Characterization of two iron bullets from the royal ammunition factory of Eugi (Spain)

Abstract

In this work, a comparative analysis of two iron bullets found in The Royal Ammunition Factory of Eugi in Navarra (Spain) was performed. Both bullets presented a spherical shape with a relatively good state of preservation, belonging to the last years of the factory production (1766-1850). Several techniques such as microhardness, X-ray fluorescence (XRF), light (LM) and scanning electron microscopy (SEM), optical mission spectroscopy (OES) and energy dispersive X-ray spectroscopy (EDX) analysis were used in order to identify the manufacturing process of the two bullets. The analyses of the microstructures carried out by LM and SEM showed that one bullet was composed of white cast iron with a pearlitic matrix, steadite and graphite; while the other was composed of grey cast iron with a pearlitic matrix, graphite and a low amount of steadite. The chemical analysis of the bullets carried out by OES indicated significant differences in the amount of silicon and phosphorous. The variation in silicon content could suggest that the foundry temperature under oxidizing environment varied during the casting. The SEM and EDX analyses showed both bullets had manganese sulphide inclusions but only one of the bullets exhibited titanium and vanadium inclusions. The microhardness analyses carried out revealed Vickers hardness differences along the diameter. This variation could be explained by the differences in cooling rate along the diameter. Based on the physical characteristics of the bullets and on the obtained results, it can be concluded that one of the bullets could have been used as a grapeshot projectile and the other one as a bullet for ribauldequins. In addition, calcined ore and slag found in this factory were also analysed. The variation found in their chemical composition corroborated that the foundry temperature employed during the manufacturing process was low, the slag being enriched in Si, Al and Mn elements.

The Production of Marine Iron Objects in Europe Following the First Industrial Revolution: The Akko Tower Shipwreck Test Case

“…Grey cast iron (ternary iron-carbon-silicon alloys) is characterised by the content of more than 2 wt% C as graphite particles, the increased carbon content reducing the melting temperature of the alloy [28,31,32]. Cast iron objects are often cast in a sand mould containing a cavity of the desired shape, consisting of cope and drag (top and bottom parts) with an upper pouring space (cup and sprue), as well as a vent and riser [33] (p. 102, Figure 6).…”

“…The high concentration of manganese in cast objects (>0.5 wt% Mn) results in high-quality products with only a small amount of porosity defects attributable to the sand casting. The presence of manganese in cast iron products, to prevent the formation of gas holes and porosity, indicates a post-1839 manufacturing date [31][32][33].…”

Archives of Metallurgy and Materials

“…The differences in the graphite morphology are attributed to the different cooling rate of the samples, there is a lower solidification rate for the samples of 25.4 mm than the samples of 12.7 mm in thickness. The center of the plates of 25.4 mm remains hotter than the ones of 12.7 mm or the external surface, therefore, a major graphite formation is induced for the thicker sample [22], the super-cooling degree of the molten iron was small and graphite had excellent nucleation ability to form type-A graphite. Lacaze et al [11] reported that a type-A graphite distribution forms at low solidification rates and as the rate increases, a transition of type-D graphite distribution will occur.…”

Estudio microestructural y elemental de una munición de la Batalla La Trinidad de Sarapiquí de 1856

“…Las técnicas de microscopía óptica, microscopía electrónica de barrido (SEM, por sus siglas en inglés) y análisis elemental por energía dispersiva de rayos X (EDX por sus siglas en inglés), han sido ampliamente utilizadas en el análisis de muestras arqueológicas, logrando información sobre la microestructura, procesos de manufactura, grietas y abolladuras que sugieren posibles usos o sucesos y la composición elemental de una serie de objetos como artefactos metálicos (Leal, 2010), cerámicas (Amaya et al, 2008), fibras (Arenas et al, 2015), obras pictóricas (Barrantes-Madrigal et al, 2021), por mencionar algunos ejemplos. En el caso del análisis de municiones arqueológicas, se han realizado numerosos estudios dentro de los cuales se mencionan por ejemplo, Zalakain et al (2017). Los autores realizaron un estudio comparativo entre dos municiones encontradas en la Real Fábrica de Municiones de Eugi en Navarra utilizando las técnicas de caracterización SEM y EDX, que les permitió conocer los procesos de manufactura.…”