Max temp before heat treating of the blade *edge* is affected

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wacki

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Sep 12, 2009
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I've read a bunch of threads talking about "best heat treat in the business" or "pick a steel and concentrate more on the maker and how good his heat treating is."

That got me wondering.... how hot can a knife get before the heat treating is negatively affected.

EDIT: This is what I was looking for. 400° is what the forum views as the lowest temperature that will impact heat treatment. Now I'm curious as to why this is the lowest temp as it's far below the melting points of Chromium, Iron and all the other components.


Examples that I had used that possibly turned the thread a little silly.
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new example: Inside a HOT CAR in death valley

Previous example:
Sometimes you use a piece of metal or a stick to poke things in a campfire fire. I'm wondering how quickly the edge (very fine tip) of a knife will change properties when exposed to heat. Obviously the spine has more mass and will have much more thermal inertia.
 
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I wouldnt ever use a knife on anything hot other than food or when making a kydex sheath,if you want to poke a camp fire a stick is your best bet,my rule of thumb is to treat my knife as if its my last one when im out in the middle of nowhere.Im not sure the temp but if its too hot to the touch or the color changes i think the heat treat is ruined or badly damaged
 
Too hot to the touch? My driveway gets that hot on a summer day. Heck, my car gets that hot on sunny days... especially in the southwest.

This is the more practical question I guess.... will a hot car in Nevada be enough?
 
What is that John Wayne movie where someone heats up a bowie knife red-hot to cauterize a wound shut? I think it's 'The Searchers', but I'm not sure...

Anyway, don't stick your knife in a fire if you don't want to ruin it. Even if you're John Wayne. If you need to poke a fire, use a stick.
 
Boiling knives in water is the traditional and correct way to disinfect blades. I don't think a sunny desert day would do it.
 
That question can only be answered on a steel by steel basis.

Carbon and spring steels are tempered in the 400 degree range. Higher, will make the steel softer.

More complex steels can have higher temp heat treats, and much higher tempering. I believe that INFI is tempered in the 900 degree range.


Just a bit ago some one posted about ruining the heat treat on his knife by poking the hot coals around for an evening.

Your car and driveway temps would not be hot enough to affect the heat treat/temper of the steel.

You are talking about "ouch, that is hot" but not leaving skin behind temps.

Tempering temps for nearly any steel you are going to find in a knife are going to be melt your skin, blister and peel it away from a touch temps. (400+ degrees).
 
Yep, the temperature range depends on the steel and how it was heat treated. For example, the current crop of super steels such as M390, S90V, Elmax, and even 440C, ATS-34, 154CM and many others have both a low and high tempering range. The low range is around 400 F, give or take, while the high range is just under 1000 F give or take. You get different properties depending on which one is used. To ruin, or effect the heat treatment, you have to exceed the tempering temperature used. If your knife is CPM M4 tempered at 1000 F, you are going to have a hard time doing anything to it heat wise, with the exception of power sharpening and overheating the edge. If you're using O1 with a 375 F temper, it pays to be a little more careful, though nothing you can do with heat from a sunny day will do it.
 
Why would you do that anyways? It takes only a few minutes to find a branch & make a notch for lifting pots & such. It can get to 120* straight temp in death valley, multiply that through glass or sitting in direct sun for a while, it can get pretty hot. How hot, IDK. I live in Buffalo & have watched people fry eggs in a pan on the dash of a car in summer. It gets MUCH hotter in DV.
 
Forget the fire poker example folks.

Stick to the hot car in Arizona or Death Valley where people can fry eggs on sidewalks. Will that ruin heat treat?
 
wacki said:
Forget the fire poker example folks.

Stick to the hot car in Arizona or Death Valley where people can fry eggs on sidewalks. Will that ruin heat treat?
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Take the temp on the sidewalk, if it's 400°, it will ruin your HT.
 
If the inside of your car is 400 degrees, I'd be more worried about things other than the heat treatment of my knife.
 
400°
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This is what I was looking for. 400° is what the forum views as the lowest temperature that will impact heat treatment. Now I'm curious as to why this is the lowest temp as it's far below the melting points of Chromium, Iron and all the other components.
 
wacki said:
This is what I was looking for. 400° is what the forum views as the lowest temperature that will impact heat treatment. Now I'm curious as to why this is the lowest temp as it's far below the melting points of Chromium, Iron and all the other components.
Click to expand...

What the forum views and what is reality are sometimes different.

You're original question was what is the lowest temperature that will affect the heat treatment. Knife steels aren't heat treated using temperatures that are near the melting points of the blade. Hardening/heat treating steel doesn't take anywhere near that much heat.
 
Cynic2701 said:
If the inside of your car is 400 degrees, I'd be more worried about things other than the heat treatment of my knife.
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Absolutely. Water boils at 212 F and nobody is poaching eggs on their car dashboard.

Your blood would be boiling in 400 F and not because you were mad over losing a few RC points on your favorite knife.
 
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