Learning Objective One

You need to have an understanding of the source, production and classifications of metals

Sources and production

With the exception of gold, all metals are found in the form of oxides or sulphates. They need to be extracted from the ore before any useful processing can take place. Click here to see extraction details.

Ferrous Metals are extensively produced in blast furnaces with the addition of carbon, in the form of coke, and limestone, and mild steel with other materials, such as chromium and tungsten. Click here to see the conversion and blast furnace process and the Basic Oxygen Furnace.

Non-ferrous metals are mainly produced by electrolysis. This is a very expensive because electrical energy costs are involved. Click here to see the Electrolysis process.

Classification

Metals are classified as ferrous, non-ferrous or as alloys. Below is a table that highlights the main differences.

 

Ferrous	Alloys	Non-ferrous
Metals that are composed mainly of ferrite or iron	Metals that have been formed by mixing two or more metals and sometimes other elements to improve their properties.	Metals that contain no iron and almost entirely consists of pure metals
Metals that are magnetic	Alloys are normally grouped into ferrous and non-ferrous alloys	Metals are non-magnetic
Metals that corrode easily (turn orange)		Examples are Aluminium, Copper, Zinc, Tin and Lead
An example is Iron

Learning Objective Two

You need to have an understanding of the formation and structure of metals

Formation

With the exception of mercury, all metals are solid at room temperature. In their molten state they are weak and flow easily. As the cool and solidify, small crystals are formed and the atoms arrange themselves in a regular pattern- a lattice structure

Structure

Finally, small crystals and grains are formed. The crystalline structures fall into one of the three basic forms and will determine the properties of the metal.

On further cooling, the crystals continue to grow in a tree-like formation called a dendrite. Each dendrite grows in a geometrical pattern consistent with the lattice structure until it meets with neighboring dendrites at which point the branches thicken to form a solid grain of metal. Each grain has the same lattice structure but a different orientation. Grains and grain boundaries are visible when viewed under a microscope. This crystalline structure generally gives the characteristics of metals which are good strength, stiffness, ductility, conductivity and toughness. In short, they are ideal structural materials.