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

8imperfections, the performance of the material will vary considerably. The properties ofthe material depend on the iron ore it was manufactured from and the individual that wasmanufacturing it. Since it is difficult to find consistency in both of these dependencies, itis also extremely difficult to find consistency in the material properties.2.1.2 Manufacturing Process of Historic Wrought IronIn 1784 Henry Cort patented a new process called the puddling process forproducing wrought iron. In this process, a reverberatory type furnace was utilized inheating the iron ore. This furnace consisted of a “firebox”, where the fuel was burned,and was separated from the hearth, which contained the iron ore, by a bridge (Dennis,1963).After separating the iron ore, from the heat source, the iron ore was placed in alarge hearth that was typically 6 feet by 4 feet in dimensions, which in Henry Cort’soriginal furnace was lined with fire-brick and sand. Unfortunately the iron ore wouldoften oxidize with the sand creating extra iron-silicate slag and therefore reducing theamount of iron produced by 30% (Aston, 1949).The amount of impurities in the wrought iron was reduced in 1830 when JosephHall modified Cort’s process, known as “dry puddling”, by lining the hearth with olderhearth material such as iron silicate which contained iron oxide. This change increasedthe yield of wrought iron from iron ore, or pig iron, to 90% (Dennis, 1963). This newprocess became known as “wet puddling”.Figure 2.2 shows a section of the puddling furnace as described above. Thepuddling furnace capacity ranged from 300 pounds to 1500 pounds of wrought iron perheat (Johnson, 1928). A single heat typically took about one and a half hours tocomplete. After heating, the wrought iron was shaped into a ball, commonly called a