Transitions in cast iron technology of the nomads in Mongolia

Metallurgical study of seven cast iron artifacts recovered from sites of the former Xiongnu (BC 3rd to AD 1st), Turk (AD 6th to 8th), Khitan (AD 10th to 12th), and Mongolian empires (AD 12th to 15th) shows that the earlier Xiongnu and Turk artifacts were made of cast iron alloys of near eutectic composition. The later Khitan and Mongol objects had greatly reduced carbon content in the range of ultrahigh carbon steel rather than cast iron, and contained more than 0.5 mass % silicon as an alloying element. Inclusions high in sulfur, phosphorus or silicon are also present. These differences suggest that Mongolia experienced a technical transition a few centuries before the establishment of the Mongolian empire, which is in agreement with some written accounts. The microstructures of the cast iron artifacts are compared with the related archaeological and documentary evidence. The results suggest that the use of fossil coal in smelting and the state policy of controlling iron production were the major factors responsible for the transition.     

Technological traditions inferred from iron artefacts of the Xiongnu Empire in Mongolia

Iron objects excavated from sites of the Xiongnu Empire (3rd century BC–2nd century AD) in Mongolia have been examined using optical and scanning electron microscopy. The results show that the Xiongnu iron tradition may be characterized by the use of low carbon iron and carbon control by carburization. Cast iron was also used in the Xiongnu Empire, but only in very limited applications and with no convincing evidence of its use for the production of low carbon iron. The Xiongnu iron technology seems to have been established on the basis of the bloomery technique, without much influence from the Chinese style of technology, based on cast iron.     

A technological transition in Mongolia evident in microstructure,chemical composition and radiocarbon age of cast iron artifacts

Metallurgical examination of cast iron objects from the Khitan period (AD 10th–12th) in Mongolia shows that they might be classified into two groups. The first is based on Fe–C alloys of near eutectic composition and the second is based on Fe–C–Si alloys with reduced carbon content and numerous sulfide inclusions. By contrast, all the objects from the succeeding Mongolian empire period (AD 12th–15th) belong to the second group, indicating that a technological transition had occurred during the Khitan period. Accelerator mass spectrometry (AMS) on carbon samples extracted from artifacts in both groups and measurement of alloy compositions suggest that the use of mineral coal in smelting was a major factor for this transition.     

A Preliminary Study on the Loss of Iron and Arsenic in the Re‐Melting of Iron‐Bearing Arsenical Copper

Re‐melting experiments were conducted with specimens made of high‐arsenic copper alloys containing lead, iron and sulphur. The melting treatment at 1000°C in ambient conditions for 5 min was found to cause an almost complete removal of iron and sulphur along with a notable reduction of arsenic levels. Evidence was found that the preferential oxidation of iron and arsenic was responsible for this change in composition. The treatment also brought about perfect dissolution of speiss particles scattered throughout the original specimen, suggesting the possibility of the addition of speiss to molten copper for the production of arsenical copper.     

The implication of the metallurgical traditions associated with Chinese style wagons from the royal Xiongnu tomb at Golmod 2 in Mongolia

Lavishly decorated wagons excavated from royal Xiongnu burials are generally regarded as tribute items from China offered to Xiongnu elites, symbolizing important political and economic interactions between the Xiongnu state (209 BC–155 AD) and the Han dynasty (206 BC–220 AD). This theory views such vehicles as having no relation to indigenous Xiongnu craftsmanship. Furthermore, specialized products delivered to the northern nomadic peoples from the Han state are often cited in support of the notion of Xiongnu dependency on foreign states for technological and political development. Expecting to find evidence of China’s traditional iron and bronze technology, we examined a number of key metallic components of these wagons excavated from the royal Xiongnu burial at Golmod 2 in central Mongolia, radiocarbon dated to 109 BC–AD 75. Surprisingly, the iron metallurgy in question was based primarily on the bloomery process while low tin bronze and arsenical copper alloys dominated the pertinent bronze production. These respective technological traditions are typical of Xiongnu manufacture but significantly different from traditional Han metallurgy. We interpret this evidence as suggesting the need for a more balanced evaluation of foreign influence on the rise and development of the Xiongnu state.