what method do you use?

R

Riced

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Aug 19, 2003
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I am curious as to the different methods some of you use to differentially heat treat your blades. I am currently forging 5160 and some 1084 I have left. I realize there are endless variables as to steel types, blade usage and so on. I am trying to get an idea from those who have gone before as to heat treat methods you prefer: edge quench, full quench with draw on spine, etc.. What do you think of a rapid full quench (in and out quickly to get past the nose of the curve on the TTT)?
I hope this question does not incite any religious wars.
I am just very curious as to what you all do.
Thanks
 
This is going to be another very interesting thread to watch from day to day, and from day to day and ....

I love these type questions.

RL
 
I hears ya Kit :) Lots of good learn'n com'n up.

I'm not maken light. I MEAN IT. I love this kind of topic.
 
OK, I'll be the first one to put/stick my neck out, and voice my opinions......:p

I am a advocate of edge quenching. It allows me to have a greater degree of control as to how the finished blade with perform. By varying the quench depth, I can control the amount of flex and toughness the blade with exhibit. (This type of quench is the one I use on "straight" steel blades).
I utilize the full quenching method for my damascus blades, if for no other reason than to ensure the patterns are smooth and even in the finished product. The flexibility and toughness aspect for damascus blades are handled through the tempering cycles. But even paying close attention to tempering will not give as much control as the edge quenching method.
At one time I advocated the soft back drawing method......but not any more. IF done correctly it will produce a blade that will pass all the ABS cutting/bending tests, but after considerable research, I've found that most people are in too big of a hurry to perform it correctly. Most folks want to hurry the soft back draw process along, and in doing so only manage to temper a thin layer on the exterior of the blade......some do greater damage by not allowing the blade to cool naturally.....they take a blade that has a nice blue back on it, and cool it in water! BAD MOVE! Even though this blade may be able to flex to 90 degrees once, it will quickly fail due to the grain structure within, that was induced by the water cooling. To be done correctly, the soft back draw should be done with the edge of the blade in water or oil, and the spine of a 3-4" bladed hunter should take 20-40 mins to reach the "spring" color. This all goes back to Time/Temp, for which there is no shortcut. Thermal cycles will make or break a blade......if it takes 2-3 hours of soaking to properly temper a blade in an oven, then how can 5-10 mins of intense heat accomplish the same thing?

There has, and always will be controversy over the triple quench. But I use it, and belive it is the best method for getting the most out of 5160 and 52100. Although there are many theories out there as to why it works, I'll not explore those here, I'll only say that it works for me, and I will continue using it until I find something better.
 
Excellent points about the soft back draw method.Tempering to color doesn't work, it takes time also.
 
Caffrey is my mentor on this subject as he was the Master that gave me my performance test. He knows what he speaks. I have had good results with this method although it varies from his somewhat: forge the blade to shape, normalize at least 3 times reducing the temp each time arriving at 1600F (just above nonmagnetic) on the 3rd or 4th thermal cycle. These thermal cycles will reduce the grain size and rduce internal stesses from forging. Next comes annealing. I heat it to 1325F and hold for 40 minutes and let the oven shut off cooling slowly overnight. Rough grind the bevels and drill any holes needed. Heat the edge with a torch or forge. Do this in the dark if possible so the colors can be read easily. Use a magnet often to check for nonmagnetic. The tip can get overheated too easy and grow grain therefore making the tip break very easily when the knife is done. Take your time and be sure it reaches nonmagnetic and quench the edge in warm 135F oil. Let it simmer, smoke and turn black before dunking the entire knife. Let it stay in the oil until cool enough to handle. If You are useing 52100 Do this 3 times. Test with a file and/or grind the bevels clean and dip in ferric cloride to see the temper-line. It should show up very even and consistant in color (dark) If it looks good temper the blade in the oven for 1 hour at 330F 3 times letting the blade cool in between. grind a temperary edge and do a brass rod test. If the edge chips retemper at 20F higher and retest. When it passes the test finish the blade.
 
I do my forging in a small peanut can forge (the little brother of a little coffee can forge). I could say it's because it allows me greater degree of control on which section of blade I heat to hammer it, but reality is I had that available and did my experiment with that. It works fine but I'll have to build a coffee can or larger.
I do my HT in a one brick forge with an oval sectioned cavity with two Rohtenberger #12 burners set at a tangent to the cavity so to get best possible heat uniformity.
After forging I triple normalize my blades. This to make sure no residue stress from forging remains. I check each heat to see if some bend developes in the blade. If it does I correct it and anneal again until I get no bends for two subsequent heats.
I made three knives with very slender and long blades so warping IS an issue.
After that I heat to non mag (with enough soak time to ensure evenness of temp also in the blade depth) and I quench vertically in warm (about 40°C) 15W40 oil, clean the blade, grind off the scale and temper it to light brown (on this thin blades, I do straw on thicker ones).
I do the cleaning and tempering process twice.
I then put the edge in water and torch the spine to blue / blue-gray up to 1/3rd of blade height.
BTW: both the forge temper to color and draw require a LOT of time, like Ed said. Especially the forge heating has to be very, very slow and even or
1) You'll get the blade there but won't be really tempered.
2) You'll overshoot the temp you want to reach and you'll get the thin edge to blue when the spine has yet to heat properly.

Same for the spine heating with edge in water. Do it quickly and it will be just superficial and, even worst, if it's not even you'll induce stresses in the blade instead of relieving them.
 
Gee....nothing is sacred anymore. Well I'll stick my foot in my mouth too.:footinmou

For 5160 and other types of good steel (unshiney stuff)

Normalize several times. I do lots of things like putting in the freezer and war dances and such but IMHO several normalizing cycles are a must.

Get a large pan of CRISCO at room temperature.

Bring the blade to critical and edge quench in the Crisco.

Do this 2 more times (total of 3)Going a little deeper in the now liquid and hot crisco each time.

When making the quench make sure to leave the blade in it for at least 5 minutes for the first time, 30 minutes the second and two hours the last.

After all that you can put it in the freezer while doing the war dance!:footinmou

Oh...almost forgot, temper in your toaster oven for at least two cycles of two hours each cycle.
 
It sounds like some common denominators are proper normalizing (three times), not overheating prior to quench, and/or a long temper if drawing on the spine.
One question however, what does the freezer do? I do not know but can only speculate it has something to do with the martensite finish temperature. If I am close on this, should all steels (I'm using 5160 and 1084) receive the same treatment??
I also recently read Japanese swordsmiths would kill each other if their heat treating secrets were revealed. I am now living in witness protection for starting this thread. Sorry.
 
Finally - something I can butt in on ;). The freezer is a reference to cryogenic treatment. Deep freezing the steel transforms retained austenite to un-tempered martensite. Tempering needs to be done after cryogenic treatment. Some swear a household freezer helps to do this. I have not done enough testing on that to convince myself it does but do have my thoughts and will not go there here except to say I believe anything below normal temperatures but higher than cryogenic is probably minimally beneficial with time.

RL
 
Rodger is right as usual. The "freezer " was thrown in with the war dance for a reason. With simple carbon steels, cryo treatment does not have nearly as much benefit as with the more complex stuff. One knife maker that I very much respect once told me that knives he forged in the winter held a better edge so he put everything in the home freezer for a temper cycle now. I do the same thing and in my mind it does help. I'm not certain about the real world though.

For the time being, I suggest you skip any cryo treatments to edge quenched steel and work on getting a good edge quench.
 
Peter, I can't argue with it and in fact really do want to do some testing myself using my deep freezer at my lady's house. But for this thread I will take your good advise and leave this for another day and thread.

RL
 
About the freezer, I put once my freezer on "super" and it freezed solid a bottle of vodka in it. I mean a full liter of red Absolut vodka, which is 50% pure ethilene. How cold did it get? I think something like 30 °C under to freeze half pure ethilene.
 
so this "cryo" in the home freezer... is done after hardening but before the tempering process?? and how long should it "soak" in the freeze?
 
Forget cryo for anything but complex steels like the tool steels and stainless steel.5160 won't have any retained austenite . 12 hours should be enough to do the job.A freezer will get you about 0 F, dry ice about -100 F and liquid nitrogen about -300 F. A snap temper of 350 F will transform some martensite to reduce the chance of cracking when frozen.
 
Forget cryo for anything but complex steels
Click to expand...

FWIW, the heattreat place I've used says, "D2 doesn't need cryo if it's treated properly. Won't do you any good." Evidently even since it's an air hardened steel, it still isn't 'complex'.

Steve
 
I use the "Danbo" method of paying an expert to forge, heat treat and complete the knife for me. :D
 
If by method we mean the logic of scientific procedure, or, the conceptual structure of analytical investigation, the preponderant weight of distinguished thought on the subject warns us of the slight gains to be derived from talking about method in general or from evaluating the belief postulates of conflicting logical or philosophical schools.





:D


I had a professor spill that crap on a class I had in college many years ago, and I thought it was so cool I would memorize it and use it whenever time and opportunity presented itself.
enjoy.
 
Originally posted by Sando
FWIW, the heattreat place I've used says, "D2 doesn't need cryo if it's treated properly. Won't do you any good." Evidently even since it's an air hardened steel, it still isn't 'complex'.

Steve
Click to expand...

cryo is being used on plastic and cast-iron too.
so it must have some benefit, for the big companies to spend the money on it..
 
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