How hot does it have to be to effect the heat treatment on a knife?

B

Bopleo

Joined
May 31, 2004
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I have a older cold steal master hunter that had a rainbow hue after washing with hot water. The water came from the tap so it wasn't to hot, but it was hot enough to prevent touching it.
 
oil or some kind of oxidation. you'd need about twice the boiling temp of water to mess with the temper, unless it's stainless, then maybe closer to five times. Depends on the alloy.
 
You have to be kidding. A liquid will never get any hotter than its boiling point. With water, I can't think of any way that the temperature could possibly affect the properties of steel. Any discoloring or rainbow hues would almost certainly be a chemical reaction.
 
popcornpicker said:
You have to be kidding. A liquid will never get any hotter than its boiling point. With water, I can't think of any way that the temperature could possibly affect the properties of steel. Any discoloring or rainbow hues would almost certainly be a chemical reaction.
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Yup, when water hits 100degrees c, it turns to vapour, when it's too hot too touch, then you MIGHT have affected the ht.
 
Roger999 said:
Yup, when water hits 100degrees c, it turns to vapour, when it's too hot too touch, then you MIGHT have affected the ht.
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Rule of thumb for "too hot to touch" with bare hands is ~140F. Not even close to affecting the heat treat.

If he pulled it out of liquid water, no way is it going to affect the heat treat.
 
(Obligatory comment about liquids exceeding their [atmospheric] boiling point in closed containers, due to the boiling point increasing with pressure.)
 
Obligatory comment not applicable to the described scenario. "water from the tap".
 
I'm thinking that to change the basic temper or any other significant property of steel has to be over 600 degrees F. I think red hot is about 1200 or more and then there are many hardening processes. Personally, my advice would be to use what you have.
 
The answer is that the hot water thinned the oil on the blade. A very thin film of oil will produce rainbow-like colorations.

Your steel is fine. For all but a handful of exotic heat treatments, the final temperature, the temperature you'd have to exceed to alter the heat treatment, is at least 400F, about twice the boiling temperature of water.

Contrary to popular myth, knives can not have their temper damages by leaving them on the dashboard of a car on a hot day. A hair dryer is perfectly safe to dry out a knife.
 
It's just light oxidation. Same as what happens when you cut acidic foods with carbon steel blades, lovely shades of pinks blues and yellows.

edit: FYI boiling hot tap water can actually be fairly corrosive. One day I had the bright idea of cleaning folder pivots by soaking them in a cup of boiling hot water. No problems with the stainless steels, though it did give them a bit of a rainbow hue. Well just for kicks I put a small carbon steel fixed blade that I had previously cleaned with soapy water (no oil for protection) and it instantly started forming a chalky oxided surface.

Your master hunter is probably Carbon V(simple carbon steel alloy), they made some stainless ones too but these were the most prevalent. Tempering for basic carbon steels starts around 325F, and to my knowlege temper of a fully heat treated knife is not affected unless you go above the temp the factory tempered at, which likely around 400F.
 
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Thanks for the replies. I just wanted to be sure so i thought i would ask.

Thanks again
 
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