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Old 03-13-2017, 11:51 PM
jimmontg jimmontg is offline
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Join Date: Jan 2016
Location: Now live in Las Cruces NM.
Posts: 1,345
13 year old thread.
Blade Runner what type of a machine are you talking about for doing cryo? For $6000 I can buy you a 24" deep Paragon oven and a $300 dewar for holding liquid nitrogen. Plus build you a dry ice freezer for metals like AEB-L which only cryo at -95F and dry ice is -109F. AeB-L is a great knife steel and one of the easier stainless to HT into knives. After all that still have $2000 leftover, are you talking about a deep freeze freezer that go to like -80F?

Properly built dry ice chest should hold dry ice for 2 to 3 weeks, please note dry ice isn't a dct or deep cryo treatment and it takes three days under the dry ice to see the difference depending on steel of course. AEB-L only needs to be dropped down to -95F and let it slowly warm up, it doesn't need to soak. I use dry ice on O1 as it definitely makes it tougher and I can temper it a point higher without the brittleness.

My friend Dtec did an experiment for me with a 440C blade. The blade was finished final HT and cryo and tempers all done. Dave left the knife all night in LN and measured to 4 x and got an increase of .9, almost a whole RC point. That is significant and a small temper would be needed afterwards, but on a finished knife the increase surprised us both.

Cryo can be kept simple or you can get complicated with it. It most definitely make blades better, and you can build an ice chest with 4" thick walls, but it has it's limits too. 3 days under dry ice will make most steels tougher as will overnight with LiqUid Nitrogen. LN also makes the little eta-carbides and will make the steel harder. As for snap tempers before subjecting the quenched metal to super cold temperature well I have been told it isn't necessary, but I would still do it to D2 as I've never had a failure with it. D2 is triple tempers with cryo in between, I get 59-61 hardness, 60 mostly and that is my target. Only ever cryoed it with dry ice.
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