Could it be the Heat Treat Foil ?

Robert Dark

Robert Dark

Joined
Aug 27, 2004
Messages
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Scenario..........

CPM 154 finished to 400 grit
Blade double wrapped in H/T foil
Pre-Heat to 1400 F. to equalize - 10 minute hold
Ramp to 1925 F. - Hold for 30 minutes
Quench (while still in the envelopes) between two 1 inch thick X 6 inch X 12 inch (frozen) aluminum plates with compressed air blown between the plates during quench.

Here is the problem....... When I take the blade out of the envelope(s), the envelope wants to slightly stick to the blade in a few places. Then, the blade is sort of "mottled" looking that requires me to either go back to the grinder or start over by hand at 220 grit, then work through the grits again.

Now, I will admit that the H/T foil is some I have had for several years. When I bought it, I didn't pay attention to the temp rating. Could this be the problem, or is my H/T recipe off? I have also had the same problem with S35VN.

As a side note, I have also tried placing a 1/4" square piece of paper towel in the foil pouch on the tang end in order to help consume any oxygen within the pouch. Doesn't seem to make a difference whether I use it or not. The problem still exists.

What "Foil" are you using and where are you getting it? Any suggestions will be appreciated.

Robert
 
Frank,

Although I haven't checked any lately, the last ones I tested (at the local Community College Machine Tool Technology Program) tested between 58-60 RC. Perhaps I am spoiled by using Paul Bos for many years and having my blades coming back needing only a short touch-up with 600 grit to get the "shine" back.

I realize that Bos' system is a bit different than mine, however, something is just not right with the way I do things. I should not have to work my fanny off slicking these blades out again.

I am satisfied that the end-result heat treat is fine. There just has to be a way to reduce the post heat treat sanding/grinding.

I have resigned myself to the fact that you are going to get a certain amount of "de-carb" with unprotected blades when doing 10XX blades and, especially O-1 in my gas fired (Don Fogg upright style) forges. I am missing something somewhere, and I have to figure out what it is.

Robert
 
I do pretty much the same....except My temp is 1975 and I don't freeze the plates. Hardness is bullseye to the chart. And my blades come out damn near white.
I think the stickiness could be from quenching on a frozen plate (moisture).
As you said if the wrap isn't rated for the temp that could also be the issue.
 
You're pretty much in line with what Crucible recommends, HT-wise, except they say to hold at temp for 1 hour. That's probably not needed for something as thin as a knife blade.

You could try not freezing the plates - although other people do freeze theirs without any apparent problems. My best guess would be the foil.
I would go for the 309 grade, rated to 2100F.
 
are both layers of foil brand new?
a friend taught me to have a used foil packet for the inside to prevent sticking.
 
Robert, I was having the same problem with the sticking on 154cm and S35vn. Using some baby powder solved the sticking for me. I am using the exact same recipe that you are.
 
I've had that too Robert. I don't take my shine up like you do, so I didn't worry about it.

Talc. Nice tip.

Edited to add that I don't freeze my plates, and still get the sticking.
 
i welded some foil to a few 10V blades before when i quenched i jsut chalked it up to hveing eveyting too clean and getting too much air out the foil pouch
i like the talc idea
 
OK, seems my H/T recipe is pretty much in line with what you guys said. I'm glad to hear that I'm not the only one who has had sticking problems.

The Talc / Baby Powder is something that I have not tried. I am assuming that you are just dusting both sides of the blade, then sealing it up.

I am going to order some of the higher temp foil. Will have to do a little searching to find a decent price on it. They don't give that stuff away.

Thanks for your input gang.

Robert
 
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