Heat Treating Steps

[Splat]

Now, I'm a total newbie to knifemaking, though not to knives. I'm good making and repairing metal contraptions, but never tried to make a knife. I'm just about done building my NWGS so I'm getting closer to attempting my first knife. I will be attempting via the stock removal method. I'm going to practice on some old saw blades I have but my first actual "keeper" blade I'd like to use AUS8.

Now, I've read WG's "$50 Knife Shop" and try to read as much here about the whole heat treating process but with so many terms and steps I'm getting confused about the whole thing. Can someone explain the steps in order and what they're trying to accomplish? Or at least point me to a page where this is explained? Also, is each step required regardless of steel type (A1, O1, 440C, etc.)? Thanks very much in advance.

 

[Justin King]

The stickies at the top of the page cover most of this info.
The main processes are :
1-austenizing (heating) the piece, this step can require soaking at certain temps, depending on steel. The sticky on the 3 different steel types will give more detail on this.
2-quenching the piece-cooling it from the austenizing heat. This also varies according to steel type, the sticky on processes and principles of quenching will cover this. After this step, most steels will be too hard/brittle for most applications, hence step 3.
3-tempering, this is done to stress relieve and soften the blade somewhat, to get the hardness and toughness of the steel to the desired parameters for the intended use. This is usually done between 300 and 600 degrees F. but the more exotic alloys sometimes benefit from higher temps.

Normalizing, annealing, spheroidizing, etc. are also heat treating processes that are used to achieve various properties, such as softening the steel to make it more machineable, or to put it into a correct state prior to the austenizing heat.

 

[silver_pilate]

A common mistake made by people starting out with heat treating is assuming that forumula "X,Y,Z" is applicable across the board. Nothing could be farther from the truth. As Justin mentioned, each steel has a specific recipe, if you will, that will produce proper results. The main differences between steels are the temperature, the time at temperature, the speed of quench, and the temper temperature. First, determine what temperature control capabilities you have. That will help you determine what steel you will be using (if you're heat treating your own work...nothing is wrong with sending blades out for heat treating). Once you have that info down, you can research the heat treating regimine for that specific steel.

--nathan

 

[Nathan the Machinist]

Yup. That said, stainless is not a good DIY project if you don't have a heat treat oven. The temperature is fairly high, the "window" is too narrow to eyeball, and there will be a "soak" time at temp. You'll probably want to send that out.