- Published: 03 February 2010
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Billy Holmes, age 10, of Coulee Dame, for his question:
What is the difference between iron and steel?
Gold and iron pyrite look enough alike to fool almost anybody, Yet they are entirely different metals, Steel and iron look so different from each other that you might never guess they are related, A iron pot is dark and dull. It is thick and rough to the touch. It is brittle and unbending and tends to crack under stress. The blade of a fine steel knife is smooth and shiny like dark silver. It is thin and shaped. to a sharp point. Most important, it gives under stress, It bends instead of cracking. Yet, for all their differences, iron and steel are made from the same basic element. Steel is made from iron. It is refined iron, alloyed with traces of toughening materials.
Iron is one of the basic elements of which the world is made. It is plentifully sprinkled through the rocks of the earth. However, it does not occur in pure form, It tends to combine with oxygen and other elements. When the content of iron is high enough, such rocks are worthwhile iron ores. The most commonly used ores are the iron oxides, hemanite, magnetite and limonite.
The trick is to extract the iron from the other elements with which it is combined. This is done by heating the ore with limestone, Forty car‑loads of iron ore, limestone and coke are loa~3ed into a furious blast furnace. This 90 foot giant is fed by four seething stoves, Blasts of hot air are piped from the stove into the load of minerals in the blast furnace. The coke catches fire. At the top of the furnace, the temperature is 400 degrees Fahrenheit, it gets hotter and hotter towards the bottom where it reaches at least 3,000 degrees.
The terrific heat starts chemical changes in the seething brew. Some impurities are driven off as gases. Other: melt and float to the top of the molten mixtures. The iron, which is heaviest, sinks to the bottom and is drawn off through a tap.
Once started, a blast furnace never stops, day or night. For every ton of extracted. iron, it uses up two tons of ore, half a ton of limestone, one ton of coke and three and half tons of hot air from the stoves. The molten iron runs into a row of little troughs. They look like a row of feeding piglets, which is why this new made iron is called pig iron. Some will be sent to be made into heavy pots and pans of cast iron. Some will be sent to be made into wrought iron for fancy scroll work. But most of the pig iron is sent to the steel mill.
There are several methods of turning iron into steel. All of them require more heating and blasts of cold air. Still more impurities are driven from the iron. Other metals are added when the brew is at the molten stage. There are countless recipes for making different types of steel for different types of work, Much depends on the extra ingredients which turn the iron into an alloy, or mixed metal. Finally, the red hot chunks of steel are rolled and pounded to press cut the last impurities. The finished alloy, which is steel, is far stronger