Steel
an alloy of iron and carbon. It is midway in structure between cast iron and wrought iron. It contains less carbon than cast iron and more carbon than wrought iron. Examined under a microscope, steel is found to be composed of many particles of extremely soft, ductile iron, and a comparatively few particles of a hard, brittle compound of iron and carbon.
There are various kinds of steel. The percentage of carbon varies from a half of one per cent to two per cent. The steel used for the armorplating of battleships contains about three per cent of nickel. Manganese steel contains about twelve per cent of manganese and one and one-half per cent of carbon. It is ductile but it is too hard to be cut by tools. It is used in the construction of burglar-proof safes. Chrome steel, used for the same purpose and for the armor of projectiles, also in the construction of stamp mills, contains about two per cent of chromium.
The greater part of what is known as iron work now consists of steel. Four-fifths of the world's steel is manufactured in the United States, Germany, and Great Britain. Next in order come Russia, France, and Austria-Hungary. The total annual production is not far from 40,000,000 tons. This enormous product is used in the manufacture of fine cutlery, tools, implements, barbed wire, wire nails, bolts, rivets, chains, pipe, sheathing, vehicles, cars, rails, locomotives, steamers, machinery, armorplate, girders, beams, pillars, bridges, firearms, and cannon. Steel is replacing wood very rapidly in the construction of machinery and as a building material.
Ordinary iron ore contains more carbon than is required for steel. In making steel it is necessary, first of all, to purify the iron by burning out the carbon. After that the elements for the alloy are introduced. The chief methods of getting rid of the carbon are known as the Bessemer process and the Siemens or open-hearth process. In the Bessemer process a powerful current of air is forced through holes in the sides of a graphite crucible containing from three to fifteen tons of molten iron. A tremendous bubbling and a shower of sparks characterizes this process. When the carbon in the iron has been burned out in this way a process occupying twenty-five to forty minutes, the converter contains pure iron. A small amount of fresh ore, containing the right quantity by weight of the various elements needed for the alloy is then added, and the contents of the converter are run into a mold to form billets of steel. In the open-hearth process the iron is melted in shallow, dish-shaped graphite crucibles. A powerful blast of air passes to and fro over the surface, thus burning out the carbon.
The steel works of the United States produce two tons of Bessemer steel to one of open-hearth steel. In Great Britain, the open-hearth method is in the lead. Blister steel is produced by sealing up carbon and bars of wrought iron hermetically and heating them for days in a furnace. Blister steel hammered at a welding heat produces the best of all steel. It is known as shear steel. It is used for fine cutlery.
The leading steel company, in fact, the richest manufacturing concern in the world, is the United States Steel Corporation, with headquarters at Pittsburg, Pennsylvania. It controls 125 lake vessels, several rail-roads, 18,000 coke furnaces, 78,000 blast furnaces for pig iron, and about 150 steel works, with an annual capacity of 9,000,000 tons of steel. The company employs nearly 200,000 men and pays anywhere from $100,000,000 to $140,000,000 a year in wages. The annual dividends to stock-holders are from $10,000,000 to $20,000,000.
See Bessemer; Carnegie; Krupp; Needle; Razor; Armor; Nail; Rail-Road; Bridge; Iron