dxb105@phys.anu.oz (David Bofinger) (06/05/90)
From: dxb105@phys.anu.oz (David Bofinger) In article <16062@cbnews.ATT.COM>, bowers@drynix (Al Bowers) writes: > [Amakuni] was the first of the old sword period makers which > culminated in the 15th century with (IMHO) the finest bladed waepons > yet created by man for the purpose of warfare. The tempering process > was refined during this time to its peak as was the folding process > which would result in over 32,000 layers of very high carbon steel for > the cutting edge. Other pieces of steel would be used for other parts > of the blade such as sping steel for the sides and back and a very > soft steel for the core. A Scientific American article from a few years ago went into the history of ultra high carbon steels in sword-making. If you put too much carbon in steel with ordinary processses, it just gets brittle, but the versions that worked fell into one of two categories: (1) Damaske (sp?) steel, where the steel is folded ~10-20 times (so there are 1000 to 1000000 layers), as used in the Middle East, Japan, Spain(?) and elsewhere (including England, much later, for shotguns). I'm not sure how high the carbon content was, here. (2) Damascus steel, named after the city where the crusaders first got a nasty shock from it. This was manufactured using sophisticated heat treatment, etc., but as far as I know the mechanical aspect was fairly straightforward. The art was lost until quite recently (the article was describing current research, emphasis on the re-). Both these techniques lead to a layered pattern on the blade (I don't know why). The second one gives steel that is _very_ flexible, perfect for the body of a sword blade (I think they used it for the edge too). The article claimed that (2) was far superior to (1), and that in some places (1) was probably an attempt to copy (2) (perhaps not in Japan :-)). It's interesting the Japanese _didn't_ use their steel for the core. It suggests it didn't have the superb flexibility of Damascus steel, but would take a good edge. Then again, maybe it just looked good :-). > Upon close examination the grain of the layers of steel are visible. Let's do some arithmetic. 8mm sword blade, 32000 layers would give a thickness of 250 nanometres, which is shorter than the wavelength of the light you were viewing it under. Whatever you were seeing, it wasn't the layers created by folding. ------------------------------------------------------------------------------ David Bofinger ACSNet: dxb105@phys.anu.oz (from outside Australia, add .au) Snail: Dept. of Theoretical Physics, RSPhysS, ANU, ACT, 2601 ------------------------------------------------------------------------------ "It is the logic of our times No subject for immortal verse That we, who lived by honest dreams Defend the bad against the worse." -- C.D. Lewis