I have some knives I made using my forge to heat treat and they are doing rather well, so I hear. That being said, I really like the ability to know what temp my blade is at and the option of holding it at that temp (within reason, anyway) for however long I want. Soaking blades at temp can also be a source of varying opinion. I have chosen to soak these knives at 1500F for 8 minutes. Some of that is arbitrary, some not. This isn't meant to be an "end all" in regards to the proper heat treat of this steel, but it has proven to work for my process and my tools. So, after the last cycle, I put the blade in and start the timer. After 8 minutes, I lift it up, grab it with tongs and slip the steel rod out of the hole in the tang. After lowering the knife to ensure I'm up to temp, it's quickly into the quench tank of Parks 50.
The first of the three was the only one that warped at all. I decided beforehand to try a method a friend told me about. Once the blade has come down under the needed temperature, you can take it out of the quenchant and do a little straightening with welding gloves on. I did a 10 count in the oil and saw the curve in the blade. The straightening went very well and set very quickly. I put the blade back into the oil to continue cooling from there. Sorry, no pics of that...
When the blade goes into the pot for the soak, the built up salts melt back into the rest of the liquid. When I quench into the oil, I'm left with a matte grey finish on the blade. I use a scotch brite pad and my water quench bucket to scrub off any bits of salt build up, then take it to my disc real quick to get to bare steel.
I grab my file and make sure things hardened nicely, which they did. I set it on top of the toaster oven where it warms slightly and waits for it's buddies to go into the oven. I did manage to get a quick shot of one blade in the quench after I saw everything went fine and no warping occurred. It was still too hot to handle when I took this.
Tempering is yet another one of those things people vary on. I fall under the "put it in for 3 cycles" umbrella. Not sure I have a great reason why, other than it was what I was taught and it has served me well with my process and my tools. 15N20 is often used with 1080 or 1084 in Damascus and many folks temper their hunters around 415, depending on who you ask. Since these are more slicing type knives that shouldn't see the tougher use possible of a bigger blade, I leave these a bit harder. I temper at about 380-385 for 2 hours, 3 times.
I'm currently using one of these in my kitchen just to test out and it's been in there a little over a month. It has stayed quite sharp and only seen a sharpening steel a few times, which has been all it's needed. I decided to check something after cutting up some meat while holding it with a fork. When the blade accidentally came up to the fork, it almost felt like it bit into the fork. Yesterday, I decided to do something dumb. I took a cheapo fork and started cutting into the handle of it. The blade didn't chip out, though you could just feel with your nail where I'd cut the fork. The fork had little marks each place I cut into it, raising a bit of the metal so it scraped against your skin (not going to be using that fork anymore...). I put the blade on the sharpening steel and it was back to good.
So, for now at least, I plan on trying to duplicate the last process and see what I can get. I'm about to go pull the knives out from their second cycle and will see if I can get the last one in tomorrow night.
Any questions/comments are welcome. Thanks for following along.