SUPPLEMENTARY TEXT:
Copper
Copper was used in prehistoric times for making weapons and tools and later was alloyed with tin to form bronze, which was the most important metal of the Greeks and Romans. It was replaced for these purposes by iron and steel. Various grades of copper are used for engineering purposes. The great development of the electric industries has resulted in such extensive uses of the metal that it now ranks next to iron in importance.
The copper alloys are more widely used. The alloying of copper with other elements increases the strength of the metal in some cases and improves the anticorrosive and antifriction properties in others. Copper alloys comprise two main groups: brasses and bronzes. Alloys of copper and zinc are called brasses. Alloys of copper with a number of elements including tin, aluminum manganese, iron and beryllium are called bronzes.
Dostları ilə paylaş: |
