Common Metals

Iron

Iron Production

Up until World War II, U.S. production represented a sizable portion of the world’s production of iron ore, but after WWII, large high-grade deposits were discovered and put into production in Canada, Brazil, and Australia.
Until 1982 most iron ore mines were owned by steel companies. Then many steel companies began to sell off mines. Many of the smaller companies in United States went out of business.

Iron Ore Company of Canada (IOC), the largest producer in Canada, came into operation in 1954, Quebec Cartier Mines started up in 1957, and Wabush Mines, the second largest producer, in the late 1960s. Today China is one of the worlds largest producers of iron.
Iron is one of the cores that the United States and many other countries were built on. Iron railroad tracks built from one end of the United States to the other opened up the country to settlers.


In spite of all that has been written about iron and steel there are many hazy notions in the minds of many mechanics regarding them. It is not always clear as to just what makes the difference between iron and steel. We know that high-carbon steel makes a better cutting tool than low-carbon steel. And yet carbon alone does not make all the difference because we know that cast iron has more carbon than tool steel and yet it does not make a good cutting tool.

Pig iron or cast iron has from 3 to 5 per cent carbon, while good tool steel rarely has more than 1¼ per cent of carbon, yet one is soft and has a coarse grain, while the other has a fine grain and can be hardened by heating and dipping in water. Most of the carbon in cast iron is in a form like graphite, which is almost pure carbon, and is therefore called graphitic carbon. The resemblance can be seen by noting how cast-iron borings blacken the hands just as does graphite, while steel turnings do not have the same effect. The difference is due to the fact that the carbon in steel is not in a graphitic form as well as because it is present in smaller quantities.

Iron Transformed Into Steel

Iron is shaped into steel for commercial use in rolling mills. Here successive passages of the red-hot ingot between variously shaped rollers give it the desired form. Pittsburgh, one of the world’s great steel centers, built its first rolling mill in 1811; Bessemer steel rails were rolled in Chicago as early as 1865.

iron industry

The Bessemer process, the open-hearth process, and the basic oxygen process are more widely used in modern iron production for steel buildings. The open-hearth uses a regenerative furnace; instead of a firebox at one end and a flue at the other, it has devices at each end for the intake and outflow of both fuel and air.The open hearth process was developed in 1866 by Sir William Siemens and is till date used in modern iron production.

In making steel in the old way the cast iron was melted and the carbon and other impurities burned out of it, the melted iron being stirred or “puddled,” meanwhile. The resulting puddled iron, also known as wrought iron, is very low in carbon; it is tough, and on being broken appears to be made up of a bundle of long fibers. Then the iron was heated to redness for several days in material containing carbon (charcoal) until it absorbed the desired amount, which made it steel, just as case-hardening iron or steel adds carbon to the outer surface of the metal. The carbon absorbed by the iron does not take on a graphitic form, however, as in the case of cast iron, but enters into a chemical compound with the iron, a hard brittle substance called “cementite” by metallurgists. In fact, the difference between the hard, brittle cementite and the soft, greasy graphite, accounts for many of the differences between steel and gray cast iron. Wrought iron, Page x which has very little carbon of any sort in it, is fairly soft and tough.

iron beams

The properties of wrought iron are the properties of pure iron. As more and more carbon is introduced into the iron, it combines with the iron and distributes itself throughout the metal in extremely small crystals of cementite, and this brittle, hard substance lends more and more hardness and strength to the steel, at the expense of the original toughness of the iron. As more and more carbon is contained in the alloy—for steel is a true alloy—it begins to appear as graphite, and its properties counteract the remaining brittle cementite. Eventually, in gray cast iron, we have properties which would be expected of wrought iron, whose tough metallic texture was shot through with flakes of slippery, weak graphite.

But to return to the methods of making steel tools in use 100 years ago.

The iron bars, after heating in charcoal, were broken and the carbon content judged by the fracture. Those which had been in the hottest part of the furnace would have the deepest “case” and highest carbon. So when the steel was graded, and separated into different piles, a few bars of like kind were broken into short lengths, melted in fire-clay crucibles at an intense white heat, cast carefully into iron molds, and the resulting ingot forged into bars under a crude trip hammer.