Investigation of a broken pile-shoe from a Roman bridge
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Published
Nov 12, 2021
Abstract
A Roman pile-shoe made from four iron bars had breaks in three bars. One break was a recent impact fracture. A sample containing one of the fracture surfaces was broken into large fragments with a hammer. These were investigated fractographically, metallographically, and by surface and bulk chemical analyses. The fractures were brittle and primarily intergranular. The metal was a coarse-grained phosphoric wrought iron (0.52wt% P) with very low silicon, manganese and sulphur contents, and extremely low
carbon content (0.0033wt% C). This extremely low carbon content and coarse grain size indicate decarburisation during smithing. Furthermore, the combination of extremely low carbon and high phosphorus contents is concluded to be the most probable reason for
the impact brittleness. This could have been facilitated by a notch effect due to surface corrosion. The significance of the embrittlement and surface corrosion is considered with respect to conservation of archaeological iron objects, including similar pile-shoes.
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References
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Campbell J and Fahy F 1984, ‘A metallurgical study of iron pile shoes from the Roman bridge at Minturnae’, Historical Metallurgy 18, 21–30.
Cüppers H 1969, Die Trierer Römerbrücken, Band V (Mainz am Rhein).
Dinnetz M K 2003, ‘Technical and archaeological investigation of an early iron sword from Sweden’, in L N Nørbach (ed), Prehistoric and Medieval Direct Iron Smelting in Scandinavia and Europe, Aspects of Technology and Society (Aarhus), 101–109.
Erhardt H and Grabke H J 1981, ‘Equilibrium segregation of phosphorus at grain boundaries of Fe-P, Fe-C-P, Fe-Cr-P, and Fe-Cr-C-P alloys’, Metal Science 15, 401–408.
Gale W F and Totemeier T C (eds) 2004, Smithells Metals Reference Book (Oxford), 21–4, 22–99–102.
Godfrey E G and Van Nie M 2004, ‘A Germanic ultra-high carbon steel punch of the Late Roman-Iron Age’, Journal of Archaeological Science 31, 1117–1125.
Godfrey E G, Vizcaino A and McDonnell J G 2003, ‘The role of phosphorus in early ironworking’, in L N Nørbach (ed), Prehistoric and Medieval Direct Iron Smelting in Scandinavia and Europe, Aspects of Technology and Society (Aarhus), 191–193.
Goudswaard B 1996, ‘Brug te water, Romeinse resten bij Cuijk’, Natuur & Techniek 64(1), 30–41.
Goudswaard B, Kroes R A C and Van der Beek H S M 2000, ‘The Late Roman bridge at Cuijk’, Proceedings of the National Service for Archaeological Heritage in the Netherlands 44, 440–560.
Gouthama and Balasubramaniam R 2003, ‘Alloy design of ductile phosphoric iron: Ideas from archaeometallurgy’, Bulletin of Materials Science 26, 483–491.
Haalebos J K, Goudswaard B, Kroes R A C and Van der Beek H 2002, ‘De laat Romeinse tijd’, in H Enckevort and J Thijssen (eds), Cuijk,
een Regionaal Centrum in de Romeinse Tijd (Utrecht), 80–95.
Hopkins B E and Tipler H R 1958, ‘The effect of phosphorus on the tensile and notch-impact properties of high-purity iron and iron−carbon
alloys’, Journal of the Iron and Steel Institute 188, 218–237.
Inman M C and Tipler H R 1958, ‘Grain-boundary segregation of phosphorus in an iron-phosphorus alloy and the effect upon mechanical properties’, Acta Metallurgica 6, 73–84.
Josefsson A 1954, ‘Pearlite-free Bessemer steel: its fabrication and properties’, Journal of the Iron and Steel Institute 177, 118–128.
Joosten I 2004, Technology of Early Historical Iron Production in the Netherlands (Amsterdam).
Krasko G L 1997, ‘Effect of impurities on the electronic structure of grain boundaries and intergranular cohesion in iron and tungsten’, Materials Science and Engineering A234–236, 1071–1074.
Kumar A and Raman V 1981, ‘Low temperature intergranular brittleness of iron’, Acta Metallurgica 29, 1131–1139.
Neff D, Dillmann P, Bellot-Gurlet L and Beranger G 2005, ‘Corrosion of iron archaeological artefacts in soil: characterisation of the corrosion
system’, Corrosion Science 47, 515–535.
Ramasubramanian P V and Stein D F 1973, ‘An investigation of grain-boundary embrittlement in Fe-P, Fe-P-S, and Fe-Sb-S alloys’, Metallurgical Transactions 4, 1735–1742.
Rees W P and Hopkins B E 1952, ‘Intergranular brittleness in iron-oxygen alloys’, Journal of the Iron and Steel Institute 172, 403–409.
Rellick J R and McMahon Jr C J 1974, ‘Intergranular embrittlement of iron-carbon alloys by impurities’, Metallurgical Transactions 5, 2439–2450.
Selwyn L 2004, Metals and Corrosion: A Handbook for the Conservation Professional (Ottawa).
Stewart J W, Charles J A and Wallach E R 2000a, ‘Iron-phosphorus-carbon system Part 1 – Mechanical properties of low carbon iron-phosphorus alloys’, Materials Science and Technology 16, 275–282.
Stewart J W, Charles J A and Wallach E R 2000b, ‘Iron-phosphorus-carbon system Part 3 – Metallography of low carbon iron-phosphorus alloys’, Materials Science and Technology 16, 291–303.
Suzuki S, Obata M, Abiko K and Kimura H 1985, ‘Role of carbon in preventing the intergranular fracture in iron-phosphorus alloys’, Transactions of the Iron and Steel Institute of Japan 25, 62–68.
Tylecote R F 1986, The Prehistory of Metallurgy in the British Isles (London).
How to Cite
Investigation of a broken pile-shoe from a Roman bridge. (2021). Historical Metallurgy, 41(1), 32-39. https://hmsjournal.org/index.php/home/article/view/220
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How to Cite
Investigation of a broken pile-shoe from a Roman bridge. (2021). Historical Metallurgy, 41(1), 32-39. https://hmsjournal.org/index.php/home/article/view/220