Metal is a broad umbrella term that can be used to include any material that is; solid, typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivity. Within the periodic table of elements 91 of the 118 are considered metals. 31 of which are known as 'transistion metals'. These are commonly used as they are typically hard, dense & have a range of practical applications
Between group 2 and 3 are 31 transistion metals which typically;
- form coloured compounds
- good conductors of heat and electricity
- can be hammered or bent into shape easily
- less reactive than alkali metals such as sodium
- have high melting points - (ex. mercury)
- are usually hard and tough
- have high densities
Further classification can be made by grouping the metals into Ferrous and Non-Ferrous categories;
Ferrous metals contain iron, which is notable by their magnetic properties and tendency to oxidize over time and form rust. Iron in its pure form is a soft and malleable material. Carbon is added to change it's properties and suitability for a range of applications. Cast Iron contains around 2-6% carbon and is very hard but brittle. Steel is typically used in favour of iron which has a lower carbon content which can be varied to achieve different properties
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Iron ore is mined and extracted from the earth as rock. The ore is mixed with limestone and carbon in a huge Blast Furnace which can produce up to 80,000 tonnes of iron per week. Hot blasts of air from copper pipes (tuyeres) at the base heat the mix to up to 1800 °C (Zone 1) . Over 6-8 hours the materials work their way down the furnace and are extracted as liquid iron and slag, the waste product. Coke, made from charcoal, is added as a fuel which due to its high carbon content speeds up the reaction. Limestone removes the impurities from the iron ore which are extracted as 'slag'
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Steel is formed by the addition of carbon (around 1%) to the iron ore in the blast furnace, forming an alloy. Oxygen is blown into the furnace which reacts with the carbon to form carbon monoxide/dioxide which escapes from the molton metal. Precisely controlling the oxygen content can change the carbon content for different grade of steel. Low carbon steel, used for car body work has a 0.5% carbon content whilst high carbon steel used for cutting tools has around 2.5%. Stainless steel removes the oxidation that occurs in ferrous metals by forming an alloy with chromium and nickel
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Alloys are a mixture of more than 1 metal that combines properties to form a new material. Providing one metal is present the material can be classed as an alloy, making Steel technically an alloy of iron & carbon. Importantly, alloys can contain atoms of differing size making it harder for the atomic layers to slide across each other increasing their hardness. Common examples are Brass (Copper & Zinc), Bronze (Copper, Tin) & Pewter (Tin, Copper, Antimony)
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Non-Ferrous metals contain no iron and are therefore not magnetic and generally have a higher resistance to corrosion. Typically they are used when properties such as conductivity (Copper), lower weight (Aluminium) and corrosion resistance (Zinc) is required. The use of non-ferrous metals such as aluminium has rapidly replaced steel due to the weight saving and durability required in the automotive and aerospace industry
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Copper is an important Non-Ferrous metal due to it's high conductivity both thermally and electricity. Conductivity is a determined by the number of free electrons in a metals outer atomic shell. This is known as the 'valence shell' and contains free electrons that can travel through the lattice structure of the metal. These electrons transfer energy between each other much like snooker balls on a table. In this analogy, a single ball hitting another transfers more energy than it hitting multiple on the table. Copper, therefore, with its single electron is a far greater conductor, as with Gold and Silver
Applications for Copper are therefore determined by this useful property.
60% is manufactured into
electrical wire (also due to the ductility of the metal),
20% used for
roofing and
plumbing for thermal conductivity and 15% for industrial machinery. Around
5% is used to
alloy (brass, bronze) with other metals to improve the
hardness due to it's inherent
malleable nature
Other useful properties are; corrosion resistant, antibacterial, easily joined, ductile, tough, non magnetic, attractive colour, easy to alloy, recyclable, catalytic (speeds up reactions)
Disadvantages include; high raw material cost, prone to oxidation and
green patina over time, low hardness so easily scratched, malluable making it easy to deform & colour change due to heat
