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  • Bending Aluminum 7175 with heat?

    I have a part made of Aluminum 7175 and one of the lugs on the part was accidentally dropped and slightly bent. Do you think I can apply heat around 180F around the Lug and bend it back to straighten it? I know it will cause a heat affected zone, therefore, I can heat treat it after I bend it back in place. and do pre- and post hardness tests. Any advice ? Picture attached.


  • #2

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    • #3
      I guess there are some real questions here.
      Like what does it do? Is it a "critical" application? Can you make another one?
      If I knew I was going to heat treat it, I would probably use more than 180F to reduce the chance of it cracking. More like 300F (knowing me probably a bit more)
      If your question is being asked because of your fear of 7175 developing problems such as micro-cracking from using heat to straighten.....then I guess the real question is, what is the max working temp of 7175?
      Last edited by FusionKing; 11-17-2016, 07:20 AM. Reason: edited because I answered with regards to 7075 vs 7175

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      • #4
        It is a critical component, its a landing gear strut. This will be my first time bending so trying to get some advice.

        1) Should I get a torch and apply heat around 180 F to the surrounding lug and bend very slowly with some kind of clamp/ pliers. I would ultimately start bending when the part is around 180 F. Or realistically, how hot should I get it to proceed to bend it.
        2) After I straighten it out, you recommend heat treating the entire part at a higher temperature right?

        -Melting point: 890 - 1175 F
        Annealing Temp: 775 F
        Solution Temp: 870-900 F
        Aging Temp 225 F

        I would guess to heat treat it around 225 F for 6 Hours ?

        http://www.alcotec.com/us/en/support...d/a7075tds.pdf

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        • #5
          Landing gear part....???.... will at least need recertified... maybe scrapped... what does the FAA inspector say..???

          The FAA will have final say...............they are pretty picky about that kind of thing.... later failure could be very ugly
          .

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          • #6
            H80N is right that part needs to be inspected and recertified. Do you have access to die pen or x-ray in your facility? Whenever we had to bend aluminum we would anneal it first then bend and reheat treat, your best chance of not cracking it is in its softest most pliable state. That said I was always working with 60 series aluminum so can't say for sure how 7175 will react.

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            • #7
              Looking at the picture more I would put a piece of plastic on the inside edge of the bent tang and dink it with a small hammer. Problem solved. But would still check for any cracking. Seriously sorry to see when something like this happens it just sucks big $ in the balance.

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              • #8
                Originally posted by ron144 View Post
                It is a critical component, its a landing gear strut. This will be my first time bending so trying to get some advice.

                1) Should I get a torch and apply heat around 180 F to the surrounding lug and bend very slowly with some kind of clamp/ pliers. I would ultimately start bending when the part is around 180 F. Or realistically, how hot should I get it to proceed to bend it.
                2) After I straighten it out, you recommend heat treating the entire part at a higher temperature right?

                -Melting point: 890 - 1175 F
                Annealing Temp: 775 F
                Solution Temp: 870-900 F
                Aging Temp 225 F

                I would guess to heat treat it around 225 F for 6 Hours ?

                http://www.alcotec.com/us/en/support...d/a7075tds.pdf
                [Disclaimer: I'm no expert, just mentioning what I have gathered from reading some heat-treatment white papers]

                Solely heating the part @ 225°F for 6 hrs is not actual "heat treatment". That won't do anything except heat the part to 225°F. That [aging] is the very last component of the full heat-treatment process. The heat-treatment would be initialized by what is called solid solution heating, quenching, and then precipitation heat treat (artificial aging), depending on the desired temper.
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                • #9
                  Looks like this could be an expensive proposition if you can't fix it; sorry to see someone in a mess like this. How about calling whoever made this part in the first place, and ask if they have any FAA-approved repair procedures? or is it from a defunct company? Production or Experimental plane? What bolts here, a wheel, or a fairing? Have you talked to an A&P with IA?

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                  • #10
                    Hi guys,

                    Thanks for the inputs. The FAA will approve it as long as its substantiated and a FAA approved Designed Engineering Repair Engineer has authority to approve the repair. We do have NDT (die) to check it. No X-ray though.

                    DER recommend putting in a heat blanket to around 180-200F to make the heat distribution even and then slowly bend it. I guess we could also heat it up with a torch but it may be risky since the rest of the part is not heated. (Would that be similar to annealing the metal?) Of course we will make a fixture to make it less prone to cracking when we do bend it. Right now I have measured pre-hardness to various surfaces on the part. After we perform the repair will check post hardness. If it does match, we will not heat treat.

                    That particular lug that is bent is connected to a rod that attaches to the main door of the opening and closing of the nose landing gear. That particular lug does not carry the great amount of the load from the aircraft. Therefore, we feel we could get away with this one. And yes, by all means if that lug connected to a drag brace or a torque link, this would be scrap.

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                    • #11
                      Glad that you will be operating with the guidance of an FAA approved Design Engineering Repair Engineer....
                      .

                      *******************************************
                      The more you know, The better you know, How little you know

                      “The bitterness of poor quality remains long after the sweetness of low price is forgotten”

                      Buy the best tools you can afford.. Learn to use them to the best of your ability.. and take care of them...

                      My Blue Stuff:
                      Dynasty 350DX Tigrunner
                      Dynasty 200DX
                      Millermatic 350P w/25ft Alumapro & 30A
                      Millermatic 200

                      TONS of Non-Blue Equip, plus CNC Mill, Lathes & a Plasmacam w/ PowerMax-1000

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                      • #12
                        Just let me know what plane NOT to get on with that part...
                        Ryan
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                        • #13
                          ...chicken...

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