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Thread: Peen Straightening

  1. #1
    Rene Van Bommel

    Peen Straightening

    We are a mid size machine shop. We are working on a project that we have a 60'' od x 40'' id ring. The ring is flame hardened along the outside edges. The flame hardening process has warped our part. We need to grind it flat, but we need to straigthen it first. We have been peening the part and we are seeing movement, but this is a fine art and hoping someone may have some experience to share.


  2. #2
    Technical Fellow
    Join Date
    Feb 2011
    Hi Welcome to the forum. I suspect you will be having more problems than just not flat.

    The flattening process, not matter how it is achieved will almost certainly cause about a zillion micro-cracks, or worse, visible cracks in the hardened section. Either way chunks will almost certainly fall out after a little use.

    I have visions of the flame hardening as a man with a gas torch and if so, the project was doomed before he lit the torch.

    Two things I can suggest for the next ones.
    Maybe look at relief slots in the back side of the ring so that the heat treatment process will allow the metal to move a little and minimize any distortion and it can then go straight to the grinder.

    Control the heat treating process better with multiple heat sources and maybe even rotate the ring as it is heating and soaking.

    I sicerely hope that someone can chime in and help you, but I suspect the fate of this project was foiled at the onset.

    Sorry to be a doomer and gloomer.

  3. #3
    Lead Engineer RWOLFEJR's Avatar
    Join Date
    Mar 2011
    Rochester Pennsylvania
    Lots of questions...
    Wondering what the material is and how thick is this ring? Are you having issues with circularity as well as flatness? Any cupping... like a bellville washer? What's approx depth of heat treat? How flat does it need to be? How much stock will be removed at grind and have you considered it may move again after grind? Maybe two grinds with a straightening in between?

    Just a guess... probably pretty thin part (relatively speaking) and guessing the start and stop points of the flame hardening process would be areas to focus attention. If the part is ground in a restrained condition... like on a magnetic vise... and it is dusted both sides for parallel... will it be an issue if it twangs on release for the application it is going to be used in?

  4. #4
    Technical Fellow
    Join Date
    Feb 2011
    Quote Originally Posted by RWOLFEJR View Post
    will it be an issue if it twangs on release
    Exactly Bob, and that's why I said this...
    "Two things I can suggest for the next ones."

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