Hi Ed,
A smith here in Arizona told me you were quenching and waiting for 24 hours before quenching again. I missed that thread. Could you point me to the info. Or if it hasn't been discussed lately could you explain why you do this? I always heard you were suppose to temper immediately after the quench. Not that I do what Im told but thats just what I always heard and have been doing.

Hi Tim!

Well........ Over the years of experimenting I have found that steels that contain a SMALL percentage of Chromium will benifit in two ways from doing a multiple quench, and allowing the blade to cool down in the oil (completely) between quenches.
The first is obvious, three quenches ensures that the steel is completely converted. The second, and what I believe is the greatest benifit is the reduction in grain size that is achieved by allowing the blade to cool down in the oil between quenches.
A few years back I did some experiments where I quenched four blades of 5160. I quenched the first blade once, the second one twice, and so on. Once each blade was quenched I never took it out of the oil. I simply set it on edge in the bottom of the tank, and allowed to cool down with the oil. (which took overnight). I continued the process until the final blade had received it's fourth quench. I then tempered each at 350F for three two hour cycles, allowing each to cool to room temp between quenches. Once all the blades were done, I sent them to be spectrographed. As a base line I also sent a blade of 5160 that had been single quenched, and then immediatly tempered (not allowed to cool in the oil)
The results made a believer out of me. Each blade, 1 through 3, had successivley smaller grain size, the blade that had been quenched four times had the same grain size as #2. The final result was that the grain size in the blade that had been quenched three times, and allowed to cool in the oil was .79 microns, as compared to the single quenched blade, which had a grain size of 1.91 microns.
The only thing that was done differently was allowing the blades to cool down in the oil between quenches.
Afterwards I made a few more blades to destroy, using the same basis and found that the blades that are cooled int he oil between quenches usually display approx. 15% more cutting ability, and much more durability. If you add a sub zero quench to that, cutting increases another 5-10%! That may not sound like much to some, but it's a pretty dramatic increase. I still have one of those blades hanging in the shop. It has been through the ABS tests 18 times, including the 90 degree bend, and the edge has not yet cracked.
Don't get me wrong, everything has to be done correctly up to the quenching point to achieve what I've talked about. But with proper handling including, forging, normalizing, annelling, and then heat treat, it is very doable.

Hopefully this will explain why I do what I do. If you have any comments or questions, throw them out there, and we can figure them out together!

Wow. 5160 seems to respond everytime you get more thorough. Each and every time you take a step deeper it reacts favorably. I will definately try the 24 hour quench next time and test the blade out to see if I can feel a difference. Thanks!

While Im on this train of thought I would like to pick your brain on some more heat treating questions. When I normalize I take the blade down to room temperature like most. Then, in some what of the same thinking as your 24 hour quench, I then take the blade and put it in the slack tub to cool it further.Probably only cooling it another 20 or 30 degrees. I have to admit I have never tested the blades with a spectrometer like you have and I cant feel any real difference in the final edge but I do it for thoroughness. There's no real heat left in the blade before it goes into the water so do you think Im just goofing off? Or is this the kind of thoroughness we should be looking at within each step? I guess you could even cryogenic after everything and probably get positive responses from the steel. The heat treatment already is taking me longer than any other part and Im very slow at the other parts. :)

Hi Ed, am I reading this correctly? You quench 5160 3 times with 24 hours between quenches?

ghostdog

Tim,
Never tried that method! Might be worth looking into, ya never know.
You hit the nail on the head when you mentioned throughness IN EACH STEP. That is the key to advancing performance. What I try to do is evaluate each step int he process. Sorta like, if this does this........then maybe this will do this. I started witht he basic anneal, quench, temper, and then just started experimenting with things to see the result. Many were useless, but some were not. I really do think that things work differently, for different bladesmiths, in their given shop/enviroment, hence the experimenting to see what works best.

Ghostdog,
Yep, you read it right. I triple quench 5160 AND 52100, letting it cool overnight between quenches. Takes about 6 days to heat treat a blade, but it's worth the time an effort!

How did you find a spectrogragh service? Is there an outfit you would reccommend or should I just look locally?

I would suggest locally. The fella that does it for me is a teacher at the local college, and does it for me when he can get the use of the schools equipment. He charges me according to his hours. I have only had one commercial outfit do a spectrograph for me, and it was $65 per sample! That can get spendy if your comparing several different blades.

Thanks Ed.

ghostdog

Yeah, thanks Ed!

This thread, the 1095 thread and the soft backed draw thread have all been extremely helpful. However I am left with a confusion, I could not find what I needed tracing the threads backwards, and the search function did not turn up the information.

I have been using the soft back draw, and can see some advantages. However there are strong arguments for edge quenching and it is time for me to try this. My question Ed (and I know you've answered it 20,000times) has to do with drawing the temper in the oven: do you do this as the final step after the edge quench? Will Brownell tough quench work for 5160 small blades, and, for blades under 4 inches is 375 F for 2 hours about right?

Thanks for your patience. I'll have all this basic stuff sorted out in another 10 years.