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  1. #1
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    Default Problems with 1.6mm Gemini rods

    I'm a beginner with a BOC Smootharc 130 inverter. I was trying to teach myself by joining small sections of 1.6mm and 2.0mm SHS using the little Gemini rods. I had a heap of problems. My (lack of) skills improved immeasurably when I bought an expensive auto-helmet and started messing around with 2.5mm 16TCs and Satincraft 3.2mm on heavier material. Now I can do alright after messing around with a bunch of bits and pieces and modifying some non-structural stuff on a trailer. I've managed clean results on downhand, horizontal across and even vertical up, on butts and fillets.

    So on the weekend I went back to making up a project out of 2.0mm galv plate and brought out the 1.6mm Geminis again. And suddenly I can't weld again. It's only marginally better than my first attempts. I tried long arcs, short arcs (almost pushing the rod into the join), current as low as 40A and as high as 60A, different drag angles, different angles into the joins. The little rods tend to burn very quickly, deposit what looks like heaps of material (but is mostly slag, so much that I can't see the weld pool) but I get weak penetration or a bit of penetration but a heap of bead and very, very often the bead seems to sit on either one surface or the other (doing fillets) and not bridging to the other. Sometimes I get beads on one surface very close to the other surface but it's almost as though there are magnetic fields pushing it away (I'm not using any magnets, worked out quickly the magnets I got didn't play well with my DC arcs).

    I did get one 4-6" section that was perfect, but unfortunately by the time I noticed I'd tried so many other techniques that I forgot what I'd done to make it work. Last thing I tried was 60A, short arc and just blasting the join. It sort of worked but lots of heat and a fair amount of spatter and way too much material deposited. That was joining a bit of scrap to some 2.0mm SHS along a corner and the fillet ended up about 4-5mm wide.

    I just want clean, ~2mm fillets done right but it seems impossible (apart from the one flukey section). Any advice on settings I should be aiming for?

  2. #2
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    Feb 2010
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    Default

    Legion, are these Gemini 12's? I use these on thin section stuff and have found them pretty good. Here's a photo I had from a previous post - this is at 45amps DCEP on 1.6mm gal SHS. A touch hotter (say 48amps) would've probably been ideal. Are you using elecrode +ve? Sounds a bit like you're on DCEN.

    You're right about burning through the rods quick. I find it a challenge to keep arc length down simply because the rod is disappearing so quickly. Apart from that I've found these rods pretty forgiving and am often pleasantly surprised after the slag comes off. Just use normal arc length (say 1 to 2mm off the work), make sure your joint is clean. It's a pretty standard rod, so no special technique.

    Cheers

    - Mick

  3. #3
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    Default

    Ive got a hunch the rods are fine .................

    Check out these tips:

    How to Weld Galvanized Metal | eHow.com

    Welding Galvanized - I Quit!

    Regards Lou
    Just Do The Best You Can With What You HAve At The Time

  4. #4
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    Default

    Quote Originally Posted by WelderMick View Post
    Legion, are these Gemini 12's? I use these on thin section stuff and have found them pretty good. Here's a photo I had from a previous post - this is at 45amps DCEP on 1.6mm gal SHS.
    That's a great looking weld, but I notice it's in the flat position. I'd be interested to see what looks to be a vertical weld at the bottom of frame

    For 1.6mm gal I use 2.5mm rods, 'cause that's what I have on hand. Even then, there's a bit of a battle at the start to strike an arc and get some heat going to establish a weld pool - make the wrong move and you build up a lump of metal and slag that shorts the arc, forcing you to move away and make another cold lump, or draw a cold bead that sits up rather than melting into the root.

    I imagine with even thinner rods, the problem becomes the short arc sitting on one side of the join or the other, not creating a weld pool that spans the join - particularly hard given that the corner radius of cold-formed sections like RHS makes for a rather deep "V" to try and get the electrode in to.

    My advice, as a similarly inexperienced welder, is to concentrate on getting the stick in close, allowing some time at the start to get some heat in the material and a weld pool forming before moving, and then try and keep that short arc, maybe with a very slight weave to ensure the edges of the weld pool make contact with each side of the join.

    Also, I've noticed that gal tube makes a distinctive sound just before you blow through - once you learn it, it's a signal to get that weld pool moving a fraction faster, as the total heat in the job is building up.

    Edit - and that suggestion from Mick about trying DCEP is a good one to try out.

  5. #5
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    I have no doubt it's the operator's fault. I'm just wondering what I'm doing wrong since I found other rods relatively easy in comparison. I'm cleaning the joints each time with a grinder, about 3-5mm each side of the fillet. I'm fitting it up so the joins are as close as possible but even having trouble with guillotine cut edges on flat plate (i.e. zero root gap). I'm not blowing holes (much) any more, so that's at least one positive, but it might be a sign there's no penetration. I'm just not getting penetration or laying down a good bead. I was using DCEN. I will try DCEP and give it another shot on the weekend. I wish my welds were as good as yours Mick.

  6. #6
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    Interesting comments RustyArc. I am not weaving at all, just straight along the join. My arcs were occasionally so short that I managed to get them to disappear halfway along some welds without sticking at ~40A DCEN. I'd have to lift the rod to reignite the arc.

    Your comment that was most interesting to me was about the arc arcing against one surface or the other. I never thought about it like that. Does the arc direct the weld metal? Could it direct the metal onto one surface or the other? I get plenty of slag coverage (of both surfaces) and all looks OK until I remove it. Maybe I should try weaving in order to direct the arc across both surfaces. Of course that might be difficult with these rods, they're very "flicky". On striking a full rod I have to guide it with my other hand for a while while the vibrations stop, otherwise it can vibrate several mm for half a rod, which doesn't work well at all. The vibrations along with the fast burning makes controlling them a challenge.

  7. #7
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    Quote Originally Posted by RustyArc View Post
    I'd be interested to see what looks to be a vertical weld at the bottom of frame .
    Ha! It would probably look like cr*p. Next time I'm out there I'll run a few and get photos.

    Quote Originally Posted by Legion View Post
    I wish my welds were as good as yours Mick.
    As above... sorry wasn't fishing for compliments - just wanted to show the result at those amps. I could probably point to some bad welds too, just that I don't tend to take photos of those!

    Quote Originally Posted by Legion View Post
    Maybe I should try weaving in order to direct the arc across both surfaces. Of course that might be difficult with these rods, they're very "flicky". .
    Yep flicky would be a good description.

    You definitely need to see your weld pool eating into the metal on both sides. I think once you start with DCEP you'll get more heat in the weld and your molten pool will join over pretty easy. With DCEP your rod will burn down slower too and you'll have less slag compared to molten metal (as more of the weld pool will come from the work rather than the rod). Do a bit of weaving as Rusty says especially at the start to make sure pool has sucked over to the other face, once a good weld pool has established it should easily adhere to both faces especially if on clean metal and you can just concentrate on keeping your arc length right. If your amps are too low or arc too short then you run the risk of only running along one face or the other. If you weave too much your fillet will grow again and the job will heat up heaps (also got to be careful not to get slag trapped between weaves). Good tip from rusty with the distinctive burn through gurgly noise - if the job's heating up too much just stop, chip off the slag and start again when cooler. Cheers - Mick

  8. #8
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    Definitely familiar with the hollow burn-through noise, both before it's too late (although there's already the hollow noise) and after it's too late and there's a big hole.

    OK, I went out the back and ran a few beads on painted 20mm SHS, not sure whether 2.0mm or 1.6mm.

    Rods are the same, 1.6mm Gemini 12s.

    Setting ~48A DCEP.

    It was super tricky striking because there was just one dim floodlight in the background. Reminded me of the fixed shade 11 helmet I started with. I got stuck several times whereas I don't stick much normally now. I couldn't see a thing in the dark.

    Anyway, the flat downhand butt welds went alright. The fillets were a different story. Even the best one attached to one surface and there's just slag on the other (bit blurry, sorry). The worst fillet was typical of the other two and is a mess. Slag inclusion and wandering weld from side to side.

    I watched the weld pool closely and on one fillet the pool was rotating in a direction and just by itself the rotation started pushing it up away from the join although the rod was moving straight along. I then moved it over the other surface and the pool jumped across and started rotating in the other direction (I think) and pushed the pool away from the join in the opposite direction to before. It might actually have been the third pic.

    DCEP definitely seemed easier and way more manageable than DCEN on this material with these rods. I remember trying it right at the start but not thinking there was much difference. I probably wouldn't have been able to tell though.

  9. #9
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    Default

    I am no expert, but just some very quick obervations are pic-1 looks like you need higher amps and a steady hand, pic-2 you are holding the electrode at the wrong angle, same in pic-3

  10. #10
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    You mean the angles between the surfaces or the drag angle? I tried to hold the material so the surfaces were at 45 degrees and I was pure downhand but maybe I was off a bit. Could that be all that I'm doing wrong - getting the angles wrong? I'll pay more attention next time.

    How critical are angles in general? E.g. if I was doing a fillet with the surfaces at 45 degrees and the rod was 40/50 degrees instead of 45/45? How about 30/60?

    Same with drag angle - I try to hold it as close to perpendicular to the surface as I can, and increase the angle as required to ensure the pool stays mostly behind the arc travel (usually about 10 degrees).

    And another question - what's the white fluffy crap that builds up everywhere on my galv welding jobs? I grind weld surfaces clean, but e.g. on the back face of a join or the inside of SHS I get white cotton wool looking stuff. I presume it's some nasty melted zinc by-product.

  11. #11
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    I gotta say, the best thing I learned, and not from my TAFE teacher, was to watch the weld pool, and learn to establish it, then lead and control it so it stays the right size and contacts both surfaces and doesn't leave gaps (inclusions).

    From the look of your fillets, you started OK, but perhaps then got too much arc distance, causing it to stick to one side. You need to slow down a bit, get and stay deep and close and allow the pool to get both sides - drive or draw it over as needed.

    Watch the pool and its edges, not the arc.

    I don't go downhand on vertical - you can't control the pool as well, unless you've got mad welding skillz. Uphand gives a gluggier weld, but you've got more control.

    One thing I've been considering when welding gal (which is probably 90% of what I weld) is setting up a fan, not just to get rid of the awful fumes, but to let me get a better look at what's going on.

    The weird white fluff on the backside with gal is normal.

  12. #12
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    Id say your rod angle is wrong say when u are doing a horzontal fillet weld if u have the rod to upright facing towards the bottom plate more u get issues with the slag going along the top of the bead,sometimes u cant see it when u are welding but as soon as u chip off the slag u got the inclusions there

  13. #13
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    Legion,

    Fundamentals of Professional Welding has a few diagrams with stick angles. Like Rusty said - it looks like your fillet welds start off OK and I reckon it's either you're bring your rod too parallel with the long bit of SHS, or your stick's burning up and you're not keeping your arc length right.

    It's interesting that your flat butt weld looked OK so if that was vertical down, it seems that direction of travel isn't the issue. What happens if you do a fillet weld horizontally? I reckon you've got to go through a process of elimination: Is it the fact that it's fillet weld that's the problem? or is it the direction of travel? Is it the rod angle? Start with what works then change one thing at a time.

    Having said that - if you were feeling impatient - I would try the following. DCEP 45 amps. Use a half electrode so you have better control. Vertical up direction. Start with your rod held horizontal, pointing into the corner of the 2 bits of metal at 45 degrees. Strike an arc and concentrate on keeping the rod about 2mm from the corner of the T. Weave the arc to make sure the weld pool grows a bit and has linked both sides. As the weld starts to fill in the fillet make sure you keep the arc length short, but not tiny (1 - 2mm). Keep your rod pointing in at 45 degrees to the 2 pieces, and horizontal, weave a bit to make sure the weld pool is aways eating into both pieces of metal. Stop after you've welded 1 cm. Even if you think you're going OK - stop at 1cm. What's it look like?

    - Mick

  14. #14
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    Quote Originally Posted by Legion View Post
    I watched the weld pool closely and on one fillet the pool was rotating in a direction and just by itself the rotation started pushing it up away from the join although the rod was moving straight along. I then moved it over the other surface and the pool jumped across and started rotating in the other direction (I think) and pushed the pool away from the join in the opposite direction to before..
    Just some other thoughts...

    your welds are clean right? no oil?

    what about arc force. My machine doesn't have it - so can't try it, but I've heard that if it's cranked right up it can cause the arc to wander?

  15. #15
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    Today I had to weld a piece of 50x50 gal angle to the side of a piece of 50mm gal RHS. The lap weld was no problem, but with a 2.5mm rod, even in the flat position, getting a decent fillet weld between the corner curve of the RHS and the flat of the angle was a nightmare. I encountered the same problem as Legion with the arc going to one side or the other, leaving a bead one one side and a bunch of flux in the root.

    In the end I scraped out all the crap and went over it with a 3.2mm rod - much better result - the larger hot pool easily spanned the gap.

    That page that Mick linked to shows fillets on sections that have a nice square intersection, but with the corner radius of cold-formed sections like RHS, the point at which the metal touches is much deeper. So far for me, the only sure-fire way of getting a decent root weld it to surrender to the MIG where the the narrow wire can poke right into the depths of the join and deposit metal where the pieces are actually touching.

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