Steel deck patching

Discussion in 'Metal Boat Building' started by Steelboat, Feb 18, 2022.

  1. Steelboat
    Joined: Feb 2022
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    Location: Seattle

    Steelboat Junior Member

    I am starting in on my first patch in the deck, and seeking advise on welding process. My experience is a fair amount of TIG and basic competency in stick welding, but never a patch in mild steel plate. It is a small insert, just 20 cm square, with rounded corners. 5mm mild steel plate is used (3/16")

    My equipment here is 200a DC TIG, and 250a DC stick welder. I have a covered area to work, and clean metals. No rod oven or MIG.

    considering so far:
    TIG weld the the insert
    stick weld with 6011 rod
    stick weld with 7018 rod

    Open to new ideas, but need simple and not too advanced (my welding training is 30 years ago)
     
  2. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    I'd use 6011/7018 rod with a backing bar and a single bevel joint. If you get a really tight root, you could use sequenced welding, multi-pass, and dispense with the backing bar; but as the smallest 6011/7018 rod is 1/8, this could be tricky. You would need some practice pieces to get the amps right to prevent melt through. As it has been a while, I would suggest you get a welding handbook and read up on methods, joints, and fits.
     
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  3. Steelboat
    Joined: Feb 2022
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    Location: Seattle

    Steelboat Junior Member

    I watched YouTube videos on ceramic backing with aluminum tape instead of a traditional backing bar. The welds look beautiful, almost like a backside pass was done.
     
  4. Barry
    Joined: Mar 2002
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    Barry Senior Member

    6011 is fine and I would go with the 3/32 inch. This should be easy to find.
    I would not consider TIG for 3/16 in a center of a steel plate due to the length of time that you will have to heat the surrounding metal to establish a weld pool. You can actually weld in distortion. Ie a long duration to bring the bead site to
    a molten state can cause large distortions.
    My first choice would be MIG but you do not own the machine.
     
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  5. Steelboat
    Joined: Feb 2022
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    Location: Seattle

    Steelboat Junior Member

    Thanks Barry, definitely easy to find that rod.

    Would you do the weld in a single pass? I just measured the steel thickness as .134" = 10 gauge (3.4mm)
    Is a ceramic or other backing preferred- considering limited skill with 100% penetration welds?
     
  6. Steelboat
    Joined: Feb 2022
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    Location: Seattle

    Steelboat Junior Member

    I am looking at flipping the ceramic backing upside down. Anybody tried this?
     

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  7. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Not recommended.
    The purpose of the groove, is to allow the gases to escape when welding. As you now show, inverted, this cannot occur.
    If they can't escape, you can get porosity and other issues.
     
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  8. Steelboat
    Joined: Feb 2022
    Posts: 52
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    Location: Seattle

    Steelboat Junior Member

    I had thought the groove was to allow a bead to form on the outside. Will look for an appropriate sized groove for my plate now.
     
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