- Joined
- Dec 21, 2006
- Messages
- 3,158
Finally got around to hardening this blade of Cru Forge V after my last attempt ended in disaster. The last attempt I had ground the edge way too thin, .015", before heat treat. After quenching, a file dug into the blade like it was mild steel, and I thought I didn't get it hot enough (first time using a kiln). I went back to my forge, re-tried the quench, same thing.....file bit right in. I had really never experienced decarb before, so I was at a loss as to what I did wrong. With the help of everyone on this forum I determined that the culprit was not my kiln, or my forge, or my calibrated Mark I eyeballs, but rather decarb. That knife was not going to be salvagable, so I made another.
This time around, I was more aware of what to expect, and left my edge around .035 or so. 1650F, cool in air. 1500F, cool in air. 1400F, cool in air. 1200 equalize, ramp to 1500 and hold for 10 minutes, quench (P50). I used a VERY THIN layer of satanite to help control some of the decarb. I checked with a file after quench and the file bit into the steel just like the last time (I was a little apprehensive, but expected this). Tempered 1.5 hours @ 350 just for stress relief, then proceeded to see just what I had. Using 80 grit paper (by hand...no grinder....no heat), I started to sand the blade, hoping that indeed there was a layer of decarb. There was indeed. Hard to say exactly how thick it was, but I would say close to .010" of decarb. While sanding I was starting to worry about having a bad batch of steel, but the more I sand, the harder it gets! You can tell when you hand sand hard steel, the feel (and look) changes. Paper wants to skate off of the blade, and it has more of shine, I suppose. Once I reached the hard layer, I put it back into the oven for another 1.5 hours @ 400F.
I wrote this in case someone down the line has the same issue. If you did everything right, don't be upset if your file test fails. You more than likely have a thick layer of decarb to get through before you reach the hardened steel. San Mai comes to mind! I REALLY hope this helps someone in the future, because I have gleened a treasure trove of info from this forum. Even if I don't end up posting a knife to sell.....the money for the membership is well worth it. Another "Thank you so much" to the Bladeforum mods, members, and posters.
I am new to hypereutectoids and don't have much experience heat treating them. I did do a blade of 52100, with basically the same heat treat as mentioned above, but didn't have the decarb problem. It was done in my forge, tho, and not the kiln. I am thoroughly impressed with the edge on that knife. For those of you who HT hypereutectoids in a kiln, do you have this much decarb to deal with, or is this something unique with CFV?
This time around, I was more aware of what to expect, and left my edge around .035 or so. 1650F, cool in air. 1500F, cool in air. 1400F, cool in air. 1200 equalize, ramp to 1500 and hold for 10 minutes, quench (P50). I used a VERY THIN layer of satanite to help control some of the decarb. I checked with a file after quench and the file bit into the steel just like the last time (I was a little apprehensive, but expected this). Tempered 1.5 hours @ 350 just for stress relief, then proceeded to see just what I had. Using 80 grit paper (by hand...no grinder....no heat), I started to sand the blade, hoping that indeed there was a layer of decarb. There was indeed. Hard to say exactly how thick it was, but I would say close to .010" of decarb. While sanding I was starting to worry about having a bad batch of steel, but the more I sand, the harder it gets! You can tell when you hand sand hard steel, the feel (and look) changes. Paper wants to skate off of the blade, and it has more of shine, I suppose. Once I reached the hard layer, I put it back into the oven for another 1.5 hours @ 400F.
I wrote this in case someone down the line has the same issue. If you did everything right, don't be upset if your file test fails. You more than likely have a thick layer of decarb to get through before you reach the hardened steel. San Mai comes to mind! I REALLY hope this helps someone in the future, because I have gleened a treasure trove of info from this forum. Even if I don't end up posting a knife to sell.....the money for the membership is well worth it. Another "Thank you so much" to the Bladeforum mods, members, and posters.
I am new to hypereutectoids and don't have much experience heat treating them. I did do a blade of 52100, with basically the same heat treat as mentioned above, but didn't have the decarb problem. It was done in my forge, tho, and not the kiln. I am thoroughly impressed with the edge on that knife. For those of you who HT hypereutectoids in a kiln, do you have this much decarb to deal with, or is this something unique with CFV?
