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Mig welding chrome moly

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  • Mig welding chrome moly

    After doing a search and reviewing past threads,I was curious if there is any one with any more info on welding CM tubing with mig.We are currently looking at a job that is being done this way and I am looking for more info.The tubing is 1" round.Thanks,COZ

  • #2
    Coz,
    Although my 4130 experience requires TIG welding due to sactioning body rules, my brother-in-law is into building light aircraft. He tells me there is a small company building small airframes using MIG welding. Not sure what process controls they've implemented to ensure penetration, but it evidently satisfied the FAA, who cetifies their airframes. I'll try to find the company name, but this may give you another area to search.

    Rob

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    • #3
      Rob,

      Did you ever find the name of the manufacturer who was Mig welding their airframes?

      Thanks in advance.
      John

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      • #4
        what specifically are you looking for? I have mig welded cromoly tube and have had no problems. I was told by a friend that it would weld different than regular steel but didnt notice any difference. The tube i welded was 1" .125 wall.
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        • #5
          df5152,

          What wire did you use to mig CM?

          Thanks,
          Joe
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          • #6
            Is this job a race chassis or roll cage? I assume not. Most people that mig weld this use the standard ER70 or ER80 wire. I don't like to mig this stuff. Too much chance of cracking under impact. So if this structure or job is not a critical weldment, go ahead. As for airframes, not sure why the gov would approve a mig welded 4130 airframe. Then again...I've seen the gov do some other things out of pure stupidity too. Just 'cause it's the government doesn't make them automatically right.

            Andy

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            • #7
              Correct me if im wrong, but i heard all welds on CM should be stress relieved, which is not a practical process for most.
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              • #8
                tom,
                On light tubing if you keep the heat and arc lengths down, no stress relieving is needed. 4130 doesn't like a lot of heat or harsh arc transfers like mig. If mig welding than I'd say yes but even then, if not done correctly, it can be a bad thing. Remember, heating the 4130 to stress relieve does change the parent metal properties some so if it's tig welded right, just leave it.

                Andy

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                • #9
                  More fuel to the fire.

                  Maule aircraft in Georgia MIG welds their fuselages which are 4130. They use ER80S-D2 and do not do any stress relieving afterwards. They have been doing it this way for some time. Another manufacturer has been MIG welding its 4130 airframes since the '70's. I have heard that back in the '40's
                  one manufacturer even stick welded its airframes. In talking with several people involved in rebuilding these aircraft after they received structural damage from bad landings, etc. I was told that the welds held very well and that often the tubing broke/tore some distance from the welds.

                  I think most would agree that TIG is a better procedure. However, MIG welding 4130 is used with good results. I plan to tour the Maule factory sometime later this year and hope to find out more about their welding procedures.


                  John

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                  • #10
                    John,
                    Finally had a chance to ask my brother-in-law about the aircraft manufacturer using the mig process of 4130. He said it is American Champion Aircraft, they took over building the Belanka Scout. I think this is a case where the FAA had to get out of the way unless they can prove a particular product flaw. In the short haul, their costs may actually be higher due to additional testing, but from a long haul volume manufacturing perspective it will no doubt be cheaper.
                    Rob

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                    • #11
                      I believe MIG welding chromoly is becoming popular because it saves so much time in production. I have no practical experience but according to the reading i have done, it should work fine. You need to determine your settings and then test coupons. In the book "Performance Welding" they talk breifly about migging Chromoly.
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