ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 22 CONCLUSIONS The objective of this study is the metallographic and historical analysis of two pieces from the Buenos Aires to Pacific Railroad. The threaded bolt is a connecting element, and there is a difference in the size of grain between the parts of the head and the stem. These differences are due to the various types of machining in the production process. These production processes give the pieces the necessary strength to withstand the mechanical stresses to which they would be subjected. Manganese, one of the chemical elements with the greatest presence, provides greater and better ductility characteristics. On the other hand, the fixing nail has a metallographic structure where the carbon is deposited at the borders of the grain edge, which gives it strength and functional characteristics. This deposited carbon would form a kind of shell or shield to protect the material and make it more resistant. It is similar to a modern thermo- chemical treatment called cementation, where the material retains a soft heart, and its surroundings are hardened as a protective shield. Being a clamping piece, it needs to behave elastically, therefore the Mn provides these characteristics with greater ductility and elastic behavior. That is, the material is able to support bending loads without breaking, and return to original form when the load is removed. In this way a fixing nail transmits efforts, deforms, and recovers, maintaining the invariability of the gauge width, the fixing of the sleepers, and electrical insulation. ~AM&P For more information: Patricia S. Carrizo, chemical engineering and archaeometallurgy specialist, National Technological University, Argentina, silvana_carrizo@hotmail.com. References 1. C.M. Lewis, British Railways in Argentina 1857-1914: A Case Study of Foreign Investment, Londres: Athlone Press, 1983. 2. S.M. Vicuña, Los Hermanos Clark, Santiago de Chile: Establecimientos Gráficos Balcells, 1929. 3. P. Lacoste, El Ferrocarril Trasandino y el Desarrollo de los Andes Centrales Argentino-chilenos, Santiago: Editorial IDEA, 2013. 4. S.F. William and J. Hashemi, Fundamentos de la Ciencia e Ingeniería de Materiales, Mexico D.F.: McGraw-Hill, 2006. 5. H.W. Hayden, W.G. Moffatt, and J. Wulff, Introducción a la Ciencia de los Materiales, Vol. III, Mexico D.F: Editorial Limusa-Wiley, S.A., 1968. Fig. 10 — The threaded bolt that was studied. Fig. 11 — A thread comb is used to measure the type of thread. Fig. 12 — Corrosive damage to threads. Fig. 13 — Thread detail with binocular stereomicroscope. GET ENGAGED, GET INVOLVED, GET CONNECTED The ASM Archaeometallurgy Committee meets regularly to connect and communicate about their shared interest in the study and characteristics of historic metals and artifacts. Visit the online community on ASM Connect at connect. asminternational.org. For more information, contact committee chair Patricia Silvana Carrizo or staff liaison Scott Henry, scott.henry@asminternational.org. Fig. 14 — Nail metallograph at 100x. Fig. 15 — Nail metallograph at 200x.
RkJQdWJsaXNoZXIy MTYyMzk3NQ==