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Thread: Straightening a weldment

  1. #26
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    Re: Straightening a weldment

    While the cooling spray boils at a low temperature, I'm pretty sure the amount of energy required to boil it off is WAY less than the same amount of water. Using something that boils at -51C rather than +100C is probably little help when the amount is so limited (not like you can dop something in it), and you start out with a weld closer to +1500C. A wet rag would probably cool things down much quicker - if that gives less distortion or not is another matter.

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  3. #27
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    Re: Straightening a weldment

    You wouldn't want to quickly cool a critical weld unless it was certain types of stainless where a water quench can anneal it. Would need to use jigs and fixtures and carful distortion control. Was reading about huge diesel engines with welded construction and distortion control takes on a whole new meaning.

  4. #28
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    Re: Straightening a weldment

    Quote Originally Posted by Lis2323 View Post
    I have often wondered for welding smaller heat critical projects if something like this would work to minimize distortion.




    Obviously if it worked it may not be cost effective on bigger jobs but has anyone ever tried something similar?
    Cool!!!!

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  6. #29
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    Re: Straightening a weldment


    ronsii


    Quote Originally Posted by ronsii View Post
    Cool!!!!
    I've used spray liquid Nitrogen to remove chewing gum
    in carpet. Freeze - hammer to a powder - and vac . . .


    Opus

  7. #30
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    Straightening a weldment

    Quote Originally Posted by OPUS FERRO View Post

    ronsii




    I've used spray liquid Nitrogen to remove chewing gum
    in carpet. Freeze - hammer to a powder - and vac . . .


    Opus
    Long ago.....I had a girl friend with long hair who chewed bubble gum. One time a bubble went astray and got stuck in her hair. What a mess.

    Wish I had known about the spray liquid nitrogen trick.....she was like a boomerang. Kept coming back.
    :

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  9. #31
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    Re: Straightening a weldment

    There's been some posts that allude to damage to the base metal when heating, and cooling. I would direct those folks to literature developed by various highway administrations across the country. I won't include a link. Y'all ought to be interested enough to do it on yer own. Hint...……..highway bridge straightening.

    Mild steel has incredible properties. One of which, is tolerance to welding, and heat straightening. You will NOT create the mythical HAZ when straightening with heat. Straightening has only one limitation...…………..critical temperature...……...1200*

    The weld, on the other hand, is more subject to heat damage. Keep your heat out of the weld area if possible.

    Water...…….Whether you use water, or let it air cool, it's all the same. The advantage of water is a rapid change.

    Heat shrinking works best when the steel is restrained during heating. It likes to expand, then contract to its normal dimensions. When you restrain it from expanding, it will shrink to what you want it to be. This is called "upset", read up on it. Heat shrinking means heat shrinking...…..again...…..read up on it.
    Last edited by farmersammm; 04-13-2020 at 10:02 PM. Reason: spelling

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  11. #32
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    Re: Straightening a weldment

    Quote Originally Posted by Lis2323 View Post
    Long ago.....I had a girl friend with long hair who chewed bubble gum. One time a bubble went astray and got stuck in her hair. What a mess.

    Wish I had known about the spray liquid nitrogen trick.....she was like a boomerang. Kept coming back.
    I think a large dose of ultracool would have solved your problem permanently

    We used to use propane upside down to cool stuff all the time.... and it seemed plenty safe at the time...

  12. #33
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    Re: Straightening a weldment

    Quote Originally Posted by ronsii View Post
    I think a large dose of ultracool would have solved your problem permanently

    ...
    If not, then the hammer Opus mentioned would have done the trick.
    :

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  14. #34
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    Re: Straightening a weldment

    I had a situation where a 1.5 inch plate was distorted by a weld. I had to remove the bend in the plate. The plate was about six inches wide so I heated the top side and use a siphon gun spraying air and water continuously on the underside. The rosebud was able to heat the top surface to red while the under surface as cold from the water spray. I took the rosebud away and continued to spray the underside until it shrunk upwards and became straight. Without the cold spray I doubt I would have been able to create the red heat on the top surface without the heat going through the thickness.

  15. #35
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    Re: Straightening a weldment

    it works doing this way like dave said, but individually before/during weld
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  17. #36
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    Re: Straightening a weldment

    It's common when welding pipe with fittings coming off the side, like above, to have to heat the back side to straighten it. Upper critical temp. is the key. You don't want to heat something up glowing orange and quench it. A few years ago I had a discussion with someone (an over confident CWI) over weave width of vertical up welds on steel plate or pipe. He was trying to say max. of 3 times rod diameter. Not finding a definitive answer I sent an e-mail to Walter Sperko who is one of the top people who works with ASME codes. He said there is no limit to weave width and more heat is actually better. The difference in grain structure is negligible. He said he would challenge any procedure limiting the weave width of a weld on standard grades of steel. He basically said it's something they did years ago that has no merit. On stainless where you want less heat input it applies.

    I had to straighten the 1 1/2" thick bottom swing mount on my backhoe. I ended up Veeing it out and welding it but being such a thick piece I couldn't brace it in position because it would have had too much internal stress from being restrained. I had it bent down about 20 deg's and after welding up the V and letting it contract some I used a piece of flat bar to limit that last bit of contraction close to where it was straight. Still had a friend come over with rosebud to tweak it a bit but it was fairly close and thankfully everything went back together. I think heating it to get it exact may have stress relieved it somewhat.
    Last edited by Welder Dave; 04-14-2020 at 12:17 AM.

  18. #37
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    Re: Straightening a weldment

    Quote Originally Posted by 123weld View Post
    it works doing this way like dave said, but individually before/during weld
    I did one like this in a processing plant, 2 water headers for a bunch of condensers, they were 60' long with a pair 1.5" thredolets 10" apart every 36" on 8" schedule 40. After all the welding they looked like a banana. Turned them 180 degrees and heated a spot the size of a silver dollar opposite each weld and they came out as straight as a stringline.

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  20. #38
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    Re: Straightening a weldment

    Quote Originally Posted by 12V71 View Post
    I did one like this in a processing plant, 2 water headers for a bunch of condensers, they were 60' long with a pair 1.5" thredolets 10" apart every 36" on 8" schedule 40. After all the welding they looked like a banana. Turned them 180 degrees and heated a spot the size of a silver dollar opposite each weld and they came out as straight as a stringline.
    thanks, i'll keep that in mind. funny how we can remember measurents and size pipe from jobs long ago, but i have hard time reembering a measuent from 5 min ago, or what i was supposed to remeber to walk out the door that morning w/. hell, i still remeber locker combos/friends phone numbers from jr high still.

    yea, banana is the word. one thing that helps w/ bananaing a lil too, is, if they drill there hole after i weld thredolet, instead of before

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  22. #39
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    Re: Straightening a weldment

    Quote Originally Posted by farmersammm View Post
    Water....Whether you use water, or let it air cool, it's all the same. The advantage of water is a rapid change..
    Probably more accurate to say that either way works, but chilling the "restraining material" with water (or whatever) will upset the hot material faster than chilling it only with air, simply because water chills more effectively than air.

    To paraphrase McDonalds, "You need the hot side hot, and the cool side cool" to effectively upset the metal to be bent/moved. Chilling with water will generally create a bigger temperature differential than chilling with air. The less the restraining material expands while the heated material expands and softens/weakens, the better.

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