Abstract: The Dongda cane cemetery is an important site in the Warring States period in western Liaoning. In this study, 15 bronze artifacts excavated from M11 were analyzed metallographically, scanning electron microscopy and energy spectroscopy, and lead isotope ratio analysis. The analysis results show that the production process of the copper excavated from M11 is mainly casting, in addition to hot forging and hot forging after cold processing; the alloy composition is mainly lead tin bronze, and only one copper axe is copper tin alloy. The relationship between the alloy composition of the bronze and the type of artifact is obvious, indicating that the maker has been able to choose the appropriate material according to the molding process and use of the bronze. The lead isotope ratio shows that although the M11 excavated bronzes have different cultural backgrounds, the sources of lead materials are relatively similar, reflecting the close connection between western Liaoning and the Central Plains in terms of material circulation.
Located in Dongda cane village, Alkali Factory Township, Jianchang County, Liaoning Province, Dongda Cane Cemetery is located in the hilly mountainous area of western Liaoning in the upper reaches of the Daling River, and is an important node for communicating the culture of the north, the Central Plains and the culture of western Liaoning. From 2000 to 2012, the Liaoning Provincial Institute of Cultural Relics and Archaeology and other units carried out 6 rescue excavations, a total of 47 tombs were cleaned up, and 28 pieces (sets) of bronze ware were excavated in the early Warring States tomb M11 excavated in 2000, which can be divided into containers, weapons, tools, carriages and horses according to the use function, which basically covers all the types of bronze artifacts excavated from the Dongda cane cemetery, and is an important physical material for the study of warring states bronzes in western Liaoning. In view of this, this paper conducts scientific analysis of copper artifacts excavated from M11 in the Dongda Cane Cemetery through various detection methods such as metallographic organization identification, alloy composition analysis, lead isotope analysis, etc., in order to reveal the process and technical information contained in it, explore its ore and origin sources, and provide more scientific basis for in-depth understanding of the production and exchange of copper artifacts in western Liaoning during the Warring States period.
1. Sampling and analysis methods
In order to maximize the protection of cultural relics, only bronze casting seams, breakages or bronze fragments with recognizable shapes are sampled. According to this sampling principle, a total of 15 matrix samples were obtained from the M11 bronzes, involving 15 bronzes, including container 7, weapon 4, tool 3 and carriage and horse ware 1. The samples were inlaid, polished and polished, and the metallographic structure, inclusions and distribution of the samples were observed without erosion and after being etched by 3% ferric chloride alcohol solution using LeicaDM-4000M metallographic microscopy, and then the samples were re-polished, and the samples were observed by hitachiTM3030 ultra-depth-of-field electron microscope of the Science and Technology Archaeology Laboratory of Peking University, and the rust-free or rust-free areas were selected, and the composition of different parts of the sample was determined by the combined EDAX energy spectrometer. Take the average value as the overall component analysis result. The test conditions are: voltage 15kV, acquisition time 90 to 120 seconds. The results of metallographic analysis and composition analysis are detailed in Table 1.
2. Identification of metallographic organization
Through metallographic analysis, it was found that the 15 pieces of bronze artifacts excavated from the M11 of Dongda Cane had three organizational forms of casting, hot forging and cold working after hot forging (Table 1). Among them, the metallographic structure of 10 bronze samples such as Ding and Jug is α solid solution branch crystal, and (α + δ) eutecsmology is distributed between the crystals, which is a typical casting organization, indicating that they are all cast and formed. Due to the different contents of lead and tin and the cooling rate, the quantity, morphology and distribution of the α solid solution, (α + δ) co-paralysists and lead particles are different; the metallographic structures of each sample contain different amounts and are mostly mixed with lead-associated blue-gray dots, granules and irregular sulfides distributed between or in the grains; pure copper grains are also found in small samples such as copper cymbals (M11:33) and caps (M11:35) (Figure 14). Pure copper grains are mostly found in holes and crevices formed by casting or rust, and free copper deposition often occurs in ancient bronzes with high tin content, serious rust, and preferential corrosion of δ phases.
The results of the metallographic experiment also showed that there were α recrystallization grains and twin crystals in the microstructure of 5 copper samples such as copper chisel (M11:9), indicating that it was hot forging, of which the metallographic structure of za (M11:2), washing (M11:3), molybdenum (M11:17), and axe (M11:19) still had a slip band in the metallographic structure, indicating that it was cold processed after hot forging. The lead in the turn and copper chisels is distributed in a circular granular dispersion between the grains, while the lead in the wash and cymbals is stretched into a strip along the processing direction, which may reflect the difference in the amount of processing. More special is the copper axe sample, locally visible large (α + δ) eulyzymes, blue-gray sulfide inclusions are also stretched into strips along the processing direction (Figure 15).
Third, the alloy composition analysis
Among the 15 samples analyzed, only the copper axe (M11:19) was tin bronze, and the remaining 14 samples were lead tin bronze, of which the Ding (M11:4) and copper sword (M11:27) samples were more corrosive, and the composition data was not counted in the statistics. Overall, the tin content in the samples fluctuated in a small range of 8.5% to 17.0%, while the lead content varied greatly, with a minimum content of 3.2% and a maximum of 23.8%. All samples contain copper sulfide inclusions, are small particles, are mostly associated with lead, or exist at the grain interface. The results of energy spectroscopy analysis showed that the sulfur content of most sample inclusions was about 20% (Figure 15 and Figure 16), and the presence of copper sulfide inclusions showed that the ore used in smelting was not pure oxide ore. It is worth noting that iron was detected in the body of the copper pot (M11:5) at a content of 1.3%, presumably due to smelting symbiotic ore.
4. Lead isotope analysis
Nine copper samples were dissolved in aqua regia, and after the resulting solution was diluted to a Pb2+ concentration of less than 0.5 mg/l, Tl2SO4 standard solution was added as the internal standard. Lead isotope ratios were tested using the VG Elemental Type Multi-Receiver Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS) from the School of Earth and Space Sciences of Peking University. The test uses the international lead isotope standard solution SRM981 calibration instrument, the relative error of the test is less than 0.05%, and the results are detailed in Table 2.
The results of lead isotope analysis showed that the ratio of 208Pb/204Pb of M11 bronze samples in dongda cane cemetery was between 37.7 and 38.6, and the ratio of 206Pb/204Pb was between 17.4 and 18.2, all of which were ordinary lead. According to the characteristics of the 206Pb/204Pb ratio, this batch of data can be divided into three categories, the first type of ratio is between 18.0 and 18.2, including engraved mounds and copper cymbals; the second type of ratio is between 17.4 and 17.8, and the typical Yan-style bronzes in M11, such as the lying beast button cover ding, the cast red copper paved round pot and the siamese chain pot common in the Warring States tombs in the Central Plains, are of this category. If the 208Pb/204Pb ratio of the M11 bronze sample is used to plot the 206Pb/204Pb ratio, the first and second types of ratio data fall roughly on a straight line, and the third analogue value is biased above the straight line (Figure 18), examples of which include Go (M11:25), curved blade shortsword (M11:27) and sharpener (M11:30).
Li Ruiliang has conducted lead isotope ratio analysis on some bronzes excavated from the M45 of dongda cane, and the results also include the above three types, and basically correspond to similar artifacts of M11. The M45 engraved disc, the motif and the M11 are closely identical in shape and ornamentation; the ratio of 206Pb/204Pb reported by Li Wen is between 17.9 and 18.0, which is also relatively close to the M11 zam, which belongs to the first type of ratio. M45:10 Ding and M11:4 Ding data are very close, the ratio of 206Pb/204Pb is around 17.7, the ratio is the second category; M45:21 Gaidou is similar to M11:27 Curved Blade Sword, which belongs to the third type of ratio. The M45 of dongda cane is relatively close to M11, the composition and style of utensils are similar, the age is slightly later than M11, and the overall distribution of the corresponding lead isotope ratio is also very similar.
The lead isotope ratio of Yan bronzes has changed greatly with the times. W.T. Chase has analyzed the Three-legged Boat (Collection No. V-79), Gaidou (V-258) and inlaid red copper ring Button (V-163) and other Yan-style bronzes from the late Spring and Autumn period to the early Warring States Period at the Sackler Museum in the United States, and the ratio of 206Pb/204Pb is between 17.5 and 17.6, which is the second type of ratio mentioned above; lead materials of such ratios are heavily used in Jindi, such as lead ingots from the Copper Foundry in Houma Niu Village, Shanxi. From the late Warring States period to the early and middle Warring States periods, the lead material of the Yan bronzes was still basically similar to the bronzes of the Three Jin Dynasties in the same period (Figure 19). The ratio of M11 of Liaoning Dongda cane is similar to that of the bronzes from the tombs of the M14-M26 group of the Changzhi watershed in Shanxi, while the ratio of M45 of the East Dacane is similar to that of the tombs of the watershed M12-M25 group. According to the analysis and research of the bronze ware of the Yan Kingdom in the middle and late Warring States period, Jin Zhengyao analyzed the different ming knives from different periods at the Yanxiadu site in Hebei Province. The ratio of the early arc back knife is more chaotic, with a 206Pb/204Pb ratio around 17.4, close to the second type of ratio mentioned above, in addition to abnormal ratio categories such as lead of high radioactive genesis and high specific value lead; the late arc back and folded back open knife are mainly high specific lead, and are similar to the knife coins and round coins minted by the State of Qi at the end of the Warring States period. According to the above analysis, the lead material of the Yan bronzes from the late Spring and Autumn period to the early Warring States period is more similar to the Bronzes of the Jin And Three Jin Dynasties, and gradually diverges from the Central Plains to the middle and late Warring States period, and has strong commonality with the Qidi in the north of Haidai.
5. Discussion
1. Craft characteristics of bronze artifacts excavated from M11 of the Dongda Cane Cemetery
From the perspective of processing technology, the bronzes excavated from the M11 of the Dongda Staff Cemetery show a variety of production methods, and this batch of bronzes is not only cast (10 pieces), but also hot forging (1 piece) and hot forging after cold working (4 pieces). Casting samples account for the largest proportion and a wide variety of artifacts, covering containers, weapons, tools, and carriages and horses. The production process of tool copper chisel is hot forging, and the production process of turning and washing is hot forging and cold working. After hot forging, the utensils can make the composition uniform and the tissue recrystallization change, thereby increasing the density and improving the mechanical properties. The metallographic structure of the axe and cymbal samples shows that its production process is hot forging and cold working, but from the appearance of its overall observation, it should be cast and formed, and it is speculated that the blade is processed and ground and used after casting. Axes and cymbals are used as tools and weapons through sharp blades, and by hot forging and cold working on their blades, they can be hardened and significantly increased in strength and hardness. This process has been found in the processing of tools and weapons in the Western Zhou Dynasty, such as 3 pieces of weapons and tools in the Western Zhou Cemetery of the Song Family of the Zhou Dynasty, 1 piece of copper ge excavated from the Yejiashan M65, 5 pieces of copper goats excavated from the Western Zhou Tombs of Liulihe in Fangshan, Beijing, 1 piece of copper halberds and 1 piece of copper knives, and 5 pieces of copper ge excavated from the Western Zhou Tomb of Zhangjiapo in Fengxi, Shaanxi, etc. have been processed by hot and cold processing. In the Eastern Zhou Dynasty, many bronzes processed using this process were found in the Central Plains: such as copper needles excavated from the Eastern Zhou Tomb of Zhongshan Guo in Pingshan, Hebei, copper knives excavated from the M84 of the Changzhi Watershed in Shanxi and copper ge from M126, copper rods excavated from the Warring States Cemetery in Yicheng, Hubei Province, and copper knives from the Eastern Zhou Dynasty in northern Shaanxi. In addition, a large number of tools and weapons such as bronze tools and weapons using this process have also been found in the border areas, such as copper cones excavated from the Shuangta Warring States Cemetery in Baicheng, Jilin Province, copper cones and copper knives excavated from the Jinggouzi West District of Linxi County, Inner Mongolia, copper knives excavated from the late Bronze Age site of Tawenduliha in Dulan County, Qinghai, bronze swords excavated from the Late Bronze Age Site of Tawen Dale, Sichuan Xuanhan Luojiaba, Warring States Bronze Swords excavated from the Yujiaba Ruins in Kaixian County, Chongqing, Copper Cuts, Copper Swords unearthed from the Hongying Pandong Zhou Cemetery in Guizhou, bronze swords, bronze swords unearthed in the Ancient Mourning Prison Area of Western Yunnan, The Hengda Road cemetery in Qujing, Yunnan Province, unearthed Eastern Zhou copper swords and copper ge. It can be seen that the technique of post-casting processing of the blades of bronze weapons and tools in the form of hot and cold forging was widely used in the Eastern Zhou Dynasty, which also confirmed the record of "preparing a bow arrow, forging a spear, forging a spear, and daring not to be good" in the "Shangshu Fei Oath".
It is worth noting that the two copper containers of turning and washing also adopt the production process of hot forging after cold processing, and the wall is extremely thin, less than 1 mm, which is the earliest hot forging thin-walled copper container found in northeast China. During the Eastern Zhou Dynasty, hot-forged copper containers appeared in large numbers in various places, such as the excavated plates and za of huo chunqiu tombs in Dingxiang, Shanxi; the spring and autumn and Warring States period copper plates and copper discs excavated from the Qiaojiayuan cemetery in Yunxian County, Hubei Province; the excavated plates and za of the Houchuan Warring States Tombs in Shaanxi County, Henan; the bronze plates of the Warring States period unearthed from the Qin Tombs in the northern suburbs of Xi'an, Shaanxi; the copper plates of the Warring States period excavated from the Zhoujiazhuang Cemetery in Xintai, Shandong; the excavated plates and plates of the Warring States period in the Warring States Tombs of Huaiyin Gaozhuang; and the Warring States copper basins, plates, and jian excavated from the Luojiaba of Xuanhan, Sichuan. These thin-walled copper containers are all hot forging molding processes, indicating that the craftsmen at that time had mastered the technology of reducing the hardness of the material by heating and insulation during the forging process, thereby restoring its ductility and making it easier to process.
2. Material characteristics of bronzes excavated from M11 in the Dongda Staff Cemetery
In terms of material composition, 14 of the 15 samples of bronzes excavated from the M11 of the Dongda Staff Cemetery are Cu-Sn-Pb ternary alloys, and only the copper axe is a Cu-Sn binary alloy. These bronzes have a high degree of alloying, and the overall average content of the main alloying elements (Sn%+Pb) is close to 22%. Among them, the tin content is relatively concentrated, basically 13% as the center of the normal distribution, tools and weapons copper ware tin content is slightly higher than that of cast copper containers. The difference in lead content is very large, with the sample of the siamese pot containing 23.8% lead, while the turn, washing, and plutonium are only slightly higher than 3%. On the whole, the lead content of forged copper is significantly lower than that of cast bronze, while the lead content of copper after cold processing after hot forging is even lower, and the lead content of cast formed copper containers is significantly higher than that of tool and weapon copper. This phenomenon has appeared since the Beginning of the Shang Dynasty, Hao Xin et al. analysis of the bronze artifacts excavated from the site of the middle Shang Dynasty in Panlongcheng shows that the lead content of the tools and weapons is significantly lower than the lead content of the ceremonial vessels; Zhang Lijie et al. also found that the type of artifacts has a close relationship with the alloy composition through the analysis of the bronzes excavated from the Western Zhou Cemetery of the Liulihe Yanguo in Beijing, and believes that the Western Zhou bronzes of the Liulihe River not only inherit the technology of the Shang Dynasty in terms of alloy composition, but also further improve. The increase of tin is to obtain higher mechanical properties, so that the utensils to obtain higher hardness, mainly used in tools and weapons, the increase of lead is mainly to improve the fluidity of the alloy solution, enhance the ability to fill the mold, more suitable for utensils with complicated ornamentation, but too high lead content will reduce the mechanical properties of copper. Taking the M11 excavation and washing samples of the Dongda Cane Cemetery as an example, because it needs to be forged and formed, it needs a certain strength, and its tin content of about 14% can provide high tensile strength, hardness and a certain elongation; and about 3% lead content can ensure that the artifact will not cause structural damage due to excessive stretching during forging and use. These all show that at that time, the craftsmen fully realized the impact of tin and lead ratios on the properties of the alloy, and could choose the appropriate tin and lead ratios according to the different production processes and use functions, showing the mature copper production technology and diversified means.
3. Analysis of lead isotope ratios of bronzes excavated from M11, Dongda Cane Cemetery
The overall distribution of lead isotope ratios of M11 bronzes in Dongda Canezi is roughly similar to that of M45, and is close to that of the Three Jin Bronzes of the same period, reflecting the more distinctive characteristics of the times, and also reflects the close correlation between Yandi bronzes and the Central Plains. The cultural backgrounds of the M11 bronze ware of the Dongda staff are different, but the sources of lead materials are relatively similar. For example, the cast-inlaid red copper pot (M11:5) is mostly found in the early tombs of the Warring States in the Central Plains and surrounding areas, and the conjoined chain pot (M11:6) is rare in the Central Plains and northern Hebei, but the lead isotope ratio of the two artifacts is basically the same, and it is also similar to the lead ingot produced by the Houma Copper Casting Workshop.
The lead isotope ratio of the M11 bronze of the Eastern Great Staff also hints at the pivotal position of the Western Liaoning region in the spread of central plains resources to the northeast. The golden-handled curved-edged sword (M11:27) has a strong local color, but the lead isotope ratio is similar to that of bronzes throughout the Central Plains in the early and middle Warring States period. Further north, in the inner Mongolia Linxi Jinggouzi West District cemetery, the lead material of the northern bronze ware also has strong commonalities with the Central Plains and Yandi. It can be seen that the traceability of bronzes in the Warring States period in Liaoning region, in addition to the need to compare with lead mines in northeast China such as Dongsheng in western Liaoning and Qingchengzi in liaodong, also needs to consider the possible circulation of metal materials with the central plains in the context of synchronicity.
VI. Conclusion
Through the scientific detection and analysis of 15 bronze artifacts excavated from M11 in the Dongda Cane Cemetery, the following conclusions are preliminarily drawn:
1. The production process of M11 excavated bronzes is diversified, and there are three production methods of casting, hot forging and cold processing after hot forging.
At that time, in order to improve the hardness and strength of the tools and weapons bronzes, the craftsmen would consciously carry out hot forging and cold processing of their sharp edges; the washing and turning of the two thin-walled copper containers also adopted the hot forging molding process and carried out cold working.
2.15 pieces of bronze samples have 14 pieces of Cu-Sn-Pb ternary alloy, only copper axe is Cu-Sn binary alloy, tin content is more concentrated, the lead content of forged copper is significantly less than that of cast bronze, and the lead content of copper after hot forging after cold processing is even lower, and the lead content of cast copper containers is significantly higher than that of tool weapons bronze, indicating that the maker has been able to choose suitable production materials according to the type, function and processing method of bronze.
3. The lead isotope ratio of the bronze artifacts excavated from the M11 of dongda cane is close to that of the bronzes of the Three Jin Dynasties in the same period, although the bronzes have different cultural factors such as the Central Plains culture, the Yan culture and the indigenous culture, but their lead sources are relatively similar, reflecting the close connection between western Liaoning and the Central Plains in terms of material circulation.
Overall, the bronze artifacts unearthed in M11 of the Dongda Cane Cemetery reflect the professional smelting technology and mature production technology, and provide new information for the study of the processing technology of bronze ware in the early Warring States period and the production and exchange of bronze ware in western Liaoning.