I was asked once why a katana was so solid compared to, say, a leaf spring of the same width. The answer is NOT the material. Not the prayers. Not what your game designer says it is. The reason for the solididity, the "stiffness" is the tension/compression created by the uneven shrinking during the differential tempering. Imagine lifting up a shelf of books by squeezing the stack of books together. You have a beam. If you really really squeezed that pile of books, you would have a beam strong enough to sit on. That's the physics behind it. If you were to go to the same trouble to heat treat a tool steel sword the same way the national treasures of Japan treat their folded swords, you would get similar results. I can't even imagine how many ways there are to screw it up though. My hat is off to the people who do this for a living!
Karl says it better....
(Karl is a regular member of the "sword forum", and is worth following ON the sword forum. Below is the nicest explanation I have ever seen of Powder Steel. And why it is a "little" better than folded steel for some purposes.)
Karl ---> I believe I read something once that said there is a difference between powdered steel, and particle steel (CPM steels). This link:
http://www.communitypc.com/wwwboard/messages/392.html
is a post by a fellow who describes the CMP process very well. He says the CPM process is a powdered metal process. If I recall, there is a difference between powder and particle methods, but it isn't significant for a person wanting a general idea of what is going on.
Advantages of the powdered methods is that you get perfectly homogeneous steel. Think of steel as a chocolate chip cookie. The dough is the regu;ar steel parts, and the chips are the carbodes. Carbides are very hard aloyed bits that can really make a nice toothy edge in a knife. Mr. Larman said that Howard Clark's 1086 blades take longer to burnish than "regula" blades, and they wear his burnishing tools faster. This is because of the vanadium carbides in the steel. There are all kinds of carbides. In stainless steel you'll get chromium carbides. Some carbon steels have chromium in them too (not at levels to make them stainless), forming chromium carbides. As you cut with yopur blade, you are going to wear away the steel. As you sharpen, you wear away the steel. Imagine if your chogolate chip cookie had clusters of chips with lots of dough spaces in it. you can pictire the dough crumbling away and leaving these odd clumps of chips, that now have little dough support and such. In regular steel, you can get clumping of carbides nad such because of migration of the carbides as the steel cools. With particle metallurgy, you start with a bunch of tiny particles of the perfect elemental make-up, and then you press them all together into a solid billet. No migration, nothing. Just a perfect chocolate chip cookie!
Oh, I think that another advantage of this method is that you can make alloyes that you can't make by traditional methods. Crucible (the company, the makers od the CPM steels among others) has steels with crazy amounts of vanadium, and amounts of carbon exceeding 2%!!!
The above was shamelessly ripped off from Karl's post on the Sword Forum.
Karl Rejmanhttp://www.swordforum.com/forums/member.php?2820-Karl-Rejman&s=d68a0f70952e557869d45ca832fb3882
Karl is a regular member of the "sword forum", and is worth following ON the sword forum. The above is the nicest explanation I have ever seen of Powder Steel. And why it is a "little" better than folded steel for some purposes.
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