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How to get metals from rocks[change | change source]
Ores are rocks that have a chemical compound of a metal with oxygen, called an oxide. Separating the oxygen from the metal is called smelting. This is done with chemistry or electricity, usually at very high temperatures. This is the first step in metallurgy. A rock containing enough metal to be profitable is called ore.
Iron is smelted from iron ore in large reactors called blast furnaces. A blast furnace is a tall vertical structure which is fed with coke, iron ore and limestone. When hot air is blown in the blast furnace, the coke will burn and reduce the oxygen off the ore, producing bare iron and carbon dioxide. The limestone will bind off any remaining bedrock. The iron melts in the hot temperature and is tapped off in liquid phase at the bottom. It is then worked into steel. The limestone and bedrock form a compound called slag. It can be used for making bricks, concrete or road topping.
Aluminum is smelted in electric ovens called electric arc furnaces. The aluminum ore is poured on the bottom of the furnace and electric current is led through the ore. The temperature rises so high that the oxygen separates, leaving metallic aluminum.
Copper is poured on naked flame which burns off sulfur and other impurities, leaving raw copper. Electrolysis uses electric current to separate the copper in big pools, which contain water solution called electrolyte. An electric current is led in the pool, and all copper will gather on the electrode called cathode.
Metal parts[change | change source]
Another part of metallurgy is making parts from metals. These parts must be made so they will not break when they are used. Metallurgists work to make the metal good when they are used. Sometimes the metal must be strong. Other times it must be tough (not easily broken). The metallurgist must follow directions when making the part to know what metal to use. Steel has a low cost, but rusts. Choosing a good metal is sometimes hard.
Making metal parts[change | change source]
A metal starts as a block, called an ingot. Metallurgists must know how to make a metal part from an ingot. Parts are made from ingots different ways. When a big hammer is used, it is called forging. To make thin metals, a metal is put between two rolls and moved, called rolling.
Making metal hot makes it easier to change the shape of a metal part. For this reason, most metal parts are made using hot metal. This is hot work.
Two metal parts can be put together with much heat. This is called welding. Iron is easy to weld.
How to know what to do to the metal[change | change source]
Metallurgists use many tools to know what to do to the metal. The most useful is the microscope. The microscope gives much information about the way the metal moves. Metals are sometimes pulled until they break. This is the tension test. Some useful information can be gotten from this test.