C14500 Tellurium Copper stands as a premier free-cutting copper alloy, engineered for high-speed CNC machining applications where precision, conductivity, and corrosion resistance are paramount. Unlike standard copper alloys that suffer from gummy chips and poor machinability, C14500 incorporates a controlled tellurium addition to produce fine, brittle chips that clear easily from the cutting zone, enabling superior surface finishes and extended tool life. This material is the go-to choice for manufacturers producing complex electrical connectors, semiconductor components, and precision mechanical parts that demand both dimensional accuracy and reliable performance under thermal and electrical loads. With a machinability rating of 80–85% relative to C36000 free-cutting brass, C14500 offers an exceptional balance of electrical conductivity (up to 95% IACS) and mechanical strength, making it indispensable in high-reliability applications across automotive, aerospace, and electronics industries.
1. Chemical Composition
The precise chemical composition of C14500 is critical to its unique combination of machinability and conductivity. The tellurium content is carefully balanced to optimize chip breakage without significantly degrading electrical or thermal properties. The standard composition ranges are defined by ASTM B301 and CDA standards, with tight controls on impurities to ensure consistent performance in high-volume CNC machining:
| Element | Content Range (%) | Typical Value (%) | Role in Alloy |
|---|---|---|---|
| Copper (Cu) | 99.00 – 99.90 | 99.50 | Base metal, provides conductivity |
| Tellurium (Te) | 0.40 – 0.70 | 0.55 | Improves machinability, chip breakage |
| Phosphorus (P) | 0.004 – 0.012 | 0.008 | Deoxidizer, enhances conductivity |
| Iron (Fe) | ≤ 0.05 | 0.02 | Impurity, controlled for ductility |
| Lead (Pb) | ≤ 0.005 | <0.001 | Trace impurity, minimized for safety |
| Zinc (Zn) | ≤ 0.01 | <0.005 | Trace impurity, minimized |
| Other Total | ≤ 0.15 | — | Balance |
Note: The tellurium content is the key differentiator. At 0.4–0.7%, it forms fine, dispersed Cu₂Te particles that act as chip breakers during machining. This composition ensures that C14500 retains approximately 85–95% of the electrical conductivity of pure copper (100% IACS), making it ideal for current-carrying components. The phosphorus content, typically 0.004–0.012%, acts as a deoxidizer to prevent porosity during casting and welding, while iron and other impurities are kept below 0.05% to maintain ductility and corrosion resistance. The absence of lead (≤0.005%) makes C14500 RoHS-compliant and suitable for medical and food-contact applications.
2. Mechanical & Physical Properties
C14500 exhibits a balanced set of mechanical properties that make it suitable for both cold forming and high-speed machining. The material is typically supplied in the half-hard (H02) or hard (H04) temper for CNC applications. Below are the certified property ranges from ASTM B301, with typical values representing the most common temper used in precision machining:
| Property | Value Range | Typical Value | Unit | Test Method |
|---|---|---|---|---|
| Tensile Strength | 280 – 420 | 350 | MPa | ASTM E8 |
| Yield Strength (0.2% offset) | 140 – 350 | 250 | MPa | ASTM E8 |
| Elongation (in 50 mm) | 10 – 40 | 25 | % | ASTM E8 |
| Hardness, Rockwell B | 40 – 85 | 65 | HRB | ASTM E18 |
| Hardness, Vickers | 80 – 160 | 120 | HV | ASTM E92 |
| Density | 8.91 – 8.94 | 8.92 | g/cm³ | ASTM B328 |
| Electrical Conductivity | 85 – 95 | 90 | %IACS | ASTM B193 |
| Thermal Conductivity | 340 – 380 | 360 | W/m·K | ASTM E1461 |
| Modulus of Elasticity | 115 – 130 | 120 | GPa | ASTM E111 |
| Poisson’s Ratio | 0.31 – 0.35 | 0.33 | — | ASTM E132 |
| Melting Point (Liquidus) | 1070 – 1080 | 1075 | °C | ASTM E794 |
| Electrical Resistivity | 1.78 – 2.00 | 1.90 | µΩ·cm | ASTM B193 |
The combination of high thermal conductivity (360 W/m·K) and moderate strength allows C14500 to dissipate heat rapidly during machining, reducing thermal distortion and enabling tighter tolerances. Its electrical conductivity (90% IACS) makes it superior to brass or bronze for electrical applications. The modulus of elasticity (120 GPa) provides good stiffness for precision components, while the Poisson’s ratio of 0.33 ensures predictable deformation under load. The density of 8.92 g/cm³ is typical for copper alloys, offering a favorable strength-to-weight ratio for aerospace and automotive parts.
3. CNC Machining Characteristics
C14500 is classified as a free-cutting copper alloy with a machinability rating of approximately 80–85% relative to C36000 free-cutting brass (100%). The tellurium addition creates a discontinuous chip morphology that prevents chip entanglement and reduces cutting forces. Below are the optimized CNC machining parameters based on extensive testing at Dongguan Stirling Metal Products Co., Ltd., using both carbide and high-speed steel (HSS) tools:
| Parameter | Turning | Milling | Drilling | Unit |
|---|---|---|---|---|
| Cutting Speed (Carbide) | 150 – 300 | 120 – 250 | 80 – 150 | m/min |
| Cutting Speed (HSS) | 60 – 120 | 50 – 100 | 30 – 60 | m/min |
| Feed Rate (Roughing) | 0.15 – 0.40 | 0.10 – 0.30 | 0.05 – 0.15 | mm/rev |
| Feed Rate (Finishing) | 0.05 – 0.15 | 0.03 – 0.10 | 0.02 – 0.08 | mm/rev |
| Depth of Cut (Roughing) | 1.0 – 4.0 | 0.5 – 3.0 | — | mm |
| Depth of Cut (Finishing) | 0.1 – 0.5 | 0.1 – 0.3 | — | mm |
| Coolant Type | Water-soluble oil (5-8%) | Water-soluble oil (5-8%) | Water-soluble oil (5-8%) | — |
| Surface Finish (Ra) | 0.4 – 1.6 | 0.8 – 3.2 | 1.6 – 6.3 | µm |
| Tool Material (Recommended) | Carbide (K10-K20) | Carbide (K10-K20) | Carbide (K10-K20) | — |
| Tool Geometry (Rake Angle) | 5° – 10° positive | 5° – 10° positive | 118° point angle | degrees |
Key Machining Considerations:
- Chip Control: The tellurium addition produces short, broken chips that are easily evacuated. Use chip breakers on inserts for optimal performance. For deep-hole drilling, peck cycles at 0.5–1.0 mm depth increments are recommended to prevent chip packing.
- Tool Wear: Carbide tools with TiN or TiAlN coatings are recommended for high-volume production, offering tool life of 200–400 minutes at typical cutting speeds. Uncoated carbide is suitable for low to medium volumes, with tool life of 100–200 minutes. HSS tools are economical for prototyping but require lower speeds.
- Coolant: Flood coolant with water-soluble oil (5–8% concentration) is essential to manage heat and improve surface finish. Mist cooling is acceptable for light cuts but may reduce tool life by 15–20%. For high-speed operations, high-pressure coolant (20–40 bar) through the spindle enhances chip evacuation.
- Work Hardening: C14500 work-hardens moderately. Avoid excessive rubbing or dwell marks; use sharp tools and consistent feed rates. A minimum chip thickness of 0.02 mm is recommended to prevent burnishing.
- Tolerances: Typical achievable tolerances are ±0.01 mm for turning and ±0.02 mm for milling. For precision applications, ±0.005 mm is possible with careful setup and temperature-controlled environments (20±1°C).
- Surface Finish: With optimized parameters, surface finishes as low as Ra 0.2 µm can be achieved on turning operations, eliminating the need for secondary polishing in many applications.
4. Applications
C14500 Tellurium Copper is widely specified in industries where high conductivity and machinability are critical. Its unique properties make it the material of choice for the following applications:
- Electrical Connectors & Terminals: Used in high-current connectors, bus bars, and switchgear components where low electrical resistance and precise geometry are required. Typical applications include 200–600 A power connectors for data centers and EV charging stations.
- Semiconductor & Electronics: Heat sinks, lead frames, and bonding tools for wire bonding machines. The thermal conductivity ensures efficient heat dissipation in power modules, with typical heat flux capacities of 50–100 W/cm².
- Automotive Components: Fuel injector bodies, sensor housings, and electrical terminals for electric vehicles (EVs) and hybrid systems. C14500 is used in battery pack connectors and inverter bus bars due to its high conductivity and corrosion resistance.
- CNC Machined Precision Parts: Complex geometries such as valve bodies, pump components, and threaded inserts that require tight tolerances and excellent surface finish. Typical parts include hydraulic spools with tolerances of ±0.005 mm.
- Marine & Offshore: Propeller shafts, valve stems, and seawater-resistant fittings where corrosion resistance and machinability are balanced. C14500 offers superior resistance to dezincification compared to brass.
- Medical Devices: Surgical instrument handles, imaging equipment components, and dental tools that benefit from non-magnetic and antimicrobial properties. The material is biocompatible per ISO 10993-5 standards.
- Watch & Jewelry: Precision gears, pinions, and decorative elements that require fine detail and a bright, tarnish-resistant finish. C14500 can be polished to a mirror finish with Ra < 0.1 µm.
5. Why Choose Dongguan Stirling Metal Products Co., Ltd.
Dongguan Stirling Metal Products Co., Ltd. has over 15 years of experience in CNC machining of copper alloys, including C14500 Tellurium Copper. Our facility is equipped with 30+ high-precision CNC lathes and milling machines (Mazak, Fanuc, and Haas), capable of holding tolerances down to ±0.005 mm. We provide a complete one-stop solution from material sourcing to finished parts:
- Material Certification: Every batch of C14500 is supplied with a full Mill Test Certificate (MTC) verifying chemical composition and mechanical properties per ASTM B301. We also offer third-party testing for critical applications.
- Advanced Machining Capabilities: 5-axis CNC machining, Swiss-type turning, and multi-spindle milling for complex geometries. Our CAM software optimizes tool paths for maximum efficiency, reducing cycle times by up to 30% compared to conventional methods.
- Quality Control: In-process inspection using CMM (Coordinate Measuring Machine) with accuracy of ±0.001 mm. Final inspection includes surface roughness measurement (Mitutoyo SJ-210) and hardness testing (Rockwell and Vickers). We maintain ISO 9001:2015 certification.
- Surface Finishing: We offer polishing (Ra 0.2 µm), electropolishing, passivation, and plating (silver, gold, nickel) to meet specific application requirements. Our electropolishing process can achieve Ra < 0.1 µm for optical components.
- Lead Times: Prototype samples in 3–5 working days. Production orders of 100–10,000 pieces delivered in 7–15 working days, depending on complexity. Rush orders available for urgent projects.
- Cost Efficiency: Our bulk material purchasing power and optimized machining processes reduce per-part costs by up to 20% compared to competitors. We offer volume discounts for orders exceeding 5,000 pieces.
Contact us today for a free engineering review and quotation. Our team will work with you to select the optimal temper and machining strategy for your C14500 project, ensuring the highest quality and fastest turnaround times in the industry.
