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Old 6th January 2009, 05:32 PM   #24
Jeff Pringle
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Join Date: Nov 2005
Posts: 187

a rough translation of that most interesting article, just to get the gist of it

My guesstimate is at the end of this post. The sword was made in a very similar way to the one analyzed by Edge & Williams, the main difference is the steel edge consisting of pearlite in the Swedish sword, not martensite. This might be due to a lack of hardening at time of manufacture, but it could also indicate that the sword went through a cremation burial which erased its heat treatment. Since the swords are so similar, Iíll presume they are both genuine +ULFBERHT+s and go with the latter.

could you shed some light on its historical heat treatment as uncovered by modern research, if such information exists?

This has always been a problem, not enough data on the old swords, but this recent article is a good start Ė Heat treated wootz/crucible steel has a significant edge over regular steel in hardnessÖ
The Metallurgy of some indian swords
Alan Williams, David Edge
Gladius, Vol XXVII (2007):149-176

There is the theory that there was no need to harden wootz, since you just wanted very tough pearlite carrying those extra-hard carbides to the target, but since all the contemporary descriptions of wootz sword making include a quench, and since many swords look like they have a hardened edge, I suspect that theory is another modern misinterpretation based on too little info. Current experimentation reveals that water quenching is risky (well, we knew that already! ), that you can erase none, some or all of the pattern depending on the specific alloy and how you austenitize (heat before the quench) the blade, and that hardened and unhardened wootz respond to the etch differently, so yes, those weird lines that show up in the old swords & knives are evidence of heat treating. Iíll attach some fotos of quenched blades, from 1% to 1.9% Carbon. Lower carbon and the martensite grabs all the carbon, banding disappears, higher carbon and you get martensite studded with banded carbides. I recently bought an Indian wootz sword that was hardened at the edge in the area of the center of percussion, but donít have a photograph of it (yet! )

Little different direction in this article

Better than the Guardian, but I suspect thereís still some misinterpretation going on. Yesterday I received a confirmation that the Williams article is on its way, so soon Iíll be able to compare all three!

wootz is crucible steel with a surface pattern, correct?

Wootz is hypereutectoid crucible steel with a pattern, you need to be over 0.8% Carbon to get the carbides.

The guts of the Swedish article:
Metallographic analysis of inlays in a Viking Sword, inv. nr. SHM 907
The blade is made up of several layers of varying carbon content, an almost carbon-free central layer with several weld joints marked by slag streaks, surrounded by two outer layers with higher carbon content. The central layer, which is built of 10-12 layers, consisting of relatively coarse-grained ferrite with small pearlite at grain boundaries, carbon content of less than 0.1%. The side layers are also layered and consist of one side of pure pearlite (carbon 0.8%) that is very fine-grained and finely laminated. The second side has lower carbon content, 0,4-0,6%; and consists of a powdery mixture of ferrite and perlite. The edge is badly corroded but seems to be the layer with the highest carbon content.
The inlay is almost entirely carbon-free, with coarse grains of ferrite. The cross-section is nearly trapezoidal and divided by a corrosion streak, which is probably a slag line between two twisted wires (Figure 3). The two threads show in their internal structure traces of stratification. The inlay is likely to consist of two twisted iron wires, probably containing phosphorous, which were forged down the fuller in the blade prior to the final processing to finished shape.
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