Spot weld penetration problem

  1. JacobKot New Member

    Messages:
    9
    Location:
    Manchester
    Hi. I'm new to welding and recently acquired 180A MIG from R-Tech. I'm trying to ma 20200115_155745.jpg ke spot welds on 1,2mm sheet and for some reason can't get proper penetration. I cleaned mill scale and tried various combination of voltage/wire speed settings but my welds won't go through on other side. As experiment I've tried to set voltage to max to burn hole in test piece but for some reason my welder wasn't able to do that. I'm using it with gas. Have you got any ideas?
     
    • 20200115_155735.jpg
  2. mike 109444

    mike 109444 Member

    Messages:
    4,144
    uk Bristol
    Wire diameter ? (0.6 maybe)
     
  3. JacobKot New Member

    Messages:
    9
    Location:
    Manchester
    Yes 0.6
     
  4. mike 109444

    mike 109444 Member

    Messages:
    4,144
    uk Bristol
    You'll get more amps in with 0.8 wire AND by keeping the wire in one spot you are just pilling the wire up and the heat is going into the pile.
    See what happens when you run a bead and you should find that the heat will gradually build up in and around the weld pool and the heat affected zone (either side of the bead) will get wider as you go along hence why when welding car bodywork it pays t do it in very short beads or a series of tacks. Known as the "thin metal technique".
     
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  5. When I read the title I assumed you were joining two pieces. If that is what you need to do, I usually drill a hole in the top piece and fill the hole with a spot from the mig.
     
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  6. JacobKot New Member

    Messages:
    9
    Location:
    Manchester
    I'll try 0.8 wire. Thank You for advice.
     
  7. eddie49 Member

    With a MIG welder you can only simulate spot welds. Are you planing to drill or punch a hole in the upper sheet? That is known as plug welding. It is best to make the hole 8mm diameter. Clamp the sheets together very tightly before welding. I don't see a second sheet - are you just practising on the "lower" sheet? For 1.2mm + 1.2mm you will need about 80 Amps. Plug welding isn't easy - why have you chosen this method, what are you working on?
    A 180A machine set to max should melt straight through 1.2mm. When you say "acquired" a 180A Rtech, is it new and are you sure it is working correctly? Are you attaching the work return cable ( "Earth" clamp ) directly to the workpiece? Could you post some photos of just plain straight beads on clean sheet steel?
     
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  8. JacobKot New Member

    Messages:
    9
    Location:
    Manchester
    I'm trying to get settings right before butt welding 2 panels. Welder is new however I can't compare it to any other one. Earth was connected to plate on which I put welded piece. I attached pictures of what I think you asked for. This time earth was connected directly to welded piece and I set machine to get that frying beacon sound.
     
    • 20200115_202642.jpg
    • 20200115_202626.jpg
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  9. eddie49 Member

    That straight bead above looks fine. For the butt weld at this thickness, the two sheets should fit closely together. It may help to put a copper bar behind the steel.
     
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  10. daedalusminos Member

    Messages:
    687
    Location:
    Norwich
    It would be best to let us know what sort of joint you're trying to achieve, ultimately the welder needs to be set up on the final joint.
     
  11. mike 109444

    mike 109444 Member

    Messages:
    4,144
    uk Bristol
    The heat affected zone (haz) is in yellow and as you can see there is less heat in the metal at the start and end of the weld.
     
    • haz.jpg
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  12. JacobKot New Member

    Messages:
    9
    Location:
    Manchester
    Thank You all for help. I've finally managed to figure out optimal settings for my needs. As suspected problem was not with machine but me :-)
     
    eddie49 and slim_boy_fat like this.
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