A scientific approach to assess the effect of direct sunlight on INFI heat treatment

Al-Sheikh

Al-Sheikh

Joined
Aug 22, 2010
Messages
867
Object of investigation:

Can direct sunlight corrupt the INFI heat treatment?


Related observation:

At 80 degrees Fahrenheit air temperature, minimum wind chill and about 50% relative humidity, a black painted car hood develops a surface temperature of approximately 160 degrees Fahrenheit.


Practical relevance:

I don't feel comfortable exposing a black or jungle green coated INFI blade to direct sunlight during our infamous Saudi summer when air temperatures reach up to 120 degrees Fahrenheit. I hope someone can scientifically assess if my worries are reasonable or not.



And now, all you scientists, shoot! :)
 
IIRC, Jerry has stated that one must heat INFI to ~900F to have any affect on the steel's properties. It strikes me as rather unlikely thay your blade could absorb enough solar radiation to approach thoses temps.


And I am a scientist. ;)
 
900F :eek:

I read so many remarks about belt sanding, that the blade "should not get warm to the touch". So I started treating my knives accordingly (put some distance between knife and camp fire, out of the sun on crazy hot days,...). But 900F literally means right into hell and back without problems. Very re-assuring :D :thumbup:
 
Al, look up phase diagrams for a few different steels. I think you'll find that 120 F will not effect much.
 
I've used mine as a fire poker, a rock chopper and a stake to keep beverages cold in the river. I think emotionally that it feels more manly now, especially since I get a rush of testosterone when I use it. The elements have not hurt my INFI in the slightest degree.
 
120F will barely heat your kydex:D

I bet INFI would need to be so hot, that the paint would would burn off first, before you could start to ruin the heat treat.

I think I saw 900F - 1200F:eek: would do it:)
Al
 
Dear scientist,

let's treat this ridiculous subject with a little bit more precision. We are on the way to the Nobel prize here. I can feel it. Therefore...

Do not mix up air temperature with surface temperature. If I extrapolate the insufficient data I found, the surface temperature of a black coated INFI blade could easily be around 240F when put in direct sunlight in the very heat of a Saudi desert summer day. This is enough to burn flesh or fry an egg. These numbers are in line with the impression I developed in extensive field testing: it's getting hot, hot hot!

Isn't there a formular like "CGFBM + B - 11 = Chopper SET" to calculate the surface temperature under given circumstances?
 
if you leave the knife on your hood/dash, you'll warp your kydex into a floppy mess but the knife will be fine. Dashboards can get to 180 degree's (and higher), and your knife will feel seering hot at that point, but it will be fine. The 'warm to the touch' comments are meant more as an assurance that theres no way the knife got near the heat necessary to affect it's temper, not that that 'warm to the touch' would be enough.

Grinders can however get your knife above the 900-1,100 degree temper limit for INFI. You can get your edge above cherry red in a couple of seconds if you just push down into the grinding or buffing wheel, the longer your hold it, the hotter it gets.

http://www.bladeforums.com/forums/s...Mistress?p=1072742&highlight=1050#post1072742
Jerry Busse said:
It is difficult, at best, to ascertain the condition of your knife without seeing it in person. If you would like to send it to the shop, we will gladly give it a once over. You may have stumbled onto a great buy as we have sold most of the Collector Grade BMs under the serial #50 for $900.00 - $1200.00. The collector grade sold out almost immediately with only 500 being produced. We are currently sending out the last of the breed.

As for INFI and temperature extremes, it is amazing. INFI is tempered at nearly 950 degrees. It does not begin to lose any significant hardness until it is held above 1050 degrees for a considerable amount of time. I have to believe that it would need to be extremely mishandled in order to do any noticeable damage.

Most of the simpler high carbon steels (of which INFI is NOT a member) can be drawn down in temper in a matter of seconds if the temperature hits above 500 - 800 degrees. Along the thin edge of a knife, a buffer or dremel can produce this level of heat and can cause serious damage if not executed by a professional. Always check the grade of steel and heat-treat specs. before assassinating it with the dremel tool Uncle Leo gave you for Christmas. Always keep the steel cool to the touch and you should be fine.

As far as INFI is concerned, care for and feed it like a friend. If the blade does get warm pour beer over it to cool it down. Stories out of Africa indicate that “Beer Tempering” only increases the performance of the steel. Is this true? I question nothing I hear from our friends in Africa.

Jerry Busse



[This message has been edited by Jerry Busse (edited 03-06-2000).]
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Al-Sheikh said:
Dear scientist,

let's treat this ridiculous subject with a little bit more precision. We are on the way to the Nobel prize here. I can feel it. Therefore...

Do not mix up air temperature with surface temperature. If I extrapolate the insufficient data I found, the surface temperature of a black coated INFI blade could easily be around 240F when put in direct sunlight in the very heat of a Saudi desert summer day. This is enough to burn flesh or fry an egg. These numbers are in line with the impression I developed in extensive field testing: it's getting hot, hot hot!

Isn't there a formular like "CGFBM + B - 11 = Chopper SET" to calculate the surface temperature under given circumstances?
Click to expand...


You won't get the knife past 400 degree's without having a heating element present near it. Be that an oven, an oxy-acetylene torch, hot lava, or surface friction heat from a grinder - you certainly won't get it past 900.
 
All of the warnings for belt sanding come from people that don't want to suggest it to others without some sort of disclaimer. It would be wrong to tell someone to just have at it. Like LVC said it is easy to overheat, especially with worn high grit belts and a buffer.

So, its better off to suggest keeping the blade as cool as possible by whatever means possible. If you have your fingers on the back side of the edge when the belt or buffer passes by and it doesn't even approach warm, well, you don't have much to worry about.

And people worry about the very thin extreme edge when using buffers and grinders. This is the area that will heat up the quickest and you may not even feel.

Not a scientist :p
 
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the reason with the "belt sander and handwarm" is in the different thinckness of the material.
the edge where there is not all too much mass will heat up way quicker and to higher degrees then the blades body. Hence when the body is hand warm the edge is much hotter and running the risk of ruining the temper - in that area( not the entire blade). The "dont let it get more then hand warm" is a gross simplification to allow users without heat sensitive cameras or laser thermometers to get a feel for the amount of heat (energy) stored in the blade.
 
Just to add to what LVC, resinguy and others have already said...

I've accidentally taken an edge to red hot on a belt grinder, just held it in one spot for a little too long (seconds). In that instance, the blade was hot to the touch a half inch behind the edge, but not so hot you couldn't hold it. Obviously, the heat treat at the edge may have been compromised.

As to guaging surface temps from other kinds of heat, the most obvious guage to me is the flash point of paper which burns at 451F. If paper won't burn or scorch from contact with a surface, obviously the surface is not hot enough to pose a threat to heat treat for INFI--although I understand other heat treatment/steels may be affected at temps of 400F or above.
 
I don't know why everyone's only looking at the temperature of direct sunlight. I'm sure the UV rays and all would give the INFI a nice dose of vitamin D, making it even stronger. Also, I have no clue how things work :)
 
All right Gentlemen, I take the belt sander. Order in the plenum! :p

I am more than happy to derive scientific findings according to democratic principles. So when the majority says "it's not getting hot enough no matter how much the sun fries your brains", who am I to contradict :) But something else makes me worry now: How fast can I baton a NMFBM through different materials (say: bamboo, tropical hardwood and concrete) without causing the friction to heat the steel to 1,000F and more? Any idea :confused: Results accepted in mph and m/s :D
 
Pardon my academic terminology but your vocabulary is far too in dubious for my comprehension, so can you please endeavor to articulate this matter more distinctly.:D


Al-Sheikh said:
All right Gentlemen, I take the belt sander. Order in the plenum! :p

I am more than happy to derive scientific findings according to democratic principles. So when the majority says "it's not getting hot enough no matter how much the sun fries your brains", who am I to contradict :) But something else makes me worry now: How fast can I baton a NMFBM through different materials (say: bamboo, tropical hardwood and concrete) without causing the friction to heat the steel to 1,000F and more? Any idea :confused: Results accepted in mph and m/s :D
Click to expand...
 
Just thrust the blade through a piece of paper after every few whacks. If it catches fire, slow down. :D
 
This is interesting information. I can't help but ask, what the limits are for SR 101 since I own both.
 
azwelke said:
Pardon my academic terminology but your vocabulary is far too in dubious for my comprehension, so can you please endeavor to articulate this matter more distinctly.:D
Click to expand...

After reading my post once more I have to admit that only Wills reply makes me understand what I was trying to say.

Will York said:
Just thrust the blade through a piece of paper after every few whacks. If it catches fire, slow down. :D
Click to expand...

Brilliant :thumbup: I'll put it to the test!
 
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