The technology of ancient and medieval directly reduced phosphoric iron
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
Godfrey, Evelyne
Archaeometallurgy ; Iron ; Phosphorus ; Smelting ; Slag ; Bloomery ; Furnace ; Smithing ; Experimental archaeology ; Metallographic analysis ; Metal ores
The technology of ancient and medieval directly reduced phosphoric iron. 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
technology ancient_medieval directly reduce iron carbon commonly detect element archaeological iron typical iron range predominant source iron_ore smelt around economic rock iron_ore formation contain fully reduce condition liquid state cast iron solid state bloomery smelting direct reduction process rock ore would predict produce iron bog iron_ore even ore metal slag ratio bloomery iron derive mean laboratory full scale experimental bloomery smelting analysis remain medieval late_roman iron_age iron_production sit england netherlands archaeological ore_slag metal residue iron_artefact analyse metallography sem_eds epma xrd effect forge iron study artefact analysis ore_slag ratio solid state reduction determine range ore metal ratio vary depend furnace operate condition archaeological