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Thread: Tungsten diameter for Lap Weld

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    Tungsten diameter for Lap Weld

    New to Tig, wondering about sizing of tungsten for lap/ filler welds. Iím running 1/16 tungsten (2% lanthanated) and 1/16 er70s-2, I was trying to run a little lap weld bead today in some 3/16 mild steel plate. The steel was ground (didnít have flap disc) until shiny on all edges and then scrubbed down with dawn dish soap and wiped dry. So Iím new to tig, and I was wondering if my tungsten sizing would be a major factor as I couldnít really form a puddle in the groove, I was only able to melt the two corners of the pieces (at the lap joint) individually. I ran it at 180 amps and 13 cfh with approx 40-45 degree torch angle.
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    Re: Tungsten diameter for Lap Weld

    1/16" is too small. 3/32" or even 1/8" for 3/16"

    More gas and straighter torch angle.

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    Re: Tungsten diameter for Lap Weld

    Size your tungsten based on amps required. Use the 1 amp for every thousandth of an inch rule, up to a max of about 200 amps. For 3/16ths you should be in the 160-190 amp range. A 1/16th tungsten is good to about 100 amps, a 3/32 is good to roughly 200 amps. Above that you need a 1/8th inch tungsten.

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    Re: Tungsten diameter for Lap Weld

    You'll get away with using a sharp 3/32" tungsten for pretty much everything up to 200 amps, usually up to 250 amps (will be pushing it on AC, but fine on DC). Apart from maybe welding razor blades...
    Last edited by Munkul; 11-30-2021 at 04:12 AM.
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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by GoK4rtFanatic View Post
    I couldn’t really form a puddle in the groove, I was only able to melt the two corners of the pieces (at the lap joint) individually.
    Start your lap welds on the bottom piece, then wick the puddle over to the top piece. If you try to melt the top piece, the corner will melt back before the bottom piece melts. It makes sense if you think about where your heat is going. If you start on the bottom piece, you are effectively starting the puddle in the middle of a plate (where the heat has two directions to escape...or three, if you count the edge of the top piece) but if you try to start the puddle on the top piece, you are effectively trying to start a puddle on an edge (where the heat has only one direction to escape) -- this is why your edge melts back before it fuses to the bottom piece.

    Start the puddle at the red dot below:



    Once you get a puddle, add filler (almost like depositing weld material on "ledges" as in vertical up) and build it up and over to the top piece. But before you do that, make sure the root (the inside corner) is fused between the two pieces, like this:



    When you're finished, a cross section should look roughly like this:



    I would use a 3/32" tungsten, as others have said.

    Also, in general -- if in doubt, turn up the heat and move faster. Lots of beginners try to creep up on the puddle too slowly, and the whole mess gets way too heat-soaked. Starting with cold material, jack up the amperage and see if you can nail it quickly.
    Last edited by Kelvin; 11-30-2021 at 08:45 AM.

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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by GoK4rtFanatic View Post
    I couldnít really form a puddle in the groove, I was only able to melt the two corners of the pieces (at the lap joint) individually. I ran it at 180 amps and 13 cfh with approx 40-45 degree torch angle.
    As others have stated your tungsten is too small. However at 180 A you should not have had an issue as far as the amount of amperage, for you to get a weld puddle. I would verify that you are actually getting 180 A to rule that out.

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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by Munkul View Post
    You'll get away with using a sharp 3/32" tungsten for pretty much everything up to 200 amps, usually up to 250 amps (will be pushing it on AC, but fine on DC). Apart from maybe welding razor blades...
    I agree with the above, with your machine 3/32" is the better choice for almost everything, for now. Its good from about 16 ga. steel to 1/4" steel, and more tolerant of dipping, and electrode to work distance. Pictures are helpful, maybe even one with the torch in the position you were welding in. Might be helpful.

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    Re: Tungsten diameter for Lap Weld

    I would start by tacking a joint most times. Touch tungsten to inside corner of joint, move tungsten away from joint only about 0.015" (yes, a really small amount), then firmly and evenly depress pedal ( or torch switch), full pedal should take between 1/2 and 1 second. As soon as you see the joint fuse in one spot , abruptly release pedal. If your torch to work distance is too far away(3-4 times the dia. of the tungsten), it won't get enough concentrated current to work well. Smaller diameter electrodes need smaller electrode to work distances.

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    Re: Tungsten diameter for Lap Weld

    I wouldn't bother with the dish soap.
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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by G-ManBart View Post
    I wouldn't bother with the dish soap.
    Lol.

    Lacquer thinner is the best IMO. It is a strong degreasing solvent and evaporates quick.

    As others have said. Put the fire to the bottom piece getting as close to top layer without it melting away and when you can see the puddle start get closer to the overlapping edge until you have included it in the puddle of course while you are starting to feed the puddle with the filler.
    Last edited by danielplace; 11-30-2021 at 11:52 AM.

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    Re: Tungsten diameter for Lap Weld

    I'll say acetone. Wear gloves, it soaks through skin. Non chlorinated brake cleaner is acetone aerosol.
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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by danielplace View Post
    Lacquer thinner is the best IMO. It is a strong degreasing solvent and evaporates quick.
    That's what I have found, as well, probably because (like brake cleaner) it's a blend of polar and non-polar solvents, as opposed to straight acetone...

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    Re: Tungsten diameter for Lap Weld

    our brake cleaner over here has no acetone in it, its a blend of other non chlorinated solvents. Slightly milder than acetone.

    lacquer or cellulose thinner can have residues that don't evaporate quickly.

    I'll use brake cleaner when i feel like being cheap, and pure acetone when I want it to be perfect.
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    Re: Tungsten diameter for Lap Weld

    I also noticed that when I form the puddle I can see what I'm assuming are oxides coming to the surface, I see super tiny bubbles form and then the molten puddle breaks the (crust?). Sometimes I get an orangish hue around the weld and I was just wondering if all of these issues would most likely be solved via acetone wipe down. I'm out of flap discs atm so I used a grinding wheel and some dawn soap (I know not recommended but don't have acetone yet). Could there be any other reason other than it not being clean enough (i.e. bad gas etc?) Obviously I'm new to this so it it likely human error as well.
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    Re: Tungsten diameter for Lap Weld

    Bubbles and orange color are indications the metal isn't clean enough or the gas is contaminated.

    So, here's the reality check...this is the third thread you've started asking about similar issues in the last six weeks or so....gray beads, porosity, and orange discoloration. The suggestions aren't going to change.

    A grinding wheel followed by a flap disc to a very shiny finish, then wipe with acetone or alcohol (or non-chlorinated carb cleaner). That's a minimum for surface prep...multiple levels of grit flap discs followed by a non-woven abrasive wheel to a mirror finish is really the right way to do it. 1 amp per thousandth inch of material + 10% or so. Gas at twice the cup diameter to start. Cup size 7 or 8 will help at this point. Minimal torch angle and keep a tight arc.

    Until you do all those things to eliminate variables you're not going to know why you're getting poor results.
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    Re: Tungsten diameter for Lap Weld

    It might be bad gas, or a leak drawing air into the gas line somewhere.

    To be honest sometimes I don't even bother cleaning with solvent. OK, quite a bit of the time I don't bother with solvent The worst two things for crap TIG welds are: Millscale/rust, and bad gas coverage/contamination. If it looks clean and shiny its usually weldable, unless you've covered it in grease...
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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by Munkul View Post
    To be honest sometimes I don't even bother cleaning with solvent. OK, quite a bit of the time I don't bother with solvent
    Same here, and as for grinding it back to 3000 grit (or whatever you need for a mirror finish), I've never done that. For 3/16" steel, I might not even remove all the mill scale, except at the edge. If it was cut with a saw or zip wheel, that would probably be good enough for me.

    What are you using to weld on? Any chance it's some OLD scrap steel? I had some scrap steel from a 1970s or 1960s mobile home frame that I once tried tigging, and no matter how well I ground it back and cleaned it with solvent, I got bubbles like you describe. Only thing I could guess was that there was some contaminant (sulfur?) in the steel that was causing the volcanoes. When all else fails, sometimes you can solve this by using SS filler. Also, tapering off your heat with the pedal slowly will sometimes eliminate the porosity, at least at the surface. If all you care about is cosmetic appearance, that may be one kludge.
    Last edited by Kelvin; 12-02-2021 at 12:18 PM.

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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by Kelvin View Post
    Same here, and as for grinding it back to 3000 grit (or whatever you need for a mirror finish), I've never done that. For 3/16" steel, I might not even remove all the mill scale, except at the edge. If it was cut with a saw or zip wheel, that would probably be good enough for me.
    No argument, but you aren't a newbie trying to solve a problem and he's been having this drag on for quite some time according to the threads he's started.

    If there's a chance the metal is contaminated it's just a guessing game that can get frustrating pretty quickly. That's why I said to get the metal absolutely clean...remove that as a variable.
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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by G-ManBart View Post
    Bubbles and orange color are indications the metal isn't clean enough or the gas is contaminated.

    So, here's the reality check...this is the third thread you've started asking about similar issues in the last six weeks or so....gray beads, porosity, and orange discoloration. The suggestions aren't going to change.

    A grinding wheel followed by a flap disc to a very shiny finish, then wipe with acetone or alcohol (or non-chlorinated carb cleaner). That's a minimum for surface prep...multiple levels of grit flap discs followed by a non-woven abrasive wheel to a mirror finish is really the right way to do it. 1 amp per thousandth inch of material + 10% or so. Gas at twice the cup diameter to start. Cup size 7 or 8 will help at this point. Minimal torch angle and keep a tight arc.

    Until you do all those things to eliminate variables you're not going to know why you're getting poor results.

    In my experience, orange is usually a result of dipping the tungsten. I remove the mill scale, usually with a flap disk. You do not need a mirror finish, multiple levels of flap disk grit, or whatever. That is maybe necessary for finishing something for paint, like if you are doing body work, but for welding, it is completely unnecessary. Get the mill scale off, a quick wipe with acetone or the solvent of your choice, and you are good to go. I do sometimes wipe the filler rod off with acetone, but usually more when TIG welding aluminum. As Jody Collier rightly points out, most problems beginning TIG welders have are too long of an arc, too much torch angle and not shielding the rod with the argon.

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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by Louie1961 View Post
    In my experience, orange is usually a result of dipping the tungsten. I remove the mill scale, usually with a flap disk. You do not need a mirror finish, multiple levels of flap disk grit, or whatever. That is maybe necessary for finishing something for paint, like if you are doing body work, but for welding, it is completely unnecessary. Get the mill scale off, a quick wipe with acetone or the solvent of your choice, and you are good to go. I do sometimes wipe the filler rod off with acetone, but usually more when TIG welding aluminum.
    And I have seen bad gas and metal contamination leave brown/orange residue. He also has issues with porosity as well and that can easily be contamination.

    The only way to know for sure is to remove variables and the easiest one to be certain of is to start with very clean metal. Being too clean won't hurt, but not being clean enough will.

    Like I said in my first reply...grinding wheel followed by a flap disc to a shiny finish, then wiped down with acetone is good enough for this purpose. When I'm doing something I care about I go beyond that and I can tell the difference.
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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by Louie1961 View Post
    In my experience, orange is usually a result of dipping the tungsten.
    Good point, I wonder if the OP has been dressing back the tungsten without chopping off the contaminated blob first.
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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by GoK4rtFanatic View Post
    New to Tig, wondering about sizing of tungsten for lap/ filler welds. I’m running 1/16 tungsten (2% lanthanated) and 1/16 er70s-2, I was trying to run a little lap weld bead today in some 3/16 mild steel plate. The steel was ground (didn’t have flap disc) until shiny on all edges and then scrubbed down with dawn dish soap and wiped dry. So I’m new to tig, and I was wondering if my tungsten sizing would be a major factor as I couldn’t really form a puddle in the groove, I was only able to melt the two corners of the pieces (at the lap joint) individually. I ran it at 180 amps and 13 cfh with approx 40-45 degree torch angle.
    Check the manual :
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    I disagree with the flow rates in the tungsten size and setting chart, yet they mention a flow rate of 15-25 cfh at least 3 time in the installation guide. Maybe a few pictures of torch angle, distance , and what you weld looked like would help. Videos can be very helpful too.

    If all else fails, call the customer service line. They always seem to pick up the phone, and have always be helpful when I've called.
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    Re: Tungsten diameter for Lap Weld

    Quote Originally Posted by albrightree View Post

    I disagree with the flow rates in the tungsten size and setting chart, yet they mention a flow rate of 15-25 cfh at least 3 time in the installation guide. Maybe a few pictures of torch angle, distance , and what you weld looked like would help. Videos can be very helpful too.

    If all else fails, call the customer service line. They always seem to pick up the phone, and have always be helpful when I've called.
    You are right. those numbers are FUBAR.

    Pick a cup size that has copious volume around the tungsten and apply 2 to 3 times the cup size in flow rate. That chart called for a #4 to #6 cup with a 1/8" tungsten flowing a paltry 14 cfh.
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