Unit 1: Metallurgy Flashcards

Metallurgy

The science and technology relating to metals, including their extraction from natural sources and preparation for practical use.

Mineral

A naturally occurring substance obtained by mining that contains a metal in its free state or in the form of compounds such as oxides or sulphides.

Ore

A mineral containing a high percentage of a metal from which that metal can be extracted conveniently and economically.

Gangue

The nonmetallic impurities, rocky materials, and siliceous matter naturally associated with an ore.

Concentration of Ore

The preliminary metallurgical step of removing gangue impurities from an ore to increase the concentration of the metal of interest.

Gravity Separation

A concentration method where finely powdered ore with high specific gravity is separated from lighter gangue particles by washing with running water.

Froth Flotation

A concentration method commonly used for sulphide ores where ore particles preferentially wetted by oil rise to the surface with froth while gangue settles at the bottom.

Depressing Agent

A reagent, such as sodium cyanide ($\text{NaCN}$), added during froth flotation to selectively prevent specific impurity metal sulphides from floating into the froth.

Leaching

A concentration process based on the solubility of an ore in a suitable solvent, converting the metal into a soluble complex while leaving gangue insoluble.

Cementation

The process of recovering a metal from a leached complex solution by reduction with a more reactive metal, such as reducing gold using zinc.

Magnetic Separation

A concentration technique applicable to ferromagnetic materials, using an electromagnetic belt separator to separate magnetic components from non-magnetic impurities.

Roasting

A process used to convert sulphide ores into oxides by heating the concentrated ore with excess oxygen below the melting point of the metal.

Calcination

A process in which a concentrated ore is strongly heated in the absence or limited supply of air to expel water of hydration or carbon dioxide.

Smelting

A process in which a flux and a reducing agent are added to concentrated ore and melted at elevated temperatures to produce crude metal.

Flux

A chemical substance added during smelting that reacts with acidic or basic gangue to form an easily fusible slag.

Slag

An easily fusible compound formed by the chemical combination of a flux and gangue during smelting.

Blistered Copper

Metallic copper obtained after conversion that has a blistered appearance due to the evolution and escape of $\text{SO}_2$ gas during solidification.

Ellingham Diagram

A graphical representation showing the variation of standard Gibbs free energy change ($\Delta G^\circ$) for the formation of various metal oxides as a function of temperature.

Hall-Heroult Process

An electrochemical method for extracting aluminium by electrolyzing alumina ($\text{Al}_2\text{O}_3$) dissolved in molten cryolite and calcium chloride using carbon electrodes.

Liquation

A refining method for metals with low melting points, where crude metal is melted on a sloping hearth so pure liquid flows down and high-melting impurities remain.

Zone Refining

A purification technique based on fractional crystallisation, where a mobile heater moves