First, many types of metals do not have to be made, for they are already elements. These elemental metals include gold, copper, silver, tin, lead, titanium, aluminum palladium and platinum. Many metals need to be extracted from ores, which are minerals that are abundant in them. The metals are then alloyed to other metals or compounds to make metals that are stronger or harder. Other metals need to be melted down or softened to be made into useful shapes. Separating metals from their ores to make them useful is called metallurgy.
Metallurgy is one of the oldest of the sciences, and even the ancient Egyptians and Assyrians practiced it very effectively. There are several ways to extract a metal from its ore.
In mineral dressing, the metal is extracted by grinding the ore. Nonmetallic substances are removed before more waste and debris are washed away, leaving the metal.
With roasting, the ore is heated so that sulfur and other contaminants are removed to leave the metal behind. Sintering is like roasting, but the temperatures are much higher. This causes some particles of the ore to melt and stick together to form lumps which are then easier to process.
Smelting occurs after these preliminary processes. In smelting, the ore is melted to remove even more impurities. Iron is extracted from its ore by smelting in a furnace. Other metals are retrieved from their ores by leaching, or hydrometallurgy. This process dissolves the metal out of the ore with a chemical, and the metal precipitates out of the chemical solution. This is how gold is usually obtained. Electrolysis is another way to separate a metal from its ore, as can be seen in aluminum:
Aluminum is silver, lightweight and does not rust but is exceptionally difficult to extract. It needs to be taken out of bauxite ore before it can be used, and this is usually done by the Bayer process. In this process, bauxite ore is crushed then added to a bath of lime, soda ash and water. It’s then sent to a digester where it is heated under steam pressure. The soda, which is caustic, dissolves aluminum oxide, or alumina from the ore and leaves impurities behind. The filter then separates the solids from the solution.
The solution cools in a precipitator, where the aluminum oxide precipitates out as crystals. The aluminum oxide mixes with water and settles to the bottom of the precipitator while the caustic soda solution returns to the digester. The aluminum oxide and water are then placed in a rotating kiln, which takes away the water and leaves the aluminum oxide. Finally, pure aluminum is retrieved when the alumina is dissolved in a cryolite solution in an electrolytic cell. The aluminum precipitates out onto the cathode. Then, workers siphon off the molten aluminum and pour it into molds. The aluminum in the mold is either a pig or a sow. A pig is a 50 pound piece of raw aluminum, while a sow is a 1000 pound piece. Then, aluminum can be placed in furnaces to be made into plates, sheets, bar, rods, tubes, wires or forgings.
Magnesium is also obtained through electrolysis, though in its case this plentiful metal is removed from seawater.
Some metals are retrieved by amalgamation. This is a popular way to separate silver and gold from their ores. The ore is finely ground then carried by a solution over mercury covered plates. The mercury attracts the metal and bonds with it to form a alloy, or an amalgam with the silver or gold. The amalgam is heated to the point where the mercury boils then off gasses. This leaves pure gold and silver behind. By the way, mercury is itself a metal, but it is unusual because it is a liquid at room temperature.
There is another type of metallurgy called physical metallurgy. This is where metals are combined to form alloys. Physical metallurgy doesn’t have to be as complicated as the metallurgy already discussed. A blacksmith is practicing it when they hammers a horseshoe and so is an ironworker when they shape iron into beautiful figures for garden furniture or railings.
Hundreds, if not thousands of metal alloys exist. They make the difficulty of metallurgy worth it, for they have made human civilization possible.