Re-quenching o-1 tool steel

J

jlm_785

Joined
Jul 28, 2012
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20
hi there, I am pretty new to knife making and I am working O-1 for the first time and during tempering it got too hot and turned a dark gold with some bluish areas which I haven’t had happen before. My question is should I normalize before re heating and quenching?
 
You're using a forge to temper them? I would suggest getting a cheap toaster oven and putting in some 1/2" flat bar for thermal mass to help regulate it. There is no way I could hold my forge at that low of a temperature with any type of precision. I'm not sure even with a PID controlled one it would be very successful at tempering temps.
 
KnuckleDownKnives said:
You're using a forge to temper them? I would suggest getting a cheap toaster oven and putting in some 1/2" flat bar for thermal mass to help regulate it. There is no way I could hold my forge at that low of a temperature with any type of precision. I'm not sure even with a PID controlled one it would be very successful at tempering temps.
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I’m sorry I thought you meant for the heat treat! I misunderstood I apologize. To temper I am just using my kitchen oven
 
jlm_785 said:
I’m sorry I thought you meant for the heat treat! I misunderstood I apologize. To temper I am just using my kitchen oven
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I'm probably wrong assuming that as well. My curiosity is how you're getting those colors as well from a kitchen oven. That is quite hot unless you're sticking the blade right on top of the element. To get bluish colors you're in the 540*F + range. Do you do a preheat and let it soak at temp for a while before putting in your blade. Almost sounds like maybe some residual quench oil may be on the blade contributing to the color. I very well could be wrong, but that seems awfully hot for a non commercial oven unless it's on cleaning cycle or using the broiler.
 
If you’re using quench like parks you’re going to get discoloration on the steel. It’s not a true temper color.
Even at 425 I’ll get blue color on my steel from the p50 oil.
 
No you can not run a forge that low on a pid control. It could be possible with a fancy auto ignition set up but the cycle time would be very quick and you forge would basically become a pulse jet. The forge has to be hotter then the auto ignition tempature of propane for a pid to work for our applications.
 
JTknives said:
No you can not run a forge that low on a pid control. It could be possible with a fancy auto ignition set up but the cycle time would be very quick and you forge would basically become a pulse jet. The forge has to be hotter then the auto ignition tempature of propane for a pid to work for our applications.
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haha, it's def not something I would ever think of trying. That's pretty much exactly what I was thinking "pulse jet" when that went through my mind.
 
No I am definitely not tempering with my forge haha. But I thought the colors were showing way too hot for what I was doing. I tempered it at 450 for 1 hour. I know the oven can vary a little bit but I didn’t think it would that much especially cause it’s always done fine with my HC knives. But I also usually clean them up a bit more before tempering ( was in a bit of a hurry). So does it sound more like it’s the oil rather than over heating?
 
And as far as a quenchant im just using canola oil. And I do let the oven pre-heat and sit for about 30 minutes before putting the knife in and I put the knife on the top shelf as far away from the burner as I can.
 
You didn’t overheat (at least not by enough to get you to blue) you just had canola left on your blade that when it burned off discolored the steel.
 
You can get all sorts of color in tempering a quenched blade in an oven. The colors mean nothing.

I wish people would stop reading the old machinist books that list temper colors. That is for a different type of tempering than an oven temper. As said by KnuckleDown, you would have to oven temper for an hour at 540+ to get a blue blade.
 
I did a file test on the edge and it didn’t phase it so I took it out and did some testing and it held up perfect! So I went ahead and just finished it and it turned out great! I appreciate all the answers and help!
 
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