Trans Indian Inst Met DOI 10.1007/s12666-011-0081-x
TECHNICAL PAPER
An Early Evidence of Hardening and Subsequent Tempering from Megalithic Sites, Maharashtra, India P. P. Deshpande • R. K. Mohanty • V. S. Shinde
Received: 23 February 2010 / Accepted: 9 September 2011 Ó Indian Institute of Metals 2011
Abstract The Metallurgical investigations of ferrous objects excavated from the early Iron Age megalithic site at Naikund and Mahurjhari in Vidarbha, Maharashtra, India were carried out The analysis shows a clear evidence of technological advance in the form of hardening and quenching followed by tempering in addition to the knowledge of steeling as early as 900 BC. Keywords Early evidence of steeling Iron age in India Tempered martensite Magalithic site
1 Introduction The antiquity of indigenous procurement, smelting, further processing and using of iron in India is not clear. It is difficult to tell in which region of India it really got emerged and who were the people. But it seems, Iron appears as an intrusion with a negligible of percentage in the copper implements found during the mature phase of Indus valley civilization [1, 2]. The occurrence of iron in these implements were not deliberate but accidental as iron came as intrusion/impurity along with copper ore processed from copper mines located in Rajasthan. The early evidence of indigenous iron production goes back to the middle of second millennium BC as evidenced from several early Iron age sites spread across the country [3]. P. P. Deshpande (&) Department of Metallurgy and Materials Science, College of Engineering, Pune 411005, India e-mail:
[email protected] R. K. Mohanty V. S. Shinde Department of Archaeology, Deccan College, Pune 411006, India
However, by twelfth–thirteenth century BC iron was well known and was used extensively in remote parts of the country in various ways starting from weaponry, agricultural and carpentry tools to household objects [4–7]. As the demand for ferrous objects increased, locally available iron ore was exploited and iron smelting technology spread to regional levels. Once the requirement of ferrous implements both for offensive and defensive use increased along with other uses, the technology kept improving indigenously. This concept percolated down to even in-assessable rural settlements where regional and local production centres came up for effective basis requirement and refinement. The process become imminent for improvement both in quantity of production and qualitative change down up to specific tool category. This technological advancement is often seen as a catalyst in the emergence of second urbanization in India, the first being the Indus Valley Civilization. To understand the process of second urbanization, technological achievements in iron age must be studied. There is a need of detailed technical investigations of the ferrous objects found during various excavations [8]. Recently, we have reported metallographic investigations of the wrought iron samples from Mahurjhari Naikund and Bhagimohari in the Vidarbha region of Maharashtra [9]. The Vidarbha region lies between 19°260 N and 21°470 N and 75°560 E and 79°230 E and forms the north-eastern part of Maharashtra State, India. The Megalithic site of Mahurjhari is one of the richest Iron Age burial site excavated in India, where thousands of Iron implements have been found. The people ceremonially buried their dead with lots of grave goods like iron implements used for various purposes starting from household objects and the agricultural implements to offensive and defensive weapons, copper and gold ornaments, earthen pots, horse and horse ornaments and several
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stone objects [4]. The evidence of iron smelting furnace at Naikund [10–14] and agricultural economy at Naikund and Bhagimohari [15, 16] tells about their other economic aspects. The analysis of ferrous implements from these sites has been very encouraging and inspired us to undertake systematic analysis of several implements in order to construct a clear picture of emerging steel technology around beginning of the first millennium BC in this region. We have already reported that the ferrous objects found at these sites were made of wrought iron [9]. This paper contains our metallo graphical investigations on ferrous objects found at Naikund and Mahurjhari sites from Vidarbha region of Maharashtra.
2 Experimental
Fig. 2 Photomicrograph of the core of the chisel showing carbide network and colonies of tempered martensite (9400)
The ferrous objects found during excavations at Naikund and Mahurjhari were cut and the samples were prepared for metallographic studies. Projectina Microscope (Swiss make) and Nital was used as etching reagent in all these investigations.
3 Results and Discussion Figure 1 shows the photo of chisel from Naikund. Figure 2 shows microstructure of the core of the chisel. It reveals carbide network and colonies of tempered martensite. The coarse grains are obtained due to slow cooing. Fig. 3 shows the microstructure of the tip of the chisel. Tempered martensite with carbide particles is clearly seen. It implies that the tip of the chisel was subjected to a sequence of hardening, quenching and tempering. Fig. 4 shows photo of the tool like object from Naikund excavations.
Fig. 3 Photomicrograph of the tip of the chisel showing tempered martensite with carbide particles (9400)
Fig. 4 Naikund tool object
Fig. 1 Naikund chisel
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Figure 5 shows the microstructure of the sample taken from the edge of this tool. The same area is shown in the Fig. 6 but at higher magnification. It reveals the ferrite plates and rapidly cooled martensite. Thus the tool has undergone hardening and quenching.
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Fig. 5 Photomicrograph showing carburized tip. Thin arrow shows ferrite particles and thick arrow shows tempered martensite (9100)
Fig. 8 Photomicrograph showing of the chisel tip. Thin arrow shows lath martensite and thick arrow shows tempered martensite. Slag is also seen (9400)
Fig. 7 shows the ferrous object obtained during excavations at Mahurjhari. Figure 8 shows the microstructure of the sample taken from its tip.
4 Conclusions
Fig. 6 Photomicrograph showing carburized tip. The thin arrow shows ferrite plates and thick arrow shows rapidly cooled martensitic. Slag is also seen (9400)
The metallographic studies reported here clearly show that the ferrous objects obtained from Naikund and Mahurjhari in the ancient Vidarbha region of Maharashtra, India were undergone similar thermo mechanical treatments. These objects were deliberately carburized at the tip to make them steel at the desired locations. In addition, these objects were hardened and quenched and subsequently tempered at lower temperature to eliminate the bad effects of hardening and quenching. Acknowledgments The authors thank Prof. A. D. Sahasrabudhe Director, College of Engineering, Pune 411005 for his encouragement and Dr. M. J. Rathod Head Department of Metallurgy and Materials Science College of Engineering, Pune 411005 for providing facilities for the work.
References
Fig. 7 Mahurjhari chisel with a ring
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