COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF UNS C54400 FREE-MACHINING PHOSPHOR BRONZE FASTENERS
UNS C54400, widely known in the industry as "Free-Cutting Phosphor Bronze" or "Alloy B-2," represents the apex of machinability within the highly resilient phosphor bronze family. While standard phosphor bronzes offer legendary fatigue life and spring memory, they are notoriously difficult to machine. C54400 solves this by precisely alloying Copper, Tin, Zinc, and approximately 4% Lead (Pb). The lead is insoluble in the solid matrix, dispersing as microscopic globules that act as built-in chip breakers and dry lubricants during CNC turning.
The result is an alloy boasting an impressive 80% Machinability Rating (compared to standard C51000 at 20%), while retaining the exceptional wear resistance, anti-galling properties, and high-cycle fatigue thresholds expected of a phosphor bronze. C54400 is the premier choice for complex, custom-threaded electromechanical fasteners, intricate thrust washers, and high-friction rotating hardware that must be mass-produced via high-speed automated screw machines.
■ Product Overview & Specifications
| Material Classification | Free-Machining Phosphor Bronze (Alloy B-2) |
|---|---|
| UNS Designation | C54400 |
| Microstructure | Alpha Solid Solution with Dispersed Lead Particles |
| Magnetic State | Completely Non-Magnetic |
| Density | 8.89 g/cm³ (0.321 lb/in³) |
| Size Range | Metric: M1.6 to M24 | Imperial: #0 to 1" |
| Primary Attribute | 80% Machinability Rating combined with High Fatigue Life |
■ Proprietary Datasheet Download (GATED)
UNS C54400 Free-Machining Phosphor Bronze — Complete Technical Datasheet
Contains detailed high-speed CNC turning feed rates, tooling tool-wear parameters, threading tolerances, and high-cycle friction resistance limits for complex turned components.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
In automated fastener manufacturing, inconsistent lead dispersion leads to tool chatter, torn threads, and component rejection. Ananka ensures that every lot of C54400 solid bar stock is backed by stringent, verifiable mill documentation for absolute metallurgical uniformity.
- EN 10204 Type 3.1: Validates the precise 4% Lead dispersion, verifies the Tin and Zinc strengthening additions, and guarantees the structural integrity of the cold-drawn temper.
- EN 10204 Type 3.2: Available upon request for highly regulated aerospace, defense instrument, or critical marine engineering contracts requiring third-party inspector verification.
■ Chemical Composition
C54400 is heavily alloyed compared to standard bronzes. The 4% Tin provides the core strength and wear resistance, while the 4% Lead ensures the metal cuts crisply. A 4% Zinc addition acts as a secondary solid-solution strengthener and aids in deoxidation, alongside the trace Phosphorus.
| Copper (Cu) | Tin (Sn) | Lead (Pb) | Zinc (Zn) | Phosphorus (P) | Iron (Fe) |
|---|---|---|---|---|---|
| Balance (~88.0) | 3.50 – 4.50 | 3.50 – 4.50 | 1.50 – 4.50 | 0.01 – 0.50 | 0.10 Max |
■ Mechanical Properties
| Mechanical Property | Typical Limits (Half-Hard to Hard Temper) |
|---|---|
| Tensile Strength | 60,000 - 85,000 psi (415 - 585 MPa) |
| Yield Strength | 50,000 - 70,000 psi (345 - 480 MPa) |
| Machinability Rating | 80% (Relative to Free-Cutting Brass at 100%) |
| Hardness (Rockwell B) | 75 - 85 HRB |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASTM Specifications | ASTM B139 (Rod, Bar, and Shapes) |
| Common Trade Names | Free-Cutting Phosphor Bronze, Alloy B-2, Alloy 544 |
| European Equivalent | EN CW456K / CuSn4Pb4Zn4 (DIN 2.1028) |
| British Standard (BS) | PB104 |
■ Applications & Industries
- Precision Electromechanical Hardware: Intricate CNC-machined standoffs, miniature switchgear components, and relay screws requiring both wear resistance and perfect thread profiles.
- High-Wear Rotating Assemblies: Specialized thrust washers, bushings, gear retaining nuts, and pinions subjected to constant frictional forces where standard brass would gall or seize.
- Aerospace & Scientific Instrumentation: Non-magnetic customized fasteners needing rapid machinability but significantly higher strength and fatigue life than free-cutting brass.
■ Compatible Fastener Assemblies
| Mating Bolts/Machine Screws | Internal Threads (Nuts) | Washers |
|---|---|---|
| C54400 CNC Turned Screws & Studs | C54400 Custom Machined Nuts | C51000 or C54400 Thrust/Flat Washers |
■ Torque & Installation Guidelines
While C54400 possesses excellent strength and fatigue resistance for a bronze, the significant lead content slightly reduces its ultimate tensile threshold compared to pure C51000. Care must be taken not to over-torque smaller diameter precision machine screws to avoid head shearing.
| Nominal Diameter | Threads Per Inch (UNC) | Max Target Torque (in-lbs) | Max Target Torque (ft-lbs) |
|---|---|---|---|
| #10 | 24 | 35 - 40 | ~ 3 |
| 1/4" | 20 | 70 - 80 | ~ 6.5 |
| 3/8" | 16 | 180 - 210 | ~ 16 |
| 1/2" | 13 | 400 - 450 | ~ 35 |
■ Frequently Asked Questions
1. How does it compare to standard C51000 Phosphor Bronze?
It is a deliberate metallurgical trade-off. By adding 4% Lead, C54400 sacrifices a small amount of absolute ductility and tensile strength to gain a massive boost in manufacturing speed. Standard C51000 has a terrible machinability rating of just 20%, generating long, tangled chips that ruin tools. C54400 cuts beautifully at an 80% rating, making complex geometries economically feasible.
2. Can C54400 Phosphor Bronze be cold-headed or forged?
No. Just like Free-Cutting Brass (C36000), the heavy 4% Lead content makes the alloy highly susceptible to cracking under extreme deformation. If you attempt to cold-head a bolt from C54400, the lead particles act as fracture points and the head will shatter. C54400 fasteners are strictly manufactured via CNC subtractive machining from solid rod or bar stock.
3. What purpose does the Zinc serve in this specific alloy?
In C54400, the ~4% Zinc addition acts primarily as an advanced deoxidizer during the initial smelting process, assisting the Phosphorus. Furthermore, Zinc greatly improves the fluidity of the molten bronze before casting, which is critical for ensuring the 4% Lead content is dispersed evenly and uniformly throughout the ingot before it is drawn into rod stock.
