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

79are not similar to that of steel and indicate the wrought iron has lower strength andductility.The non-uniform nature of the microstructure of the wrought iron caused by theamount and irregular distribution of impurities and inclusions in the material create pointsof higher stresses that initiate crack growth through out the material. This reduces thestrength and ductility of the material. The lack of uniformity also makes it difficult toaccurately determine a definite yield and ultimate strength, since the amount of inclusionsfound in wrought iron varies considerably. This variation in microstructure is the reasonwhy a significant variation in mechanical properties was observed in the historical datagathered for wrought iron.4.2 Chemical AnalysisA chemical analysis of the wrought iron test material was completed to determinethe elements present. Table 4.1 shows the results from this chemical analysis. Theelements that were found to be prevalent in Eyebars E1 and E2 included carbon,phosphorous, sulfur, and most importantly, silicon.The amount of silicon present in the wrought iron and was between 0.12 and 0.15percent by weight. In steel, silicon amounts exceeding 0.3% are sometimes used incertain heat-treatable alloy steels and electrical steels (Linnert, 1994). Silicon typicallypromotes the fluidity of the metal while it is being processed into shapes and it alsopromotes hardenability. In wrought iron, silicon can be found mainly in the slag that isdispersed in pockets through out the metal. This slag causes an overall decrease instrength, but also helps to prevent corrosion. Since slag is a major component in thedefinition of wrought iron, the presence of silicon in excess of what is typically found insteel would be a crucial step in identifying an unknown metal as wrought iron.