metallurgy and archaeology
TRANSCRIPT
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Metallurgy and Archaeology
A case study on iron objects
from the megalithic sites in Nagpur, India
Jang-Sik Park
Department of Metallurgical Engineering, Hongik University, Korea
Vasant Shinde
Deccan College, Post-Graduate & Research Institute, India
ICTS Mini Workshop on
Future Of the Past November 22-26, 2011, Gateway Hotel, Mangalore, India
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Acknowledgement
The people of Deccan College are acknowledged for the hospitality
they showed to me and my wife when we visited Pune last summer
to take samples for examination.
We also appreciate Dr. James Lankton, the previous speaker, for his
crucial role in the initiation of this collaborative project.
The analytical part of this project was supported by the Korea National
Research Foundation (NRF-2010-0028714).
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Why Metallurgy (Iron and bronze) in Archaeology?
Major engineering processes in Metallurgy
1. Smelting
2. Making of alloys
3. Fabrication
-shaping: casting and forging
-thermo-mechanical treatments: quenching, tempering, work-hardening, annealing
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Individual engineering processes
-achieved in a number of different ways
depending on
technological and sociopolitical environments.
Combination of the individual processes
-lead to the establishment of
a unique technological tradition
reflecting temporal and regional characteristics.
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Major assumption
Individual engineering processes &
their unique combination, i.e., technological traditions
can be traced through the application of
scientific methodologies developed in metallurgy,
for the better understanding of history.
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Case study
Iron tradition of
the megalithic communities
at Nagpur, India
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Iron metallurgy
1. Smelting -bloomery iron
-cast iron
2. Steelmaking -carburization (carbon added)
-decarburization (carbon removed)
3. Fabrication -shaping: casting and forging
-thermo-mechanical treatments: quenching, tempering,
work-hardening, annealing
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I. Smelting
Microstructure typical of the bloomery process Slag produced in iron smelting
Naikund, Nagpur AMS dated: approximately 5,000±42 yr BP
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Bloomery process (low temperature reduction process)
-Low carbon iron (named bloomery or sponge iron) produced
at relatively low temperatures.
-Reaction occurring in a solid state without melting.
! One of the 2 major smelting processes practiced in antiquity.
!! Invented in the West or India.
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II. Steelmaking
-To adjust the carbon level of the smelted iron
for better functional properties.
-Carbon addition needed for bloomery iron
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Dagger
from the megalithic site
at Mahurjhari
Optical micrograph showing the structure at the end of the tang at d
High C layer surrounding the low C interior
-Representative of the steelmaking by carburization
-Low carbon iron heated in a burning charcoal environment to raise carbon levels.
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Plate-type object from the megalithic site at Khairwada
Forged out of almost pure iron and then the whole part carburized. Intermediary or currency?
Microstructure at the flank: b; Pure iron
Structure similar in a and c
Microstructure at the flank: b; High C steel
Structure similar in a and c
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III. Fabrication
-Shaping
-Thermal treatments for adjusting functional properties
1) Quenching for hardening
2) Tempering or annealing for reducing brittleness
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Microstructure at the blade: a
High C steel
Microstructure at the rear: c
High C steel
Microstructure at the flank: b
Almost pure iron
Axe from the megalithic site at Khairwada: 7-B3-1
Shaping by forging
Steelmaking either by carburization or welding
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Axe from the megalithic site at Mahurjhari: 18-D1-1
Microstructure at the blade: a
High C steel
Microstructure at the rear: c
High C steel
Microstructure at the flank: b
Low C iron
Shaping by forging
Steelmaking
Quenching and then tempering
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Major factors
-Bloomery process in smelting
-Carburization in steelmaking
-Advanced thermal techniques practiced
Iron tradition of megalithic Nagpur characterized
Plate-type objects
-Intermediaries to be forged into critical parts
of various tools and weapons
-A means for trade (Value would depend on size
and carbon levels)
Iron tradition
-Standardized
-Efficient and versatile
-Fully developed
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Topics of the future research
The existence of an advanced technology raising questions
-Origin,
-Development
-Diffusion
- Innovations made during the megalithic period?
- Inheritance from the previous native civilizations?
- Driven by foreign Influences?
Iron objects from the megalithic sites within the district of Nagpur
- Share a common iron tradition
- What about the other megalithic sites scattered over the
territory of the Indian subcontinent?
Another topic of significance to study
Evolution and diffusion of this particular iron tradition
in the subsequent generations within and without
the Indian subcontinent
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Concluding remarks
Our collaborative research is just beginning and many more iron and bronze objects from
collections with varying chronological and regional contexts must be subjected to a rigorous
scientific examination to reach a more general conclusion.
Nevertheless, the results presented above reveal important information that can hardly be
obtained without the integration of metallurgy and archaeology.
More importantly, this information stimulates numerous well-defined questions of substantial
significance to be generated, which may readily be solved in the future research for the better
understanding of the history of India and Korea and their probable interaction in the past.