The melting point of copper is 1083℃, which is lower than that of nickel and iron, and the evaporation rate of copper is much higher than that of nickel and iron, which limits the application of copper in the structure of electric light sources. Its working temperature should not be higher than 400~500℃.
Copper is a reddish metal. Its biggest feature is that its electrical conductivity and thermal conductivity are better than other metals (second only to silver); its thermal expansion coefficient is very large, so it cannot be matched with glass for sealing.
In terms of mechanical properties, copper has good toughness and ductility, and great plasticity, so it can be non-matched with glass for sealing. Even cold copper can be processed well. After processing, its elongation decreases, while its strength increases. The annealing temperature of copper is 600~650℃. When heated above the annealing temperature, copper recrystallizes and causes grain growth, resulting in reduced mechanical strength.
The creep limit of copper is very low, so copper parts are prone to deformation when working for a long time at high temperature.
Copper has another advantage, that is, it has low gas permeability and will not leak even if it is very thin. This is very valuable for vacuum technology and can be used to make bellows in vacuum systems.