Will,
Tim has pretty well covered the basics of heat treating non-stainless, the subject can get out of hand because it seems every knifemaker develops their own "tricks" of the trade when heat treating/tempering steel, and can get quite,uh, excited about the subject. For a good on line tutorial on heat treating carbon steel that pretty much follows Tim's suggestions, but goes into more detail, I suggest going to
http://www.ckdforums.com and clicking on the how to/tutorial button. Under the forging section, the first tutorial by Max Burnett called "heat treat" will give you a really good reference to get you started. There are a number of other tutorials there that will probably interest you as well.
Far as stainless steels go...it's a different ball game for most of them. As Tim has pointed out, they tend to use a different, more complex process, than the carbon varieties. While the heating to critical temperature is pretty much the same(you heat to non-magnetic), the temperatures involved are different, and the "quenching Mediums" are different......many are air cooled vice oil or brine(water) cooled as carbon steels are; although some carbon steels such as A-2 are also air cooled. The amount of chromium present seems to be the main determining factor here. After the initial heat treat to critical temperature, most (probably all) stainless blades are then stress relieved at a Temperature of around of 1200F for up to two hours(varies), then enter a tempering cycle(often more than one) plus often, to get the optimum performance, a cryogenic cycle. Cryogenics means cooling the blade in liquid Nitrogen to -305F, or in dryice/acetone(dangerous!!!) to -110 degrees to change(shrink/homogenize) the grain structure to create greater toughness(will bend more before breaking) and edge holding. Also raises the Rc around a point or so. All this is usually done using digitally controlled ovens and some sort of liquid nitrogen set up. All this translates into money for the initial setup and a fairly long learning curve....some stainless steels are forgiving, and some are not. While I read constantly on the subject, the science/art of metallurgy is facinating, I opt at this point to send my blades to an experienced heat treat person who will charge me anywhere from $7.00-$14.00 a blade. I can get a lot of blades heat treated for the cost of equipment/operating costs. Such people as Paul Bos or D'holder, or Texas Knifemakers Supply and, I think, K & G supply offer reasonable prices. Having used mainly D'holder and TKS I have never received a poor blade from either...they come back properly HT'd and straightened( I should have mentioned that stainless also warps like crazy unless you are careful). Up to you. Again, the one forum at CKD(high performance blades) is interesting to read, and there are any number of expert knifemakers there who can answer any questions you have about stainless, or carbon, or talonite....etc, in considerable detail, and will provide many other sources of info for your,uh, reading pleasure. Good luck.
