Copper is a reddish-brown metal with high electrical conductivity, high malleability (ability to be formed into shape) and a natural corrosion-resistant oxide layer. The combination of many of these properties makes it useful in a variety of applications, from cooking to decorative items and engineering applications.
Pure copper has limited uses, it is specifically used in electronic connectors, wires and communication wirings, but alloying copper with different metals expands its uses and changes its properties.
In this blog, you’ll learn about pure copper, different types of copper alloys and copper properties that make it a useful metal since history.
What Is Copper?
Copper is a metal and an element on the periodic table with the atomic number 29 and an atomic mass of 63.546. Copper has the symbol “Cu” and the name copper is derived from the latin word “cuprum”
The appearance of copper ranges in different hues but a red or orange hue dominates the copper color. Copper has a natural shine and is a reflective metal. Copper can have a different appearance in air and moisture.
In air, the bright copper color dulls to a brown-red color and in salty water, the copper develops a green patina.
What Is Copper Made of?
Copper is an element (a pure substance) with just one type of atoms. Copper is made up of copper atoms and exists naturally in the form of copper ore like chalcopyrite or cuprite. These ores are mined and processed into copper.
Copper can also exist as a pure metal, and this form of copper is called native copper. Copper atoms are bonded together in a crystal lattice structure, and the attractive forces between these atoms are metallic bonds.
Copper has a face-centred cubic (FCC) lattice, and each copper atom is surrounded by 12 other packing densities and maximising stability.
Physical Properties of Copper
Property
Value (Units)
Density
8.96 g/cm³
Melting Point
1,085 °C
Boiling Point
2927 °C
Electrical Conductivity
100% IACS at 20°C
Thermal Conductivity
400 W m‑1 K‑1
Electrical Resistivity
1.72 × 10‑8 Ω m
Source: webelements
Electrical Conductivity of Copper
Pure copper is one of the most conductive materials. According to International Annealed Copper Standard (IACS), copper has 100% IACS at 20°C and in S/m copper has an electrical conductivity of 58 x 106 S/m.
Property
Value (Units)
Young's modulus
130 GPa
Poisson’s ratio
0.34
Brinell hardness
874 MN m-2
Ductility
High (0.62) out of 1 (being perfect ductility)
Malleability
High
Fatigue Strength
100 MPa for 100 x 10^6 cycles (CW 21%) Strip form
Table of mechanical properties of copper. Source: failure criteria & webelements & MDPI
Copper Tensile Strength
The tensile strength of copper is the maximum stress that it can endure without thinning or breaking.
Annealed copper has a tensile strength of 210 MPa, and cold-worked copper can have a tensile strength of up to 400 MPa. Copper cold worked (30%) at room temperature has a tensile strength above 300 MPa.
Source: Researchgate
Ductility of Copper
Copper has excellent ductility. It is used in power transmission lines and electrical wiring in household wires. Ductility is the ability of a material to be stretched into thin forms or bent into tight shapes.
Copper is ductile because of its FCC structure, which allows layers of atoms to easily slide over each other. Copper can be easily shaped and formed into coils; this is another reason copper wiring is used in motors.
Copper Corrosion Resistance
Copper has good corrosion resistance. In open air and freshwater (unsalted) water, copper can last a long time. Copper’s corrosion resistance comes from a natural oxide formation in air and water.
Copper forms a thin copper oxide that prevents the underlying copper from further oxidizing. Copper develops a green patina layer (copper carbonate) or copper sulfate that protects pure copper in moist environments.
Many copper alloys have increased corrosion resistance for specific applications and environments. For example, copper alloys like bronze can resist corrosion better than pure copper.
The tin mixed with copper in bronze reduced pitting and erosion. Many ship propellers are alloy copper and brass with other metals and non-metals like phosphorus to increase corrosion resistance in seawater.
Different Types of Copper Alloys
Different types of copper grades refer to the amount of alloying elements with copper. Increasing the composition of different alloying elements produces different copper alloys.
Common copper alloys include:
Brass
Brass is a copper and zinc alloy with excellent corrosion resistance and machinability. Brass itself has many alloys, but brass is mostly used in ammunition casings and decorative items. Brass CNC machining is relatively easy and this allows brass applications in valves and pipe fittings.
Bronze
Bronze is another alloy of copper with a typical composition of 85 – 95 % Copper and 5 – 12% tin with other metals or non metals like silicon for strength. Bronze has excellent corrosion resistance in seawater and has many marine applications.
Bronze has good resistance against pitting corrosion and has a higher tensile strength than pure copper. It has better wear resistance and hardness than pure copper, but reduced ductility.
Nickel Silvers
Nickel silvers mainly alloy copper, zinc and nickel. There’s no silver in this copper alloy and the “silver” is only added for its shiny appearance.
Nickel silvers are typically used in musical instruments, keys and jewellery. Nickel silvers have reduced ductility, hardness and strength compared to brass and bronze copper alloys but they have a shiny desirable finish that resembles silver.
Cupro Nickels
Cupro-nickels are alloys of copper and nickel with alloying metals like iron or manganese in small quantities.
Cupro-nickels have moderate tensile strength but excellent corrosion resistance. Cupro-nickel types like C71500 are used in ships, hulls and seawater processing plants like desalination tanks.
Different Forms of Copper
Solid copper is rarely used in applications and in copper manufacturing, most of the copper processed from copper ores is turned into pure copper forms like wires and plates or copper alloys like different brasses and bronze.
Other than copper alloys, you can also find different forms of copper suitable for your needs.
Pure Copper Cathode
This is the purest type of copper you can find. Copper cathodes are purified using an electrolytic process where pure copper ions (Cu2+) form on a cathode. Copper cathode plates are useful for their mechanical and electrical properties.
Most copper products use copper cathodes as a starting point for another product and wires, connectors and electrical pins require copper cathodes.
Copper Wire
Copper wires are usually cut from larger rolls and coils of copper wire. These copper wire rods are hot-rolled from copper cathodes and drawn into wires.
Copper wires are used in electrical wiring and about most electrical motors, transformers and lines use copper’s excellent electrical conductivity. Copper wires typically have a thickness of 0.1 mm but you can find thinner or coarser wires.
Copper Plate
Copper plates are flat, hot rolled thick rectangular pieces with a thickness larger than 6 mm. Copper sheets have a smaller thickness and are used in stamping, CNC cutting and bending operations to produce various parts.
Copper Tubing
Copper compared to other metals is a ductile metal and can be easily drawn into hollow cylinders, copper pipes and copper bars.
Copper can be welded, brazed and joined using soldering which makes copper tubing ideal for heating systems and transporting cold fluids in refrigeration lines.
Powdered Copper (for Metal 3D Printing)
Copper powder is used in metal 3d printing and sintering applications to repair any critical copper components. Copper has high thermal conductivity and elemental copper can be used in powder metallurgy applications.
Copper powder is also used in inks and sintering parts.
Copper Manufacturing Process
Metals like gold and silver are often found in their pure form. Copper exists mainly in mineral ores, and extracting pure copper from these ores is a step-by-step process.
Mining Copper
Solid copper occurs in sulfide ores and cuprous oxide ores. These ores are found underground and a combination of both open-pit mining and underground mining is used to extract the cuprous sulfide ores.
This is the first step in the extraction of natural copper.
Crushing Copper Ores
The next step in copper production requires copper ore crushing and grinding. Most of the copper ore is sulfide ore, forth flotation (hydrophobic and hydrophilic separation) separates copper compounds from waste rocks.
Smelting
The skimmed slurry mixture with a concentrate of around 40% copper is dried and sent to a furnace for melting. In the furnace, any sulfur and iron oxidize to form sulfer oxide and iron silicate that can be removed easily.
This concentrates copper further, the molten copper is a mixture of copper sulfide and impurities.
Refining
Just before refining, the copper sulfide and impurities are passed through hot air above 1000°C oxidizing and burning any impurities. While this gives a purified copper, the copper forms tiny air bubbles.
The copper is melted again in a furnace with air that removes residual sulfur and stirring the mixture with green wood, releases other gases giving almost pure copper grades. Copper at this stage is about 99% pure.
For even higher purifying, an electrolytic cell is used. This process is used based on copper demand. The purified copper is made the anode in a copper sulfate and sulfuric acid bath. When a current is applied, the copper dissolves from the anode and copper ions deposit on the cathode leaving behind almost 99.9% copper. Other metal impurities (nickel, silvers, gold) and alloying elements settle at the bottom of the bath.
Applications of Copper
Electrical Uses of Copper
Copper has the second-best electrical conductivity behind silver. Copper Development Association classifies different copper grades according to International Annealed Copper Standard (IACS) and pure copper has 100% IACS.
Most of the mined copper is refined and used in electrical systems, electrical contacts and wiring for cables.
Motors: Copper plates, and wires are wound into coils for electric motors, it has high thermal conductivity and efficiently dissipates heat.
PCBs: Copper foils conduct signals and copper is used in printable circuits and printable circuit boards (PCB).
Terminals: High performance batteries, and in automotive applications, copper bars are used as terminals.
Plumbing
Copper is widely used in the plumbing industry. Copper tubing carries water while resisting corrosion and maintaining integrity under high pressures.
Different copper grades are also used in heat exchangers and refrigeration that take advantage of copper’s high thermal conductivity.
Industrial Machinery
Copper bearings, gears especially phosphorus bronze are widely used in industrial machinery for low friction, electrical spark resistanc and high wear resistance components.
Sculptures
Many copper grades and alloys like bronze are used in sculptures, displays and decorative items. Copper plays an important role because it is easy to machine and offers aesthetic value with high corrosion resistance.
Jewellery
Nickel silver is used in decorative pieces, charms and acessorizing any copper pendant.
Conclusion
Copper as a metal has many anti-microbial properties, high thermal and electrical conductivity making it useful in various industries and applications. It is essential to match the right copper grade with your part application.
Copper has some limitations and challenges in machining. For instance, its expensive compared to alternatives, and can oxidize. The right CNC machining partner can help you produce copper parts and custom pieces with practical copper solutions.
FAQs
What does copper do to your body?
Copper is important for the human body because it helps red blood cells, creates nerve cells and boosts immune.
What is copper as a metal?
Copper is a ductile, malleable reddish brown metal with a high electrical conductivity and thermal conductivity. It has the atomic number 29 and is the second most conductive metal.
Which is better Type L or Type M copper?
Type L copper is ideal for high-pressure water lines and exposed water tubing. Type L is also used in commercial building and hot water systems. Type L is more durable compared to Type M, which does not meet some standards.
What are the 3 grades of copper?
Copper type M: Type M is the thinnest copper tubing grade and a cost effective solution to low pressure applications.
Cpper type L: For general plumbing applications
Copper type K: Type K has the thickest walls and is suitable for underground lines and tubings.