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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making. |
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#1
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Dry Ice - Probably Good Enough
I was making a knife making tool and needed a hardened part. I chose S30V, but I'm out of LN. So, I thought I'd run a dry ice test.
2 pieces of steel: S30V and ATS34. I set my oven to 2020 degrees (which I believe gives me about 1990). Put the steel in a cold oven ran up to 1800, with a 10 minute rest. Then a 20 Minute soak at ~1990. Quench with plates. The S30V came out at 63HRC and the ATS34 at 56HRC. Well those are the expected numbers based on the data sheets. Then I placed them on a block of dry ice for 3 hours. No acetone or anything, just set them there. The S30V block rose to 63.5 - that's what I usually get with LN and my process - not much change. ------ATS 34 block went from 56 to 62. Again that's on par with the data sheets. Obviously, the dry ice was capable of transforming a large percentage of retained austentite. Maybe doesn't transform all of it. Maybe requires longer soak times than LN. But it certainly works. Steve |
#2
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Steve: Yes, dry ice is cold enough to benefit both of those steels greatly. LN2 is still better, because it's a lot colder. How much better? I'm not going to argue that........
Just a suggestion-rather than equalizing at 1800F, try 1550/1600 for S30V and 1500 for ATS34. A brief hold at these temps will set these alloys up for a better transformation later on. __________________ Stay Sharp, RJ Martin Knifemaker www.rjmartinknives.com |
#3
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how cold do you think dry ice will get with acetone added?
__________________ Kevin W Vogl |
#4
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The mixture is the same temperature as the dry ice, -78C.
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#5
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many thanks for the info
__________________ Kevin W Vogl |
#6
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I think the reason folks use the acetone thing is to get a better thermal transfer. But steel being what it is and these thin strips we use, I don't think it's an issue.
It sure works in a pinch. Steve |
#7
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Stay away from Acetone! Highly flammable and noxious vapors. Kerosene or alcohol is a much better choice. Yes, the liquid is just for more even thermal conductivity.
__________________ Stay Sharp, RJ Martin Knifemaker www.rjmartinknives.com |
#8
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Isopropyl alcohol will make a pretty nice "slush" with dry ice. It's not as volatile as acetone, but it does make everything smell like a doctor's office. As far as acetone being "noxious", it's not one of the more toxic solvents. (Fingernail polish remover is acetone.)
If using a solvent/dry ice mix, cover it (if possible) to minimize water condensing into it, but don't seal it closed. __________________ God bless Texas! Now let's secede!! |
#9
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I use a cold spray - gives instantly -55C.
__________________ T?nu Arrak |
Tags |
knife, knife making |
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