Appropriate Cryo Methods

I use cryo on pretty much all high alloy steels, stainless or not. I don't use cryo on simple carbon steels. First, cryo is best as a continuation of quench and I keep hearing how important it is to get carbon blades straight into temper from room temperature or close. It just doesn't seem the risk is worth it. For the high alloy stuff, it at least meets the test of "do no harm" and usually appears to do measureable good. That's my path for now.
 
Shane Wink said:
So what is the informed consensus concerning carbon steels and cryo? If its better to manage RA during the heat treating before the quench and RA is at a minimum is it really worth the cost and trouble to maybe get a point more in hardness?

I asked the same thing last fall and got the answer that if you normalize at the right temperature, harden at the right temperature with enough soak, and quench properly, that you would not see any increase in hardness. Those that claim a drastic increase in hardness with carbon steel have usually not followed "established practices" in there heat treatment.
here is the link, http://knifedogs.com/showthread.php?26777-heat-treating-52100
scott

"Old sailors never die, they just hang around forums and look up stuff"
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What do you consider a "carbon steel" ? 10xx only, low alloy steels like 52100 and 5160, high alloy steels like M2, A2, 3v?
 
I'd like to ask a question on something brought up earlier in this thread regarding increasing the tempering temperature. All the charts for CM154 and D2 both show as quenched of 62/63, temper at 400-450 to get to 61, but that's without cryo. I've got 5 blades of each steel that tested at 64/65 after dry ice cryo and are still at 62/63 after a 550 temper, walking the temp up 25 degrees at a time for one hour cycles. Does that sound about right? Seems high to me, but I'm out of my league.
 
Yes, that does sound like the way to go to reach the HRc that you want. The data sheets for steels are a good starting point but due to variations in exact steel composition and differences in heat treating equipment they are only guidelines. With the two steels that you have listed be aware that there may also be a secondary hardening node at around 1000° that could give you more wear resistance at the same hardness that can be obtained at lower temperatures. You might want to check a table of tempering temperatures. Of course, if you don't have a kiln that can obtain those temperatures it's a moot point.

Doug
 
me2 said:
What do you consider a "carbon steel" ? 10xx only, low alloy steels like 52100 and 5160, high alloy steels like M2, A2, 3v?
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Fair question. Normally I'd be referring to the 10XX stuff we use,. Things like 5160, 52100 and even O1, I've tried cryo and seen little difference so I don't unless requested. M2 - yes 3V yes Rex121 Oh ya!
 
Somewhere I thought I read about using antifreeze and dri ice instead of acetone,would antifreeze work and has anyone here used it?
 
I would not think it would work because it would actually freeze. I looked up the freezing point of some antifreeze but it was not rated for 100 below.

Yes when speaking of carbon steels I was referring to simple carbon steels.
 
Mystery partly solved on my too-hard cryo'ed steel. After I ground off the surface oxidation, both the D2 and the CM154 tested 60 after the 550 temper. Although these were done in foil packets and came out barely gray, that little bit of oxidation was making them show harder on the RC tester. Since RC was acting funny, I put an edge on one. Brass rod showed no chipping and no flattening or deformation, which tells me I didn't get them too soft nor too hard.
 
I tried my first heat treat using dry ice last night,with a twist,I used 91% isopropyl alcohol instead of acetone.I was going to use kerosene but all I could find was quarts at wallyworld for$6.00 and the alcohol was on sale at walgreens.So here's what I did, 13C26 foil wrapped brought up to 1950 and soaked for 15 min. then plate cooled. next up was the freeze treatment,about 2# dry ice in broken up in small pieces and placed in my double duty lunch cooler,blades were placed in between the chunks and the alcohol was poured in to cover up all the ice. then it got wierd,it was bubbleing away and the alcohol turned into a kind of thin melted plastic consistincy.I dipped some small plants in this stuff and they broke like glass when I pulled them out so I assume the soup was working.I left it in the mix for two hours.after it came back to room temp I tempered in my oven at 345 for 2 hours. I rockwell tested at a friends dowel rod manufacturing plant and it came out at 60-61 RC.unfortunatly I did'nt have it tested before the freeze treatment but I'm thinking that it did make a differance.any opinions of this as this is my first shot at this? also I found a supply of kerosene at a home-commercial fuel oil company for$5.00 a gallon,does the kerosene thicken up like alcohol? thanks for any input.
 
Use 97 or 98 percent alchohol. It's sold in drug stores as hospital sterilizing grade. The lower % turn to dry ice slushies.
 
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