I know, I'm an idiot...

Kbrasmodeler

Kbrasmodeler

Joined
Mar 18, 2008
Messages
3,371
...But you can tell me anyway.

So, I'm making a camp/bushcraft knife out of mystery steel.:rolleyes: I know, but it is the second one I've made with this bar, and the first, although not pretty, did harden and temper well, and since the steel stains and rusts, as well as hardens, I figure it is somewhere in the range of high carbon, plain old non-stainless steel. So, we haven't got to the real idiot part, yet.

I heated to non-magnetic with my home-made coal forge, let it sit there for about fifteen minutes, then quenched in ATF. It seemed to harden just like the first one. Then, I put it in the oven at 450 degrees, intending to get it out in an hour. Well, (here is the idiot part) I forgot about it, and left it in the oven all night. When I get up the next morning, the house hasn't burned down, although it was hot in the kitchen, but the knife is a dark blue all over, like I had had it blued by a gunsmith. So, what I want to know is, did I ruin the heat-treat? Is 450 degrees enough to soften it so much it won't hold an edge? Do I have to re-harden? If I don't have to, I'd like to leave the blue. It's real pretty. I'm on lunch at work right now, so no pics, but, if you'd like to see it, maybe I can snap a few when I get home. Thanks in advance for any help!
 
I've left some blades in my tempering muffle for 2.5-3 hours at 400F and they started turning blue from the oxides.

It's hard to say with that particular blade, I would say do the brass rod test and see if the edge rolls. If it rolls, re-HT it. the ridge on the bottom of an aluminum pop can works if you don't have a 1/4" brass rod.
 
If your oven temperature is stable, the time at temper alone shouldn't damage the heat treat that much. I'm more concerned about letting the blade sit at "non-magnetic" in a coal forge for 15 minutes. Unless you really managed to keep the forge temperature to around 1450-1500 degrees F for that whole time, you probably caused *a lot* of grain growth.
 
You can also just check it with a file, if it skates you should be fine. I can't imagine it ruining the blade, just don't do it again :p dangerous to the house.
 
65535 said:
You can also just check it with a file, if it skates you should be fine. I can't imagine it ruining the blade, just don't do it again :p dangerous to the house.
Click to expand...

Yeah, that was the first thought that ran through my mind. It was just a good thing that the wife was out of town at the time! :eek:
 
I would say that the blade now has more toughness than hardness. It may very well make an excellent camp knife with a lot of flex. But I would have to agree with Dan that leaving a blade in coal will cause grain growth. Coal is uneven in temperature and can over heat very easily. Rather Normalise three time allowing to cool to black heat each time. This will give you a more even grain structure. Not the best, but more even.

Also try and quench the blade after the first normalise then raise non magnetic temperature again before allowing to cool. This quench will reduce the size of the grain for the final hardening quench.
 
I think I'm going to re HT this knife, using your suggestions. I really like the blue color, but i want good grain structure more. Thanks!
 
Kbrasmodeler said:
...But you can tell me anyway.

So, I'm making a camp/bushcraft knife out of mystery steel.:rolleyes: I know, but it is the second one I've made with this bar, and the first, although not pretty, did harden and temper well, and since the steel stains and rusts, as well as hardens, I figure it is somewhere in the range of high carbon, plain old non-stainless steel. So, we haven't got to the real idiot part, yet.

I heated to non-magnetic with my home-made coal forge, let it sit there for about fifteen minutes, then quenched in ATF. It seemed to harden just like the first one. Then, I put it in the oven at 450 degrees, intending to get it out in an hour. Well, (here is the idiot part) I forgot about it, and left it in the oven all night. When I get up the next morning, the house hasn't burned down, although it was hot in the kitchen, but the knife is a dark blue all over, like I had had it blued by a gunsmith. So, what I want to know is, did I ruin the heat-treat? Is 450 degrees enough to soften it so much it won't hold an edge? Do I have to re-harden? If I don't have to, I'd like to leave the blue. It's real pretty. I'm on lunch at work right now, so no pics, but, if you'd like to see it, maybe I can snap a few when I get home. Thanks in advance for any help!
Click to expand...


You would be doing yourself a Big Favor, and increase your current knowledge of Heat Treat Procedure exponentially, by going to the top of this "ShopTalk-BladeSmith Question and Answers" Sub-Forum and read (2) Stickys.

First : Working the three steel types , (4th one from the top) http://www.bladeforums.com/forums/showthread.php?t=673173

Second : The process and principles of quenching ,(the 1st one)http://www.bladeforums.com/forums/showthread.php?t=639019



:thumbup:
 
I actually did read those stickies last year, when I was laid off and had the time to try my hand at bladesmithing. Of course, it appears that a refresher is necessary.
 
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