The Critical Node of the Transmission of Iron and Steel Technology on the Silk Road in the Han Dynasty: Study on the Iron artifacts from the Han Dynasty Tombs in Xingfucheng, Guyuan, Ningxia Hui Autonomous Region, Northwest China, ca. 202 BC-141 BC

doi:10.21203/rs.3.rs-2880295/v1

Download PDF

Research Article

The Critical Node of the Transmission of Iron and Steel Technology on the Silk Road in the Han Dynasty: Study on the Iron artifacts from the Han Dynasty Tombs in Xingfucheng, Guyuan, Ningxia Hui Autonomous Region, Northwest China, ca. 202 BC-141 BC

https://doi.org/10.21203/rs.3.rs-2880295/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

In the past few decades, many iron artifacts have been excavated in the Ningxia Hui Autonomous Region, which was the critical node that connected the Eastern and Western civilizations on the ancient Silk Road. However, the exploration into the iron and steel metallurgy technology prevalent in Ningxia during that period has been inadequate. In this paper, metallurgical analysis has been conducted on the iron artifacts excavated from the tombs of the early Western Han Dynasty (202-141BC) in Xingfucheng (XFC), Guyuan, Ningxia. Results show that weapons and farming implements were made of decarburized steel and Chaogang. Furthermore, there is evidence of the use of surface carburizing and quenching technologies to control the performance of the iron. In addition, this research also uncovered the utilization of carburized bloomery steel. The iron objects excavated in XFC show traits of bloomery smelting technology from Europe, and Asia, in addition to the steel making techniques found in the Central Plains. Hence, it can be concluded that the iron and steel smelting technology developed in XFC is a result of the confluence of Eastern and Western technologies. The trend of replacing bloomery smelting technology with cast iron appeared in the early Western Han Dynasty, which establishes that Ningxia played an important role in the exchange of ancient metallurgical technology between the East and the West, thus filling the gap of iron archaeometallurgy in Ningxia after the 2nd century BC.

archaeometallurgy

Han Dynasty

Ningxia

foundry technology

cast iron industry

The Ningxia Hui Autonomous Region is located in northwest China in the upper reaches of the Yellow River (Fig. 1). This region has a long and narrow territory that runs from north to south, bordering Shaanxi, Gansu, and Inner Mongolia. Historically, it has been a place of cultural exchange between the Central Plains and the neighbouring regions. Xiaoguan road, that passed through Guyuan in Ningxia, gained importance after the Warring States Period (770BC-221BC), and the reign of the Qin (221BC-207BC), and Han (202BC-220AD) Dynasties. It had become one of the virtual channels of the ancient Silk Road that extended from Chang'an to ancient Rome. After the completion of the Silk Road during the Han Dynasty, Guyuan played an essential role in the cultural, economic, and technological exchanges between the Guanzhong Plain and other regions. With respect to the exchange of metallurgical technology between northwest China and Eurasia, Ningxia is undoubtedly a critical link and is particularly interesting to archaeologists. In this study, the production process of iron artifacts excavated from Xingfucheng (XFC) tombs of the western Han Dynasty was analyzed through a metallurgical perspective. For the first time, archaeometallurgy research is being conducted on the iron artifacts excavated in Ningxia, with the goal of bridging the gap of iron and steel smelting technology in the Han Dynasty at the nodes of the Silk Road in Ningxia.

According to current archaeological findings, many early iron tools have been found in Guyuan in south Ningxia (Han and Ko 2007). There is also evidence that Ningxia entered the Iron Age during the Spring and Autumn Period and the Warring States Period (5th-4th century BC). Iron tools were widely used in the Han Dynasty (202BC-220AD) for producing other tools and weapons. From the shape of the excavated cultural relics, Luo (2002) speculated that the Ningxia culture was unified with the Qin Dynasty in the Central Plains after the late Warring States Period. The burial objects of hundreds of Han tombs excavated were similar to those found in the Central Plains system. However, a small number of tombs could be differentiated from the rest due to their unique characteristics. After studying the ironware unearthed from the Xiongnu tombs in Ningxia, Shan (2009) believed that the Xiongnu culture was unique and had developed ironware-making techniques. However, there are no instances of in-depth research into the iron and steel metallurgy technology in Ningxia, and there is a need for further exploration to gather more data.

Since there is no evidence of iron and steel smelting in Ningxia during the Han Dynasty, it is unclear if tools were locally produced in Ningxia as a result of the westward spread of advanced cast iron technology. Additionally, the connection between the production technology of Han Dynasty ironware in Ningxia and the technology of Central Plains and various places along the Silk Road still needs to be unearthed. The XFC is a group of Han Dynasty tombs excavated scientifically by the archaeological department in southern Ningxia with accurate dating information. Further research on the buried iron objects in the tombs can reveal critical details relating to the technical aspects of the buried iron objects. This will aid in understanding the metallurgical technology exchange on the Silk Road during the Han Dynasty, which is of great significance to the ancient East-West technology and cultural exchange.

The samples of this study are sourced from the XFC cemetery, Pengyang County, Guyuan City, Ningxia Hui Autonomous Region. The cemetery was first discovered on July 15, 2013. Upon archaeological examination by experts from the Ningxia Institute of Cultural Relics and Archaeology, it was determined that the site consisted of ancient tombs. Approval for archaeological rescue excavation was granted to Ningxia Institute of Cultural Relics and Archaeology, and Pengyang County Cultural Relics Management Institute by the Ningxia Cultural Relics Bureau.

The excavation took over two months, from July 26 to September 10. The burial depth of some of the tombs in this batch was found to be 1 m deeper than the excavated foundation. A total of 10 tombs were excavated (Fig. 2). Tombs denoted by M1, M3 and M6 are catacombs with long entry slopes. Whereas tombs denoted by M2, M4, M5, M7, M8 and M9 are shaft-pit tombs. Tomb denoted by M10 is an earthen-pit tomb. Over 260 cultural relics have been unearthed from these 10 tombs (Archaeological Society of China 2015). Iron farming implements and weapons were found among the relics, which were located in the front chamber of the tomb, and within the tomb chamber, respectively. According to the types of pottery unearthed in the tombs and the half-Liang coins, it can be concluded that these tombs were built in the early Western Han Dynasty, no later than the period of Emperor Wu of the Han Dynasty (202BC-141BC). The shape and type of the unearthed ironware resembles the artifacts of the same period in the Central Plains. Since the style of the ironware of Central Plains appeared at the key node of the Silk Road in the Han Dynasty, it is imperative to conduct metallurgical analysis in order to study ironware production technology in this region.

In order to determine the production technology used to produce the Han Dynasty ironware unearthed from XFC, 13 representative ironware samples were selected from 4 tombs. The samples were selected through random sampling according to the preservation status and types of the unearthed ironware, following the principle of minimum intervention. The recognizable types include cooking pots, farming implements, weapons, and other utensils. Figure 3 shows the photographs of the samples (except sample XFC-15), and the sampling parts that are located in the residue of the iron objects.

XFC-1.M5:10Axe XFC-4.M3:85Farming Implement XFC-9.M3:66Hoop XFC-13.M3:70Iron Lute-shaped XFC-11.M3:59Iron Plate-shaped XFC-8.M3:65Ring-pommel Knife XFC-10.M1:23Knife XFC-17.M3:57Hoop XFC-18.M3:105Hoop XFC-19.M4:10Lamp XFC-21.M3:64Ironware Remnant XFC-22.M3Lamp:122

The 13 samples were mounted in epoxy resin blocks, where the mixing ratio of epoxy resin and the curing agent was 2:1. The samples were then ground abrasive paper from coarse (P180) to fine (P4000) grits. The surface was then polished and etched with a solution of 4 vol.% Nital. Metallography was carried out using a Zeiss Axioscope 5 microscope at Guangxi Minzu University, China, and the distribution of carbon content, casting and forging processes, morphology, and distribution of inclusions were observed.

After metallographic analysis, the matrix composition of the samples was analyzed by energy dispersive X-ray fluorescence spectrometer (ED-XRF, Shimadzu EDX-8100) at Guangxi Minzu University. The acceleration voltage of the ED-XRF instrument was set to 50 kV, and the live collection duration was 30 s.

The scanning electron microscope energy dispersive spectrometer (SEM-EDS) at the School of Materials and Environment, Guangxi Minzu University, was used as the main instrument to detect inclusions and metal matrix composition. The Zeiss EVO18 SEM was used along with the Bruker Nano XFlash Detector 5010 EDS system. The accelerating voltage was set to 20 kV, and the live collecting duration was 60 s.

4.1 Metallography

The metallographic study of iron samples revealed some important insights into the composition of the samples. Although some of the 13 samples in this study were severely rusted or damaged, all the samples had some metal residues. Among them, the metallographic structures of XFC-9 (Fig. 4) were found to contain ledeburite and cementite, with a carbon content of 4.3%~6.68%. This was consistent with hypereutectic white cast iron, which was also detected in XFC-15, XFC-11, XFC-13, and XFC-21. XFC-22 (Fig. 4, 5) was mostly composed of ledeburite, but also contained small amounts of pearlite and graphite. XFC-17 and XFC-19 (Fig. 5) were mottled iron composed of white iron structure, pearlite, and slice graphite.

XFC-4, XFC-8, and XFC-10 (Fig. 6) did not have slag inclusion in the matrix and were identified as decarburized steel. XFC-4 had a uniform structure composed of pearlite and ferrite, along with a small amount of nodular graphite. XFC-8 was composed of hypoeutectoid steel with pearlite and ferrite, and uniform carbon content. A large amount of graphite precipitated during annealing with large deformation and was arranged along the processing direction. The core of XFC-10 was composed of pearlite and ferrite, whereas the edge consisted only of pearlite. A gradient of the carbon content was observed along with a small number of martensite structures in the edge. This was indicative of the fact that the artifacts had undergone surface carburization and quenching during production.

XFC-1 (Fig. 7) exhibited pearlite and ferrite structures, where the microstructures were stratified. The carbon content of each layer was similar and the layers exhibited uniformity. The layer with high carbon content was mainly comprised of pearlite with a small amount of ferrite. Whereas the layer with low carbon content was found to be distributed with ferrite and pearlite.

In addition, XFC-18 (Fig. 7) was composed of ferrite and a small amount of pearlite. The grain size was uneven, and the microstructures were stratified. Distinct carbon content and particle size was observed in each layer. Many slag inclusions were embedded in the metal matrix.

XFC-1 and XFC-18 exhibited microstructures of Chaogang and carburised bloomery steel, respectively. Additionally, various types of slag inclusions were found to be embedded in the metal matrix. Further slag inclusion analysis was conducted for these samples to study their production technology.Results of the metallographic structural analysis is listed in Table 1.

Table 1

Metallographic structure of samples.
Category	Type	Original record no.	GXMZULab no.	Description	Material and techniques
Farming implement	Farming implement	M3:85	XFC-4	Pearlite + ferrite matrix with temper-carbon graphite.	Decarburized steel,cast
Weapons	Axe	M5:10	XFC-1	Pearlite + ferrite matrix with layered microstructures, inclusions are smaller size and large deformation.	Chaogang,forged
	Ring-pommel Knife	M3:65	XFC-8	Pearlitic + ferritic matrix with consistent carbon content, graphite are large deformation along the processing direction.	Decarburized steel, forged
	Knife	M1:23	XFC-10	Pearlite + ferrite, and martensite structure at the edge.	Decarburized steel,forged, carburized and quenched
Cooking pot	Cauldron	M2:15	XFC-15	Serious corrosion, only a small amount of metal remains, and ledeburite + cementite can be seen.	Hypereutectic white iron
Others	Hoop	M3:66	XFC-9	Ledeburite + cementite.	Hypereutectic white iron
	Iron Plate-shaped	M3:59	XFC-11	Serious corrosion, only a small amount of metal remains, and ledeburite + cementite can be seen.	Hypereutectic white iron
	Iron Lute-shaped	M3:70	XFC-13	Ledeburite + cementite, the black lump in the matrix may be rust.	Hypereutectic white iron
	Hoop	M3:57	XFC-17	Ledeburite + pearlite matrix with slice graphite, pearlite is distributed on both sides of the graphite.	Mottled cast iron
	Hoop	M3:105	XFC-18	Ferrite + pearlite matrix, ferrite grain size is uneven, and there is pearlite banded structure in the centre; A large number of wüstite-fayalite eutectic inclusions are distributed unevenly in the matrix, with large deformation and stretching along the processing direction.	Carburised bloomery steel
	Lamp	M4:10	XFC-19	Ledeburite + pearlite matrix with slice graphite, pearlite is distributed on both sides of the graphite.	Mottled cast iron
	Ironware Remnant	M3:64	XFC-21	Ledeburite + cementite.	Hypereutectic white iron
	Lamp	M3:122	XFC-22	Ledeburite + cementite matrix, and a small amount of pearlite is distributed around temper-carbon graphite.	Hypereutectic white iron

4.2 ED-XRF and SEM-EDS slag inclusions analysis

All the 13 samples were analyzed using XRF, where the content of P in the metal matrix of samples was found to be between 0.6% and 3.0%, with an average value of 1.5%. The content of Ca content was between 0.2% and 1.2%, with an average value of 0.27% (Table 2).

Table 2

EDX results of metal matrix. (wt%)
Lab. No.	Fe	Si	Mn	Ca	P
XFC-1	95.4	4.0	-	0.2	-
XFC-4	96.0	3.8	0.1	0.1	-
XFC-8	95.9	3.3	-	0.1	0.6
XFC-9	96.5	3.3	-	-	-
XFC-10	97.2	2.5	0.1	0.2	-
XFC-11	94.4	3.4	-	0.2	1.8
XFC-13	93.9	4.2	0.1	0.1	1.4
XFC-15	95.3	-	-	1.2	3.0
XFC-17	96.5	3.2	0.1	-	-
XFC-18	95.6	3.8	0.1	0.2	-
XFC-19	95.0	3.4	0.1	0.1	1.0
XFC-21	95.7	2.8	0.1	-	1.3
XFC-22	93.2	4.2	0.1	-	1.4
^* “-” means below detection limit.

XFC-1 is mainly composed of single-phase glassy silicate inclusions, which are residual silica calcium slag that have deformed along the processing direction, shown in Fig. 8a and 8b. From the result of metallographic analysis, it can be concluded that XFC-1 was forged from Chaogang. The matrix of XFC-18 was found to be distributed with many wüstite-fayalite eutectic inclusions, with large deformations and stretching along the processing direction (Fig. 8c and 8d), which is determined to be carburized bloomery steel. The compositions of inclusions are listed in Table 3.

Table 3

Result of chemical compositions of slag inclusions (normalized wt%)
Sample	Area	Na₂O	MgO	Al₂O₃	SiO₂	P₂O₅	K₂O	CaO	FeO
XFC-1	Spot1	1.2	2.8	9.5	37.3	-	4.2	24.0	21.1
XFC-1	Spot2	1.2	2.5	14.2	53.6	0.1	4.2	17.2	6.8
XFC-18	Zone1	1.2	4.5	6.3	29.2	6.0	2.7	20.0	30.1
	Zone1	0.3	0.9	0.8	2.7	-	-	2.6	92.8
	Spot1	-	0.6	0.4	1.3	-	-	0.7	97.0
	Spot2	-	3.6	-	21.4	1.9	-	2.3	70.8
	Spot3	-	1.3	1.1	2.1	0.8	-	0.9	93.8
	Spot4	0.7	4.9	2.3	25.5	4.3	2.5	17.6	42.3
	Spot5	1.0	1.9	2.1	9.1	23.6	2.6	48.5	11.2
^* “-” means below detection limit.

Table 1 Metallographic structure of samples.

Table 2 EDX results of metal matrix. (wt%)

Table 3 Result of chemical compositions of slag inclusions (normalized wt%)

5.1 Technology

The Western Han Dynasty ironware samples unearthed from the XFC cemetery included a diverse set of materials, which can be categorized into cast iron, decarburized cast iron, Chaogang, and carburized bloomery steel.

Cast iron products can be further divided into 6 pieces of white cast iron (XFC-9, XFC-11, XFC-13, XFC-15, XFC-21, XFC-22)and 2 pieces of mottled cast iron (XFC-17, XFC-19). The white iron matrix also a large amount of cementite, a hard and brittle material with low strength. Most of the white iron archaeologically unearthed from the Warring States Period to the Western Han Dynasty were cast waste pieces or unannealed funeral objects (Rong et al. 2013). It was detected that XFC white cast iron products were artifacts with relatively low strength requirements. In addition, the XFC-22 sample was composed of hypereutectic white iron, where slice graphite and pearlite were precipitated by the annealing process in the matrix. Further, a small amount of grey cast iron structure can also be observed in the metallographic studies. Based on these observations, it can be hypothesized that the sample was not fully annealed or special heat preservation and cooling processes were used. As the artisans’ understanding of the casting process improved, grey and mottled cast iron were successively produced during the mid-Warring States Period (Wagner 1993:115–170). The mottled cast iron is a composite structure of white and grey cast iron, which has better casting, wear resistance and cutting properties than white cast iron (Rong et al., 2013). A considerable fraction of ledeburite was retained in the structure of grey cast iron, which was the characteristic of the mottled cast iron detected in XFC. The Si contents of these two samples were 3.2% and 3.4%, and their higher silica contents may also be conducive to the graphitization process of cast iron (Song1989).

The production of steel from cast iron was achieved using two methods in ancient China. One method involved the heating of cast iron plates or artifacts to a certain temperature in a specific annealing kiln and then annealing at high temperature in the solid state for several days to decarburise the castings. This process could be used to obtain three types of steel based on the carbon content, namely, high carbon steel, medium carbon steel, and low carbon steel (Wagner 1993: 257–334; Han and Ko 2007: 604). Decarburised steel is characterised by little or no graphite precipitation, and it retains the advantage of fewer inclusions in cast iron products (Yang et al. 2014; Liu et al. 2022). The metallographic structures of XFC-4 are pearlite and ferrite, with a small amount of graphite precipitation, which is consistent with the composition of decarburised steel. XFC-8 was composed of hypoeutectoid steel with a uniform metallographic microstructure. A large amount of graphite precipitated during the annealing process and deformed along the processing direction, which indicates that the sample was initially formed by casting, which was then followed by annealing and forging. XFC-10 was an iron knife that was sampled from the blade. The left side was the core, whereas the right side was the blade. The blade structure was composed of pearlite, while the core was comprised of pearlite and ferrite. The carbon content was found to increase from the left side to the right side. Additionally, the needle-like martensite structure was also found in the blade. From these results it can be concluded that this artifact was forged with low carbon steel blank. The artifact contacted the carbon fire when it was forged and carburised from the surface to the inside to increase the surface carbon content. After processing and forming, the cutting edge was quenched to improve the hardness of the cutting edge and enhance the performance of the ironware. Results from the analysis of these three decarburised steel products show that different post-casting treatment technologies were widely used in XFC.

The other method was called the Chaogang (“Chaogang” is the description in Chinese, directly translated as “puddling steel” under modern terminology). This method involved heating cast iron to a semi-molten state in order to decarburise it into steel. Many scholars have proposed various criteria to ascertain if an artifact indeed belonged to Chaogang products. The inclusions in Chaogang products were found to be arranged and deformed along the processing direction. They were mainly composed of single-phase silicate (SiO2) inclusions or wüstite-fayalite eutectic inclusions, and the presence of high content of phosphorus and calcium compounds in the inclusions was used as a criterion for Chaogang steel (Dillmann and L’Héritier2007; Yang et al. 2014; Huang et al. 2016a; Chen and Zhang 2016; Lam et al. 2018; Liu Y et al. 2019; Zou G et al. 2022; Jiang J et al. 2022). Among the XFC ironware identified in this study, XFC-1 is made of Chaogang. Its microstructures are stratified with different carbon content and particle size, and silicate single-phase inclusions are fine and arranged along the processing direction. This is indicative of the fact that the sample is made of Chaogang by forging several times to produce an iron axe that can satisfy the requirements for use in combat. With the maturing Chaogang technique, the Western Han Dynasty then witnessed the emergence of “Bailiangang” produced through repeated heating, folding and tempering procedure from the raw material Chaogang. In this terminology, the character “Bai” (referred to as hundred in English) is an exaggerated description. This is because the “Chaogang” that has been generally folded over 30 times can already be confirmed as “Bailiangang” (Zhao et al. 2020). In this comparison, the XFC-1 fails to reach the layer standard of Bailiangang, thus it can be exempted from this kind.

Bloomery iron is a direct reduction product that reduces iron from ore at low temperatures (Huang et al. 2016a), which has a wrought iron structure. During reheating and forging process of bloomery iron production, it contacts with charcoal fire, where carbon infiltrates into iron to increase its carbon content and hardness (Han1998). The melting point of iron (1537°C) is much higher than the smelting temperature of bloomery smelting technology, which is about 1200–1400°C (Huang 2013). The product is a slag-iron mixture containing many inclusions, showing significant wüstite-fayalite eutectic inclusions in the metal matrix. Many wüstite-fayalite eutectic inclusions were found to be distributed in the XFC-18 matrix, with large deformation and stretching along the processing direction. Prominent microstructural stratification was observed with 19 layers in the sampling part. Additionally, the carbon content of each layer was different. High carbon layers consisted of pearlite and ferrite, whereas the low carbon layer was ferrite, which is attributed to the overlapping forging of multiple materials.

Hence, it can be concluded from the microstructural analysis shows that the iron objects unearthed from XFC have both products of the bloomery smelting technology and cast iron smelting technology systems.

5.2 Spread and application of bloomery ironmaking technology in northwest China

Archaeological data shows that the earliest manufactured iron smelting products unearthed in China were found at the Mogou Site, Gansu Province (Chen et al. 2012). These products belonged to the Qijia culture during the iron age (about 14th century BC), which is later than the early iron age (about 15th century BC) in Western Asia (Tylecote 2002). Research shows that the early period of iron smelting products unearthed in Xinjiang was from the 9th to the 8th century BC, which was dominated by bloomery iron and carburized bloomery steel (Tang 1993; Qian and Chen 2002; Chen 2014). Scholars believe that the emergence of northwest China's iron smelting technology may have been influenced by Western Asia and was introduced into the Central Plains from Tianshan Beilu of Xinjiang through the Hexi Corridor of Gansu Province (Tang 1993).

In the Eastern Zhou Dynasty (770 − 256 BC), Xirong was mainly distributed in southern Ningxia, eastern Gansu, and northern Shaanxi, where XFC was located. It was also one the regions where large amounts of iron artifacts were unearthed in China before the 5th century BC (Han and Ko 2007:363–364). Han (1998) examined some of the Eastern Zhou ironware (about 8BC to 5BC) excavated from Lingtai in eastern Gansu Province and Guyuan, Xiji, and Pengyang in southern Ningxia, and found that they were all made of carburized bloomery steel. The iron portion of the iron sword with the golden handle (about 8BC-6BC) unearthed from the tomb (M2) of Rong-barbarian in Yimen Village, Baoji, Shaanxi Province, was also made of carburized bloomery steel (Bai1994). Over the years, research has shown that the northern zone steppe near Xirong continued to maintain the tradition of the bloomery iron smelting until about 3BC-2BC (Park et al. 2010). It is speculated that the bloomery iron smelting or carburized bloomery steel unearthed from the Warring States cemetery of the Rong-Barbarian in Zhaitouhe, Shaanxi may have inherited the tradition of early iron smelting technology in northwest China (Guo et al. 2014).

Several wars fought between Qin State and Xirong in the Eastern Zhou Dynasty brought about various cultural exchanges. Evidence suggests that the iron-making technology of early Qin culture may have originated from Xirong (Liang 2016) in Ningxia. After Qin State occupied areas of Xirong, the southern part of Ningxia came under the jurisdiction of the Qin State. Liang (2017) believed that the ironware of the Qin State did not originate from the eastern countries but were more likely introduced from the west. Therefore, before the Qin Dynasty, the ironware used south of Ningxia mainly consisted of bloomery iron and carburized bloomery steel.

XFC-18 was identified as carburized bloomery steel, which indicated that bloomery smelting technology existed in Ningxia in the early Western Han Dynasty. The reason for this phenomenon may be that the central government of the Han Dynasty did not set up a cast iron smelting base in Ningxia, and the craftsmen in Ningxia had not mastered the bloomery iron smelting technology. Or the need for some objects to be made with cast iron is not particularly strong. Based on this analysis, it is likely that the carburized bloomery steel from XFC was directly inherited from the Xirong culture. However, a deeper exploration is warranted in order to ascertain if local ironware processing existed in southern Ningxia or if the owners of XFC cemetery had mastered the bloomery smelting technology. It is also necessary to discuss the iron smelting technology in a broader archaeological context in combination with the research on other artifacts, burial forms, burial types, ethnic groups, etc. from these tombs. However, this study is able to establish that the bloomery smelting technology system was not the leading technology in producing XFC ironware in the early Western Han Dynasty.

5.3 The spread and application of cast iron technology in northwest China

The appearance of the original liquid cast iron and steel technology in the Central Plains promoted the large-scale popularization of ironware and played an important role in promoting social and economic development. Cast iron smelting technology differs from bloomery iron smelting technology and its products are composed of white iron with carbon content higher than 2%. In order to overcome the hard and brittle weakness of the white iron, the technology for achieving annealing decarburization of white iron was invented no later than the 5th century BC (Han and Ko 2007:387). According to the technical evidence of the iron artifacts unearthed in Niejiagou, Xianyang, Shaanxi (about 475BC-221BC), the Chaogang technique was invented no later than the late Warring States Period (Liu et al. 2019). The research on the production technology of Han Dynasty iron swords unearthed in Xi'an shows that the Chaogang technique and decarburized steel were widely used in the production of weapons during the Western Han Dynasty. Furthermore, evidence suggest that the technology of multiple-refined steel-making appeared no later than the late Western Han Dynasty (Zhao et al. 2020; Jiang J et al. 2022).

Once the cast iron smelting technology matured in the Central Plains, it gradually spread to surrounding areas. The spread and exchange of iron and steel technology between Central Plains and south of the Lingnan region (usually considered to include Guangdong, Guangxi, Hainan, Hong Kong and Macau) began after Warring States Period at the latest (Huang et al. 2016b). Sichuan, located on the technology transmission route from Central Plains to Southwest China, discovered cast iron decarburised steel from the late Warring States Period to the early Western Han Dynasty (Li et al. 2019). Iron was supplied south of the Lingnan region through the transportation network developed during the reign of the Han Dynasty (Lam et al. 2020). Zou et al. (2022) discovered that Yunnan had mastered the technology of Chaogang in the Han-Jin period. Furthermore, there is evidence that northeast China become one of the channels for spreading cast iron smelting technology to the Korean Peninsula and Japan (Chen2014).

Two pieces of cast iron decarburised steel were unearthed from the Subei site in Shanshan, Xinjiang, belonging to the 4th-2nd century BC (Qian and Chen2002). Cast iron decarburised products were also found at the Dongheigou site (Chen et al. 2013). By the late Han Dynasty, cast iron smelting technology or the making of ironware had spread from the Central Plains along the Hexi Corridor to Xinjiang and beyond through the early Silk Road. In the process of cast iron smelting technology spreading to the northwest along the Silk Road in the Han Dynasty, it is unlikely that Xinjiang in the northwest was first impacted. Therefore, it is necessary to find the intermediate link that connected the spread of cast iron smelting technology between the Central Plains, Xinjiang, and Hexi Corridor in Gansu. This study provides new evidence to address this important academic question, investigation of the iron artifacts unearthed in XFC indicate that household and burial utensils are mainly made of cast iron. At the same time, farming implements and weapons adopted cast iron decarburisation, Chaogang processes, quenching, and surface carburizing technology, among them, XFC-1 is a Chaogang product found in the most northwest of China during the Han Dynasty.

5.4 Technology convergence

During the early Iron Age, there was frequent cultural exchange between Ningxia and the northern zone steppe. Guyuan area in Ningxia is said to be the site of Wu's Rong-Barbarian activities, which occurred during the Spring and Autumn Periods to Warring States Period. Since the 1970s, many bronze and gold ornaments with Eurasian grassland style have been unearthed there. Based on key characteristics of the excavations, it can be deduced that extensive cultural exchanges exist between Wu's Rong-Barbarian and Altai tribes (Ma2006). Recent genetic sequencing analysis of ancient human DNA in Ningxia revealed that the demographics of Han Dynasty residents in Ningxia was more complex and diverse than that of the pre-Qin period due to the cohabitation of Han and Xiongnu in some areas of Ningxia (Li et al. 2021).

Large-scale iron production and a dense exchange network made the economy of the Han Dynasty flourish and develop continuously (Lam et al. 2018). Various types of ironware unearthed in XFC manufactured using mature decarburised steel from cast iron, quenching, and carburizing technologies indicate that the exchange of iron and steel metallurgy technology between Ningxia and Central Plains may have been quite frequent until the early Western Han Dynasty. The biography of Mu Tianzi records the westbound trade scene of the Central Plains caravan reaching Central Asia through Guyuan, Ningxia, during the Spring and Autumn Period to the Warring States Period. This route was the most convenient route from Chang'an to Hexi in Qin and Han Dynasties (Chen1995). In 119 BC, Zhang Qian hollowed out the Western Regions, creating a smooth Silk Road. Since then, the momentum of Chinese culture spreading westward has never been stoped. As a gateway for the exchange of technology and culture between northwest China and the West on the ancient Silk Road, Ningxia undoubtedly played an essential role in facilitating the continuation of the westward spread after assimilating the iron and steel smelting technology in the Central Plains.

This research shows that Ningxia was the first region affected by the bloomery ironmaking technology from the West in the technical exchange between northwest China and the West in the early Iron Age. Further, the bloomery ironmaking tradition was maintained in Ningxia for a long time. While inventing cast iron smelting technology in Central Plains and spreading it to the West, Ningxia absorbed cast iron smelting technology and realized large-scale applications. At one time, Ningxia was the center of exchange and convergence of bloomery and cast iron smelting technologies, which is evident from the fact that the iron objects unearthed in XFC are a product of the confluence between the metallurgical technologies of the East and West. Although the two technologies existed concurrently, it seems that there is a trend in XFC, where cast iron smelting technology is gradually replacing bloomery smelting technology.

In this study, several ironware objects unearthed from the early Western Han Dynasty cemetery in XFC were analyzed using a combination of characterization methods such as XRF, SEM and EDS. The experimental results show that the farming implements, weapons, and living utensils unearthed from the XFC cemetery exhibited prominent technical characteristics, diverse materials and microstructures. The analysis of 13 pieces of iron reveals the use of two production methods, namely, bloomery ironmaking and cast iron smelting. Among them, one iron hoop was forged with carburized bloomery steel, while the rest of the 12 pieces were cast iron products. Three weapons were made of Chaogang, the farming implement was made of decarburised steel from cast iron, and other miscellaneous tools are made of white cast iron and mottled cast iron. Due to its unique geographical location, Ningxia had become the frontier of technology and culture exchange between the Central Plains and the West. According to the research of archaeometry, the technology of iron and steel production found in XFC is representative of the integration of central Chinese and Western Asia technologies. As far as the exchange of iron and steel metallurgy technology between northwest China and the west Asia is concerned, Ningxia being an important node on the Silk Road, played an important role in the spread of ancient cast iron metallurgy and bloomery ironmaking metallurgy between Eastern and Western civilizations.

Although this study fills the gap in the metallurgical archaeology in Ningxia during Han Dynasty, further research needs to be carried out to comprehensively understand the history of ancient Chinese iron and steel metallurgy technology.

Funding:

This research received funding from the National Natural Science Foundation of China (No. 51764004), Natural Science Foundation of Guangxi (No. 2020GXNSFAA297210), and Innovation Project of Guangxi Graduate Education (No. YCSW2023285).

Acknowledgements:

We would like to express our gratitude to the Ningxia Institute of Cultural Relics and Archaeology, for all the help and facilities that made this research possible, especially the support from the staff JingJing Song and Yao Yao.

Author Contributions:

Jin Zhu: Performed the experiment;

Quansheng Huang and Guisen Zou: Contributed to the conception of the study

Quansheng Huang: Contributed significantly to analysis and manuscript preparation;

Jin Zhu and Guisen Zou: Performed the data analyses and wrote the manuscript;

Cunshi Zhu and Jialong Guo: Helped perform the analysis with constructive discussions.

All authors reviewed the manuscript.

Competing interests: The authors declare no competing interests.

Archaeological Society of China (2015) Chinese Archaeology Almanac. China Social Sciences Press, Beijing (in Chinese).
Bai C (1994) Analytical report of the sword fragment unearthed from Tomb 2 in Yimen, Baoji. Cultural Relics 9:82–85 (in Chinese).
Chen J et al. (2013) Study of ironware unearthed from Dongheigou Site, Barikun, Xinjiang. Cultural Relics 10:77–84 (in Chinese).
Chen J (2014) New Progress in Research on the Development and Dissemination of Steel Technology During the Qin and Han Dynasties. Southern Ethnology and Archaeology 0:251–262 (in Chinese).
Chen J, Zhang Z (2016) Methods to differentiate finning technique based on slag analysis. Cultural Relics in Southern China 1:115–121 (in Chinese).
Chen J et al. (2012) Iron objects unearthed from Siwa culture tomb in Gansu and the origin of the iron metallurgy in China. Cultural Relics 8:45–53 (in Chinese).
Chen Y (1995) The influence of cultural exchanges along the Silk Road on Ningxia. Historical and Geographical Review of Northwest China 1:1–10 (in Chinese).
Dillmann P, L’Héritier M (2007) Slag inclusion analyses for studying ferrous alloys employed in French medieval buildings: supply of materials and diffusion of smelting processes. J Archaeol Sci 34(11):1810–1823.
Guo M et al. (2014) Scientific study of the iron objects unearthed from a Warring State cemetery in Zhaitouhe, Huangling, Shaanxi Province. Archaeology And Cultural Relics 2:114–120 (in Chinese).
Han R (1998) Metallographic study of the iron objects in China dated before 5th century BC. Cultural Relics 2:87–96 (in Chinese).
Han R, Ko T (2007) History of science and technology in China: mining and metallurgy. Science Press, Beijing (in Chinese).
Huang Q (2013) Investigation and slag analysis on iron smelting sites in Guigang district, Guangxi, Lijiang, Lijiang Publishing house (in Chinese).
Huang Q et al. (2016a) Study of early iron metallurgy based on slag analysis. Journal of National Museum of China 11:145–153 (in Chinese).
Huang Q et al. (2016b) The scientific research of the ironware unearthed from the tombs of the Warring States and the Han Dynasty in Guangxi. Cultural Relics Southern China 1:109–114 (in Chinese).
Jiang J et al. (2022) Scientific Analysis of Iron Weapons Unearthed from the Tomb of Liu He, the Marquis of Hai Hun in the Western Han Dynasty. Cultural Relics in Southern China 5:219–229 (in Chinese).
Lam W et al. (2018) An iron production and exchange system at the center of the Western Han Empire: scientific study of iron products and manufacturing remains from the Taicheng site complex. J Archaeol Sci 100:88–101.
Lam W et al. (2020) Provision of iron objects in the southern borderlands of the Han Empire: a metallurgical study of iron objects from Han tombs in Guangzhou. Archaeol Anthropol Sci 12:230.
Li Y et al. (2019) Early iron objects of southwest China: a case study of iron objects excavated from Qiaogoutou cemetery site, Sichuan Province. Archaeol Anthropol Sci 11:1187–1198.
Liang Y (2016) The Relationship between Qin and Xiong in the View of Archaeology. Archaeology of the west 2:112–146 (in Chinese).
Liang Y (2017) On the Origins and Formation of Early Qin Culture. Acta Archaeologica Sinica 2:149–174 (in Chinese).
Liu Y et al. (2019) Iron decarburisation techniques in the eastern Guanzhong Plain, China, during Late Warring States period: an investigation based on slag inclusion analyses. Archaeol Anthropol Sci 11:6537–6549.
Liu Y et al. (2022) Archaeometallurgical study of iron objects from a third century BC bone workshop in Xianyang, Shaanxi Province, China. Archaeol Anthropol Sci 14:71.
Li P et al. (2021) A Research on Human Skull Unearthed from the Han Period Cem etery at the Zhoujiazuitou Site in Longde County, Ningxia. Research of China's Frontier Archaeology 2:243–250 (in Chinese).
Luo F (2002) A Review and Consideration of Ningxia Archaeology in the 20th Century, Archaeology 8:3–18 (in Chinese).
Ma J (2006) Sayane-altai culture exchange in the Eastern Eurasian steppe during the Early Iron Age in the 8th ~ 3rd century BC. Eurasian Studies (Series 8):38–84 (in Chinese).
Park SP et al. (2010) Technological traditions inferred from iron artifacts of the Xiongnu Empire in Mongolia, J Archaeol Sci 37:2689–2697.
Qian W, Chen G (2002) The iron artifacts unearthed from Yanbulake Cemetery and the beginning use of iron in China. in BUMA- Fifth International Conference on the Beginnings of the Use of Metals and Alloys, The Korea Institute of Metals and Materials, Gyeongju.
Rong Y et al. (2013) Study on manufacturing technique for iron artifacts unearthed from the Shenmingpu site 25(3):64–70 (in Chinese).
Shan Y (2009) A Study of Xiongnu Tombs, Acta Archaeologica Sinica 1:25–68 (in Chinese).
Song W (1989) Metallurgy. Metallurgical Industry Press, Beijing (in Chinese).
Tang (1993) The Origin of Iron Smelting in China, Archaeology 6:536–545 (in Chinese).
Tylecote RF (2002) A History of Metallurgy (2nd Edition).The Metals Society, London.
Wagner DB (1993) Iron and steel in ancient China. E.J. Brill, Leiden.
Yang J et al. (2014) Scientific analysis of iron objects unearthed from a military camp in Paomaquan Great wall in Changping, Beijing—discussion about the identification method for finning technique. The Chinese Journal for The History of Science and Technology 35(2):177–187 (in Chinese).
Zhao F et al. (2020) The manufacturing technology of iron swords from the capital of the Han Empire in China. SN Applied Sci 2(9):1510.
Zou G et al. (2022) Where did Yunnan’s puddling steel technology come from? Preliminary analysis of metallurgical relics unearthed from the Shushi Ancient City Site in Zhaotong, Yunnan Province, China. Archaeol Anthropol Sci 14:171.

No competing interests reported.

Download PDF

Version 1

posted

You are reading this latest preprint version

The Critical Node of the Transmission of Iron and Steel Technology on the Silk Road in the Han Dynasty: Study on the Iron artifacts from the Han Dynasty Tombs in Xingfucheng, Guyuan, Ningxia Hui Autonomous Region, Northwest China, ca. 202 BC-141 BC

Status:

Version 1

Abstract

Figures

1. Introduction

2. Background

3. Materials and analytical methods

4. Analytical results

4.1 Metallography

4.2 ED-XRF and SEM-EDS slag inclusions analysis

5. Discussion

5.1 Technology

5.2 Spread and application of bloomery ironmaking technology in northwest China

5.3 The spread and application of cast iron technology in northwest China

5.4 Technology convergence

6. Conclusion

Declarations

References

Additional Declarations

Status:

Version 1