how do I heat treat file steel to 60-62 hrc?

DeadboxHero

DeadboxHero

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Mar 22, 2014
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Howdy.

I want to make puuko style knives with high scandi zero grinds using old USA made files. What are some tips to get the steel hardened? Right now I'm using peanut oil to quench and a household oven at 475F for 120 minutes, then cool to room temp. to temper.

Does the type of oil change the quench?
How long should I temper less?
Duel quenching?
Quench with Ice water?

I'm lost.

Any book recommendations are appreciate d

Thanks,
Shawn
 
What heat source are you using, and do you have temp control prior to the quench?

Yes, the oil absolutely changes the quench. Peanut is a decent place to start... better than motor oil, etc.

I typically do two 60 minute cycles of tempering. Unless you're accidentally getting the austentizing temp and quench speed just right, 475 is too high of a temper to hit 60 RC. Try 400 on the first cycle, 425 on the second. I assume you don't have a hardness tester?

If you want your nice one-piece knife to become two or more pieces, go ahead and quench with ice water. Recipe for disaster.

Plenty more to this topic than I gave you... just wanted to answer your questions directly. In the stickies, or in the count's reply, there are some instructions on file knives. Google it.... you can use site:bladeforums.com in the google bar after your search terms to limit your search to only these forums.
 
Jason is correct....it would be nice to know what your heat source is. Also would be nice to know how you annealed that file in order to work on it.

If you have controlled heat source with a readout, 1475F or thereabouts with a 10 or 15 minutes soak is highly recommended. File steel, if old Nicholson, should be either 1095, W1, or W2, requiring a fast quench medium. Quench in 130F peanut or canola oil if you don't have a fast commercial oil. If you want to take the risk on a water quench, don't use ice water. Use a brine solution at room temp. No need to do multiple quenches. File steel is already very fine grain.

If you don't have controlled heat source and are using forge to heat treat, then judging temperature becomes necessary. You can use a magnet to judge the temp. The magnet will stop sticking to the steel at around 1414F. You still need to be about 80F hotter.....so you'll need to judge by eye "another shade of red hotter". Then you will be close to the 1500F mark. If there is a way that you can cycle the blade in and out of the heat, in order to keep it right at 1500F, then try to do that for 10 minutes or so.....this will help the excess carbon come into solution. If you don't cycle, but simply quench as soon as you reach 1475-1500F, you'll have a blade like 1080 or so. But file steel usually has more carbon.....so if you can "soak" at temp, it helps add that extra carbon. Trying not to get too technical here.

Temper times should be, IMVHO, one hour minimum. Two cycles minimum. No need for more than three. If you are able to achieve max hardness out of the quench, as in 66-67 or so, then in order to hit 62HRC I would go with 375F and see where you are at. Maybe 420F for 60HRC. Just a guesstimate.
 
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Wow guys great advice thank you.

My heating methods are crude.
I use a MAP as torch and feather the steel with the flame while to file rests on a refactory brick. I use another brick and a oven MIT to make a lean to and trap more heat.
I anneal the steel this way too by heating it to a cherry red/ dull orange and letting it cool in the oven for 3 hours at 475 F then cool to room temp. I then check the steel with a bastard file to see if its soft.

I'd invest in a better set up but cash is at a premium and I live in a apartment.

I know I could use a magnet to double check if I'm at the right heat but seems redundant.

Peanut oil is more expensive and has a higher flash point,does it make a difference for the quench?

Again appreciate the information.

Shawn
 
Using a magnet to test the steel is not redundant. You have no other objective means of checking the temperature of your steel.

With your primitive heat treat setup I wouldn't worry about hitting an actual hrc number. I would worry more about the performance of the blade. Start your temper at 350, then test the edge. If it chips too much, then bump the temper up a bit. Continue this until you have satisfactory results.
 
Shane is correct. The magnet is your best bet to get it close, and you'll have to just walk the temper temp up and see how the edge works. You can make a usable knife with that method, but don't expect super high performance unless you just get lucky.
 
There is another method besides the magnet that I had typed, and then deleted. Magnet works really well, but so does DECALESCENCE. Once the steel passes thru it's critical temperature, you will notice a shadow dancing across the blade. Sort of hard to see if the knife is in the oven/forge, but it is a method used quite extensively to judge actual critical temp for that given steel.
 
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