- Joined
- Dec 21, 2006
- Messages
- 3,158
Larrin I have the “carbide refining” article, but if you have another you recommend, please do send it. Samuraistuart@yahoo.com
I do want to reiterate that Kevin has always been adamant about the prior microstructure of 52100 when using the low temp protocol. If the steel was especially “heavily” or “coarse” spheroidize annealed, the low temp hardening was not hot enough and thus resulting in something like 63HRC max post quench. He was the one brought in to figure out how to heat treat Aldo’s 52100 and it turned out that the heavy annealing the 52100 received was the culprit. It required a MUCH higher heat to harden “as received”.
He even mentions on his website when heat treating 52100 to use 1475-1550, but what temp you use is based upon the carbide structure prior to hardening.
My understanding, in my layman way of saying it, after the normalizing (and then cycling), the carbon is now freed from the chromium bond and is now ready to be put into solution. 1475f PLUS the soak puts about .7%-.8% in solution thus resulting in maximum as quenched hardness. If you just used 1475f and NO soak, it would not be enough carbon in solution for maximum post quenched hardness. And if the soak was too long (how long I don’t know) the result would be like using too high of a temp (too much carbon in solution, higher RA, and generally undesirable plate martensite).
I also don’t care to name drop and throw names around, but this particular heat treatment for 52100 has been thoroughly discussed on the “inter webs” for quite some time now, so I am sure Kevin doesn’t mind. It has been cussed and discussed on just about every single knife forum out there.
And for any interested in what many of us are doing in recipe form for 52100:
1. Normalize 1650f (I actually use 1700f and soak for 20 minutes). Air cool only
2. Thermal cycle 3 times 1500f, air cool all 3 cycles or quench on last cycle especially if it’s lower than the hardening temp (I quench from 1440f on last cycle for a martensitic structure rather than pearlite after reading some of Larrins articles)
3. Austenitize 1475f, 10-15 minute soak
4. Quench in 80f Parks 50, ~66-67HRC
5. 2 (or 3) 2 hour tempers 375f, ~63HRC
I do want to reiterate that Kevin has always been adamant about the prior microstructure of 52100 when using the low temp protocol. If the steel was especially “heavily” or “coarse” spheroidize annealed, the low temp hardening was not hot enough and thus resulting in something like 63HRC max post quench. He was the one brought in to figure out how to heat treat Aldo’s 52100 and it turned out that the heavy annealing the 52100 received was the culprit. It required a MUCH higher heat to harden “as received”.
He even mentions on his website when heat treating 52100 to use 1475-1550, but what temp you use is based upon the carbide structure prior to hardening.
My understanding, in my layman way of saying it, after the normalizing (and then cycling), the carbon is now freed from the chromium bond and is now ready to be put into solution. 1475f PLUS the soak puts about .7%-.8% in solution thus resulting in maximum as quenched hardness. If you just used 1475f and NO soak, it would not be enough carbon in solution for maximum post quenched hardness. And if the soak was too long (how long I don’t know) the result would be like using too high of a temp (too much carbon in solution, higher RA, and generally undesirable plate martensite).
I also don’t care to name drop and throw names around, but this particular heat treatment for 52100 has been thoroughly discussed on the “inter webs” for quite some time now, so I am sure Kevin doesn’t mind. It has been cussed and discussed on just about every single knife forum out there.
And for any interested in what many of us are doing in recipe form for 52100:
1. Normalize 1650f (I actually use 1700f and soak for 20 minutes). Air cool only
2. Thermal cycle 3 times 1500f, air cool all 3 cycles or quench on last cycle especially if it’s lower than the hardening temp (I quench from 1440f on last cycle for a martensitic structure rather than pearlite after reading some of Larrins articles)
3. Austenitize 1475f, 10-15 minute soak
4. Quench in 80f Parks 50, ~66-67HRC
5. 2 (or 3) 2 hour tempers 375f, ~63HRC
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