Copper is a versatile metal that plays a crucial role in various industries, with applications ranging from electrical wiring to industrial machinery. Known for its excellent conductivity, copper has been an essential material throughout human history, particularly as we entered the 21st century. Let’s explore the different types of copper and their unique properties.
What is Copper?
Copper, symbolized as Cu with an atomic number of 29, is a transition metal known for its high electrical and thermal conductivity, second only to silver. It is primarily used in manufacturing electrical wires, where its excellent conductivity makes it an ideal material.
Common Types of Copper
Many people think of copper as a single, uniform material, but in reality, there are several types of copper, each with distinct characteristics. These include pure copper, various copper alloys, and copper compounds.
1. Pure Copper
Characteristics: Pure copper is a reddish metal that turns purple after forming a copper oxide film, earning it the name “red copper” or “electrolytic copper.” It has a density of 8–9 g/cm³ and a melting point of 1083°C.
Uses: Due to its excellent electrical conductivity, pure copper is widely used in making electrical wires, cables, and brushes. Its thermal conductivity makes it suitable for manufacturing non-magnetic instruments and devices, such as compasses and aviation instruments. Pure copper is also highly malleable, making it easy to process into various forms like tubes, rods, wires, strips, and foils.
Types in China: In China, pure copper processing materials are classified into four categories: ordinary copper (T1, T2, T3, T4), oxygen-free copper (TU1, TU2, high-purity vacuum oxygen-free copper), deoxidized copper (TUP, TUMn), and special copper alloys with small amounts of added elements (arsenic copper, tellurium copper, silver copper).
2. Brass
Composition: Brass is an alloy of copper and zinc. The simplest form is a binary alloy containing only copper and zinc, known as simple brass or ordinary brass. By adjusting the zinc content, the mechanical properties of brass can be altered. The zinc content in brass typically does not exceed 45%, as higher levels can cause brittleness, negatively affecting the alloy’s properties.
Types:
- Ordinary Brass: Composed of copper and zinc, this type of brass is categorized into single-phase brass (when zinc content is below 39%) and dual-phase brass (when zinc content is above 39%). Single-phase brass is more malleable and suitable for both hot and cold processing.
- Special Brass: This includes brass with added elements such as lead, tin, or aluminum to improve tensile strength and processability. These are often referred to as lead brass, tin brass, and aluminum brass, respectively.
3. Bronze
Definition: Originally, bronze referred to a copper-tin alloy, named for its greenish-gray color. Modern bronzes may include other elements like lead, zinc, and phosphorus to enhance their properties.
Types:
- Tin Bronze: Contains tin as the main additive. When the tin content is below 5-6%, the alloy is more malleable. Tin bronzes with higher tin content are used for casting due to their low shrinkage and good wear resistance.
- Special Bronze (Non-Tin Bronze): These bronzes replace tin with other elements, such as aluminum or lead, offering improved mechanical properties, wear resistance, and corrosion resistance. Aluminum bronze and lead bronze are common examples.
4. Nickel Silver (White Copper)
Composition: White copper, also known as nickel silver, is an alloy primarily composed of copper and nickel, often with additional elements like manganese, iron, zinc, and aluminum. This alloy has a silver-white appearance and is known for its high strength, corrosion resistance, and thermal stability.
Types: Industrial white copper is divided into structural and electrical categories, depending on the specific performance requirements.
Differences Between Copper Alloys
| Type | Color | Composition | Applications | Properties |
|---|---|---|---|---|
| Pure Copper (Red Copper) | Reddish, turns black on oxidation | 99.9% copper | Electrical wires, cables, brushes, non-magnetic instruments | High electrical and thermal conductivity, malleable |
| Oxygen-Free Copper | Reddish | 99.95% copper, low oxygen content | High-conductivity applications, vacuum tubes, semiconductors | Extremely high conductivity, ductile, low impurities |
| Brass | Golden yellow | Copper (60-70%), Zinc (30-40%) | Plumbing, valves, musical instruments, decorative objects | Good corrosion resistance, easy to form and machine |
| Tin Bronze | Greenish-gray or yellowish | Copper (85-90%), Tin (5-15%) | Bearings, bushings, gears, marine applications | High wear resistance, good casting properties |
| Aluminum Bronze | Reddish to golden | Copper (80-85%), Aluminum (5-10%) | Shipbuilding, aircraft parts, corrosion-resistant valves | High strength, corrosion resistance, wear-resistant |
| Lead Brass | Golden yellow | Copper (58-60%), Zinc (35-40%), Lead (1-3%) | Plumbing, bearings, hardware | Excellent machinability, moderate strength |
| Phosphor Bronze | Reddish-brown | Copper (88-92%), Tin (4-6%), Phosphorus (0.1-0.3%) | Springs, electrical connectors, fasteners | High fatigue resistance, good wear and corrosion resistance |
| Nickel Silver (White Copper) | Silver-white | Copper (55-65%), Nickel (15-20%), Zinc (10-25%) | Jewelry, musical instruments, coins | Corrosion-resistant, strong, resembles silver |
