Well, L6 is a low alloy, high carbon steel with a carbon content of between 0.65 and 0.75%. Because of it's make up it is extremely resilient and can take a beating and that, without using flowery speech, is it's main selling point. The nickel that they use in the formula gives it a good resistance to any percussive wear and tear the blade might take in its day to day use and the chromium gives it the extra spring that is desirable in a blade that ends up through hardened. L6 however, does respond well to differential hardening although it's been said that it is a more difficult steel to consistently heat treat. I can only assume that the increased failure rate because of this is what contributes to its almost exorbitant pricing and why there are reputedly more 'lemons' sold with this particular steel than many others.
Practically speaking though, is it any good?
Yeh, well now I've sucked all the magic out of this metal, (sorry about that) I suppose I should get down to whether or not it's any good. Theres a wide and varied opinion on this steel, mainly fuelled by stories of blades that have been successfully produced by high profile forges, and put through their paces both in destructive and normal test cutting. There are as many stories told on forums and on facebook of how indestructible it is as there are negative stories about how it's pretty much a marketing gimmick.
For those that are interested, here is the makeup of L6 steel.
|Carbon||0.65 - 0.75|
|Chromium||0.6 - 1.2|
|Manganese||0.25 - 0.8|
|Nickel||0.25 - 2|
It's worth noting I think that both Chromium and Silicon are usually added in very carefully measured amounts to give spring to an existing sword steel. (5160 & 9260 being the two steels that instantly spring to everyones mind) Silicon is a deoxidant, removing unwanted oxygen bubbles from the molten steel. It also increases the overall strength of the steel as well as adding corrosion resistance. Chromium on the other hand is never added in amounts large enough to help with overall corrosion resistance, but instead helps almost exclusively with the spring hardening. I'm not a metallurgist, but this is what I have come to understand through talking with people who work with these sorts of steels.
You have to remember that there is no perfect steel and each different steel choice comes with its own ups and downs. There are positive and negative points to every material and when talking like this about L6 or indeed any steel, you talking about the _beginning_ of the sword, it's possibilities and what it _could_ be. To be blunt, L6, 9260, 1065, 5160... They're all good steels. It's the smith that turns that into something spectacular. or not. Just think about the quite frankly crappy materials that the smiths of ancient Japan had to work with and the labour that they had to go through just to get to a point where they had a raw material that was good enough to begin working on. We're still admiring the beauty of their work today. The same principle rings true here. If the sword was made well, then you'll have a good sword. If it wasn't then you'll have a sword shaped object. Given the price, it certainly makes you think. :)