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Title: The technology of ancient and medieval directly reduced phosphoric iron
Author: Godfrey, Evelyne
ISNI:       0000 0004 2730 7037
Awarding Body: University of Bradford
Current Institution: University of Bradford
Date of Award: 2007
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After carbon, phosphorus is the most commonly detected element in archaeological iron. The typical phosphoric iron range is 0.1wt% to 1wt%P. The predominant source of phosphorus in iron is the ore smelted. Around 60% of economic UK rock iron ore formations contain over 0.2%P. Under fully reducing conditions, both in liquid-state (cast iron) and solid-state bloomery smelting (direct reduction) processes, such rock ores would be predicted to produce phosphoric iron, and bog iron ores even more so. Ore-metal-slag phosphorus ratios for bloomery iron are derived here, by means of: laboratory experiments; full-scale experimental bloomery smelting; and analysis of remains from three Medieval and two Late Roman-Iron Age iron production sites in England and the Netherlands. Archaeological ore, slag, metal residues (gromps), and iron artefacts were analysed by metallography, SEM-EDS, EPMA, and XRD. The effects of forging and carburising on phosphoric iron were studied by experiment and artefact analysis. The ore to slag %P ratio for solid-state reduction was determined to range from 1:1.2 to 1: 1.8. The ore to metal %P ratio varied from 1:0.2 to 1:0.7-1.4, depending on furnace operating conditions. Archaeological phosphoric iron and steel microstructures resulting from non-equilibrium reduction, heat treatment, and mechanical processing are presented to define the technology of early phosphoric iron. Microstructures were identified by a combination of metallography and chemical analysis. The phosphoric iron artefacts examined appear to be fully functional objects, some cold-worked and carburised. Modern concepts of 'quality' and workability are shown to be inapplicable to the archaeological material.
Supervisor: McDonnell, Gerry; Pollard, A. Mark; Schmidt, Armin R. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Archaeometallurgy ; Iron ; Phosphorus ; Smelting ; Slag ; Bloomery ; Furnace ; Smithing ; Experimental archaeology ; Metallographic analysis ; Metal ores