STEEL

STEEL

Steel is the sinews of our modern civilization. Everywhere we turn, we see structures of steel buildings, bridges, railroads, factories, machinery, as well as many smaller things, tools, household appliances, furniture. In fact, some scientists who have traced the history of man through the Stone Age, the Bronze Age, call the present the Steel Age.

Steel is made from iron by the removal of impurities and the addition of small amounts of other substances. Iron is one of the most plentiful of elements on our earth. Dig a spadeful of earth anywhere and you are practically sure to find some iron in it.

The earth in which there is a proportion of iron high enough to make its extraction commercially profitable is called "ore." The United States is rich in iron ore; there are especially large deposits in Minnesota and Pennsylvania.

Iron rarely occurs in pure form; it is almost always found in chemical combination with other elements, such as oxygen, sulphur, silica. The process of extracting pure iron from the ore is called "smelting." This process consists essentially of heating the ore so as to liquefy it. The iron, being the heaviest ingredient, sinks to the bottom and so can be drawn off the bottom of the smelting furnace, while the lighter materials float to the top as "slag." Iron is turned into steel by further heating and purification, plus the addition of manganese and other elements to give the desired qualities of hardness, ductility, and so on.