Iron decarburisation techniques in the eastern Guanzhong Plain, China, during Late Warring States period: an investigation based on slag inclusion analyses

Abstract

Iron production in the Central Plains area of China has been largely based on cast iron smelting since ca. fifth century BC, with different techniques developed in the following Warring States period and Han dynasty to convert this material into malleable soft iron. Whilst there is a broad consensus about the evolution of technological traditions in the Early Iron Age, the methodologies employed for differentiating artefacts derived from different iron smelting and decarburisation methods have been variable and not sufficiently conclusive. Taking advantage of renewed analytical approaches and archaeological evidence recovered in recent years, this paper summarises our current understanding of the decarburisation techniques employed in Early Iron Age China and sheds new light on this subject through the analysis of archaeological artefacts from two civilian cemeteries in the eastern part of the Guanzhong Plain (Shaanxi), dated to the third century BC. The analytical results indicate that both solid-state and liquid-state decarburisation were employed for soft iron production in this area during the Late Warring States period. The methodology employed in this paper, based on slag inclusion analysis, also provides a more systematic approach to differentiating soft iron production techniques in future archaeometallurgical research in China.

The manufacturing technology of iron swords from the capital of the Han Empire in China

“…By contrast, swords TJ020 and TJ021 are laminated with approximately 10 layers, ruling out the possibility of Bailiangang. Similar laminations of iron objects were also found in other areas [18,26,40].…”

“…This produces malleable soft iron as either wrought iron or steel (carbon content of 0.3-1%). The first of these decarburization processes, Chaogang, is a fining technique that consists of re-melting cast iron in a hearth or open fire; it may have been employed for soft iron production since the late Warring States period, around the third century BC [18].…”

Ancient metalworking at Yodhawewa site, Sri Lanka: tracing the archaeological and geochemical relationship by analyzing soil and slags

“…Iron production by smelting ore was a revolutionary invention in pre-modern times. The ancient metalworkers developed the technology through long-term experience to separate "raw iron" from ores by the bloomery furnace at temperatures around 1200 o C or a blast furnace (indirect/cast iron followed by the decarburization process) temperature around 1400 o C (Liu et al, 2019;Pleiner, 2000). The main by-product of this smelting process is "slags" rich in iron oxide, formed by the reaction between iron oxide and silica; other contaminants in ore often include slag in the process (Blakelock et al, 2009;Dill et al, 2013;Tylecote, 2002;Warchulski et al, 2018).…”

Early use and production of iron in the northern Shaanxi: A perspective on iron objects excavated from the Yuejiazhuang cemetery site

“…For example, iron objects excavated from Mogou reveal that the earliest use of bloomery iron in China could be dated to the 14th century BCE (Chen et al, 2012), and cast iron was adopted no later than the eighth century BCE (Han, 2000). Studies of ferrous metals, such as excavation of iron smelting sites and metallurgical study of iron objects and slags have developed rapidly in most areas in China (Lam et al, 2018, 2020; Li et al, 2019,b,c; Liu et al, 2020, 2022; Liu, Martinón‐Torres, et al, 2019; Zhang, 2020; Zhang et al, 2020, 2021; Zou et al, 2022, 2019). However, study of ferrous metals in the Northern Shaanxi is limited.…”