Journal of Archaeological Science 47 (2014) 53e63

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Journal of Archaeological Science

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A view of and making technology in the region during the and the dynasty: scientific study of iron objects excavated from Dongheishan site, province, China

Haifeng Liu a,*, Jianli b, Jianjun Mei a, Jinbiao Jia c, Lei Shi c a Institute of Historical Metallurgy and Materials, University of Science and Technology , Haidian District, Beijing 100083, China b School of Archaeology and Museology, Peking University, Haidian District, Beijing 100871, China c Hebei Provincial Institute of Culture Relics, China article info abstract

Article history: Iron objects excavated from the Dongheishan site provided a chance to systematically study the iron and Received 9 January 2013 steel making technology during the Warring States period and the in the Yan region, north Received in revised form China. According to the results of radiocarbon dating, metallographic and inclusions analysis, it was 30 March 2014 found that they were made of or cast iron subsequently processed into steel, and most Accepted 1 April 2014 radiocarbon dates of iron artefacts were consistent with the determination from their archaeological Available online xxx context. The technology in this region was as advanced as the Central Plain China, and it was probably a previously unknown centre of technological innovation during this period. Meanwhile, the results Keywords: Iron objects analysis showed that the local craftsmen used different types of iron and steel and different technologies to The Warring States period and the Han produce different types of objects. dynasty Ó 2014 Elsevier Ltd. All rights reserved. Dongheishan site The Yan region China

1. Introduction Hebei province. Here, not only iron objects but also iron-casting works were found near the imperial palace (Hebei Provincial From 475 BCE to 220 CE China experienced three important Institute of Culture Relics (1996)). Besides iron objects, casting periods: the Warring States period (475 BCEe221 BCE), the moulds made from irondwhich could be used repeatedly were dynasty (221 BCEe206 BCE) and the Han dynasty (206 BCEe220 found in the Shouwangfeng site, Xinglong county, Hebei province CE). During this period a technological system of cast iron and (, 1956: 1). Among these objects, 14 agricultural implements was established and consolidated, while iron and steel and 21 weapons from the Yanxiadu site were analysed (Beijing products came to be used in many areas of China (Bai, 2005:116; University of Iron and Steel Technology (1975): 4; et al., 1996: Han and Ko, 2007: 440; Wagner, 2008: 115). 881). The results show that all agricultural implements were made The Yan state was one of the seven big states in the Warring of cast iron and some had experienced a process- States period, extending from the Taihang Mountain in the west to ing. The weapons were made of cast iron or steel. The steel, which the north part of Korean Peninsula in the east, and from the Liao was made from both cast iron and iron, was very River in the Northeast to the state in the southeast and to the different from the iron used to make agricultural implements. state in the southwest. Up to the present, about 2800 iron The Qin and Han dynasties mark the beginning of Imperial objects from 38 sites or tombs were found within the Yan state’s China and established many of the institutions that would define territory, and they may therefore be defined as Yan-state iron ob- the period. For instance, in 117 BCE Emperor -di introduced a jects. The most important excavation took place at the Yanxiadu state monopoly on the salt and iron industries, the policy set iron site, the capital of the Yan state which is now located in Yi county, and steel production on a course towards industrialization and standardization throughout China. A large number of state’s monopoly-run have been located, and several have been excavated; meanwhile, lots of iron objects have been excavated * Corresponding author. from Han-period settlements, tombs and ironworks (Li, 1994: 158; E-mail addresses: [email protected], [email protected] (H. Liu). Han and Ko, 2007: 502; Wagner, 2008: 198). At this time, the Yan http://dx.doi.org/10.1016/j.jas.2014.04.001 0305-4403/Ó 2014 Elsevier Ltd. All rights reserved. 54 H. Liu et al. / Journal of Archaeological Science 47 (2014) 53e63

Fig. 1. The location of the Dongheishan site and the Yan state. region was divided into several provinces or states, including the spectrometry radiocarbon dating (AMS-14C dating), optical micro- northern part of the state, which also had a state’s scopy, and scanning electron microscopy (SEM) with energy monopoly-run ironwork. The Zhongshan ironwork has not yet been dispersive spectrometry (EDS). located, but is the apparent source of the considerable quantity of iron objects unearthed in the Mancheng tomb (Institute of Archaeology, Chinese Academy of Social Sciences, 1980). Twenty- 2. Background of the site and iron artefacts six iron objects from the Mancheng tomb were analysed (Beijing University of Iron and Steel Technology, 1980: 369; Tsinghua The Dongheishan site, located in Xushui county, Hebei province, University, 1980: 388). The results concluded that most were China, roughly 120 km southwest of Beijing city (Fig. 1), was made of cast iron and steel; the steel had been converted from cast excavated by the Hebei Provincial Institute of Culture Relics in iron via a decarburization processing and had been quenched to 2006. The excavations uncovered a long period of occupation, from improve mechanical performance. Meanwhile, scholars (Beijing the late Warring States period to the Qing dynasty, with rich as- University of Iron and Steel Technology (1980): 369) have stated semblages of pottery, porcelain, bronze, and iron artefacts, and that objects from the Mancheng tomb appear to be a primitive form other materials. Finds dating to the period from the late Warring of Bailian steel (hundred refining steel). In addition, bloomery iron States period into the Han dynasty were deemed to be the most objects were also found in the Dabaotai tomb in Beijing (Beijing important. Because the site was located on the south boundary of University of Iron and Steel Technology (1989): 125), which the Yan state e facing the Zhao state directly e and only 30 km proved that bloomery iron was still in use, though they only south of the capital, it is considered to be an important military occupied 6% among all the iron objects. stronghold of the state in the late Warring States period (Jia et al., Past research has answered many questions about the iron in- 2007). In the Han dynasty, the site was a more residential area dustry of the Warring States period and the Han dynasty. However, belonging to the Zhongshan state. the use of iron artefacts and the development of iron and steel 175 iron objects were excavated, with 137 of those from layers making technology during this period in the Yan region need dating to the late Warring States period or the Han dynasty. Among further research. The large quantity of iron objects excavated from them, 26% are agricultural implements, 23% belong to other im- the Dongheishan site in Xushui county, Hebei province, provide an plements, and 18% are weapons (Table 1, Fig. 2). 66 iron objects opportunity to carry out fresh research. The present study of the were analysed, of which 51 were excavated from the layers of the Dongheishan iron objects will characterize their chronology, late Warring States and the Han dynasty, in order to investigate microstructure, and chemistry through the use of accelerator mass local iron and steel making technology of this period. H. Liu et al. / Journal of Archaeological Science 47 (2014) 53e63 55

Table 1 The iron objects excavated from the Dongheishan site.

Types Late Warring Early Western Mid-late Eastern Han Tang- -Yuan Ming-Qing Age Total States period Han dynasty Western dynasty period period period uncertain Han dynasty

Agricultural Unearthed number 4 13 19 6 1 1 1 45 implement Sampled number 2 4 6 4 16 Other implement Unearthed number 2 13 11 10 2 1 2 41 Sampled number 4 7 1 1 1 2 16 Weapon Unearthed number 1 7 9 6 2 5 1 31 Sampled number 3 4 2 1 10 Other kinds Unearthed number 2 9 12 13 9 4 9 58 Sampled number 1 3 4 6 6 1 3 24 Total Unearthed number 9 42 51 35 12 12 1 13 175 Sampled number 3 14 21 13 6 3 1 5 66

Fig. 2. Selected iron objects from the Dongheishan site.

3. Experiments and results one standard deviation, and background is 43,000 years. Calibrated dates were determined using the software Oxcal v3.10. The radio- 3.1. Radiocarbon dating carbon dates and calibrated dates of objects from the site are shown in Table 2. Artefacts are often assigned a date via their archaeological context, but it is necessary to consider that many objects may have 3.2. Metallographic and SEM-EDS analysis been deposited only after a long use life. By employing AMS-14C dating on iron objects, a date of manufacture can be established Using metallographic and SEM-EDS analysis to reveal the with confidence (Craddock et al., 2002: 717). In order to compare metallographic and slag inclusion structure as well as chemical the radiocarbon dates of iron objects with contextually determined composition of artefacts can help to understand the materials and dates, we chose 15 samples which have high concentrations of technologies used in the past. Small samples were cut from the iron carbon for AMS-14C dating. The method used to extract carbon from objects where metallic remains were found by observation and the iron samples is as follows: 1) cut the samples to the appro- were set in phenolic resin. After being ground and polished, sam- priated size; 2) wash; 3) vacuum-seal in pre-baked 6 mm quartz ples were etched with 4% natal. The revealed microstructure was tubes with CuO and suffix particles; 4) combust at 850 C for 3 h; 4) observed and photographed with a Leica DM4000M microscope in purify the CO2 and deoxidize it to graphite; and 5) press it into the Archaeometallurgy Laboratory at Peking University. Slag in- targets for AMS measurement. Radiocarbon dating was conducted clusions were analysed by using a Hitachi S-3600N scanning elec- at Peking University. The values used were as follows: half-life tron microscope with EDAX Genesis 2000 XMS in the Chinese period of 14C is 5568 years, the start point is 1950, the error is Academy of Cultural Heritage. The excitation voltage is 20 kV, and 56 H. Liu et al. / Journal of Archaeological Science 47 (2014) 53e63

Table 2 Radiocarbon dating results of iron objects from the Dongheishan site.

Lab no. Sample no. Archaeological date 14C Age (BP) 95.4% (2s) calibrated age

BA101285 T1217⑧:1 Late Warring States period 2145 25 354BC(23.8%) 294BC 230BC (1.7%) 219BC 212BC (69.9%) 92BC BA101286 T1116⑦H99:1 Early Western Han dynasty 2135 25 350BC(12.2%) 309BC 210BC (80.0%) 88BC 77BC (3.1%) 57BC BA101287 T1217⑦:5 Early Western Han dynasty 2190 30 365BC(95.4%) 176BC BA101288 T1116⑥:3 Middle-Late Western Han dynasty 2035 25 156BC (2.5%) 139BC 112BC (92.2%) 27AD 43AD (0.7%) 47AD BA101289 T1217⑥H156:1 Middle-Late Western Han dynasty 1890 25 59AD (89.5%) 180AD 189AD (5.9%) 214AD BA101290 T1419⑥:3 Middle-Late Western Han dynasty 1615 25 395AD (95.4%) 535AD BA101291 T1216⑤:5 Eastern Han dynasty 2095 25 191BC (95.4%) 47BC BA101292 T1418⑤H149:1 Eastern Han dynasty 2270 35 400BC (42.6%) 349BC 313BC (52.8%) 208BC BA101293 T1216④:1 Tang-Song period 2205 25 367BC (95.4%) 200BC BA101294 T1217④:1 Tang-Song period 1990 25 44BC (95.4%) 64AD BA101295 T1416④:1 Tang-Song period 2300 25 406BC (84.0%) 357BC 284BC (9.2%) 256BC 246BC (2.2%) 235BC BA101296 T1316③:4 Jin-Yuan period 33,280 300 Dead carbon BA101297 T1319②:2 Ming-Qing period 26,690 150 Dead carbon BA101298 e Unknown age 1925 30 2AD (95.4%) 134AD BA101299 e Unknown age 2125 25 345BC (4.6%) 323BC 206BC (90.8%) 54BC

the collecting time is 75 s. Slag inclusions were spot scanned and in used continually over a long time, and it is common to find an order to obtain accurate results points chosen for measurement earlier object in a later layer; a later object found in an earlier layer were relatively large inclusions from different locations within the probably resulted from the unnoticed problem in the excavation of sample. The results are shown in Tables 3e4. Some photos can be a deposition which formed over a long period of time. found in Figs. 3e15. These concerns about the use of radiocarbon dating on iron objects can be mitigated in several ways: 1) Compare the 14C dating 4. Discussion results and contextual dates. For iron artefacts from the Dong- heishan site, radiocarbon dates are all between the Warring States 4.1. The manufacturing date of iron objects and the Han dynasty and mostly correspond with the contextual dates, which suggest the radiocarbon results are reliable in this The radio carbon dating results show that 12 samples date to the case. 2) Do not use radiocarbon dating on iron objects that seem to Warring States period or the Han dynasty. One sample have gone through any secondary processing, it’s better to use cast (No.BA101290) dates to the -Jin period, despite an earlier iron implements rather than other kinds of objects which were contextual date. The carbon in two other samples (No.BA101296, made of steel to take the test. So, it is very important to determine No.BA101297), which were contextually dated to the Jin-Yuan the differences between original and the second processing prac- period, was determined to be dead carbon. Together with chemi- tices using a metallographic approach. 3) It is believable that cal compositions measured to contain significant amounts of sul- craftsmen in the past might not use 100-year-old (or more) trees as phide, the dead carbon strongly suggests that the iron in these fuel, because they were more valuable to use in other ways and artefacts had been smelted or melted or heat treated with fossil fuel there were not a lot of old trees to be found in Hebei province since () rather than with (Qiu and , 1986: 359). Research Han dynasty. 4) Follow good excavation practices to avoid confu- from the examination of iron coins show that coal was at least first sion in contextual dating. With these cautions having been taken used in the Song period (, 2006: 79), and the results from the into mind, the results from the Dongheishan site show clearly that Dongheishan site are consistent with that examination result. In AMS radiocarbon dating can be used to date iron objects to their contrast to the contextual dates, the radiocarbon dates strongly time of production. demonstrate that most iron artefacts from the Dongheishan site were made during the Warring States period and the Han dynasty. 4.2. Materials and techniques of iron objects The fact that some of them were excavated from a later layer il- lustrates that they were continually using for a long time, and “Direct” or bloomery method and “indirect” or cast method mostly were abandoned or buried in the Tang-Song period. were two different ways of iron in the ancient world. Several issues related to the radiocarbon dating of iron artefacts Bloomery smelting was the main method used in ancient Europe, continue to be hotly debated. Firstly, because some iron objects India, and the Near East. As for China, the earliest bloomery iron may have gone through a decarburization, carburization, hard- objects which dated to the 14th century BCE were found in Gansu ening, or re-smelting process after the initial smelt, they may have province; they provide significant information on the origin of iron taken in new carbon. This could produce incorrect 14C dating re- technology in China (Chen et al., 2012). However, it was the cast sults. Secondly, the age of the wood used for charcoal fuel is un- method that occupied the main position of iron and steel making known. Though young trees or shrubs were most commonly used technology in ancient China. The earliest cast iron objects appeared as fuel, older trees may also have been used, which could result in in China no later than the (8th century erroneously old radiocarbon dates. Third, some iron objects were BCE) (Han, 2000:1178), and then cast iron was used as raw material H. Liu et al. / Journal of Archaeological Science 47 (2014) 53e63 57

Table 3 The metallographic and slag inclusions structure of the samples.

No. Excavation no. Name Metallographic and slag inclusions structure Materials and techniques

1 T1119⑧:2 Spade Hypereutectic white cast iron and pearlite with Mottled iron strip-shaped graphite and very a few spherical graphite 2 T1217⑧ H191:1 Sickle Martensite structure, see Fig. 14 Decarburized steel with 3 T1217⑧:1 Mouth rim Pearlite þ proeutectoid cementite þ ledeburite Hypoeutectic white cast iron of a basin 4 T1116⑦ H99:1 Plough Pearlite þ proeutectoid cementite þ ledeburite, see Fig. 3 Hypoeutectic white cast iron 5 T1217⑦:2 Spade Ledeburite þ proeuteciccementite Hypereutectic white cast iron 6 T1217⑦:5 Adz From core to edge are hypereutectic white cast iron Decarburized cast iron and pearlite, see Fig. 5 7 T1318⑦ F7:5 Plough Pearlite þ proeutectoid cementite þ ledeburite Hypoeutectic white cast iron 8 T1219⑦:2 Arrowhead Ferrite þ pearlite, carbon content are different from Puddled steel layers which among 0.2% and 0.4% 9 T1219⑦ L4:1 Spear Ferrite þ pearlite with widmanstatten structure on the edge, Puddled steel with hot forging carbon content are different from layers which among 0.1% and 0.2%; slag inclusions are small with large amounts of deformation and they were arranged along the direction of processing 10 T1318⑦:1 Arrowhead Ferrite, grain sizes are between 2 and 4 grade; slag inclusions are Puddled steel () small with large amounts of deformation and they were arranged along the direction of processing 11 T1117⑦H135:4 Nail Ferrite, grain sizes are between 2 and 4 grade; few single Decarburized steel (wrought iron) phase slag inclusions 12 T1216⑦:3 Nail Ferrite þ pearlite, carbon content is about 0.2e0.5% Decarburized steel 13 T1219⑦:7 Serious corrosion Uncertain 14 T1416⑦ J2:4 Knife Ferrite and pearlite with widmanstatten structure, carbon content is about 0.6% Decarburized steel 15 T1417⑦H85:1 Hook Hypereutectoid steel (pearlite þ proeutectoid cementite), carbon Decarburized steel content is about 1.4% 16 T1418⑦:5 Mouth rim Ledeburite Eutectic white cast iron 17 T1117⑦H135:2 Uncertain Ferrite and pearlite with widmanstatten structure in the core, ferrite on the edge Decarburized steel 18 T0127⑥H221:1 Hoe Ferrite and pearlite with corrosion Decarburized steel 19 T1219⑥H108:2 Spade From core to edge are pearlite, ferrite þ pearlite, ferrite Decarburized steel 20 T1316⑥H69:4 Adz Hypereutectoid steel (pearlite þ proeutectoid cementite) with Decarburized steel with martensite structure along blade, carbon content is about 1.4% selective quenching 21 T1317⑥ H68:6 Sickle Hypereutectoid steel (pearlite þ proeutectoid cementite), carbon content is about 1.8% Decarburized steel 22 T1318⑥ G10:6 Ploughshare Pearlite þ proeutectoid cementite þ ledeburite Hypoeutectic white cast iron 23 T1419⑥:3 Ploughshare From cote to edge are hypereutectic white cast iron, ferrite þ pearlite, ferrite Decarburized cast iron 24 T0131⑥:1 Arrowhead One side is totally ferrite, the grain sizes are among 2-5 grade; another side is Puddled steel ferrite þ pearlite, carbon content are different from layers which is about 0.15%, see Fig. 8 25 T0131⑥F4:3 Arrowhead Ferrite, the grain sizes are among 2-5 grade; slag inclusions are small with large Puddled steel (wrought iron) amounts of deformation and they were arranged along the direction of processing with hot forging 26 T1418⑥F1:1 Arrowhead Ferrite þ pearlite, carbon content is about 0.2e0.6% with uniform layers Puddled steel 27 T1118⑥ H126:2 Arrowhead Ferrite, the grain sizes are among 2-4 grade; slag inclusions are small with large Puddled steel (wrought iron) amounts of deformation and they were arranged along the direction of processing with hot forging 28 T1118⑥:1 Hammer Hypoeutectoid steel (ferrite þ pearlite) with grain deformation, carbon Decarburized steel with content is about 0.4%, see Fig. 12 cold harmmering 29 T1118⑥ H126:3 Knife Hypereutectoid steel (pearlite þ proeutectoid cementite), carbon content is about 1.8% Decarburized steel 30 T1416⑥:7 Knife Hypoeutectoid steel (a few ferrite þ pearlite) with martensite structure along Decarburized steel with blade, carbon content is about 0.7% selective quenching 31 T1217⑥ H156:1 Knife From core to edge are hypereutectic white cast iron, pearlite, ferrite þ pearlite, Decarburized cast iron ferrite, see Fig. 6 32 T1318⑥ G10:3 Knife Hypereutectoid steel (pearlite þ proeutectoid cementite), carbon content is about 0.8% Decarburized steel 33 T1318⑥ G10:5 Knife Pearlite in the core with 0.6% carbon content, martensite structure along blade, Decarburized steel with hot single phase slag inclusions along the direction of processing, see Fig. 15 forging and selective quenching 34 T1319⑥:3 Chisel From core to edge of the cross section are wrought iron, low , high Maybe co-fusion steel carbon steel, low carbon steel, corrosion, low carbon steel, high carbon steel, white cast iron, wrought iron and corrosion, each layer is about 0.2e0.7 mm thickness, no slag inclusion, see Fig. 13 35 T1117⑥ G7:1 Chariot horses Hypereutectoid steel (pearlite þ proeutectoid cementite), carbon content is Decarburized steel about 0.8e1.4% 36 T1217⑥H181:3 Hook Ferrite þ pearlite structure with uniform layers, carbon content is about Puddled steel with hot forging 0.1e0.2%; small single slag inclusions along the direction of processing, see Fig. 10 37 T1217⑥:1 Uncertain Ferrite structure with 2e4 grades of grain size; small single slag inclusions along Puddled steel (wrought iron) the direction of processing as well as a few double phases slag inclusions with hot forging 38 T1217⑥:2 Uncertain Ferrite with corrosion, small single slag inclusions along the direction of processing Puddled steel (wrought iron) with hot forging 39 T0131⑤:6 Sickle Serious corrosion Uncertain 40 T1416⑤:1 Sickle Hypoeutectoid steel (ferrite þ pearlite), carbon content is about 0.6% Decarburized steel 41 T1216⑤H48:1 Adz Hypereutectic white cast iron with strip-shaped graphite Mottled iron 42 T0131⑤:1 Knife Hypoeutectoid steel (ferrite þ pearlite), carbon content is among 0.1e0.3% Decarburized steel 43 T1418⑤ H138:1 Arrowhead Ferrite structure with 2e3 grades of grain size, small slag inclusions with large Puddled steel (wrought iron) amounts of deformation and they were arranged along the direction of processing with hot forging 44 T1418⑤ H150:1 Arrowhead Ferrite structure with 3e5 grades of grain size Decarburized steel (wrought iron) 45 T1418⑤ H138:2 Hook (continued on next page) 58 H. Liu et al. / Journal of Archaeological Science 47 (2014) 53e63

Table 3 (continued )

No. Excavation no. Name Metallographic and slag inclusions structure Materials and techniques

Ferrite structure with 2e4 grades of grain size, small slag inclusions with large Puddled steel (wrought iron) amounts of deformation and they were arranged along the direction of processing with hot forging 46 T1116⑤:3 Uncertain Hypoeutectic white cast iron with a lot of strip-shaped graphite, see Fig. 4 Mottled iron 47 T1216⑤:5 Uncertain From core to edge are hypereutectic white cast iron with flocculent-shaped Malleable cast iron graphite, ferrite þ pearlite, ferrite 48 T1216⑤:6 Uncertain Ledeburite þ proeuteciccementite, and corrosion Hypereutectic white cast iron 49 T1418⑤ H149:1 Uncertain Pearlite þ proeutectoid cementite þ ledeburite Hypoeutectic white cast iron 50 T1418⑤ H149:2 Uncertain Ferrite þ very a few pearlite structure with uniform layers, Puddled steel with hot forging small slag inclusions along the direction of processing 51 T1116⑤:2 Uncertain Ferrite structure with 2e4 grades of grain size Decarburized steel (wrought iron) 52 T1416④:1 Spade Ledeburite þ proeuteciccementite Hypereutectic white cast iron 53 T1820④:1 Belt hook Ledeburite Eutectic white cast iron 54 T0129④:2 Uncertain From core to edge are pearlite þ very a few proeutectoid cementite, Decarburized cast iron ferrite þ pearlite, ferrite, see Fig. 7 55 T0131④:1 Uncertain Ferrite structure with 2-5grades of grain size, small slag inclusions Puddled steel (wrought iron) with large amounts of deformation, very a few ghosting structure 56 T1216④:1 Uncertain Pearlite þ proeutectoid cementite þ ledeburite Hypoeutectic white cast iron 57 T1219④:1 Uncertain Ferrite þ very a few pearlite, carbon content is about 0.1% Decarburized steel 58 T1219③:2 Arrowhead Ferrite þ a few pearlite, small slag inclusions with large amounts of Puddled steel with hot forging deformation and they were arranged along the direction of processing 59 T1316③:2 Nail Pearlite þ proeutectoid cementite þ ledeburite Hypoeutectic white cast iron 60 T0131③:1 Uncertain From core to edge are hypereutectic white cast iron, ferrite þ pearlite, ferrite Decarburized cast iron 61 T0738②:1 Nail Ferrite structure with 2-5grades of grain size and with twin crystal and Puddled steel with hot forging ghosting structure, small double phases slag inclusions with large amounts of deformation and they were arranged along the direction of processing, see Figs. 9 and 11 62 Age uncertain Nail Ferrite and pearlite with widmanstatten structure, carbon content is about 0.4% Decarburized steel 63 Age uncertain Axe Hypereutectoid steel (pearlite þ proeutectoid cementite), carbon content is about 1.2% Decarburized steel 64 Age uncertain Uncertain Ferrite and pearlite with widmanstatten structure, carbon content is about 0.1%, Puddled steel small single phase slag inclusions with large amounts of deformation 65 Age uncertain Uncertain Hypereutectic white cast iron and pearlite with strip-shaped graphite Mottled iron 66 Age uncertain Uncertain Hypereutectic white cast iron and pearlite with strip-shaped graphite Mottled iron

Remark of layers: ⑧ e Late Warring States Period; ⑦ e Early Western Han dynasty; ⑥ e Mid-Late Western Han dynasty; ⑤ e Eastern Han dynasty; ④ e Tang-Song Period; ③ e Jin-Yuan Period; ② e Ming-Qing Period. to make steel or wrought iron by different ways. and process that involved stirring liquid iron in a hearth to make high puddling were two main decarburization methods to make steel. carbon cast iron decarburized (by oxidization) into low carbon steel The former one decarburized iron objects or plates in the solid or wrought iron. Such hearths have been found in several sites of state, and under different conditions it produced different products, the Han dynasty, like Tieshenggou iron smelting site (Zhao et al., mainly decarburized steel, decarburized cast iron and malleable 1985) and Wafangzhuang iron casting site ( Provincial cast iron. Puddling technique in ancient China was more likely a Institute of Culture Relics (1991)) both in Henan province.

Table 4 The chemical compositions of slag inclusions in several puddled steel objects from the Dongheishan site (wt%).

Sample no. Appearance Scanning part FeO Na2O MgO Al2O3 SiO2 P2O5 SO3 K2O TiO2 MnO2 T1219⑦L4:1 Sub-double phase Scanning 86.8 e 0.5 0.6 6.1 3.9 ee2.1 ee Dark phase 64.5 e 1.3 e 25.9 5.8 ee2.5 ee T1318⑦:1 Sub-double phase Scanning 91.3 ee 0.3 4.9 1.5 0.6 e 1.2 e 0.4 Dark phase 78.0 e 1.0 0.4 17.9 1.2 ee0.7 e 0.8 Single phase Scanning 78.4 eee 16.0 2.8 eee e 2.7 T0131⑥F4:3 Sub-double phase Scanning 60.9 0.7 0.9 3.1 19.2 8.3 e 0.7 5.3 e 0.9 Bright phase 61.0 0.1 1.6 3.2 26.7 3.0 e 1.5 2.4 e 0.6 Dark phase 38.0 1.4 1.0 11.4 17.3 12.8 e 8.1 9.5 e 0.5 T1118⑥H126:2 Sub-double phase Scanning 89.7 eee 3.9 1.7 2.3 e 2.4 ee Dark phase 91.4 ee 0.3 2.8 0.7 2.3 e 2.2 e 0.4 T1217⑥:2 Sub-double phase Scanning 85.6 eee 7.6 5.5 eee e 1.3 Bright phase 87.0 eee 8.9 2.9 eee e 1.2 Dark phase 65.4 eee 27.0 4.7 eee e 2.9 Single phase Scanning 66.2 eee 15.6 14.1 ee1.9 e 2.2 T1217⑥H181:3 Sub-double phase Dark phase 7.3 0.2 1.3 3.2 67.4 ee1.2 5.1 3.4 10.9 Bright phase 30.8 0.3 0.7 4.9 48.0 5.8 0.6 2.0 4.4 e 2.5 T1418⑤H138:2 Sub-double phase Scanning 76.2 e 0.6 e 15.8 1.4 1.3 e 2.2 e 2.5 Bright phase 34.3 e 1.2 2.4 40.0 2.5 2.8 0.5 7.5 e 8.7 Dark phase 48.0 eee 40.2 2.0 ee5.3 e 4.6 Single phase Scanning 39.9 e 0.6 1.9 36.8 3.1 3.0 0.5 5.3 0.3 8.7 T1219③:2 Double phase Scanning 79.3 ee 2.7 12.0 1.7 2.2 0.3 1.8 ee Dark phase 56.3 0.4 0.5 4.6 24.8 3.9 5.4 0.6 3.0 e 0.4 T0738②:1 Double phase Scanning 66.6 0.1 0.3 6.6 15.0 5.4 0.9 0.4 1.7 e 3.1 Dark phase 60.2 e 1.0 1.9 23.7 6.7 e 0.9 1.7 e 3.8 Dark particle 43.2 e 1.7 52.3 0.7 eeee0.4 1.7 H. Liu et al. / Journal of Archaeological Science 47 (2014) 53e63 59

Fig. 3. T1116⑦H99:1, Early Western Han, ploughshare, pearlite þ secondary Fig. 6. T1217⑥H156:1, Mid-late Western Han, knife, from the core to the side are cementite þ ledeburite; white cast iron. hypereutectic white iron, steel and wrought iron; decarburized cast iron.

Fig. 4. T1116⑤:3, Eastern Han, hypereutectic white iron þ pearlite þ strip graphite; Fig. 7. T0129④:2, Tang-Song period, from the core to the side are hyper-eutectoid mottled cast iron. steel, hypo-eutectoid steel and wrought iron; decarburized steel.

⑦ þ Fig. 5. T1217 :5, Early Western Han, adze, hypereutectic white iron temper carbon; Fig. 8. T0131⑥:1, Mid-late Western Han, arrowhead, hypo-eutectoid steel, carbon malleable cast iron. content was uniform layered, small slag inclusions; puddled steel. 60 H. Liu et al. / Journal of Archaeological Science 47 (2014) 53e63

which made the slag inclusions complex. The features of puddled steel’s slag inclusions are different from those found in cast iron and bloomery iron. Always, the slag inclusions in puddled steel have two types: one type contains both FeO and SiO2 (sometimes with Mn), but it does not display a clear euctectoid phase-separated microstructure like in bloomery iron’s double phase inclusions; these inclusions can be defined as ”sub-double phase” inclusions (Fig. 10). Meanwhile, many single phase inclusions also exist in puddled steel. In addition, it was found that after coal began to be used as smelting fuel, the slag inclusions in puddled steel became more complex, even similar to bloomery iron’s double phase in- clusions (Fig. 11). However, the reason why it changed is still un- known and needs more research. Based on the criteria described above for distinguishing different ancient iron products, we found cast iron, decarburized cast iron, decarburized steel, puddled steel, malleable cast iron, and possibly co-fusion steel in the samples. The results of materials and techniques analysis of the iron objects are shown in Table 5. From the table, it is apparent that people at that time had already chosen Fig. 9. T0738②:1, Ming-Qing period, nail, wrought iron, inclusions are along the to use different materials to make different types of objects. Im- processing direction, the content of Fe is higher than Si; puddled steel. plements, especially agricultural implements, were mostly made of cast iron and decarburized steel. This means an annealing tech- Besides, five iron objects from Shizishan tomb in Xuzhou city, nique was used to reduce the brittleness of cast iron in the solid Jiangsu province were considered the earliest puddled steel (no state. These materials processing choices likely had a positive later than the early Western Han dynasty) in China (Institute of impact on agricultural production and on the ancient economy, in Historical Metallurgy and Materials, USTB, 1999: 7). After that, general. Weapons, especially small weapons were mostly made of puddled steel was used very commonly throughout China. Some puddled steel, which experienced a special puddling step in order foreign scholars prefer to call the technique “fining”. to make a higher-quality steel by reducing carbon of cast iron. Bloomery iron, cast iron and other products can be distin- Weapons with improved material properties could increase the guished by slag inclusions analysis. Chen and Han (2007:37) military effectiveness. Additionally, the puddled steel implements concluded that slag inclusions in bloomery iron and its products excavated from the layer corresponding to the early Western Han have both fayalite and glass (double phase inclusion), while cast dynasty date to the same period of the earliest five puddled steel iron and its annealing products typically have only glass (single implements unearthed in the Shizishan tomb, Xuzhou city, Jiangsu. phase inclusions). Moreover, the chemical compositions are Hot forging, cold hammering, and quenching were used for different: bloomery iron inclusions always have high Fe, low Si, and subsequent manipulation of iron-based products. Hot forging was non-uniform chemical compositions of other elements relative to always used with the puddling process when making weapons. inclusions in cast iron. However, slag inclusions in puddled steel are Only one implement has a microstructure indicative of cold much more complex than in other types. This is because while hammering (Fig. 12). An agricultural implement from the late puddled steel was made from cast iron, it experienced a decarbu- Warring States period had been quenched (Fig. 14). This is the same rization process followed by carburization and hammering steps period as the earliest known quenched iron artefact (also an agri- cultural implement), found in the Qiaocun tomb, Houma city, province (Han and Duan, 2009: 99). Additionally, three

Fig. 10. T1217⑥H181:3, Western Han dynasty, puddled steel, the slag inclusions in early times when coal was not used always have this type of microstructure, which includes both fayalite and glass but does not display eutectoid phase separation as in Fig. 11. T0738②:1, Ming-Qing period, nail, puddled steel, the puddled steel in later double phase inclusions. Its chemical composition is purer than in bloomery iron in- period always have double phase inclusions, like in bloomery iron, it’s probably clusions. This type is defined as “sub-double phase inclusions”. because coal was used for smelting. H. Liu et al. / Journal of Archaeological Science 47 (2014) 53e63 61

Table 5 Materials and techniques observed in the samples from the Dongheishan site (number).

Type Cast iron Decarburized cast iron Decarburized steel Puddled steel Others Total

Agricultural implements 7 2 6 1 (uncertain) 16 Other implements 1 1 11 1 2 (1 maybe co-fusion steel, 1 uncertain) 16 Weapons 1 9 10 Other kinds 9 2 5 7 1 (malleable cast iron) 24 Total 17 5 23 17 4 66 implements from the middle-late Western Han Dynasty contained workshop was continually in use until the Han dynasty. Besides, martensite along the blade (Fig. 15), indicating the use of selective there were another three Han-period iron workshops found in quenching to improve blade hardness without sacrificing overall Beijing (Beijing Institute of Culture Relics, 1990:97;Jumahe toughness of the implement. Archaeological Team, Beijing Institute of Culture Relics, 1992: The chisel excavated from a middle-late Western Han dynasty 705) and Chengde (Zheng, 1956: 1). , furnace remains, casting layer has layers of different carbon content. From core to edge of the moulds and iron products were found in these sites, strongly cross section, there are layers of wrought iron, low carbon steel, illustrating that there was a flourishing iron industry in this region high carbon steel, low carbon steel, corrosion, low carbon steel, during that time. high carbon steel, white iron, wrought iron and corrosion (Fig. 13). By comparing iron objects found in the Dongheishan site, the This structure is reminiscent of a previously documented example Mancheng tomb and the Dabaotai tomb, most objects were made of of co-fusion steel and of experimental products (Needham, 1958: cast iron or decarburized steel, except several bloomery iron 30; Ko et al., 1993: 1). However, the layer of each structure is just products found in the tombs. Very early puddled steel was found in 0.2e0.8 mm thick which is much thinner than the experimental the Dongheishan site and the earliest selective quenching tech- products. nique both in the Dongheishan site and the Mancheng tomb; and it might appear the earliest co-fusion steel in the Dongheishan site, the earliest Balian steel in the Mancheng tomb. So, it seems that this 4.3. Iron and steel making technology in the Yan region from the area played an important role in the improvement of iron and steel Warring States period to the Han dynasty technology in the Han dynasty, and it might be a previously un- known centre of technological innovation at that time. The time that iron and steel making technology appeared in the There is no doubt that the iron-based implements (including Yan state was later than that of Central Plain China, and the tech- agriculture implements) excavated from the Dongheishan site were nological development also followed the same route as that of made by casting, sometimes followed by decarburization. Cast iron Central Plain China, strongly suggesting that the technology in the implements have been found all around the Yan region, with a large Yan state was introduced from Central Plain China. However, the quantity dating to the Warring States period and the Han dynasty. metallurgical study of iron objects from the Yanxiadu site and the This technology is believed to have improved the production of Dongheishan site showed that in the Warring States period the implements, because casting technology made the production technology was as advanced as that of Central Plain China. It is more efficient. Furthermore, the annealing process reduced the believed that the Yan people adopted the technology very well and brittleness of cast iron and improved its mechanical performance, caught up with other areas quickly. thereby enabling the production of large ploughshares for deep Additionally, there were two iron-casting sites found nearby the furrowing, as well as sharp, strong, and inexpensive sickles for imperial palace of the Yan state, suggesting that the Yan govern- harvesting, a development likely related to increasing agricultural ment directly controlled the iron industry. The same thing also yields during this period (Han and Duan, 2009: 105). Improvements happened in the capital () of the Zhao state (Institute of in iron production technology were likely a significant factor in the Culture Relics Preservation in Handan, 1980: 142), which is located to the south of the Dongheishan site, where the iron

Fig. 13. T1319⑥:3, Mid-late Western Han dynasty, Chisel, from the inside to the outside of the cross section, there are layers of wrought iron, low carbon steel, high Fig. 12. T1118⑥:1, Mid-late Western Han, hammer, hypo-eutectoid steel; decarburized carbon steel, low carbon steel, corrosion, low carbon steel, high carbon steel, white steel with cold hammering. iron, wrought iron and corrosion; maybe co-fusion steel. 62 H. Liu et al. / Journal of Archaeological Science 47 (2014) 53e63

decarburizing technologies were already mature by the late War- ring States period and puddled steel, Bailian steel, co-fusion steel, and quenching techniques appeared very early. Furthermore, peo- ple chose different materials and techniques to make different types of products.

5. Conclusions

Iron objects from the Dongheishan site provide a chance to systematically study iron and steel making technology in the Yan region between the Warring States period and the Han dynasty. Radiocarbon dating of the iron objects showed that most of them were made in this period, though some of them were continually used for a long time until the Tang-Song period. The metallurgical study illustrated that all the objects examined were made of cast iron or cast iron subsequently processed into steel. Cast iron and decarburized products were used mainly to make implements, while weapons were made mostly of puddled steel. Additionally, Fig. 14. T1217⑧H191:1, Late Warring States period, Sickle, martensite; Decarburized the appearance of puddling and quenching techniques at the steel, quenched. Dongheishan site appeared to be contemporaneous with the emergence of these techniques elsewhere in China, and the use of co-fusion processing may be the earliest documented in China. economic and societal development of the Yan state, and later in This research also demonstrated that cast iron technological the developments in the Han dynasty in this region. system was always dominant in the agricultural sector, while Analytical results from weapons stand in contrast to those from bloomery iron technology had fallen out of use in the military the implements. Most weapons from the Yanxiadu site were shown production only in the Han dynasty. This region was once an to be made from bloomery iron and carburized steel (Beijing innovative centre of iron industry during the late Warring States University of Iron and Steel Technology, 1975: 4). However, period and the early Western Han dynasty. The Yan region, there- weapons from the Dongheishan site were made from puddled steel fore, must have played an important role in the development and (mostly) and decarburized steel (only one). This difference seems to use of cast iron technologies in ancient China. be due to the fact that weapons from the Yanxiadu site were made Moreover, it has become clear that cast iron technology and in the Warring States period, while weapons from the Dongheishan bloomery iron technology both existed in the Yan region during this site were made in the Han dynasty. In the Warring States period period. Considering the unmistakable transmission from the Yan bloomery technology was used exclusively (or at least primarily) to region to of iron artefacts and of cast iron technology (Nelson, make iron for weapons. After the collapse of the Yan state, people in 1993: 183; Park and Rehren, 2011; Shiomi, 1982; Wang, 1997: 285e this region appear to have abandoned bloomery technology and 340; Yoon, 1984; Yoon, 1986:68e75; Yoon, 1989:92e99), it is chosen to use puddled steel to make weapons. reasonable to suppose that also the bloomery iron technology may The result indicate that during this period the iron and steel have been transported to , Korea and Japan making technology in the Yan region was based on the co-existence following the same route. It is clear that additional excavation and of cast iron and bloomery iron technology; the cast iron-based analytical work are called for on Yan-state iron objects, iron system always occupied the main position in agriculture produc- smelting sites and on other materials found in Northeast Asia in tion; however, the system only occupied a prominent position in order to better understand the very real way that social and tech- military production in the Han dynasty. Meanwhile, casting and nological interactions in this area shaped the development of the Iron Age in East Asia.

Acknowledgements

The authors would like to thank Mr. Lisen Han, the Director of the Hebei Provincial Institute of Culture Relics, and Prof. Rubin Han, for giving us great support on the research. Many thanks are due to Prof. Shuyun Sun, Prof. Wei Qian, Prof. Yanxiang Li, Prof. Xiuhui Li, Dr. Meifang Zhang and Dr. Kunlong Chen, all of the University of Science and Technology Beijing, for their advice and help in many ways. Thanks also go to Prof. Xiaohong Wu, Mrs. Yan Pan, Mr. Shijun Gao, all of the Peking University, and to Siran Liu, Wenli Zhou, Matthew L. Chastain and Xiangwei Meng, for their kind support and assistance. This work was supported by the Natural Science Foundation of China (NO. 51074010).

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