The Microscopic Studies on the Ancient Iron Objects from Archaeological Excavation of the North of Iran

The metal working is an ancient art. There are evidences that, already millennia before Christ, metals were known and used. Knowledge of using metals in manufacturing various objects is one of the oldest technologies in ancient time. It is proved that many Ancient iron objects are helding at museum of worldwide were found from different archaeological excavations. In the history of ancient metallurgy, Iran is one of the important regions and many of metallic collections have been found from the different periods of Iranian historical sites. The origin of using metals in this country dated back to 9000 B.C. The evolution of the metal processing depends on several: chemical, physical, technological etc. The initial metals were produced via working on the metallic material that there were in the nature as natural mode. Afterwards, with the introduction of the possibility of melting down the metals, they passed to Copper, Bronze and then Iron age. The usage of iron in metal’s production is so important insofar as it has even given its name to an era, exactly “the Iron age” that, started of the First millennium B.C. and continued until few years ago. Once ignited the fire, it was fed by an opposite ventilation to increase its temperature that did not anyway exceed 1,200 degrees and then in sufficient to liquefy a steel. Vice versa they obtained a reduction of the Iron oxides in practically pure Iron, which at the end of the process appeared as a spongy mass mixed with scales and slags. It started at this point tiring process of forging and successive heatings of the mass separate Iron form impurities. The result was very mild steel, easily workable, called also “wrought Iron”. Nowadays, defining of characteristic of anceint metals is a vital issue for researchers. Identifying the different features of materials, producing methods, etc are the main subjects in the studying of ancient metals. From varied aspects, the microstructure of Iron Artifact is an important question. Conservation seeks to preserve as much evidence about the past as possible without alteration of the original fabric or form of the artefact. In this article, the microstructure of five ancient metal objects have been studied with microscopic, metallographic and SEM-EDS methods. Identifying microstructures of the objects and their manufacure methods are the aims of this research. Samples included two nails and one Iron blade and one Iron lancehead and one blade that have been collected from Pahlooj site (dated to Sassanid) and Lafoorak site (dated to Iron Age III) respectively. These sites are located in Lafoor region, Mazandaran Province, the north of Iran that have been excavated under rescue excavation in 2008 (1387 H.). The aim of selecting these samples in two adjacent sites that belong to two different periods is to study the possible differences or similarities of producing techniques and utilization of iron for making objects. Samples were selected form the sites of Lafoorak and Pohlouj in terms of geographic coordination. Microscopic observation and elemental analysis of these objects is representing the high purity of Iron in structure of used ore. Long and round inclusions with high abundance of Fe, O2, Si elements have been distinguished as main structure in all samples. Moreover, other elements have been identified. These elements considered as impurities in inclusions and incompleteness in manufacturing of objects. In microscopic pictures, distinct grain sizes of ferric structures with diffused inclusions in different proportion are seen. These differences are considered as a result of hot and cold working with forging on the objects. In contrast with other samples, one object with needle shape and martensitic structure has been observed. Overall, all of the evidences are in line with producing wrought Iron in manufacturing the objects in ancient times.