How hot do you have to get a knife to ruin heat treat?

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Bungwrench

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Can you leave knives in your car in the sun and will the heat treat be OK?

What about letting a black coated fixed blade sit outside in the sun? I've done this and the blade was so hot that I couldn't touch it without getting burned.

Does anyone know what temperature will damage heat treat?
 
If you start to see discoloration it is ruining the heat treatment. That usually occurs at a few hundred degrees well over 300F, so I think that they should be fine.
 
if its tempered at for example 200°C then you dont wanna go over 200 and if its 550 you want to stay below that. all temperatures above the tempering temperature will make it softer, however its depending on how long time you leave it at that temperature and what steel is used.
 
So if you stick it in a fire in order to sear a wound shut like they do in the movies,
would that void your HT?
 
From my experience, a light yellow color on plain carbon steel is about as high as I would go. That is above my tempering temperature for 1095, which is 325-335 F. Other steels take different colors at different temperature, and I havent done enough research to make any useful statements. Something to think about is that colors are a surface oxide, and stainless steels resist oxide growth past a certain point, so how hot is a stainless when it finally turns blue? Basically, what M Wadel described is the practical limit. Temperature has a MUCH greater effect than time, as an increase in tempering time from 1-4 hours only produces a loss of about 1 point of hardness. IIRC, this was a plain carbon steel, and alloy steels will be slower than that. Something thats been nagging me is how can heat treatment be "ruined" by say, sharpening on a sander, where the blade heats up then immediately cools down, when tempering times are generally 1 hour or more? Seems the heat treaters could save some time by bringing the piece to tempereture for a few seconds then immediately cooling it, assuming the piece took less than an hour to come up to temperature. I need to do some more digging on the matter.
 
Grinding can get temperatures very high, above the hardening temperature !!! Even though the time may be short. I've broken tips of some good quality knives without any abuse -I conclude it's grinding damage.I've seen lots of grinding damage on things like bearings even though coolant was used in grinding....For the original question I would say 400 F.
 
You can not go simply by colors because the colors are much higher temperatures in stainless. You can burn them long before they discolor. Do not exceed the tempering temperature which can be as low as 325 F.

-Cliff
 
1whitefoot said:
So if you stick it in a fire in order to sear a wound shut like they do in the movies,
would that void your HT?
Click to expand...

Yes, if you do it just like they do in the movies (I.E. get it red hot) you will ruin your heat treat. As everyone has said, your knife begins to change when its temperature exceeds the tempering temperature used when the knife was made. Thus, I suppose that for some steels/HTs there would be a "golden" temperature range that would still cauterize a wound but still wouldn't ruin the heat treat. Getting there would be very tricky.
 
Not to be too off-topic but the whole idea of heating your knife red hot and "searing a wound shut" has to be one of the most ridiculous things Hollywood ever cooked up (pun intended). Cooking your flesh to control bleeding? You can't be serious. Not to mention pain beyond belief. Only the insane or delerious would ever attempt it, and probably immediately regret it.

Can anyone think of any other reason to heat your knife like that? If not, that whole point is moot.

To the original question: Leaving you knife in the sun may get it hot enough to hurt your fingers perhaps but it will never get it hot enought to affect it's temper. Would a glass of water ever start to boil on your dash? No, so it's temperature never exceeds 212 deg F, which is still well below any tempering temperature.
 
Cliff Stamp said:
Some, actually many, knot books will flame heat a knife to seal the rope after it is cut.

-Cliff
Click to expand...

I've got a cheap SAK knockoff that I use that way. . . I actually heat the knife and cut the rope with the hot knife. Makes nice finished ends. I wouldn't do it with a nicer knife though.
 
Blue Sky said:
Not to be too off-topic but the whole idea of heating your knife red hot and "searing a wound shut" has to be one of the most ridiculous things Hollywood ever cooked up (pun intended). Cooking your flesh to control bleeding? You can't be serious. Not to mention pain beyond belief. Only the insane or delerious would ever attempt it, and probably immediately regret it.

Can anyone think of any other reason to heat your knife like that? If not, that whole point is moot.

To the original question: Leaving you knife in the sun may get it hot enough to hurt your fingers perhaps but it will never get it hot enought to affect it's temper. Would a glass of water ever start to boil on your dash? No, so it's temperature never exceeds 212 deg F, which is still well below any tempering temperature.
Click to expand...

I worked in an operating room for a while. I can assure you that "searing a wound shut" is an extremely common thing to do and is "best practice" for many procedures.

It's like... there's a word for the procedure-- "cauterize". People have been doing it for millennia.

The most memorable thing about my vasectomy was the smell of burning flesh as they cauterized the wound ("cut, tied and cauterized; that's not reversing" as my surgeon put it).

(also your water argument is non-nonsensical, but I'll let you figure out why).
 
It's OK, the OP has been banned since 2009. So I am sure he will come back to read these recent posts.
As far as Blue Sky goes, they were active today, so there still may be hope for closure, pardon the poor pun.

I Really do love how your Very first post is a necro-post (against the rules) and on top of that, it was to try to correct someone who posted a statement over 11 years ago.

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Regarding cauterization, it is an affective means of closing a wound. But, (and this is the important part) only when done in sterile or at the Very least, under Very Clean circumstances.
Skin that is burned That badly would likely increase the open surface area of the wound to the environment and be an exponential cause for concern due to infection.

If you are going to bleed out, sure, give it a shot if you can't make a tourniquet. But if it is for a 2" deep puncture to soft tissue (calf, shoulder, exterior of the thigh) then clean it as best as you can and use pressure and elevate it and stay hydrated...
 
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Blue Sky said:
Not to be too off-topic but the whole idea of heating your knife red hot and "searing a wound shut" has to be one of the most ridiculous things Hollywood ever cooked up (pun intended). Cooking your flesh to control bleeding? You can't be serious. Not to mention pain beyond belief. Only the insane or delerious would ever attempt it, and probably immediately regret it.

Can anyone think of any other reason to heat your knife like that? If not, that whole point is moot.

To the original question: Leaving you knife in the sun may get it hot enough to hurt your fingers perhaps but it will never get it hot enought to affect it's temper. Would a glass of water ever start to boil on your dash? No, so it's temperature never exceeds 212 deg F, which is still well below any tempering temperature.
Click to expand...
Actually cauterizing a wound is a very common practice throughout history
And still done today even in hospitals and dentist office. Although not with a red hot knife. I actually did it once on accident building corral panels once because the panels had to get done and I got cut by a sharp corner that I had just welded up. Left a good inch and a half cut in my arm but it didn't bleed because it was cauterized.

Also to answer the question you can heat a blade up to tempering temp but no hotter

Sent from my SAMSUNG-SM-G870A using Tapatalk
 
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