Cryoing??

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by R-WEST, Oct 27, 2003.

  1. R-WEST

    R-WEST Active Member

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    A few years ago, all we heard was "cryo everything", it was supposed to cure all ills, etc..., but, lately, I haven't heard much. Did/does it work? Anybody here have any thoughts?
    Thanx,
    R-WEST
     
  2. RBrowning

    RBrowning Well-Known Member

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    Cryo treating a barrel is primarially a stress relieving mechanism. A few years ago the popularity of longer range shooting was just begining to rise and so more people were looking for better toys to play with. Also with the economy doing so well, more folks had more $ to spend and were glad to do it on what appeared as a better product. This tended to get the notice of those companies that were seeing a drop in sales of "off the shelf" guns and a rise in the custom guns. Thus the popularity of it a few years ago.

    Does it work. Yes. If a piece of steel has been machined it will have residule stress in it. Conventional heat treating took most of it out or you would never get a good group. You POI would move as the barrel heated up. Enter Cryo treatment. It relieved more of the stress and gave you a more stable product.

    Is it the only way to stress relieve a barrrel? No. you can double or triple temper the steel. Each reduces the stress and converts more of the austinite to martinsite than the previous. That is why some of the better barrel makers do it right and see no benifit from cryo treament. Factory barrels probably would be a good canidate for cryo treatment, especially if you notice your POI moving as it heats up.

    Read Dan Lilja's article at his web site.
     

  3. CharlieK

    CharlieK Member

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    Will someone please explain to me the mechanism -- the process -- by which cryo treatment relieves stresses in a barrel? Yes, I've read Dan Lilja's website, and his consulting metallurgist doesn't think it relieves any more than 6% of the "remaining" stresses. I'm an engineer with a significant metallurgy background, so would someone please expain how cryo treatment relieves stresses? Low tempertures prevent dislocations from moving, which are required to relieve stresses. So what does it?

    [ 11-21-2003: Message edited by: CharlieK ]
     
  4. dbhostler

    dbhostler Well-Known Member

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    CharlieK,
    I believe the process involves 300 degrees above as well as the 300 degrees below.
    I think Krieger used to cryo all their bbls. I don't know if they still do this or not. I have several rifles with Krieger bbls and no matter how hot you get them POI doesn't change. You might email them and ask your question. www.kriegerbarrels.com www.cryogenicsociety.org is another site that could possibily give insite to what is actually happening to the metal. Let us know.
    db

    [ 11-22-2003: Message edited by: dbhostler ]
     
  5. RBrowning

    RBrowning Well-Known Member

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  6. CharlieK

    CharlieK Member

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    db,
    Here is Krieger's response:

    <BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Due to patent litigation we do not cryo treat any barrels/steel once production has begun.

    Thanks for your inquiry,

    Jim Duchow
    Krieger Barrels, Inc.<HR></BLOCKQUOTE>

    Also, the process, the mechanism, that I'm asking about is what happens inside the metal, at the microstructural or grainboundary level, that causes the stresses to be relieved by cryo temperatures. I haven't seen anything, yet, that explains how very low temperatures can relieve stresses in metals. Anecdotal testimony is not an explanation.
     
  7. CharlieK

    CharlieK Member

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    RBrowning,
    The link that you provided has so many misconceptions in it that it's pitiful. Cryo treatment might very well produce more martensite and reduce the austenite, which would make the steel harder, but I'm convinced that the reduction in residual stresses actually occurs AFTER the cryo treatment when the temperature is cycled from room temperature to +300ºF and back to room temperature three times. The cryo hype even says that without the final heating to +300ºF and back to room temperature, then there is little or no benefit.

    Other cryo-treatment hype also claims (not in your link) that music CDs, audio cables, and recording cartridges sound better after being cryo treated. Yeh, right. I waiting for some of the proponents to claim that it cures cancer, too.

    [ 11-26-2003: Message edited by: CharlieK ]
     
  8. 4mesh063

    4mesh063 Well-Known Member

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    Charlie,

    What does Cyro do?

    A year ago I'd have said, "It lightens your checkbook by ~$100.00"

    Now, you're safe because the barrel mfgr's are not allowed to do it. (after production).

    I was told (by a representative of Kreiger) that initally, it is done because the barrels are less likely to be scrapped in the machining process. I believe most of that was in the tapering process but it has been a long time. I paid for the 2nd cryo on my barrels and I thought they were just great. Then I chose to not do it and that barrel was fine. Then I decided to do it to the next and was told that 2nd cryo wasn't offered. Because of the above mentioned litigation. That's a bunch of bunk, but, we have laws and someone feels infringed upon.

    According to Kreiger, it made NO difference to the barrel for the customers sake, only that it was easier for them to machine and less likely to be scrapped. That's why they do every single barrel they make (pre-production). Even knowing this, (like every other crazy gun person) I paid for the "possibility" that it may help because I need every .001% I can get. It doesn't bother me a bit that it's not offered anymore, and I don't think my gun knows the difference.

    From a metalurgical standpoint, most people who know anything about steel like to avoid the subject. That's what I've found. They don't seem to beleive that it does anything. I can think of one in particular who has worked with cryo'd parts 3 decades ago and said it was an outright waste of time.

    For stress relief, I would say, take the gun out in 100 degree heat and shoot 100 rounds rapidly or until you smell the stock smoking. There, all the stress is gone! This freezer thing (from the stress point of view) i don't buy a bit. Not saying I don't like the idea, just that for "stress" I don't think there's anything to fix.

    Now, if someone told me that they wanted to ship my barrel by rail to the west coast, then back to the east coast and that that would relieve stress, now I'll buy that.

    But then, this is usually 416 stainless, not L6 or A2 or 01. I can see with my own eyes how a slug of A2 shatters in a day or two if you don't draw it after it comes out of the oven. There's one on the bench at work right now, a rockwell test piece that didn't come out as planned and wasn't drawn. But, Leaded 416SS to have stress that needs removed? I could beleive that it could change some property of the steel, though I don't know what and however slightly it may change, but it's stress relief claim is going a bit far I think.
     
  9. 4mesh063

    4mesh063 Well-Known Member

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    Charlie,

    You said you have some background with metals, so here's a question for you.

    If, IF, the steel actually had stress in it and we magically removed it in the cryo process, or even if it got removed in an oven, wouldn't the barrel warp to some degree? My barrels have allways been pretty straight when I got em, and when I took em off. (rolled on a surface plate). Is it possible to remove any stress (of any significance) and have a 30" piece of steel 1.250 dia stay straight within .005, like well within). Actually our surface plate is only 24" but diagonally, it's almost long enough to check the whole 30". Even over 24", they just don't wobble. Even after I've tapered em with one end chucked up and the other in a center, they're straight as a pin. If I did that with a piece of cold rolled, it'd be a banana when I unchucked it.
     
  10. CharlieK

    CharlieK Member

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    <BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>If, IF, the steel actually had stress in it and we magically removed it in the cryo process, or even if it got removed in an oven, wouldn't the barrel warp to some degree?<HR></BLOCKQUOTE>

    Yes, but it might be only an imperceptable amount.

    <BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Is it possible to remove any stress (of any significance) and have a 30" piece of steel 1.250 dia stay straight within .005, like well within).<HR></BLOCKQUOTE>

    If the stresses had been almost uniformly distributed around its circumference and along its length, you might not ever see any wrapping after they were relieved. The important thing is for the barrel to heat up uniformly as you shoot. Having the barrel free-floated helps the cooling process. With a forearm that is snug to the bottom half of the barrel, it can't cool as well as the rest of the barrel, so some warping could occur as the barrel cools more on top than the bottom. Of course, the stock can warp from the heating, too.

    In 1961, I bought a used Winchester Model 70 in .264 Win Magnum. It had a 26" stainless barrel, and that was my first rifle. God, I wish I had it back!! Shooting off of sand bags with a 6x Weaver scope, I couldn't keep five shots on a 8-1/2" x 11" piece of paper at 100 yards. I asked a local gunsmith about it. He said that some of Winchester's early stainless steel barrels were not properly heat treated and that they warped when being heated from shooting. He said that, even though I bought it used, Winchester still had its name on it and that I should write to Winchester and see what they say. I did, and they said to send it to them...scope, stock, and all. I got it back in about six weeks... with a new barrel ... and no charge. After that, I was getting 3/4" to 1" five-shot groups with 140gr Sierra BTs. How I wish I had that rifle back!!

    My original barrel was warping badly after each shot; that was what was scattering the shots all over the paper. Apparently, Winchester had not drawn the steel adequately after the heat-treatment process. Drawing, for non metallurgists and non engineers, is bringing the steel up to an intermediate temperature and allowing it to cool slowly, thus, relieving the internal stresses that were trapped during the previous heat-treatment and quenching operation. Drawing also reduces the hardness, making the steel less brittle, and more ductile and tougher. This is the tempering, or moderation, of the earlier harsh heat treatment that you would get by only quenching the steel. This is the original meaning of the word "temper," which was to moderate, make less harsh, or to reduce the severity of something.

    Krieger's website says that cryo-treating reduces the waste, presumably, as you said, from the taper machining operation. The cryo hype says that the cryo treatment makes the steel harder. If that's correct, then the machining operation would be more difficult, not easier. The harder the steel, the harder it is to machine. It could be that the cryo treatment actually improves the machining by making the steel less likely to gall, which could cause unrecoverable errors in machining. I'm guessing on that one.

    [ 11-26-2003: Message edited by: CharlieK ]
     
  11. 4mesh063

    4mesh063 Well-Known Member

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    Harder material isn't always harder to machine...

    I'd much rather cut a piece of tool steel at 30rc than cut a piece of cold rolled. L6 after heattreat and then a draw at 950 (38-40rc) is much nicer to machine than most any softer metal is when annealed. Yes, you have to use coolant, but it cuts beautiful and even tapping it is nice.

    I have too much yet to learn on barrels to argue the "bad barrel" deal. I have to say I'd be skeptical of a gun shooting that bad and not having another problem... But... if changing the barrel helped, I'll agree to disagree.