A question about CPM3V...

Phillip Patton

Phillip Patton

Knifemaker / Craftsman / Service Provider
Joined
Jul 25, 2005
Messages
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...for those of you who have experience heat treating it.

I just hardened a blade of it, tempered it at 1000 degrees 3 times, and it's showing a hardness of about 54RC, and a dull file will bite it, but not aggressively. I'm testing the hardness on an inclined surface (tapered tang) so that might explain the low RC, but is it normal for a file to bite hardened 3V?
 
what temp did you quench from and did you cryo it
air cool, plate quench or oil
that will help me greatly
butch
 
butcher_block said:
what temp did you quench from and did you cryo it
air cool, plate quench or oil
that will help me greatly
butch
Click to expand...

Hi Butch,
I quenched it from 1950, tried to oil quench it but it took so long to get it out of the foil, the thinner parts were getting dark.
No cryo, but I did put it in the freezer. :D
 
ok so lets say you got a mostly good quench and say 60-61 before tempering
at 1000F temper you would be some place around 57-58 RC now then if your kiln was even just a hair off and was really 1025 your hardness could easy be 55-56RC
im working out a heat treat that tempers at 400 like most of my other steels i use cause of the fast drop off in hardness after 1000 for 3v
 
butcher_block said:
ok so lets say you got a mostly good quench and say 60-61 before tempering
at 1000F temper you would be some place around 57-58 RC now then if your kiln was even just a hair off and was really 1025 your hardness could easy be 55-56RC
im working out a heat treat that tempers at 400 like most of my other steels i use cause of the fast drop off in hardness after 1000 for 3v
Click to expand...

So do you think I should re-harden it, and if so, do I have to anneal it first?
I appreciate your help, Butch.
 
Plate quench, Phillip. I used Butch's HT formula and a LN cryo and got 63 before temper. 1000F temper cycles and I ended up at 60-61.

The only thing I'll do different in the future is temper in foil. That scale is thicker than it looks, and can give false readings until ground off.
 
fitzo said:
Plate quench, Phillip. I used Butch's HT formula and a LN cryo and got 63 before temper. 1000F temper cycles and I ended up at 60-61.

The only thing I'll do different in the future is temper in foil. That scale is thicker than it looks, and can give false readings until ground off.
Click to expand...

I'd love to plate quench it, but the tang and blade both are tapered, so the only part that would be in contact with the plates is the ricasso. Maybe that would still work though?

Good point about the scale. I'll grind that off and see if the readings are still low. But what about the file biting? I ground the edge down to fresh steel, and the file still bites.
 
I think you took too long to get it quenched. Plate quenching doesn't have to have full contact to work.I would temper at 1200 F [subcritical anneal] then harden again.
 
mete you see any glaring problem with a temper of 400 if i am doing a cryo to try and get full conversion
the 1000f temper is because of 3v s use as a tool/die steel and its more about size change/ right?
i have a necker that i have been beatign on that i ran a heat treat of
1500 5 in
2050 20 min
plate quench -room temp
right into cryo over night a
then temper in the morning

i had not got the Rc of the test blade cause i wanted to see how it held up without knowinig how hard/soft it is to skew my thoughts on how it should act
 
Here is an example of difference between factory recommendations and some of the knife practices. Alloys with good amounts of V,Mo,W give secondary hardening which is useful for tooling working at high temperatures but no real benefit to knives. Some like the 1000F which gives a bit better corrosion resistance .You should try both and pick the one you prefer. There's certainly no problem with 400 F.
 
mete said:
Here is an example of difference between factory recommendations and some of the knife practices. Alloys with good amounts of V,Mo,W give secondary hardening which is useful for tooling working at high temperatures but no real benefit to knives. Some like the 1000F which gives a bit better corrosion resistance .You should try both and pick the one you prefer. There's certainly no problem with 400 F.
Click to expand...

Mete, doesn't the higher tempering temps convert retained austenite to martensite?

Anyway, yesterday I annealed it like you said, then today I re-hardened it, this time from 2000 degrees, and plate quenched it, blowing compressed air between plates to speed things up. As quenched hardness was about 61-61.5
 
OK, I think I have the 3V heat treated well, now, here's another question:
How do you guys finish it? Bead blast, hand sand, scotchbrite belts, coatings????
I tried to give it a hand rubbed finish like I always do, and the paper went dull very quick and didn't get much work done....
 
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