Smallshop
KNIFE MAKER
The most detailed info I could find on heat treating 5160 was from Ed Caffrey on another forum 13 yrs ago:
(Thank you Mr. Caffrey! I appreciate this kind of detail and the analysis you did to prove your reason for multiple quench.)
"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."
I know this was a while ago. Have any of you also used this method? Mr Caffrey, if you happen across this, have you modified this technique any? It sounds well worth the extra work. Would you use the same oil for all three quenchs? And if so, which would be best for 5160.
Thanks for any input from you experienced heat treat/knife making guys. I'm thinking of playing with this to learn my new furnace (if it ever arrives....) It's fairly cheap to buy and while the triple quench is more work I think perhaps more forgiving if I'm off a bit on something. (time/temp/quench motion/etc)
I do have a Rockwell tester so I can at least test for final hardness.
(Thank you Mr. Caffrey! I appreciate this kind of detail and the analysis you did to prove your reason for multiple quench.)
"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."
I know this was a while ago. Have any of you also used this method? Mr Caffrey, if you happen across this, have you modified this technique any? It sounds well worth the extra work. Would you use the same oil for all three quenchs? And if so, which would be best for 5160.
Thanks for any input from you experienced heat treat/knife making guys. I'm thinking of playing with this to learn my new furnace (if it ever arrives....) It's fairly cheap to buy and while the triple quench is more work I think perhaps more forgiving if I'm off a bit on something. (time/temp/quench motion/etc)
I do have a Rockwell tester so I can at least test for final hardness.