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cracking aluminum welds

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  • tarry99
    replied
    Pre & Post heat...when in doubt...can be a PITA but you probably already knew that before you started........heat / colored sticks gets you in the ballpark........then controlling the cool down,,,,,1st a doubled up welding blankets on top , then a few moving blankets for added retention , I even left a small portable heater running facing into the cavity for hours ......later I started to unwrap and could not touch with a bare finger.......warm enough to cook a few hot dogs ....finally took it apart that night and was still warm............the good news is the part is still in service and never cracked nor failed!

    Leave a comment:


  • dvice
    replied
    Originally posted by Burnt hands View Post
    Just for curiosity, do you have a local scrap metal dealer with one of those "nuclear ray guns"
    they use to identify a piece of scrap metal.?

    Might shed some light on the alloy involved.
    i could call....... i tried to search alloy for firearm receiver, and got no where. I dont thiunk they want to divulkge that info

    Leave a comment:


  • Willvis
    replied
    Those guns are called pmi guns. Any of the nde companies should have them aswell.

    Leave a comment:


  • Burnt hands
    replied
    Just for curiosity, do you have a local scrap metal dealer with one of those "nuclear ray guns"
    they use to identify a piece of scrap metal.?

    Might shed some light on the alloy involved.

    Leave a comment:


  • Noel
    replied
    Well I'll be darned. I'm thinking there is something to be learned in all this? And someone learned it. Guess this is how a welder gets his wings? Funny thing, I think somewhere in the past I repaired one, or something like it. Just had this deja vu feeling it could be welded? Glad it worked out.
    Last edited by Noel; 02-06-2019, 05:35 PM. Reason: Darn stickly key board.

    Leave a comment:


  • dvice
    replied
    well I just couldnt stand it.... since the Benelli dealer said the factory would NOT sell just a bare reciever... I went back and turned down the power and I welded the crack closed... I I rough machined the weld down....and no crack so far...I have to get the other parts to trial fit how much to machine down...so Im thinking...( just a guess), maybe too much heat .....itys just a tough job with the metal threads underneath and the thin wall above those threads....

    Leave a comment:


  • FusionKing
    replied
    I wasn't really intending to be offensive.....even though I can see where you could easily take it that way. I do come off pretty arrogant at times. I am sorry.
    I guess a better way to have phrased it would have been....In retrospect, the entire part should have been pre and post heated.
    I've ruined my fair share of things that I could have saved if someone would have handed me another after I trashed the first one. It's how you gain wisdom.
    I doubt they forged it. That would have been the best IMO though. I can tell a lot when it's in my hand. Pics are hard to guess sometimes.
    I usually don't go into that much detail when I critique other peoples work. In your case I judged it as harsh as I would have if I had done it myself.
    Once again I apologize.

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  • dvice
    replied
    Originally posted by FusionKing View Post
    I do think it's safe to say that it's definitely junk now.
    That shape would have had a tendency to crack no matter what the material was.
    The entire part should have been pre-heated before welding and kept hot uniformly until cooled. And that is welding it like Noel describes.
    If the part is Billet then there is a good chance it could be 7075. If it is cast there is a possibility it could be a pot metal.
    By the picture I would seem much effort was not to disturb the surrounding area...as in grinding through 100% and worries in regard to requiring additional machining. I get that. But you usually only get one good shot at a part like that.
    I would say from the pic you have way too much dilution from the parent metal and too much contraction from the rest of the part not being up to temp.
    When you commit to welding a piece like that you pretty much threw heat treat out the window, but you can't have the only soft area the spot that is the weakest. It's no different when you weld a small area in the middle of a transmission case. Pre and post heat are vital when welding a bridged area.
    treat it like it's cast iron and you can't go wrong.
    This is simply my opinion, based on all the junk I've either succeeded or failed at repairing. Either way if you haven't determined if it's cast or billet you are simply guessing blindfolded. (and once again in my opinion and with no intent to offend anyone)
    I can easily see it is a machined part..... I of course dont know its origin.. it could be billet, it could be forged, it could be cast( i doubt the last part)

    Leave a comment:


  • dvice
    replied
    Originally posted by FusionKing View Post
    I do think it's safe to say that it's definitely junk now.
    That shape would have had a tendency to crack no matter what the material was.
    The entire part should have been pre-heated before welding and kept hot uniformly until cooled. And that is welding it like Noel describes.
    If the part is Billet then there is a good chance it could be 7075. If it is cast there is a possibility it could be a pot metal.
    By the picture I would seem much effort was not to disturb the surrounding area...as in grinding through 100% and worries in regard to requiring additional machining. I get that. But you usually only get one good shot at a part like that.
    I would say from the pic you have way too much dilution from the parent metal and too much contraction from the rest of the part not being up to temp.
    When you commit to welding a piece like that you pretty much threw heat treat out the window, but you can't have the only soft area the spot that is the weakest. It's no different when you weld a small area in the middle of a transmission case. Pre and post heat are vital when welding a bridged area.
    treat it like it's cast iron and you can't go wrong.
    This is simply my opinion, based on all the junk I've either succeeded or failed at repairing. Either way if you haven't determined if it's cast or billet you are simply guessing blindfolded. (and once again in my opinion and with no intent to offend anyone)
    there was NOTHING to lose trying to repair this reciever... the first issue was contamination.. from anodization UNDERNEAT where I was welding..eventually I sand blasted it..i think it welds fine..it just cracks.. afterwards.. and since it was such a THIN section( thinner than most thinking because of acme threads underneath) I had to build it up and try to flow it out to the receiver... I dont mind the blob as I machine it back down to size!... Ive dont many welds....I dont do it for money and if it is good enough Im happy... I welded this gas tank filler 3 weeks ago... and i build an 8 foot long fuel tank for my boat out of .090" aluminum 24" wide and v shaped on the bottom...i tacked it at home with my MIG machine and brought it to work and tigged it closed. just sometimes you get a DIFFICULT job... for your own skill level

    Leave a comment:


  • FusionKing
    replied
    I doubt it

    Leave a comment:


  • ryanjones2150
    replied
    If we pool our money together we might be able to afford a tube of the stuff.

    Leave a comment:


  • FusionKing
    replied
    OK.....where do I get my Nano-rod ?

    Leave a comment:


  • Noel
    replied
    https://phys.org/news/2019-01-nanote...n-weldable.amp

    When ever there is a problem, someone goes looking for a solution, seems they've found one? Shout out to the folks at UCLA.

    https://www.nature.com/articles/s41467-018-07989-y
    Last edited by Noel; 01-26-2019, 11:09 AM. Reason: Just read the original article.Interesting enough I thought to add the link, explanation is highly understandable.

    Leave a comment:


  • FusionKing
    replied
    I do think it's safe to say that it's definitely junk now.
    That shape would have had a tendency to crack no matter what the material was.
    The entire part should have been pre-heated before welding and kept hot uniformly until cooled. And that is welding it like Noel describes.
    If the part is Billet then there is a good chance it could be 7075. If it is cast there is a possibility it could be a pot metal.
    By the picture I would seem much effort was not to disturb the surrounding area...as in grinding through 100% and worries in regard to requiring additional machining. I get that. But you usually only get one good shot at a part like that.
    I would say from the pic you have way too much dilution from the parent metal and too much contraction from the rest of the part not being up to temp.
    When you commit to welding a piece like that you pretty much threw heat treat out the window, but you can't have the only soft area the spot that is the weakest. It's no different when you weld a small area in the middle of a transmission case. Pre and post heat are vital when welding a bridged area.
    treat it like it's cast iron and you can't go wrong.
    This is simply my opinion, based on all the junk I've either succeeded or failed at repairing. Either way if you haven't determined if it's cast or billet you are simply guessing blindfolded. (and once again in my opinion and with no intent to offend anyone)

    Leave a comment:


  • Helios
    replied
    Fatigue failure. I'd say the receiver is roached. Not that it owes you anything after 40 cases of 3.5" shells...

    Leave a comment:

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