Analytical and microstructural approach to the study of historical ultra-high carbon (UHC) steel plaques belong to the Malek National Library and Museum Institution, Iran

A number of steel plaques in Iran belong to Safavid period (17th century) were examined for their chemical composition and microstructure. The artefacts were analyzed using micro-PIXE, SEM-EDS and reflected light microscopy (OM). According to SEM-EDS and micro-PIXE analyses, it was revealed that the plaques were made of mostly pure iron (approximately 99 wt%). Presence of trace amounts of manganese, sulfur, chromium, silicon, titanium and potassium were identified in the plaques. Metallographic investigation showed that the plaques were made of hypereutectoid steel with a microstructure consisting of spherical particles of carbide in the ferrite and pearlite background. Moreover, the use of ultra-high carbon (UHC) steel with microstructure of pearlite matrix and needle-like Widmanstätten cementite was identified in one plaque. These features showed that Safavid plaques have been made of crucible steel. In addition, it demonstrated that complicated forging/heating cycles have been used for manufacturing of these openwork steel plaques. It was also revealed that in addition to arms and armors, crucible steel has served as an everyday work material in Safavid period in Iran.