Copper is typically categorized based on purity, processing state, or alloy composition-the "four types" most commonly referenced in industry and manufacturing are defined by purity and application, as follows:
Also known as "oxygen-free copper" (OFC) or "electrolytic tough pitch copper" (ETP), this is the most common type of pure copper (purity ≥99.3%). It is further divided into grades (e.g., ASTM C11000, C10200) based on trace impurities (e.g., oxygen, phosphorus). Key traits: excellent electrical/thermal conductivity, high ductility, and ease of forming. Uses include electrical wiring, heat sinks, and freshwater plumbing.
A premium subset of pure copper with ultra-high purity (≥99.995%) and minimal oxygen content (<0.003%). Its low oxygen levels eliminate "hydrogen embrittlement" (cracking in high-temperature hydrogen environments) and maximize conductivity. Uses: high-performance electronics (e.g., semiconductor chips, microwave components), cryogenics, and medical devices (e.g., MRI machines).
Copper combined with other metals to enhance specific properties (e.g., strength, corrosion resistance). The most common copper alloys include:
Brass: Copper + zinc (e.g., 60/40 brass, C26000) – ductile, machinable, and cost-effective; used for valves, decorative hardware, and musical instruments.
Bronze: Copper + tin (traditional bronze) or copper + aluminum/nickel (modern bronzes, e.g., aluminum bronze C60800) – strong, wear-resistant, and corrosion-resistant; used for bearings, ship propellers, and industrial gears.
Copper-Nickel (Cupronickel): Copper + nickel (e.g., 90/10 Cu-Ni, C70600) – excellent seawater corrosion resistance; used for marine pipes, heat exchangers, and coinage.
Recycled copper sorted by purity and form for reuse. It is classified into grades (e.g., #1 Bare Bright Copper, #2 Copper) based on cleanliness (e.g., presence of insulation, solder) and purity. Scrap copper retains most of pure copper's properties and is critical for sustainable manufacturing, as recycling copper uses 90% less energy than mining new copper.
There is no universal "better" form of copper-the choice depends on the application's core requirements, such as conductivity, strength, corrosion resistance, and cost. Key considerations for common scenarios:
For electrical/thermal applications: Oxygen-Free High-Conductivity (OFHC) copper is best for high-performance needs (e.g., semiconductors), as its ultra-high purity maximizes conductivity. For everyday uses (e.g., household wiring), Commercially Pure (CP) copper (e.g., ETP C11000) is more cost-effective while still delivering sufficient conductivity.
For corrosion-prone environments: Copper alloys (e.g., copper-nickel for seawater, aluminum bronze for industrial chemicals) outperform pure copper, which tarnishes or corrodes in saltwater/strong acids.
For strength or wear resistance: Copper alloys (e.g., bronze, brass) are better than pure copper, which is soft and prone to deformation under load. For example, aluminum bronze is used for heavy-duty gears because it is 3–4 times stronger than pure copper.
For sustainability or cost: Scrap copper is ideal for non-critical applications (e.g., low-grade electrical components) if purity requirements are low, as it reduces material costs and environmental impact.
Among all copper types, copper alloys are significantly stronger than pure copper-with aluminum bronze (a type of bronze alloy: copper + aluminum, often with iron/nickel additions) being the strongest common copper-based material. Here's a detailed breakdown:
Pure Copper (CP/OFHC): Weak and soft, with a tensile strength of ~220–300 MPa (annealed state) and low wear resistance. It deforms easily under load, making it unsuitable for high-strength applications.
Common Copper Alloys (Strength Comparison):
Aluminum bronze's high strength comes from its microstructure (intermetallic compounds formed by aluminum and copper) and heat-treatability. It is used in demanding applications like heavy machinery bearings, offshore oil rig components, and military vehicle armor-where pure copper or weaker alloys would fail under stress.
