ZIMSEC O Level Geography Notes:Iron and Steel Industry:A case study of ZISCO
- This kind of industry is raw material based.
Raw materials required
- Iron ore (Fe) is used to make pig iron or steel; scrap metal may be used in its place.
- Limestone (CaCO3) is used to act as a flux, mixing with and removing impurities and forming slag in the process.
- Coke from coal is used to provide the heat to smelt the iron ore and the limestone.
- The raw materials stated above are poured at the top of the blast furnace using skips.
- Hot air is introduced at the base of the blast furnace and fires up the furnace
- At very high temperatures (1 500° C), the iron ore and the limestone smelt.
- Molten pig iron being heavier settles at the bottom of the blast furnace and slag settles on top of it as it is lighter.
- These are drawn out of the furnace through different holes.
- The slag will later be used to make fertilizer or can be used in the manufacture of bricks.
- The pig iron can directly be cast into ingots or into tools such as those at ZIMCAST in Gweru where it is used to make products such as three legged pots, charcoal irons, sewage and drains lids and wheels of steel ploughs.
- More importantly, the pig iron can be converted into steel.
- Here the pig iron is mixed with pure carbon or with manganese or with vanadium or chromium or nickel in a furnace, depending on the degree of technological advancement of the country or company involved:
- The open heath method
- The Bessemer convertor method
- The electric arc method and
- The oxyacetylene method
- The resultant steel can then be modulated into blooms or rolled into thin sheets, ready for sale.
- A lot of water (input) is required to cool the pig iron, the steel, the blast furnaces and steel mills.
- In the past, blast furnaces and steel mills were located at different site.
- However, modern trends have shown that it is more economical to have the two at one site.
- This is termed an integrated iron and steel works such as ZISCO in Zimbabwe.
To access more topics go to the O Level Geography Notes page