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Thread: Welding 3mm RHS

  1. #1
    Join Date
    Mar 2017
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    Default Welding 3mm RHS

    Just started stick welding again and I'm trying some 3mm 50x50 RHS, got a couple of questions.

    I found some good instructional vids for fillet welds but I couldn't find many for the join you get when you're putting one bit of SHS on another in its middle, making a "T". There are two fillet welds but the side welds I saw are 'flare bevel joints'? Is there any good documentation on how to make these? I saw you spend 'a bit longer on the bottom thicker piece' but is this the legit way?

    Is 7018 usually a bit of a bastard when it comes to sticking? I'm using 2.5mm.

    What sort of amps should I be using for the joints, same for all for 2.5mm? What about 6013 sticks? Thanks.

  2. #2
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    Default

    In short, you want to be focussing most of your weld pool on the curved part (as it'll take more heat) while letting the edge of the weld pool wash against the open edge of the other piece.

  3. #3
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    Quote Originally Posted by RustyArc View Post
    In short, you want to be focussing most of your weld pool on the curved part (as it'll take more heat) while letting the edge of the weld pool wash against the open edge of the other piece.
    That's my experience, tho I have never had any training. The exposed end of the vertical piece will burn thru quicker than the closed horizontal fillet, although 3mm is a good thickness to practice on.

    Good luck. I have never had any great success with arc fillet welding. I usually start getting better near the end of a project, get cocky, all goes to $%*@ and the project is finished. Next project I am back to the start again. I just use mig for the difficult welds now, and to cover up the messy ones.

    Dean

  4. #4
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    My advice is don't overthink it, just have at it on practise pieces, see what comes out best really

  5. #5
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    Default

    There is a technique which can be used.

    As Dean has said using the arc on the open cut end just melts away the cut edge as heat cannot dissipate fast enough before a melt away.

    Best to fill it from the opposite way around. Tack at stop and start-it helps to hold the bead from dribbling over the edge.

    Weld the rolled face opposite the cut edge. Low amps quick bead and let it cool.

    The trick is to do a number of beads to fill that rolled edge. Small quick beads cooling between each individual bead. Thia will fill the gap until you can manage a bridging pass to join the 2 members.

    Lay the electrode down 20° above the horizontal until you get close enough to bridge..2.6diam 6012 if you have them. 6013 can be a bit sloppy to fill gaps.

    Below is a flare bevel -similar but not the same. It is closed in either side unlike the RHS joint. Using the other pic below as a guide the electrode is placed with the rod along the length of the RH member,but 20° angle to its horizontal surface.

    Flared welding bevel.jpgbutt joint for tack.JPG

  6. #6
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    Default

    Another way is to put some offcut or old welding rod(flux removed) in the gap to act as a bridge for the first bead... low amps!
    You can also allow an extra couple mm on the lenght and notch the open end of the tube and flare out the "wings" over an anvil
    ....................................................................

  7. #7
    Join Date
    Jul 2013
    Location
    nsw
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    256

    Default flares and fillets

    i find this worth worth the effort sometimes.

    grinder required!

    allows for fairly thin stock to be welded with stick and takes blow through almost out of the equation

    FullSizeRender.jpg

  8. #8
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    Feb 2015
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    Default

    Being RHS with 3mm walls I really can't see any problems with burning through as long as the amps are right and the gap reasonably short. On joins where one piece is thinner than the other I weave, concentrating mostly on the thicker section. no idea what the amp settings are. I'm not in Graham's league, I did my 5-6 years and got out quick, welding has only been a hobby for me since. Don't know if it's me being lazy or not but I never look at the gauge, I listen to the sound and watch the puddle to set the amps.

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