Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ...

13Since there was such a demand for wrought iron in the late 19 th century, manymechanical processes were invented to increase the production and quality of wroughtiron. These mechanical processes were needed to increase production capacity andreduce the amount of labor dependence that existed in the previous processes. Many newfurnaces were introduced, but none were very successful in their attempts.Concurrent with the attempts to improve the mechanical manufacture of wroughtiron, Henry Bessemer developed a new process for making steel, which was introducedaround 1855. Before this, the methods for making steel were very complex and tedious,therefore making steel was rare and more expensive to use for any sort of buildingpurposes. These processes are known as the cementation and crucible processes.Developed many years before-hand, these steel-making processes involved the additionof carbon to iron by soaking iron in carbon and letting it set over time, or meltingwrought iron and mixing it with a carbonaceous material (Stoughton, 1934).The basic concept of the Bessemer process depends on the successful rapidoxidation of the impurities (Si, Mn and C) by keeping the iron ore in a fluid molten bathwith extreme heat, thus forcing the slag to separate from the steel by floatation (Johnson1928). This was done by subjecting molten pig iron to a superheated pressured blast forabout twelve to fifteen minutes. Figure 2.5 depicts a picture of a Bessemer Converterduring one of these blasts. After oxidizing all the impurities out of the molten iron, analuminum and manganese alloy carrying several percent carbon was added. Theintroduction of this alloy resulted in the addition of carbon to the molten iron, making itsteel. Then the molten steel is poured and solidified into ingots and castings which arethen rolled into shapes (Johnson, 1928).The original Bessemer process created a brittle steel that was not useful. Then in1856 Robert Mushet discovered that by adding a compound containing manganese andiron to the molten iron in Bessemer’s process, the resulting steel could be made moreductile and have superior strength (Fisher, 1963). Bessemer and Mushet received many