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  1. #1
    Join Date
    Sep 2006
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    Australind , WA
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    Default Advice on welding thin steel plate

    Chaps,
    I'm making a stand for a wood fire and I got some 3mm steel plate cut for it.
    Now I need to weld the uprights into a box, I'm wondering if it is doable with an arc welder( all I've got)......
    I can clamp the sides into right angles, but what is the best position to clamp the material ? ( one side overlaps the over or both even with just the inside corners touching?)
    If even I could try and fill in the filet from the outside or try and weld on the inside of the join and hide the weld. The second option have prove difficult when I go the join the two right angled sections into the final 'box'.
    Is it worth trying to arc weld such thin material in the first place?
    Its just for a shed fire but I don't want it to collapse on me....lol

    A mate has a gasless MIG but I have never used a MIG before and its too much to ask him to do for me. Would that be a better option?

    Steve

  2. #2
    Join Date
    Apr 2012
    Location
    Healesville
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    2,129

    Default

    G/day Steve, it sounds to me like you need to have a good practice before you start, then I would suggest that you try to position and reposition the job so that all your welds are horizontal.

    I have many times welded 1.6mm with 2,5 rods, bzzzt stop bzzzt stop bzzzt stop ect, if you are using 2.5 rods on 3mm you should go ok but you will need to practice until you feel confident first.

    john

  3. #3
    Join Date
    Aug 2008
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    near Rockhampton
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    6,216

    Default

    3mm is very easy with a stick welder.... Use satincraft 13, 2.5mm..
    Gold, the colour of choice for the discerning person.

  4. #4
    Join Date
    Feb 2012
    Location
    Adelaide
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    Default

    I weld 1.6mm all the time with 2mm rods, 1.2 and below you might need to stitch it. Mig does make it easier though.

  5. #5
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    Default

    Thanks guys. I'll give it a go, but I think I'll try and find some smaller rods. I only have 2.5's and I think the small, the better....

    What do think about where to weld. Inside or outside of the join?

    Steve

  6. #6
    Join Date
    Aug 2010
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    Near Bendigo, Victoria, AUS
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    Default

    As already said, 3mm is fine to arc weld. But expect some distortion. You dhoud tack it in a few places first, then weld in short sections - say 50mm at a time - to reduce one panel heating up much more than an adjacent on.If you find distortion developing, stretch neaby welds by hammering until the distortion disappears befor continuing. It's the shrinking of the welds which causes distortion. That's revesible by stretching (hammering thinner and therefore longer) those welds.

    Re your last question: use 2.5mm rods. Thinner may need more than 1 pass and that will make distortion more difficult to control.

    I would suggest outside fillet welding wherever possible and dressing them with an angle grinder if you need to. That's much more difficult to do (as is stretching) with inside welds.

    Cheers,
    Joe

  7. #7
    Join Date
    Jun 2010
    Location
    Canberra
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    Default

    +1 for an external fillet - just make sure the pieces are set up well with the edges touching - no gap in the root, and as suggested, try and do the welds in the horizontal position in short stitches (on alternating edges even) to limit the heat build-up and distortion. 2.5mm should be fine - as you go thinner it can get harder to maintain the arc.

  8. #8
    Andy Mac Guest

    Default

    Something that may help, but will only work with an old fashioned helmet (not one of these new auto darkening ones). Weld a short stretch until you see the surrounding area heat up, glow, and almost to the point of blowing a hole.. then
    break the arc by raising the rod, but keep it in position, hovering. Observe very closely the glow dissipating, indicating the heat build up has subsided, then strike the arc at the same point and continue. For a stretch, and repeat. It does work, the worst of it may be the areas where you take up again will have an inclusion of slag, so a bit of fiddling around after chipping.
    One of my several bugs about auto helmets... The sudden changes from dark to light eliminate the nuances of hot metal.

  9. #9
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    Sep 2006
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    Australind , WA
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    Default

    Quote Originally Posted by RustyArc View Post
    +1 for an external fillet - just make sure the pieces are set up well with the edges touching - no gap in the root, and as suggested, try and do the welds in the horizontal position in short stitches (on alternating edges even) to limit the heat build-up and distortion. 2.5mm should be fine - as you go thinner it can get harder to maintain the arc.
    Sounds good. I'll give it a crack tomorrow, if I get time.

    Steve

  10. #10
    Join Date
    May 2011
    Location
    Murray Bridge S Aust.
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    Default

    Not knowing how good you are at stick welding, I would weld it on the outside on a slight downward angle, that way if it is untidy you could always grind it off and
    redo it,
    Kryn

  11. #11
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    Default

    Quote Originally Posted by KBs PensNmore View Post
    Not knowing how good you are at stick welding, I would weld it on the outside on a slight downward angle, that way if it is untidy you could always grind it off and
    redo it,
    Kryn
    Sometimes I'm good.......

  12. #12
    Join Date
    Feb 2012
    Location
    Adelaide
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    153

    Default A cat among the pigeons

    I disagree with pretty well everyone here; but, I’ve never been accused of being easy to get along with. Now before anyone gets upset, I’m not saying I’m right and everyone else is wrong, I’m just applying my brand of logic! So, so here’s my two bobs worth:
    Smaller rods = lower amps, lower amps = less heat, less heat = less distortion.
    Your welding a heater that is vented via a flue I assume, it’s not a pressure vessel, smaller welds should be the ideal.
    If your welding a heat box: tack it inside to hold it in position and run a bead around the outside edge to seal it, distortion should be minimal. If your worried about a getting a straight run, cut your rods in half and/or run your pinky of your rod holder hand along the surface of the work to steady it, if that’s not enough, clamp a straight edge on the work to run your pinky along that.
    Rods, there is nothing wrong with Chinese rods (won’t this statement create a furore); they’re often a third of the price and meet Australian standards. Some are better than others, as are Australian, British or American brands, some prefer CIG and hate Austarc, etc, or visa versa, personal preference rules.
    If the box is largish, distortion from the fire may become a problem, particularly on the bottom, line it with fire bricks. What's the difference between a nice neat weld and an ugly weld? A file.

  13. #13
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    Default

    Thanks Tongleh,

    It is just a stand for the wood heater, not the heater itself.

  14. #14
    Join Date
    Apr 2008
    Location
    Perth
    Posts
    269

    Default Fuse Welding

    Hi Bloke

    I know you only have a stick welder, try the real small welding rods, you just about need to hang onto the bleeding things with two hands when you weld, maybe thats just me with the wobbly shakes.

    I would be more inclined to fuse weld 3mm plate with a gas set. You must have a mate somewheres with an oxy/acet kit. Have fused welded that size plate together making a long range tank for an old Tojo. Is easy to do.

    DD

  15. #15
    Join Date
    Feb 2012
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    Adelaide
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    Default Oops

    Sorry Steve, your "I need to weld the uprights into a box" statement threw me; however, my same "il-logic" applies.

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