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  1. #1
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    Default How to get square cornered welds

    Hi guys, I'd like a little advice from the welding gurus here if possible.
    I've just finished welding up a wood heater firebox. I put a posting up here in May last year with the details. Yes it's taken me that long to get it done!!
    The material is 12mm plate with full open corner welds. I used Kobelco LB52 for the root run and five passes with Ferrocraft 22. It all turned out fine, but I would really like to have a sharper corner with less radius on clean up.
    I was thinking of clamping a strip of copper to the side of the weld and have it above the weld by 20mm or so and then doing another run close to the edge and letting the copper act as a dam. I could then grind that weld flush with the top, roll the box 90 degrees and do the same on the other plane. Would this work OK? If I had some copper handy I'd just give it a try, but I'd be interested in hearing what the gurus have to say.
    Thanks.
    Eric

  2. #2
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    I do use copper bars and blocks to form welds but only on thin material. I can't see why it wouldn't work in your situation though. You might need some big blocks of copper ...

  3. #3
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    Sounds like you need a pack of square electrodes

  4. #4
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    Aluminium works well also.
    Kryn
    To grow old is mandatory, growing up is optional.

  5. #5
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    Default

    Thanks Guys, I can get hold of some 2mm copper sheet to give it a try. Might be a little thin, but I could back it up with some 6mm aluminium that I have on hand. I wouldn't have thought that aluminium in contact with the weld pool would work that well Kryn, what with the low melting point. Wouldn't it contaminate the weld? Have you used this technique? I'd be interested in hearing your experiences with this. I'm certainly no expert.
    I love the idea of the square electrodes Nedshead, but the guy at bunnings had never heard of them and recommended that I contact a specialist welding supplier. He was pretty helpful though and also suggested that I could probably make my own. I told him what I was trying to achieve and he suggested that I buy some 4mm key steel, some iron filings and some powdered borax. He even wrote out the recipe on how to mix the iron filings with the borax. I'll give that a try tomorrow and see how we go. Thanks again.
    Eric

  6. #6
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    I have used the aluminium on the sides to help build up the weldment, but not to the extent that you're wanting to do. What is normally done is that the welds are built up in layers, one run alongside the next, as in multiple fillet welds, it's not something that's going to be a quick fix. You could tip the box at about a 45 degree angle, and lay the welds down, decreasing in width as you build up, be aware that constant welding at the one edge/corner may cause distortion. There shouldn't be a need for something to go along side of the welds.
    Kryn
    To grow old is mandatory, growing up is optional.

  7. #7
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    nsw
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    Default

    it seems you only have stick process, so i would run the largest 6013 electrode on the cold side along the edges to build up material. down hill.

    grind/machine down to the required sharp radius.

    certainly try the copper forms too.

    good luck with it!

  8. #8
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    Thanks Kryn and meadow street, yes I've done multiple runs and filled the open corners, but I would guess that I'd need another four or five runs to get it to clean up to a sharper corner. I thought that by using something on the side I could reduce the number of runs and also the time in grinding. I'll give it a try at the weekend if it's not raining (I'm doing all this outside)
    Eric

  9. #9
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    The edges can be built with 6012 electrode. Hold the electrode horizontal to the bead and use an extremely short arc. Travel fairly quickly so the arc makes a very small pool and solidifies quickly.

    Build the bead up layer by layer to fill the radiused corner.The arc force will push the depositing bead up fairly vertical. Over build it slightly.Two or three passes should be enough.

    No need for copper and ali chill bars.

    Grahame

  10. #10
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    Quote Originally Posted by Grahame Collins View Post
    The edges can be built with 6012 electrode. Hold the electrode horizontal to the bead and use an extremely short arc. Travel fairly quickly so the arc makes a very small pool and solidifies quickly.

    Build the bead up layer by layer to fill the radiused corner.The arc force will push the depositing bead up fairly vertical. Over build it slightly.Two or three passes should be enough.

    No need for copper and ali chill bars.

    Grahame
    Thanks for the detailed advice Grahame. I'm not that good at welding really and would imagine that this technique would require some skill level that I probably don't have. I'll give it a shot though and post some pictures on the results.
    Thanks again.
    Eric

  11. #11
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    Hi Guys, now that winter is over I'm getting back onto the firebox project. The corners turned out great, but it took a lot of runs and grinding back. I've just got to weld the flange onto the firebox now and this part of the project is complete.
    There's a couple of spots around the flange that has quite a gap, something like 3mm. Any suggestions on the best way to fill this gap without the weld pulling too much.
    thanks.
    Eric






    grinding backfirebox and bell.jpgfirebox.jpgfirebox and bell2.jpg

  12. #12
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    3mm gap for 12mm material is about what I'd be looking for as a root gap anyway. As a backyard hack, that is. I'm sure there are official guidelines that are more specific.

  13. #13
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    Hi Eric,
    When I get to a situation like that, I use a couple of bits of scrap flat bar made into a cross and a wedge similar to (a) in the attached link.
    welding 2.gif

    Hope this helps,
    Kryn
    To grow old is mandatory, growing up is optional.

  14. #14
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    Quote Originally Posted by Legion View Post
    3mm gap for 12mm material is about what I'd be looking for as a root gap anyway. As a backyard hack, that is. I'm sure there are official guidelines that are more specific.
    Actually there are a couple of spots on the end of the arched lid that are closer to 6mm gap. It's probably visible in the centre picture. I guess I'll just fill them and hope that the mounting holes still align.

  15. #15
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    Quote Originally Posted by KBs PensNmore View Post
    Hi Eric,
    When I get to a situation like that, I use a couple of bits of scrap flat bar made into a cross and a wedge similar to (a) in the attached link.
    welding 2.gif

    Hope this helps,
    Kryn
    Thanks Kryn, that's good info, but I can't flex anything here. Check the middle picture. It's where the bolted on flange gets welded to the firebox.

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