Penetration & fusion - Part 1

  1. MichaelV

    MichaelV Forum Supporter

    Messages:
    217
    Location:
    Co. Antrim
    In view of the conversations (passionate debates?) that happen here periodically, discussing how various types of MMA electrode perform, in various positions, I thought it would be interesting to carry out a series of test welds, then cut and etch.

    This is the first of, hopefully, a wee series. The thought is that this exercise might feed into the discussions, with no promises of firm conclusions, of course ;). No attempt will be made to justify the "quality" of the welding!

    Position & material:
    PB (2F), tee joint between 10 mm thick mild steel, rolled flat bars (hence rolled edges; see below).

    Parameters:
    3 passes each side with 3.2 mm, 6013 (INE 46), DC negative, 125A, zero arc force. Passes were made on alternating basis, rather than building up complete weld on one side of the joint.

    Remarks:
    Lack of penetration/fusion at the root is the most obvious feature, perhaps. The effect on fit-up of the rolled edges of the oncoming plate might have played a part, but probably isn't the whole story. Penetration seems a bit better on the (vertical) faces of the oncoming plate, and I probably made a more conscious effort to direct the arc onto them - excessively, on the first pass. Toes washed in fine, albeit fillet profile is lumpy at best :whistle:

    Michael

    01.JPEG 03.JPEG 04.JPEG
     
  2. nickk Forum Supporter

    Messages:
    2,523
    Location:
    Hay-on-wye
    Good profiles even with poor fit up,but how many jobs call for a pre milled face?
    Less penetration on the horizontal though ,as stated.
     
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  3. TechnicAl

    TechnicAl Member

    Messages:
    7,792
    Location:
    Rotherham
    Thats what you would expect from that type of rod...some of the really soft arcs will have even less pen....now try some Vodex and you will see a difference

    A 2.5 for the root should improve the pen
     
  4. Brad93

    Brad93 M J B Engineering

    Messages:
    9,241
    Location:
    Essex
    That will hold for a lot longer than the base metal welded both sides as it is.

    Usually try to do a gas cut edge and get it bang on 90, then take a good pass with the grinder to make sure there’s no oxides present.

    I can probably aid you with some samples if you’re interested of different rod types. I’ll knock up a fresh batch of Nital.
     
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  5. MichaelV

    MichaelV Forum Supporter

    Messages:
    217
    Location:
    Co. Antrim
    Absolutely, Brad, please do. This type of exercise can only benefit from other contributions :thumbup:

     
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  6. Brad93

    Brad93 M J B Engineering

    Messages:
    9,241
    Location:
    Essex
    To expand on Al’s post above, for members who may not be aware, a smaller electrode for the root pass will normally give a greater depth of fusion/more penetration than a larger electrode even though the amps are lower due to the current density for the cross-sectional area.
     
  7. MichaelV

    MichaelV Forum Supporter

    Messages:
    217
    Location:
    Co. Antrim
    @Brad93 and @TechnicAl have just defined the next test ;)

     
  8. TechnicAl

    TechnicAl Member

    Messages:
    7,792
    Location:
    Rotherham
    Well put Brad.....I should have explained

    Should also add that when doing comparison tests you need to limit the variables as much as possible......so you should use the same plate, same dimensions and same fit up etc etc.........Those pictures are valid for what they are but if that flange had a straighter cut face the result would be different.......the shape it is, is difficult to reproduce time after time

    So really those pictures are actually useless for comparison purposes

    Should really only do one side as well......by doing both you are not comparing like with like

    I have done probably thousands of comparison tests
     
  9. Brad93

    Brad93 M J B Engineering

    Messages:
    9,241
    Location:
    Essex
    Rule of Roughly 1 Amp per Thousandth/Inch (Taking into account most 3/32” (2.5mm) rods won’t run nice past 90A.

    125 / (3.2 • 3.1415) = 12.5A/mm2

    90 / (2.5 • 3.1415) = 11.5A/mm2

    Almost as much poke, a lot less filler metal going into the weld.
     
    Mid Wales welder and metalmelt like this.
  10. Brad93

    Brad93 M J B Engineering

    Messages:
    9,241
    Location:
    Essex
    When you’re doing real controlled tests it can get very laborious!

    A PAMS unit makes things a fair bit simpler. They’re a lot more high tech now days.
     
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    • 1C66EDA1-5593-481A-9BD5-4F8EE3C1C919.jpeg
    MichaelV likes this.
  11. TechnicAl

    TechnicAl Member

    Messages:
    7,792
    Location:
    Rotherham
    I had the first one when Chris and Kim were working with the TWI......Later we converted one for testing MIG wire, which was then copied and installed in every Lincoln MIG wire factory
     
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  12. Brad93

    Brad93 M J B Engineering

    Messages:
    9,241
    Location:
    Essex
    Great tools. Love that ticker tape sound!

    Had about 4 of this type in varying states of working order - maintaining one with spares from the others.

    Gets serviced and calibrated every year by TVC.
     
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