Properties of pig iron
Pig iron is also known as crude iron. It is obtained from a smelting furnace in the form of oblong blocks and has a very high carbon content of 3.5 – 4.5 as it contains 90% of iron. It is produced by smelting iron ore with high-carbon fuel and reductant such as, coke usually with limestone which serve flux. Other materials like anthracite and charcoal are used as fuel.
The term ‘pig iron’ derives from the old manner of dealing with molten iron. It was run off direct from the furnace into, open channels which feed into numerous short channels on either side, bearing a faint semblance to a sow suckling iron piglets. Pig iron was broken off from the sow when solid. A small amount of cold iron is still known as pig iron today. The term ‘hot metal’ is used to denote molten iron.
Composition of Pig iron
Pig iron contains about 90-95% of elemental iron together with a number of other elements mainly carbon, silicon, phosphorus, manganese and sulphur – in varying proportions depending on the compositions of the raw materials and the mode of an operating blast furnace.
Pigs may hold from 3.0 – 4.5% of carbon, 0.5 – 4.0% of silicon, 0.025 – 2.5% phosphorus, 0.15 – 2.15% manganese and up to 0.2% sulphur. The composition required for steel making differs from that required for use in foundries to make iron castings.
Merchant pig iron
Merchant pigs are cold pig iron cast ingots. It’s then sold to third parties as feedstock for steel and ferrous casting industries. It is produced by the dedicated merchant plant (all production is sold to external customer), an integrated steel mills with iron that is surplus to their internal requirements and cast into ingots and sold to the merchant market.
Types of merchant pig iron
Merchant pigs are basically of three main types:
1. Basic: it is mainly used in electric arc steelmaking
2. Foundry: it is known as hematite pig iron, used mainly in manufacturing of grey iron castings in cupola furnaces.
3. High purity: it is known as nodular pig iron, used for manufacturing ductile. High purity pig iron is also called spheroidal graphite – SG iron castings.
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