.commonly used ferrous metals
. main raw materials used for the smelting of pig-pron and their uses
. constructional features of a blast furnace
. properties and uses of pig iron
Metals which contain iron as a major content are called ferrous metals. Ferrous metals of different properties are used for various purposes.
The ferrous metals and alloys used commonly are
-pig iron
-cast iron
-wrought iron
-steel and alloy steels
Different processes are used to produce iron and steel.
Pig-iron obtained by the chemical reduction of iron ore. This process of reduction of the iron ore to pig-iron is known as SMELTING.
The main raw accoutrements needed for producing gormandizer-iron are
-iron ore
-coke
-flux
IRON ORE
The cheif iron ores used are
-magnetite
-hematite
-limonite
-carbonite
These ores contain iron in different proportions and are 'naturally ' available.
COKE
Coke is the fuel used to give the necessary heat to carry on the reducing action. The carbon from the coke in the form of carbon monoxide combines with the iron ore to reduce it to iron.
FLUX
This is the mineral substance charged into a blast furnace to lower the melting point of the ore, and it combines with the non-metalic portion of the ore to form a molten slag.
Limestone is the most commonly used flux in the blast furnace.
BLAST FURNACE
The furnace used for smelting iron ore is the blast furnace. The product obtained from smelting in the blast furnace is pig-iron. The main parts of the blast furnace are
-throat
-stack
-bosh
-hearth
-double bell charging mechanism
-tuyeres
SMELTING IN A BLAST FURNACE
The raw materials are charged in alternate layers of iron ore, coke and flux in the furnace by means of a double bell mechanism.
The hot blast is forced into the furnace through a number of nozzles called tuyeres.
The temparature of the furnace just above the level of the tuyeres is between 1000°c to 1700° c when all the substance start smelting.
The limestone, which serves as a flux, combines with the non metalic substances in the ore to form a molten slag which floats on the top of the molten iron. The slag is tapped off through the slag hole.
The molten iron is trapped at intervals through a separate tapping hole.
The molten iron may be cast in pig beds or used in other processing plansts of steel making.
PROPERTIES AND USE OF PIG-IRON
Pig iron absorbs varying amount of carbon,silicon, suphur, phosphorus and manganese during the smelting process. A high amount of carbon makes the pig-iron very hard and brittle and unsuitable for making any useful article.
Pig iron is therefore refined and remelted and used to produce other varieties of iron and steel.
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