i am an idiot

[MikeT36]

Hey guys, i look a lot and post very little but i have a question due to my own stupidity. I heat treated a couple 1095 knives last night in my even heat oven. Took them inside, cleaned them up and put them in the oven at 450 degrees for two hours. Well, thats what i meant to do. What i actually did was put them in and proceed to fall asleep and leave them in overnight until about 6 this morning. They are both stock removal blades and my question is do i just heat treat again or are they ok?

 

[Maelstrom78]

If the oven kept the temperature constant I would think they should be just fine.

 

[Stacy E. Apelt - Bladesmith]

You did no harm. Just give them a second temper and all will be good. Time is far less important than temperature. A rise in 10-20 degrees will make a measurable difference. An additional ten hours at a controlled temperature will make almost no difference.

 

[MikeT36]

Thanks, that is kind of what i figured, but wanted to make sure. Thanks again

 

[Nic.]

I've done that before...felt pretty stupid, but like what's been said, an easy fix.

 

[Nathan the Machinist]

I don't know, the effects of time at tempering temperature is a logarithmic curve and you're out a full order of magnitude longer than a normal temper cycle. It doesn't hit a particular hardness at a particular temperature and just stop there, hardness continues to drop over time, just at an increasingly reduced rate. After ten hours I'll bet it's a point or two softer than it would have been, if that matters.

 

[Will52100]

What Nathan said. I'd do another temper at a lower temp and then test with the brass rod. Should be OK, though.

 

[Stacy E. Apelt - Bladesmith]

A second temper is needed, but lowering it won't increase the hardness any.

From what I have determined in researching this for a nearly identical past thread, the 12 hour temper might lower the hardness a point. It will probably increase toughness slightly. From what I saw on charts, it takes twenty to thirty hours to start getting much of a cumulative effect.

If the HT was for something that needed an exact hardness, the re-doing the HT would be a good idea. But for a knife, the difference is within the normal +/- 1 point variance of any HT.

 

[Matthew Gregory]

Only you can determine how accurately you wish to control the making of your own knives. Lots of conjecture in this thread. Only you can decide if the postulations offered are better than knowing for sure...