Bevel or Square Edge

  1. Brad93

    Brad93 M J B Engineering

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    I’m starting a new contract next week that involves quite a bit of welding of 5/6mm sheet.
    All MIG onsite (indoors).

    It’s a load of sheet metal ductwork so cutting out damage, plating repairs, making new lobster backs up to about 72”.

    Now I’m okay a Mig but it’s been years since I’ve done such thin stuff that’s not box section etc. Just having a play on 4mm in the workshop and I’ve got the butt welds dialed in on a 2G using about 2.5mm gap but really struggling with doing a 3G.
    I’ve tried various gaps but it’s just coming out really poor.

    Any tips?
     
  2. Brad93

    Brad93 M J B Engineering

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    2G
     
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  3. Brad93

    Brad93 M J B Engineering

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    Forgot to say as far as I know everything will be a square edge.

    I think that rules out stoving the first pass on an open root butt.

    I’ve has the neatest results at 3.2mm gap, square edge, 65A, 16.5V, 2.5m/min
     
  4. Brad93

    Brad93 M J B Engineering

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  5. Brad93

    Brad93 M J B Engineering

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    Shame they haven’t got a lorch there or I could speedroot the thing and be done with it.
     
  6. Richard.

    Richard. Member

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    So you can’t use the S3 then?
     
  7. Brad93

    Brad93 M J B Engineering

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    No I’m being a subbie for two weeks
     
  8. Richard.

    Richard. Member

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    Does it need to be full pen? Some repair patches on some ducts?
    Lobster back will be good fun. I’ve made a few of those at smaller diameters.
     
    Hitch likes this.
  9. 3G on 6mm plate with no bevel is going it a bit with standard MAG to be honest
     
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  10. Hitch

    Hitch Moderator Staff Member

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    11,959
    Somerset
    Big lobsterbacks really show up any errors in the development. Nice if they're lasered ready to roll.

    As Richard said, is there any need to get a textbook full pen weld? Will the fitup be good enough to weld it up nicely?

    Is it an option to run a beveller round the sides of the patches to give you a partial prep?

    Done quite a bit of 6mm square edge butts where part pen is acceptable, leave about 4mm.
     
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  11. Brad93

    Brad93 M J B Engineering

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    It’s a new company I’m starting to sub for so not sure what their standards are.

    It’s on an incinerator plant and carried the fume and dust from the economiser to the filters if I remember correctly.

    The main lobster backs should be done just a case of welding them up, plating holes and welding new flanges on etc.
     
  12. Brad93

    Brad93 M J B Engineering

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    I see some tig they done in their workshop and it wasn’t the best, I’ve seen better from people on here.

    This is one of the smaller ones.
     
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  13. Brad93

    Brad93 M J B Engineering

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    They don’t do any rolling in house - I know that much.
     
  14. Brad93

    Brad93 M J B Engineering

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    I need more practice if it needs full pen that’s for certain.
     
  15. Hitch

    Hitch Moderator Staff Member

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    What sort of incinerator?

    I did a lot of work at an animal incineration plant about 9/10 years ago. Some sights in there mind!

    If it's anything like that was, they won't be fussy :laughing:

    Doesn't sound like the sort of stuff that anyone's ever going to take a second look at.
    Has any of it got refractory linings?
     
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  16. Brad93

    Brad93 M J B Engineering

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    Power from waste. At Thames Water. £250m pound plant converting sea water to drinking water
     
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  17. Brad93

    Brad93 M J B Engineering

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    5,910
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    Don’t be silly, just mild steel!
     
  18. Brad93

    Brad93 M J B Engineering

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    No idea if it’s before or after the scrubbers so I’m wearing my adflo permanently!
     
  19. zeppelin builder

    zeppelin builder Member

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    bang em hard together weld inside first then grind to clean and fill n cap or ceramic tiles on inside big gap eg 5mm and weld from outside
    probably being too fussy if it ducting though as it wont be no great pressure involved
    just sealed probably !

    different if it was the steamline to turbine though that would be full on stuff
     
  20. Kent

    Kent Member

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    10,002
    Location:
    Bowland, Lanacshire,UK
    It won't be full penitration. Dont fret it
     
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