Characterization of Sternpost Gudgeon of a Ship Found in the City of Buenos Aires

In December 2008 the remains of a wooden ship was discovered in Puerto Madero, down town in Buenos Aires. At preliminary observations, it would be a Spanish merchant ship from XVIII century. During the dig, remains from ship and loading were found. Among different kind of things, a sternpost gudgeon was found separated from the rest. This element has an important structural function in the ship associated with the support and guide of the rudder. The objective of the present paper is to analyze the geometric, structural and metallurgic characteristics from the mentioned artifact obtained at the archaeological site Zencity, to get a best understanding about the technology used to manufacture it, and a best knowledge of the complete finding. To this purpose, several analytical techniques were performed. First of all a visual and dimensional analysis was done on the piece. Then material was characterized by optical and scanning electron microscopy and chemical composition was determined by energy dispersive X ray spectrometry (EDS). Also microhardness was measured and non metallic inclusions were analyzed. According to results the piece would have been made of forged ferrous alloy with a significant complexity in its manufacturing. It presents forge welded areas with large slag inclusions. Ferritic-pearlitic structures differentiated according to the area were detected with different grain sizes, which would indicate heterogeneous temperature of hot working. Some Adjacent areas that show different contents of carbon were identified indicating the use of different materials, especially to form parts of larger thickness.