Copper grades form one of the major groups of commercial metals, valued for their excellent electrical and thermal conductivity, corrosion resistance, and ease of fabrication. They are nonmagnetic and can be readily joined by soldering and brazing, while many copper grades can also be welded using various gas, arc, and resistance methods. Understanding how these grades are grouped and designated is the starting point for selecting the right material for a given job.
Copper grades are divided into six families: coppers, dilute copper alloys, brasses, bronzes, copper-nickel alloys, and nickel-silver alloys. Each family is defined by its principal alloying elements and occupies a distinct range within the Unified Numbering System (UNS).
Figure 1: Overview of the six families of copper grades
The first family, the coppers, is essentially commercially pure copper. This material is normally soft and ductile and contains less than about 0.7% total impurities. Commercially pure copper grades are designated by UNS numbers C10100 to C13000.
Within this family, electrolytic tough pitch copper (C11000) is made from cathode copper, meaning copper that has been refined electrolytically. It is the most common of all the electrical copper grades and offers high electrical conductivity in excess of 100% IACS. Although C11000 has the same oxygen content as C12500, it differs in sulfur content and in overall purity, containing less than 50 ppm of total metallic impurities, including sulfur.
Oxygen-free copper grades C10100 and C10200 also belong to this family. They are produced by induction melting prime-quality cathode copper under nonoxidizing conditions, created using a granulated graphite bath covering together with a protective reducing atmosphere that is low in hydrogen. Their high purity makes them particularly suitable for demanding electrical and electronic applications.
The second family, the dilute copper alloys, contains small amounts of various alloying elements added to modify one or more of copper's basic properties. These additions are kept low so that the material retains much of the conductivity and workability of pure copper while gaining improvements such as greater strength, hardness, or resistance to softening.
Brasses form the third family and are copper alloys in which zinc is the principal alloying element. Varying the zinc content, and adding smaller amounts of elements such as lead, tin, or aluminium, produces a wide range of colors, strengths, and levels of formability and machinability. As a group, wrought brasses occupy the UNS range beginning at C20500. They are among the most widely used copper alloys, appearing in plumbing fittings, fasteners, decorative hardware, and electrical components.
The fourth family, the bronzes, were traditionally copper-tin alloys, but the term now covers several groups defined by their main alloying element. These include tin bronzes (also called phosphor bronzes), aluminium bronzes, silicon bronzes, and others. Bronzes generally offer higher strength than the coppers and brasses, together with good corrosion resistance and wear resistance, which makes them well suited to bearings, bushings, springs, and marine components. As a group, the bronzes occupy the UNS ranges from C50000 through C69999.
The fifth family, the copper-nickel alloys, are also known as copper-nickels or cupro-nickels. They contain 1.5% to 45% nickel as the major alloying element. Under the UNS, wrought copper-nickel alloys are designated with numbers from C70000 through C73499. These alloys are widely used to manufacture coins, seawater equipment, evaporators, heat exchanger tubes, and automotive hydraulic and cooling systems, largely because of their strong resistance to seawater corrosion.
The sixth family is nickel silver. Despite its name, nickel silver contains no silver and can be regarded as a brass to which nickel has been added. The nickel content varies considerably but usually lies between 9% and 30% depending on the application. The copper content tends to remain fairly constant at approximately 60% to 65%, while the zinc content is reduced as the nickel content increases. A higher nickel content produces a whiter color and greater corrosion resistance, though it also reduces ductility.
Nickel silver is valued for its corrosion resistance, attractive color, and good cold-forming qualities. Typical products range from car radiators, ballpoint pens, and musical instrument keys to transistor casings, electrical contacts, architectural ironmongery, and cutlery. Under the UNS, wrought nickel silvers are designated with numbers from C73500 through C79999.
This article classifies copper by its six alloy families. The related guides in the Copper series cover the topics you will need alongside it. Copper Properties details the conductivity, corrosion resistance, and strength that distinguish one family from another. Copper Specifications explains the designation systems used to define each grade precisely, and Copper Standards sets out the frameworks that govern those designations across different regions. Together, they connect grade classification with the properties, designations, and standards behind it.
Copper grades are divided into coppers, dilute copper alloys, brasses, bronzes, copper-nickel alloys, and nickel-silver alloys. Each family offers a distinct balance of conductivity, strength, corrosion resistance, and workability.
Commercially pure copper (UNS C10100 to C13000) is soft, ductile, and contains less than about 0.7% total impurities. Dilute copper alloys contain small deliberate additions of alloying elements that modify one or more of copper's basic properties while retaining much of its conductivity and workability.
Brass is a copper alloy in which zinc is the principal alloying element, while bronze was traditionally a copper-tin alloy. Today the term bronze also covers aluminium bronzes, silicon bronzes, and similar alloys. Bronzes generally provide higher strength and better wear resistance, whereas brasses are prized for their workability, machinability, and appearance.
Electrolytic tough pitch copper (C11000) is the most common electrical copper grade, offering high electrical conductivity in excess of 100% IACS. Oxygen-free grades C10100 and C10200 are used where even higher purity is required.
Copper-nickel alloys, which contain 1.5% to 45% nickel, are used for coins, seawater equipment, evaporators, heat exchanger tubes, and automotive hydraulic and cooling systems, largely because of their strong resistance to seawater corrosion.