demoman_chaos said:
Is that why the very same techniques they used were outdated by the Roman era? The Pre-Roman Celts folded their steel exactly as the Japanese did about two THOUSAND years after them. By the time the Japanese were folding their steel, Europeans had moved on to pattern welding. Pattern welding allows swords to be very flexible and recover their shape after they bend. This is something the katana doesn't do very well due to the high iron conent.
What has folding steel got to do with anything? Any movie that ever says the blade was folded "a thousand times" is full of shit. You MAY see a sword whose original billet was folded 16 or so times. What people probably confused with folding is the number of layers. Each fold created a geometrically higher amount of layers (15 folds = 1->2->4->8->16->32->64->128->256->512->1,024->2,048->4,096->8,192->16,384 layers). All folding does is make the metal more uniform in its microstructure. If you've ever smelted iron and then tried to work with it (as I have), you'll note that the first billet form you get is really rough with large grain structure that practically screams crap. But as you fold it, that structure gets more and more refined and quickly becomes useable. Every time you fold the billet, you are essentially forge welding it to itself. Each time it's folded, the billet loses material as well. So for someone to be able to fold it a 1,000 times you'd have to start with some kind of mile long (exaggerated guess that may be underestimated) billet to end up with enough material to forge a sword.
So their folding technique is a necessary technique, but it isn't all that special. What was special was the carbon content of the steel and their heat treat/tempering techniques. The reason why the blade curves (they are forged straight) is because they are rapidly cooled from a high temperature and the spine of the blade is thicker and cools slower than the edge of the blade. That rapid cooling changes the structure of the grain in such a way as to make the blade a LOT harder. Then oven heat treating can bring the structure to a level that maximizes the blades strength and brings the hardness (martensite) down to a level that is no longer as brittle. Hardness here is the same kind of term as you'd use for a diamond or another rock. Resistence to abrasion. It literally changes the structure of the metal to be crystaline and then the further tempering brings the amoutn of martensite down to appropriate levels for the tool.
The Romans did not have tempering which makes all the difference. The reason for that is because Romans didn't have Steel. At least, not high quality high carbon steel. As such, they also didn't know how to temper steel as that only works with high-carbon steel. That the Japanese did was figure out how to make a high quality blade using the right amount of carbon and combining that with cutting edge (haha) tempering technology.
If you want to look at higher quality steel production even earlier, you'll have to look at India for their Wootz steel production. But the Romans never figured it out.
So, crappy steel if steel was ever accidentally produced, no good tempering as tempering requires higher carbon contents of steel. So the Romans are a piss-poor route to go. India would be much better
Oh, and the Japanese seem to have actually understood the properties of high-carbon vs low-carbon steel. The blades weren't just one type. For example, they'd use lower carbon steel as a core. The Japanese understood steel carbon content in a way the western world wouldn't figure out for some time afterwards and even then western smithing didn't commonly use different types of steel within the same blade to make it better.
Having forged tanto blades and damascus blades (high ticket items for us to sell as quick as we could make them) I can tell you that understanding the properties of different metal types and how they can benefit the finished product differently can do wonders. For example, I'd often make a tomahawk with a wrought iron outside/jacket and a high carbon core (52/100 steel). This meant a very strong bit that could hold an edge like few other types of steel while having a jacket that can be etched to have a wood-like pattern and is resistent to corrosion like rust.
I'm not saying that Japanese blades are some mythical superhuman feat. Just that they were a very advanced technology in their era.
No matter how sharp something is, just touching it won't lead you being cut. Edges do not work that way. As for Japan having better sharpening techniques, that is just plain ridiculous. The katanas you see cutting things today have edges very different than historical ones. You can't have a "razor" sharp edge and expect to keep it. Katanas did have harder edges, so in theory they could take a sharper edge. In practice, that edge is very brittle and would chip very easily.
Depends on the amount of pressure you apply. But yes, edges generally require some motion to slice.
What I created with my chisel was a paper thin edge. That will break and warp easily. I actually made it curl the first time I tried to use it.
But harder does not always make something brittle. Not when the sword recieves further tempering to reduce the martensite. I'm not familiar with how the Japanese temper their blades after the initial rapid cooling or if they did that at all. From what I've seen, their work was no more brittle than other high carbon blades.