Metallurgy may be described as the process of working metal into tools and artifacts. Metals are less commonly found in their pure form; in most of the cases they are found as their ores. Copper and iron were the first metals used by early man. Metallurgy is the process of extracting valuable metals from their ores and refining the extracted metals to a more pure form.
Minerals from which the metals can be extracted economically are called ores. Metals occur in their free or combined state. Metals that are non-reactive, such as gold, platinum and silver, are usually found in their free state. Metals such as aluminum, iron and copper, those that are more chemically reactive, are found in the combined state.
Classification of Ores
Ores are classified based on the type of compound that the metal forms.
- Native Ores – Those that contain metal in their free state
- Sulphurised and Arsenical Ores – These contain the metals as sulphides or arsenides
- Oxide Ores – These ores contain the oxide form of metals
- Halide Ores – These ores consist of the metallic halides.
The chief metallurgical processes are described below.
Concentration of Ore
Concentration of ore involves the removal of impurities and other physical processes, such as magnetic separation, hydraulic washing, and froth floatation.
Conversion of Ore Concentrate to Oxide
The concentrated ore is then converted into its oxide form by way of roasting, calcinations, and reduction.
Refining of the metal is done by processes such as liquidation, electrolysis, and distillation.