Journal of Archaeological Science
Available online 23 September 2020, 105224
In Press, Corrected Proof
Abstract
For more than a century, evidence for the production of crucible steel in Central and
Southern Asia, prior to the European Industrial Revolution, has fascinated and challenged
material scientists, historians and archaeologists. At the same time, chromium-alloyed
stainless steel was developed in the early 20th century, building upon 19th century
experiments with low chromium steel. Here we demonstrate new evidence of the
intentional addition of chromium to steel nearly a millennium earlier, as part of the
Persian crucible steel (pulad) tradition including the production of low-chromium
crucible steel in early 2nd millennium CE Persia. We analysed archaeological finds
from the 11th c. CE site of Chahak in Iran showing the intentional and regular addition
of chromium mineral to the crucible charge, resulting in steel containing around 1 wt%
chromium. A contemporaneous crucible steel flint striker held in the Tanavoli Collection is
reported to also contain chromium, suggesting its origin from Chahak. We argue that the
mysterious compound 'rusakhtaj' from Biruni's (10th – 11th c. CE) recipe for crucible steel
making refers to the mineral chromite. Additional historical sources up to the mid-2nd
millennium CE refer to crucible steel from Chahak as being particularly brittle, consistent
with its increased phosphorus content.
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