1. Thermal Expansion Coefficient of Pure Copper
Pure copper (oxygen-free copper or commercial pure copper such as T2, C11000) has a relatively high linear thermal expansion coefficient, which is one of its important physical properties in engineering applications.
From 20 ℃ to 100 ℃: approximately 16.5 × 10⁻⁶ /℃
From 20 ℃ to 200 ℃: approximately 17.3 × 10⁻⁶ /℃
From 20 ℃ to 300 ℃: approximately 17.7 × 10⁻⁶ /℃
This means that when temperature increases, pure copper expands noticeably, which must be considered in thermal design, assembly fits, and high-temperature structural components.
2. Is Pure Copper Suitable for Long-Term High-Temperature Service?
2.1 Conclusion
Pure copper is NOT suitable for long-term use at high temperatures, especially above 250 ℃.
It can only maintain stable performance for long-term service at below 150 ℃ in non‑corrosive atmospheres. Above this temperature, oxidation, softening, strength loss, and structural degradation become severe and limit its service life.
2.2 Performance Degradation of Pure Copper at High Temperatures
(1) Accelerated Oxidation
Below 300 ℃, copper forms a thin oxide film (Cu₂O and CuO) that provides limited protection.
Above 300 ℃, oxidation accelerates significantly. The oxide layer becomes thick, loose, and non‑protective, continuously penetrating inward.Above 500 ℃, oxidation is extremely rapid, leading to material consumption, surface embrittlement, and cracking.
In environments containing sulfur, chlorine, or other corrosive elements, high-temperature corrosion is further accelerated, causing early failure.
(2) Significant Loss of Mechanical Strength
Pure copper has low high‑temperature strength and is prone to softening and creep.
At 100–200 ℃, strength decreases by about 10%–20%.At 300–400 ℃, strength drops by 30%–50%, and plastic deformation under load becomes unavoidable.
Above 500 ℃, residual strength is less than one‑third of room‑temperature strength, making it unsuitable for any load‑bearing structure.
(3) Deterioration of Electrical and Thermal Conductivity
Although copper remains highly conductive at high temperatures, its electrical resistivity increases with temperature (approximately +0.4% per ℃).
At 500 ℃, resistivity nearly doubles, reducing conduction efficiency and increasing heat generation.
Thermal conductivity also decreases gradually at elevated temperatures, weakening its heat‑dissipation advantage.
2.3 Recommended Long‑Term Operating Temperature Ranges
<= 120 ℃: Standard long‑service temperature for electrical components, cables, and heat exchangers; stable and reliable.
120–250 ℃: Acceptable for medium‑term service but with accelerated aging; requires regular inspection.
> 250 ℃: Not recommended for continuous long‑term use.
> 500 ℃: Only for extremely short‑term exposure; long‑term use will lead to rapid failure.
2.4 Improvement Measures for High‑Temperature Applications
Surface coating: Nickel‑plating, tin‑plating, or silver‑plating to isolate oxygen.
Controlled atmosphere: Use in inert or reducing atmospheres (nitrogen, hydrogen) to suppress oxidation.
Alloy substitution: Brass, bronze, or copper‑nickel alloys provide much better high‑temperature stability.
Structural design: Allow thermal expansion space and reduce thermal stress.
2.5 Summary
Pure copper is excellent for thermal and electrical conduction at low to moderate temperatures (<= 150 ℃).
However, due to rapid oxidation, severe softening, and declining mechanical properties, it is not suitable for long‑term high‑temperature service above 250 ℃.For high‑temperature engineering applications, material selection should favor heat‑resistant copper alloys or surface‑protected copper components, with strict limits on operating temperature and service environment.
