Manufacturing processes are the means used to change a material from one state to another state of higher value. For example, iron ore is smelted to make pig iron that is converted to make steel. Next, the steel might be continuous cast before rolling to make sheet steel. This can be blanked to make car body frames; these frames are then assembled to other components to produce a finished car.
Although manufacturing is a secondary industry, it relies on primary industries such as mining and quarrying to supply the raw materials. Some materials used by manufacturing industry were examined in Chapter 6; in this chapter, we will look at the production of the metals iron, steel, copper and aluminium, and also basic polymer production. Most metals require to be mined since they are found in naturally occurring mineral deposits known as ‘ores’. In the natural state the metals are usually combined with other, undesired, elements. This ‘gangue’, is removed to leave the concentrated ore ready for the metal extraction process.
7.2 Ferrous Metals Production
7.2.1 Pig Iron
Pig iron is the initial raw material for all ferrous metals. The composition of the pig iron will determine how it will be used. Along with iron the alloys usually contain between 3 and 4% carbon plus a total of about another 3 or 4% of the elements silicon, manganese, sulfur and phosphorous.
Figure 7.1 shows the blast furnace, which is used for smelting the ore along with coke ...