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Offline Filip Vološin

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How to find out amount of carboon in metal
« on: February 17, 2022, 06:14:57 AM »
Good evening,

I am an student of archaeology and on my final work I am working with mining hammers, on which metallography was used. But my supervisor want to use some kind of acid on the surface of the metal so it would be visible difference between parts witch higher amount of carbon in steel and in those that don’t have any or low amount. Is it even possible? Or if it would help, would it be visible just under microscope. Thans for any answers.   

Offline Borek

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Re: How to find out amount of carboon in metal
« Reply #1 on: February 17, 2022, 07:13:29 AM »
Isn't metallography capable of detecting the differences? You would definitely need to check properties of the material in multiple points but it should give similar information.

OTOH yes, depending on the composition etching figures on the surface will be different. Not that I can point you to any particular papers/books/resources.
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Re: How to find out amount of carboon in metal
« Reply #2 on: February 21, 2022, 11:53:19 AM »
I think that your supervisor is referring to the use of a Nital solution (1- 2% nitric acid in ethanol) that is applied briefly (10-20 seconds) to the surface of a previously polished steel surface.
After rinsing and drying, the surface is examined under the microscope.
The surface will be found to have been preferentially etched depending on presence of carbon.
See, below paper; I have only copied the first page, because it has many photographs, and the references.

Ann Feuerbach iams 25 for 2005, 27-43
In 1999, IAMS generously provided the author with a grant
for travel to Russia to study the microstructure of blades
from the Russian Northern Caucasus. Thirty-seven blades
were studied including knives, daggers, spearheads, sabres,
single-edged and double-edged swords, ranging in date from
the 3rd to the 12th century AD (Figures 1-35). Vickers hardness tests were only performed on a few samples because
the original purpose of the study was solely to determine if
any of the blades were made of crucible steel. However, it
was later decided that it was important to publish the results
of the metallographic investigations of all the samples due
to the fact that there are few published reports on blades
from this region.
The first group of eighteen blades were excavated
in the Kislovodsk depression, and are now housed in the
Kislovodsk Museum, Russia. These were dated by associated finds or by stylistic attributes. The second group is
comprised of nineteen blades from the Upper Kuban River
region, and are now in the Jewish University Museum in
Moscow, Russia. These blades were not uncovered during
controlled excavations and therefore have no associated
archaeological contexts or firm date; however their style
indicates that they are late Medieval.
Metallographic Examination of the Blades
A section of each blade was removed using a Plas-plug tile
cutting saw with a wafer thin diamond impregnated blade.
The Kislovodsk samples (KIS) were often taken from less
corroded areas or where the blades would not be disfigured.
All the samples of the Jewish University Museum blades
(JUM) were taken from the area near the handle so as not
to disfigure the blade. The reader should be aware that in
using this method of sampling, the sample taken may not
always be representative of the entire blade. For example,
if the edge near the tip was carburised, or if a piece of steel
was forge welded to the tip, the sample will not necessarily
exhibit these features, and therefore will not be characteristic of the blade as a whole. However, any disfiguration to
the blade is minimal and easily disguised by filling the hole
with resin, if desired, or by placing the mount fixtures over
the hole.
The samples were mounted in resin with the transverse
side positioned for examination. The mounted samples were
ground and polished using standard metallographic procedures (e.g. Scott 1991, 63-66). All the samples, except those
that were completely corroded, were examined before and
after etching in 3% Nital. The examination of the samples
indicated the use of iron, carburised iron, crucible steel,
forge welded or piled iron and steel (Table 1). The samples
are now housed at the Ashmolean Museum, Oxford, UK.
Iron Blades
Nine blades seem to be composed solely of iron: three from
Kislovodsk (KIS #4, #5, #14) and six from the Upper Kuban
River region (JUM #5, #10, #11, #12, #13, and #16). The
microstructures were composed of ferrite grains with varying amounts of slag inclusions. It seems possible that at least
some of the blades had either a carburised steel edge or an
edge of steel forge welded onto an iron core. A purely iron
blade would not have held its shape or an edge during use,
unless the purpose of the blade was for display or ceremony;
however, blades composed solely of iron are known from
numerous time periods, such as those from Celtic contexts.
It is more likely that the evidence for steel may have corroded away or is not observed because the sample is not representative of the entire blade. In the iron sword KIS #4, the
occurrence of intergranular corrosion is clear. The possible
exception to this is blade KIS #14, which was ritually bent.
Some of the ferrite grains are 0.5 mm in length, indicating a
very soft blade that would be beneficial in bending the sword
to such a twisted shape. It may have been deliberately made
for a ritual and/or burial and therefore there was not necessarily a need to give the blade a sharp edge and the presence
of carbon would have impeded bending.
The microstructure of the sabres reveals iron and not
steel. It may be that the area near the handle was made from
a softer metal to provide some flexibility to the blade, but
the edge of the blade may have been made of steel. Although
the samples are composed of iron rather than steel, three
blades show evidence of quenching (JUM #11, #13 and
#16). JUM #13 appears to have carbide or nitride etch pits
which, according to Samuels (1980, 69), often appear in
quenched ferrous objects. JUM #11 and JUM #16 have laths
inside the ferrite grains. These may also be a form of carbides or nitrides that sometimes appear as laths in ferrite (see
Tylecote and Gilmour 1986, 5). Quenching is usually associated with steel and not iron, as quenching has a dramatic
hardening effect on steel, but virtually no effect on iron. The
process involves heating steel to between 700 - 850 °C and
then suddenly cooling it in water or another substance such
as oil. The evidence of quenching suggests that either part
of the blade was composed of steel, and the smith may have
quenched the blade as a matter of course, or the sample did
not reflect the composition of the entire blade.
An investigation of the varied technology found in swords,
sabres and blades from the Russian Northern Caucasus...

Allan, J.W. and Gilmour, B. 2000. Persian Steel: The Tanavoli Collection.
Oxford: Oxford University Press.
Craddock, P. 1998. New Light on the Production of Crucible Steel in Asia.
Bulletin of the Metals Museum 29: 41-66.
Feuerbach, A. unpublished. Crucible Steel in Central Asia: Production,
Use and Origins. PhD submitted to Institute of Archaeology, University
College London.
France-Lanord, A. 1969. Le Fer en Iran au Premier Millénaire Avant JésusChrist. Revue d’Historie des Mines et de la Métallurgie 1: 75-127.
Harsh, M. 2001. Crucible Iron: Yesterday and Today. Undergraduate Senior
Research Project, Northwestern University.
Kaminsky, V. 1996. Early Medieval Weapons in the North Caucasus – A
Preliminary Review. Oxford Journal of Archaeology 15: 95-105.
Lang, J., Craddock, P. and Simpson, St.J. 1998. New Evidence for Early
Crucible Steel. Historical Metallurgy 32: 7-14.
Nicolle, D. 1999. Arms and Armour of the Crusading Era, 1050-1350:
Islam, Eastern Europe and Asia. Stackpole Books, Pennsylvania.
Samuels, L.E. 1980. Optical Microscopy of Carbon Steels. Washington:
American Society of Metals.
Scott, D. 1991. Metallography and Microstructures of Ancient and Historic
Metals. Malibu, Calif.: Getty Trust.
Tylecote, R.F. and Gilmore, B.J. 1986. The Metallography of Early Ferrous
Edge Tools and Edged Weapons. BAR British Series 155.
Verhoeven, J., Pendray, A.H. and Dauksch, W.E. 1998. The Key Role of
Impurities in Ancient Damascus Steel Blades. JOM 50(9): 58-64.
Wagner, D. 1993. Iron and Steel in Ancient China. Brill: Leiden.
Zschokke, B. 1924. Du Damasse et des Lames de Damas. Rev. Met. 21:


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Re: How to find out amount of carboon in metal
« Reply #3 on: February 21, 2022, 12:01:11 PM »

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