Nagoya University
NagoyaUniversity

ApplicationofAccelerator

Mass Spectrometryin Establishing
theChronologicalFramework ofAncient

Iron TechnologyinKorea

Jang-SikPark
Department of MetallurgicalEngineering,
Hongik University,
Chochiwon, 339-701,

Korea

Synopsis:Iron technology plays an important role in many of the mechanisms
crucial inthe fbrmationand developmentof early Korean states. Despiteits
postulated
importanceinKorean historyand the abundance of material evidence recovered in thethe study on the ancient ironproductionbased strictly on scientific evidences
peninsula,isstillinitsinfantstage. Two major problernsconfronting the archaeological study on
the appearance and the laterdiffusionof ironthroughout the Korean peninsula
includethe uncertainties in chronology
arisingfrom reliance on relative dating based on
typology and the lack of metallurgical studies on itsproductiontechniques, It isimperative,
therefbre, to remove
such uncertainties
if the iron industryand its
integration
intosociety can be compared and contrasted in different
areas and thereby
the historyofiron productionisto be better
understood in terms of state fbrmation.
The
review recent metallurgical works on ancient ironartifacts andpresentstudy will briefiy
then test the possibilityof introducing
the accelerator mass spectrometry (AMS) inestablishing
the chronologicalframework of ancient irontechnology inKorea.
1. Microstructure Examination

duringthe Korean Three Kingdoms
Period.i)The axes in Figure la and Ib were recovered from the forTnerSillaand
Paekche territory,respectively.2'3) Specimens were taken from theirbladeand body part
noted inbothfiguresby arrows 1 and 2, respectively.
Figure 1c isan optical micrographof the microstructure observedat the bladeof Figure1a. Here, the gray region
near the leftedge isfi11ed
with a corrosion product,indicatingthat itcorresponds
to the cutting edge that was exposed, The region next tothe corroded layerisseen to consist of dark pearlitethat isreplacedby white ferrite
asFigures la and lb present2 iron axes made-13NII-Electronic Library Service

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'si,

aj

agv
dis't

Ltve#emt'
ln'ti

Figure1. Ancient iron axes and their microstructure.
ax, (b)Paekche ax,(a)Silla(c)& (d)microstructureof(a)and (b),respecUvely.

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from the body, arrow 2 in Figurela,was fbund toconsist mostlyof ferrite.
The most apparent featurehereisthat the highC concentration
regionuntil itat the near-surfaceof the blade graduallydeoreasesto the interior
that the ax was given a carburization
becomesnegligible, This is a strong indication
indicates
treatment at the surface. The original patternof C distribution
stillmaintainedone

goes to the right The specimenthat carburization

wasapplied

atthe laststage,

rnostupon
probably

the completionoffbrging.Ifthe C content
supplied
does not have enoughisraised at the laststage, itimpliesthatthe raw material
C to meet the strength requirement.
The present
ax was,of low C iron,which
wasfirst
forgedfbrshaping and thentherefbre,evidently madecarburized fbrthe sake of hardening.
showing
the microstructure
at the body ofFigure ld isan optical micrographlayersrunning venically, They are
the ax inFigure lb.The structure consists of many
microstructures
apparent becauseof the diffbrentcaused by the uneven C content. Thespecimen taken from the bladewas fbundto have the similar layeredstructure. Theindicatesdifferent
originating from the varying C content betweenlayers,
gray ievel,
thatthe raw material supplied fbrmaking the ax was not unifbrm in itslocalC content.
shape

The numerous finelayersmust then haveresulted fromthe unique mechanical treatment
can emerge when the fbrging
and fblding
giveninthe ax making. Such a layered
pattern
operation
isapplied repeatedty incycles on a pieoeof steel withuneven C distribution.
The above

2 axesin a raw material, which

arecomedistinguishedinthe amount and distributionof Cto determine
thekindof themio-mechanical treatmentsnamed
steel making,is an indispensablestep to beclearly

The C adjustment,
incorporated
fbrhardening
somewhererequired.

in the processof every ax making. Itis fbund
fbllowing2 diffbrent
engineering
sequencesthat the 2 axes were manufactured
dependingon the time thissteel making isperfbrmedrelative to shape fbrging,The one
in Figure la may be characterized
by the sequence
offbrgingprior to steel
making'
as epposedto that ofmaking
inpriorto shape fbrging'that isidentified`shape`steel

the otherax,

2.Acceleratormass spectrometric (AMS)dating
A brokencast ironcauldron was excavated from the Hwangnam Great Tomb,
together with the ax in Figure la. The tomb islocatedin Kyongiu, a former capital offrom the cauldron was subjected to the nmS dating,Table 1 presentsSilla.
A fragment
theresult basedon a 5568-yr halflifeand corrected fbr carbon-isotopic fractionation.
The age is estimated to be 1619± 24 in yr BP with the most probable calibrated age
in 425 M. Itisnoted thatthe probabilities
ofthe
calibrated
age fa11ing
inthe
positioned-15NII-Electronic Library ServiceNagoya University
NagoyaUniversityof 404-441,450-466 and518-529M are of 62.9,16,3and 11,2%, respectively.
The constructionof the Hwananm
GreatTomb isclosely associated with theperiod Sillastarted on her way to becominga powerfUlancient state, which would
finally
unify the Korean Peninsula forthe firsttime in historyin 668 AD,i} The burial
in studying the material culture of notgoods recovered from itholdspecial importanceonly Sillabut alsothe two kingdomsinrivalry at the time, Paekche and Koguryo, sincelittlewritten
account isavailable, They are also importantin the study of Japanese
Kofun periodduringwhich there had been a constant cultural influence
betweenthe
Korean Peninsulaand the JapaneseArchipelago.Unfbrtunately,
however,the exact dateof itsconstruction, and thereby the incubationperiod fbrthe powerfu1 Silla,
is inrangesdisagreement
among
range

scholars.

predictedby some

The presentAMS

archaeologists

result isfound to fa11within

the age

Additionalcast irontypologicalgrounds,`)
measurements
to testfurther
the use of the AMS
onfrom the tomb are awaiting
technique inestablishing a reliable chronology.
samples

Table 1.Resultof the accelerator
the Nagoya University,
Japan,

massspectrometric(AMS)ctating
perfbrmed at

LabCode6i3C[O/oo]i4cAgerBPCalibrated
Aecal,ADCalibratedAgerange
cal.AD
404-441(62,90/e)
rruTA2-4233-29.3 ± O.11619± 24425450-466(16.3e/,)518-52911.20/e

3.Summary
The microstructural
datasuggest that there were at least2 distinctiron
infrastructures
established in ancient Korea. They may be characterized by the uniquesequence of manufacturing
fbrgingpriorto steel making' andprocesses,
making priorto shape fbrging'.
The distinction
isseen to arise fromthe selection of a`shape`steelstaning material and the pertinentmechanicaltreatment, The combination
particular
was apparently based on such importanttechnical aspects of ironindustry
as ironsmelting and steel making. There isno doubt that such a technological frameworkofa
certain society is established in close association
with the socio-political andgeographical conditions itisin.The properrecognition of ironindustryin terms of its
could therefbre Iead to the betterunderstanding
general and panicularfeaturesofancient societies, especiallywith regard
to the flow and developmentof technicalideas-16NII-Electronic Library ServiceNagoya University
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them. This can only

among

be attained

there isa wide spectrum

when

data
as well'as inof reliable

in metallurgy
in ancientscientific chronology,
The overall pictureof the historyof ironproduction
Korea cannot be drawn until a reliable chronological framework has been established in
aspects. Itis,
therefbre,too early to draw
association with technical and socio-politicalavailableover

any conclusion

spaceand time through extensiveof the regionalor

temporalresearches

variations

incorporated
due perhapsto theiron technology. The presentstudy, however,differentroutes taken in adopting
inironproductionthat might exist insuch a dynamic
highlights
the potential
diversitiesstates. Moreperiodof Korean historythroughout the riseand developmentofthe firstof detecting
importantly,
this article has tested,on scientific grounds,the possibility
such diversities
in association with the scientific datingbased on muS to the better
understandingof ancient societies. The results are indeedencouraging.

Acknowledgement
H. Enami atCenter fbr
The help from Dr. T. Nakamura
invaluablein thetheradiocarbon
age
ChronologicalResearch,Nagoya University,andwasMr.
measurement.

References
1, C, J.Eckert,K, B, Lee, Y. I,Lew, M, Robinson,and E, W. Wagner; Korea Old andNew - A History,The Korea Instituteat Harvard University,Seoul,Korea(1990).
2.J.G. Kim, D. H Kim, B. H. Choi,Y. B. Park, J. S.Lee, K I.Yoon, Y. J.Cho, and C.
S.Shin;The GreatHwangnam Tomb-Excavation Report on the South Tomb (Text
National Research Instituteof CulturalProperties,and Photoes),Kyongiu
Kyongiu, Korea (1994)
3. 0. S, Seo, H. H. Lee; 1995, Habongni-I,NationalKongiu Museum(1995)

of the4. Y. S Kim; Chronology of the Hwangnam GreatTornb-Dateof the Construction

SouthTomb as Estimatedfrom EarthenWares, Proceedings of the 1StInternationalof CulturalPropenies(eds.,
Conferenceof the Kyongtu NationalResearch Institute
OrganizingCommittee),p.275, Kyongiu,Korea (2000).

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