Definition (Encyclopedia of Global Resources)
In the 1850’s, Henry Bessemer, looking for a way to improve cast iron, stumbled upon a way to make a new kind of steel. By blowing air through molten iron in a crucible, he was able to burn off the carbon and many harmful impurities, and then the iron was heated to the point that it could be poured into molds.
Bessemer eventually learned to add Spiegeleisen, a manganese-rich cast iron, to the molten iron after the carbon and impurities were burned off. The manganese countered the effects of the remaining traces of oxygen and sulfur, while the carbon (always present in cast iron) helped create the properties of steel.
(The entire section is 110 words.)
Overview (Encyclopedia of Global Resources)
Prior to the late 1850’s, there were two common iron-based construction materials. One was cast iron, an impure, brittle, high-carbon material used in columns, piers, and other load-bearing members. The other was wrought iron, a workable, low-carbon material used in girders, rails, and other spans. The word “steel” usually referred to a custom material produced in very small quantities by adding carbon to high-quality wrought iron.
Bessemer’s resulting product, which came to be known as “mild steel,” proved to be reliable and durable. Because of these qualities, and because it could be produced in large quantities, mild steel quickly found widespread use in rails, ship plates, girders, and many other applications, often replacing wrought iron.
(The entire section is 116 words.)