The seawater effectively dissolves and washes away the Zinc, leaving behind a highly porous, sponge-like copper structure that will crumble under the slightest physical load. Naval Brass's 1% Tin content effectively paralyzes this reaction.
Generally, no. Because C46400 contains a "beta" phase in its microstructure, it is quite rigid and resistant to deformation at room temperature. Attempting to aggressively cold-head it will result in cracking. Therefore, Naval Brass fasteners—especially large heavy hex bolts for shipyards—are almost entirely manufactured via hot-forging (heating the metal until it is glowing red and malleable) or CNC machining.
Silicon Bronze (such as C65100 or C65500) is generally superior to Naval Brass in terms of pure tensile strength and absolute corrosion resistance, making it the top-tier choice for marine environments. However, Naval Brass is far more cost-effective, offers significantly better machinability, and can be hot-forged much easier. Naval Brass is often preferred for massive, bulky marine components where the higher cost of Silicon Bronze is prohibitive.
