Over the years various countries have excelled in making steel. During the eighteenth century a relatively small amount of steel was made, but Sweden was the main producer. In the nineteenth century Great Britain became dominant. In the twentieth century the United States was the largest steel producer in the world until about 1970, when it was surpassed by the Soviet Union. At the start of the twenty-first century, China led the world in steel production.
Three primary installations in an integrated steel plant are the blast furnace, the steel furnaces, and the rolling mills. The blast furnace converts iron ore to pig iron; the steel furnaces convert the pig iron to steel; and the rolling mills shape the steel into sheets, slabs, or bars.
Blast furnace. A blast furnace is a chimney-like structure in which iron ores (mainly FeO, Fe 2 O 3 , and Fe 3 O 4 ) are converted into iron metal. Iron ore, coke, and limestone are loaded into the top of the furnace, while air is blown in from below. The coke is converted to carbon monoxide (CO), which then acts as the reducing agent:
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