Thursday, February 25, 2010

History of Iron Production

If you are interested in the process of turning iron ore to various forms of usable iron and steel (and I know you are), then this is a good overview.

To sum up so far: wrought iron has a little carbon (.02 to .08 percent), just enough to make it hard without losing its malleability. Cast iron, in contrast, has a lot of carbon (3 to 4.5 percent), which makes it hard but brittle and nonmalleable. In between these is steel, with .2 to 1.5 percent carbon, making it harder than wrought iron, yet malleable and flexible, unlike cast iron. These properties make steel more useful than either wrought or cast iron, yet prior to 1856, there was no easy way to control the carbon level in iron so as to manufacture steel cheaply and efficiently. Yet the growth of railroads in the 1800s created a huge market for steel. The first railroads ran on wrought iron rails which were too soft to be durable. On some busy stretches, and on the outer edges of curves, the wrought iron rails had to be replaced every six to eight weeks. Steel rails would be far more durable, yet the labor- and energy-intensive process of cementation made steel prohibitively expensive for such large-scale uses.

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