Tig welding with no filler questions
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  1. #1
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    Default Tig welding with no filler questions

    Hello,
    Lately I have been doing a lot of tig welding on steel parts without filler rod.
    I call it fusion welding but not sure if that is correct.
    I am really happy with the results, excellent looking welds and strong enough for the purpose.

    My questions relate to the process and do's and don'ts if any, thoughts?
    I get a bit of under cutting on fillet welds, the inside corner of square tubing mitres, not a problem as it looks quite good and is very clean. Any flat welds are amazingly almost flush with the surface and at worst just below.
    I can post some pics of the results but I just sent out a large order and didn't take any good pics of those welds.

    I have been welding mitred frames out of square tubing mostly, it is fast and there is no cleanup after, the weld is smooth, clean, flush and looks good. I have only recently been able to do the "fusion" welding because I am cutting my stock with a semi-auto cold saw and the cuts are superb. The joints fit nearly perfectly right off the saw and are very easy to weld without filler rod.

    I have a Miller 200 synchro and an air cooled torch. I use the rare earth tungstens which IMHO are excellent.

    Thanks for any input,
    Cheers,
    Michael

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    Fusion welding (that's what I'd call it too) has its place. If you're sure you've got enough penetration and
    strength then I see nothing wrong with it. Just remember that tig welding is about more than just appearance.
    I've seen stuff that was welded with "stack o' dimes" precision that didn't stand up at all when it came to real
    strength. Trick is to find a balance...

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    Autogenous welding requires better fitup as you point out, but also better cleanliness, good shielding and proper technique. without the extra deoxidizers in the filler it is more susceptible to external contaminants and also to impurities and defects in the stock being welded. Filler rod is far more controlled and consistent than most stock.

    The technique is also far more susceptible to hydrogen embrittlement, as it is usually a faster and lower heat input process. That is why it is most commonly used on Austenitic stainless.

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    I do it as well- small parts where strength is no issue like caps on thin pipe- decorative stuff.
    More generally I would say fillet welds are going to wash away plate thickness so you are losing strength there.
    Probably every other sort of weld as well.
    There are standards for this stuff- allowed cross section etc.
    ANY undercut is a fail.

    The welder here would just sort of laugh and shake his head.
    “Well no- you need filler rod”..
    He will wash over small caps etc as well if the finish radius allows it but generally rod- lots of filler rod.

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    There is also a welding technique called lay wire. Basically, you just lay the wire on top of the joint while welding. The amount of reinforcement for the joint can be controlled by selection of wire diameter.

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    Weld specs dictate the welding process for everything. Most I have ran across require minimum of 1.5T for fillet joints(not getting that without filler rod). If in doubt its easier to just go to a weld spec for piece of mind and a place for answers.

    If you seam up say a cylinder or any butt joint you can normally get away without filler metal given that you have 100% penetration. Most of the time you do that you have underfill on the top which gets solved with planishing.

    If its just for personal use and you know the stresses on the joint you can get away with not using filler metal. There is more involved in it than just with or without filler metal. A full pen weld(butt joint) without filler can be just as strong as the unwelded base metal. Weld that barely penetrates without filler metal is near worthless structural but have done more than I care to think about in the food industry where no place for junk to grow is top priority.

    Also in low carbon steel welds without filler is much easier to machine than with filler.

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    If it meets the structural requirements of the weld then its perfectly fine to do... without knowing exactly what you are doing its impossible to know if you are in fact meeting the structural requirement of the weld. Without going super deep into things filler adds strength to the weld roughly speaking.

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    When I've done it on steel the welds seem to be real brittle, easy to crack with the slightest deflection.

    A shop near me specializes in food industry piping, they fill the SS tubing with argon then TIG the outside w/o rod, and the inside looks just like the outside. I don't know about strength on a joint like that, but a tube/pipe joint isn't going to bend much once complete even if brittle.

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    Quote Originally Posted by Mud View Post
    When I've done it on steel the welds seem to be real brittle, easy to crack with the slightest deflection.

    A shop near me specializes in food industry piping, they fill the SS tubing with argon then TIG the outside w/o rod, and the inside looks just like the outside. I don't know about strength on a joint like that, but a tube/pipe joint isn't going to bend much once complete even if brittle.
    Automated orbital welds on pipe like that can be perfect for the application... but again these are fully engineered and processed parts.

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    Thanks for all the replies.
    Most of my work is furniture components like table bases and legs.
    I usually combine mig and tig where I can to add strength. The tig welds need to hold together and look good.
    I am fairly confident in the strength of the autogenous (thanks cyanide) as I have done a couple of destruction tests and was quite surprised with the effort it took.
    Normal furniture loads are quite small, if it can be made from wood then steel is plenty strong!
    I have made wooden furniture for 25 years and the steel is easy to engineer for the loads.

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    The question isn’t if steel is strong enough or stronger than wood.
    The question is if sub par welds are going to fatigue and crack with time.
    A tiny tack weld seems plenty strong when you need to break one loose but it isn’t going to last in service.

    I would cut some of your work to see what the penetration is like- skimming a shallow puddle over a butt joint isn’t worth much.

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    This will be long winded but might help you think about it in a different way. This is just broad and general info from my experience.

    This has helped me a lot thinking about strengths of welds without filler metal.

    If you take say two 3/16" thick plates and butt them together and do a simple quick fuse weld across one side with an average penetration of .040 deep and try to bend it weld out it will hold very well. If you bend it weld in it will break off in your hands.

    With that said think of it as if you took the same two plates and bolt a .040 piece on top to cover the joint. Same thing will happen if you try to bend it. Thin plate out on the bend and it will hold nicely. If you bend it the other way you'll easily bend the .040 piece.

    If you take the same two plates but weld it with the same penetration but add enough filler metal to make a nice crown on the weld(.06-.09)the amount of force required to bend the plates with weld in will go way up. Its still not nearly as strong as a full penetration weld but much better than without filler metal.

    Also as stated before the impurities of steel tubing with mill scale on it makes for a very poor joint unless additional metal is added. Corrosion is another issue. With thin low penetration welds it doesn't take much corrosion to make a weld joint weak and fail.

    Anyway just my thoughts on it.

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    Don't try this in aluminum - the heat contraction means it will crack without filler. (Sometimes it cracks with filler....)

    To see a straightforward way to do a penetration test, look up Jody Collier / WeldingTipsAndTricks on youtube and or his web page, probably linked to from weldmonger.com (an associated business.) A couple of his videos show doing 1st order penetration evaluation using hardware store substances - it's easy to do and quite informative (yes, even I have done it. Shows you a lot.)

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    More good info for the record from all the replies.
    I am going to have to post some pictures of the work I am doing.

    Like I said earlier I am mainly welding square tubing mitred corners. Mostly 1”, 1.25” and 1.5”.
    Fusion welding all four sides is actually very strong. Then combine that with 3 other corners into a full frame the strength increases given that all four joints now have to fail at the same time.
    I also mig weld where it doesn’t show to increase strength.

    What I am not doing is making parts for submarines or nuclear reactors.

    I am also not clear on how welds on a table base will fatigue over time? Is that 1000 years?
    I have trouble imagining the force required to cause these frames to fail. If I was making mountain bikes then yes, significant forces involved, furniture not so much. It is relevant the strength of wood to steel as the wood components will fail way before the steel parts.

    I also have fusion welded aluminum rectangle tubing, no cracking, excellent strong joints.

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    Corrosion/rust over time from the inside out not really external stress cycles. I have repaired many steel folding chairs and tables at their tack/spot welds the rust inside makes it a pain to repair. Without the rust Im sure they wouldn't have broke under normal use.

    The full pen welds will still rust on the backside but will take about the same amount of time to rust through as the base metal. Its the welds that still leave a joint on the back side that seem to rust through much faster.

    Not saying your method won't work or you won't have good results just giving out some info from what I have seen.

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    Quote Originally Posted by Mud View Post
    A shop near me specializes in food industry piping, they fill the SS tubing with argon then TIG the outside w/o rod, and the inside looks just like the outside. I don't know about strength on a joint like that, but a tube/pipe joint isn't going to bend much once complete even if brittle.
    Back purge works good for stainless exhaust headers too.

  23. #17
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    Thanks turn,
    I am not making folding chairs or any outdoor furniture.
    My OP was actually meant to elicit responses regarding actual technique not so quite so many responses on how weak the joints will be if xxxx. It is fine to comment on weld strength if it is relevant.

    Things like amp settings for different thickness’ or how is fusion welding different than regular tig if you end up grinding the weld completey flush? Weld test techniques would also he helpful.

    Some of the fusion welding I have done is on ERW material which is .063 or 1/16”. I am getting full penetration on that and the welds are strong. I have had to cut a few apart and you need to cut completely through to separate the parts. The fitup needs to be very good for ERW fusion welding any gaps lead to much larger holes. I run a 1/16” tungsten at 65 amps for ERW.

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    You kind of need to approach this type of stuff a little differently, minimum structure requirements with aesthetics at the forefront. This guy is at the top of his game in the realm with the metal works.

    Brandon Roettjer (@blend_fabrication) • Instagram photos and videos

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    Kustom,

    Thanks for the link, very nice work by Brandon.

    You summed it up perfectly, minimum structure with maximum aesthetics.

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    I think you would be better off to think of the tubing as steel folding chairs. Like I could resist.

    Welder settings for me would be 40 amps(for .062), 3/32 1.5% lanthanated tungsten with a 30 degree included angle and a .005 flat tip. Gas lens not collet body with a #6 cup. 45 degree or greater torch angle to push the puddle some and a slight sweeping motion. I use a short arc length to where the force of the arc just starts to make a slight indent in the puddle. 10 start amps around 90-100ms long. 3 end amps. I prefer lower amps to give more time for nasty junk to burn off along with the slight sweeping motion really makes a difference in keeping the impurities as low as you can get it. Also if my welds are coming out gray or black Ill slow my process down and or go with a larger cup. Any color less gray or black is fine.

    If running straight beads(no weave) Id run pulse with a near 90 degree torch angle. Pulse settings 50 main amps 85% peak 50 background 4-5 pulses per sec.


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