I hear this term used when makers refer to how they heat treat their blades,but what exactly does this mean?What advantages does a triple drawn blade have over others?Also why do I see a lot of D2 steel done this way and at the same time not cry treated?
There are several steps in hardening a blade. You heat the steel up past the point where it becomes nonmagnetic and cool it very slowly to remove hardness (annealing) before you cut out your blade and do rough grinding. About the time you are finished with the blade you heat it up to nonmagnetic again and cool it to room temperature very quickly (such as by dipping in oil) to harden the blade. The hardened blade is hard and brittle like a file at this point. Now you need to temper the blade by heating it up to some more moderate temperature and leaving it for a while. This might be by puting it in an oven at 450 for an hour. Tempering reduces the hardness of the steel somewhat and makes it tougher. Sometimes people repeat the tempering process three times, I think this is triple drawing. Usually you can accomplish a similar tempering effect by doing one hotter or longer tempering cycle. If you break up the cycles you can test the blade hardness at each step and be sure to get your desired finished hardness without risk of messing up the grain stucture or getting the blade too soft.
To cryo you need to put the blade in liquid nitrogen somewhere between your first quench and your last tempering cycle. I am not sure where is the best point. This works on a lot of stainless alloys. I guess that various makers don't think it does what they want for D2. It is supposed to make the steel finer-grained so that it is tougher and takes a finer edge. Some people really like the type of edge that you get on D2 with normal heat treatment and wouldn't want to change the grain structure through cryo. It is also possible that D2 doesn't do well with cryo.
Esav, we read this section of the forum too!! The proper term for draw is temper. The simplest steels require just one temper and only the most complex steels like S30V benefit from a triple temper. The general rule is that the more complex the steel the more complex the heat treatment and the more complex the steel the more critical are the times and temperatures. ..It is generally accepted that Bob Dozier is the best when it comes to heat treating D2. Cryo is sometimes used for D2. Much of cryo however is hype !