Heat Treat 5160

R

rookie

Joined
Jan 16, 2000
Messages
60
I know it is an oil quench steel what is the critical temp. how long do you hold before quench?Is it possible to heat in a kiln to temp then quench?one last question, I've always heardtou can't heat treat steel with oxy/acetylene torch,some thing about not enough oxygen or something to that effect,FACT OR FICTION?

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Shane ------------------- If you don't have time to do it right the first time, When do you think you'll have time to fix it!!!
 
I put my 5160 blades in a stainless steel foil envelope and put them on a rack in the kiln. After the temperature comes up to between 1525°F and 1550°F I hold them at that for half an hour. Then I take them out and cut the end of the envelope and let the knife drop out into a can of olive oil to quench. Then wash them off and temper them.
 
Yes you can heat treat 5160 with a torch. Use a small tip and play the flame evenly on the edge portion until it is nonmagnetic, quench in warm oil (125 degrees) and temper 2 hours at 350 degrees. This gives a nice temper line also. Bruce
 


Fall, why the stainless envelope? Is it just to cut back on fire scale, otherwise I can't see a purpose.

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KSwinamer

Atheism....A non-prophet organization
 
5160, like 52100 is at it's best when multiple quenched, with only 1/3-1/2 of the blades width being hardened.(edge quenched). I recommend ZERO soak time for these steels. Neither contain elements that require soak time for the steel to attain solution. Soaking will increase the grain size, resulting in a weaker internal matrix.
So, what I recommend is:
Multiple quench, from 1550. Allow the blade to cool in the quench to room temp, and repeat for a total of 3 times. Temper at 350 for 2 hr. (do this three times, allowing the blade to cool to room temp between cycles)
If you have Liquid Nirtogen available, you may use it at this point. About 6 hours in the Ni will work. The Ni completes the martensite transformation. Afterwards, allow the blade to warm up slowly, and then re-temper at 25 degrees hight than the previous tempering cycles.
It sounds like a lot, but the resulting performance is well worth the effort.

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com

[This message has been edited by Ed Caffrey (edited 03-29-2000).]
 
Ed, I,m a little confused !when you multiple quench the blade your medium needs to be 150 deg.,after heating the blade and quenching do you let the oil and the blade cool to room temp. ?and how many times?and heating it with a torch will suffice?do you bother with the tang or is that taken care of during the temper?thanks ahead of time!!!

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Shane ------------------- If you don't have time to do it right the first time, When do you think you'll have time to fix it!!!
 
rookie,
The oil is pre-heated to 130-160, the only portion of the blade that is brought to critical temp is the edge section (1/3-1/2 of the blades witdth as viewed edge to spine)
The torch works great, just don't get in a hurry. By this I mean use a "soft" flame (one wheret he torch is not hissing loudly)
A magnet is the best indicator of critical temp there is. It never needs calibrating, and it will not give you incorrect readings. When the steel is no longer attracted to the magnet your ready to quench.
As to the cool down, leave the blade in the oil, and let them cool down together. This has the effect of helping to maintain/decrease the grain size (almost like annealing it again) I preform this operation 3 times, allowing the blade to cool overnight in the oil between the quenches. It is time consuming, the entire heat treat cycle that I use takes 5-6 days depending depending on whether or not the sub-zero quench is employed.
This, combined with the proper blade geometry makes for a high performace package. Edges can be expected to be Rc 57-59, with the spine being Rc 38-40.
Your objective is NOT to get the spine or the tang even up to critical temp. 5160/52100 have a tendency to mildly air harden, even when the temp is kept below critical. What I seek is a blade with a hard edge, soft back, and a dead soft tang.
Take Care,

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
 
Ed - is there a reason why you could not - or would not use the liquid nitrogen before tempering? What would be the result if you did the cryo treatment right after hardening and then tempered three times?

 
Another Question - how effective would dry ice be (-109F) instead of liquid nitrogen.

Is an overnight soak in dry ice worth the trouble? Can I expect a measurable amount of improved performance?
 
Dry ice alone would just harden in select spots, where the ice is touching the blade. The reccomendation that I've got from Hrisoulas is to use a solution of dry ice in acetone for full immersion. I honestly don't know if that's cold enough, but I'm going to try it on my next batch of heat treatings. I'm interested in what Ed has to say on the matter, though.

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Oz

Now, what other news did I have? Oh yes, IT'S A GIRL!!!
See her and my latest blades @
http://www.freespeech.org/oz/
 
Here's a question concerning heating the quenching oil. The directions to Brownells Tough Quench Oil says NOT to heat the oil but to use it at room temperature.
What would be best for a knife blade. Heated Tough Quench oil, or room temperature Tough Quench oil?
 
thanks Ed!, i'm going to try my first comeplete knife from start to finish by myself . I've allready got the blade ready for heat treat and the rest is just waiting!! allthough Iam really curios about the dry ice thing though ?

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Shane ------------------- If you don't have time to do it right the first time, When do you think you'll have time to fix it!!!
 
The sub-zero quench can be done after hardening, but I have had some minor instances of blades developing very fine cracks, that I believed were caused by the stress from going straight into the sub-zero quench before tempering. When I switched to doing the sub-zero portion after tempering, the cracks never occurred again. I had to add the step of another tempering cycle, but eliminating the cracks were worth it to me.
The dry ice/acetone mix will achieve a temp of -70. There may be some fluctuation to that depending on the atmospheric temp, but not enough to matter. You will get a minor transformation at that temp, but it is likely not enough that the average person will notice any increase in performance. I don't have the exact temp off the top of my head, but if I remember correctly, the total transformation occurred once I got past the -250 range. I'm sure that soak time has a great deal to do with it, but I would be lying if I gave an exact time frame. In my shop, with the liquid Ni, my best results have come from a soak lasting at least 4 hours, and using the methods/cycles I listed in an earlier post.
The multiple quench is not a "cure-all" for every steel, but it certainly has a strong positive effect on those steels that contain low to medium amounts of Cr, at least up to the 5% range, as these are the only ones I have fully tested to date.

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
 
Ok, so that would be 5160, D2, assorted stainlesses and 52100 in the steels that I can get ahold of. If the dry ice/acetone will give a minor boost in performance, then I'll give it a try, but I'd much rather go with liquid Ni. Where did you get your rig for it, Ed? And how much does it cost? I think I'd like to get set up for it. I don't like the idea of making an inferior blade from the lack of one step.

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Oz

Now, what other news did I have? Oh yes, IT'S A GIRL!!!
See her and my latest blades @
http://www.freespeech.org/oz/
 
Another question about the steps to heat treating 5160. Assuming one were to harden the entire blade, is it best to use a torch to draw back the spine right after hardening and before tempering?
 
Oz,
My dewer tank came to me second hand from a rancher. I paid $350 for it in used condition. Hospitals might be a good source for locating one. Also Horse or cattle breeders. Mine is rather large, it holds 56 lbs of Ni. Most others I've seen used by makers are about 1/2 that size. I do know that a new one that holds 25lbs, is around the $700-$800 range.

Tejas,
Drawing with the torch is an option, as to doing it before or after. That process would be doing the opposite of what the sub-zero is doing. Basically with the sub-zero, your increasing stresses within the steel, when it is done immediatly following hardening. The application of heat would act as a stress reliever. In fact, there are some 5160 blades that I do not sub-zero, and those are tempered to only 350 degrees. At that temp I'm really doing nothing more than stress relieving.
The only caution I would advise when soft back drawing, is that you let the steel cool down on it's own. If your not careful with the heat, and you cool it quickly in water or whatever you use, it does funny things to the matrix structure. Some have held up just fine, but others have failed under the 90 degree flex test, after I got in a hurry and cooled them in water. That's another quirk that I'll get figured out one of these days.

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
 
Some time ago, I treated a 5160 blade by heating it to non-magnetic, then edge only quenched it in a hot brine solution. It was an interrupted quench, otherwise I'm pretty sure I would have snapped it for sure. That seemed to give it full martensitic conversion, but I don't know that I'd do it again because of the risk.

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Oz

Now, what other news did I have? Oh yes, IT'S A GIRL!!!
See her and my latest blades @
http://www.freespeech.org/oz/
 
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