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Metallography of 8th / 9th
Century Swords and Saxes
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The
Saxes |
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What follows is essentially an
excerpt of Erik Szameit's and Mathias Mehofer's paper entitled (translated to
English) "Technological Investigations of Early Medieval Weapons from
Upper Austria"1). All the
pictures in what follows are (somewhat edited) pictures from this quite
interesting publication in an obscure journal.
The guys investigated these weapons in some detail: |
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| The weapons investigated. 3 Saxes, 3 swords,
1 lance point |
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It's a long paper with
many pictures. Unfortunately the authors did not look into faggoting and
confuse the issue considerably by invoking "carburization" during the
forging many times.
I will only give you the highlights, and I will add my own interpretations of
the pictures. |
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First some data about the saxes: |
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Auhof
sax (see below): Several slag bands, possibly from a few foldings.
Otherwise not much slag inclusions in in the bulk. High carbon steel for the
edges was joined with low carbon steel for the bulk. Microstructure and
hardness values indicate successful quench hardening of only the edge parts to
extreme hardness values. The weld seam is a bit strange and I don't know what
to make of it except to point out once more that fire welding is a
difficult process,
especially if you can't easily get up to 1200 oC (2192
oF) in your forge hearth, as we assume was the case in days of yore.
This sax is quite comparable to Japanese swords and seems to be similar to the
sax from approximately the same time span investigated in some detail by
Stefan Maeder . |
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| Etched cross section and schematic structure
of Auhof sax |
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| Weld seam of edge part and slag
inclusions |
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Gusen and
Enns sax: The pictures tell it all. The construction is similar to
the sax above. We have a rather well constructed weapons even so the steel is a
bit on the slag-rich side: |
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| Etched cross section and schematic structure
of Enns and Gusen sax |
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It is clear that those Austrian
smiths and / or their suppliers knew how to select proper grades of carbon
steel and how to tell phosphorous steel from carbon steel. The smiths knew a
lot about quench hardening and most likely about faggoting, even so we cannot
deduce this from the investigations shown here. If they used differential
hardening by protecting parts of the blade from cooling too rapidly, i.e. by
coating it with mud, cannot be told from the pictures here either. |
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The Swords
/ Spatha |
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Now to the swords. First the
relatively well preserved pattern welded sword from Enns / Lauriacum, from the
same burial that also yielded the sax and the lance point. Here is what one
gets in about half of a cross-section: |
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| Etched cross-sections of the pattern welded
sword from Enns/Lauriacum |
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A twisted rod texture is visible in
the center. The contrast is supposed to result from a combination of ferritic /
ferritic-pearlitic steel (i.e. low and medium carbon) but I'm pretty sure that
phosphorous was involved (the term "phosphorous" was never mentioned
by the authors).
It appears that just four twisted rods are used for the center of the blade as
opposed to four one each side as would be required for the inferred pattern
with the typical curlicues only obtainable if the rods are ground down a lot.
Whatever. While the blade might have sported a nice pattern, it was inferior to
its sax companion in terms of hardness. Nevertheless, an attempt to have a hard
edge was made, and we might simply have lost the real hard edge to
corrosion. |
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The two remaining swords are not
pattern welded but piled without a pattern (edges hard steel, inside softer
steel). They are quite interesting because both of them contain remains of a
simple inscription that
was obtained by hammering a small striped rod into the blade. Here is the one
of the St. Georgen spatha: |
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| Two "O" shaped inlays of striped
rods in the blade |
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Here is a partial cross-section
cutting through the inlay of the St. Georgen spatha: |
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| Etched cross-sections of the St. Georgen
sword with an inlay |
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The Schwödiau spatha looks much
the same. One might guess in both cases that the striped rod "wire"
was just hammered in without making a groove first because the slag trails in
the bulk just curve around and are not interrupted. |
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From the picture above it is clear
that quench hardening was applied, producing an extreme hardness of 761 at the
edge of the blade. The body of the blade was quite soft, on the other hand.
Again it appears that the smith knew exactly what he was doing. His raw
materials, however could have been a bit better with respect to the slag
content.
The inlays are significant, I think. They take us right to the famous
"+VLFBERH+T swords of chapter 11.4. |
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© H. Föll (Iron, Steel and Swords script)
With frame
Fire Welding