Puddle Size for TIG

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Can anyone tell me if there some rule you use for the size of the puddle based on the thickness of the metal to be welded with TIG?  I have searched but have not found a definite answer.  Most say "when the puddle is the correct size start to move".Obviously with TIG, you have more control over puddle size than MIG, so what what be a good rule of thumb if there is any...And is it different for fillet -vs- butt joints etc?Thanks in advance!Build a Barstool Racer at BarFlyRacers.com!
Reply:I haven't heard of an exact size to thickness formula. But, for a general rule of thumb, most welds are going to be about the same width as the thickness of the material you are welding on.Give or take a little. Some beads, like flat seams may get wider to "grab" both sides of the metal. Some welds, like on SS tubing, will be very small. Aluminum beads tend to be a little wider, but that will depend on machine setup.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:2 or 3 rod diameters ?   What ever it takes to be fused to both pieces with the correct amount of filler.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Puddle size has alot to do with cup size..Amperage..Tungestion size..All of the above..There is no way you will get a puddle the same width if you ran a bead with 3/32" VS 1/16"... If the cup size is around the size of your pinkey..Then you change it to one the size of your thumb and leave the amps alone..You will see a big diffrence right there... I stay on the smaller size cups myself...Play around and figure out what you get with what set-up..Take notes for further reference.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:The "rule" that I use for the minimum size of the puddle, is where I can just heat it up to the point that it is fluid and the the puddle wets in all the way around.  That is the minimum...the maximum is based on your setup and what your base metal and your machine will handle.  Other than that, just listen to Zap!  he knows what there is to know about Tig...
Reply:hmmm... interesting.  I thought cup size would affect your gas coverage and not puddle.  I am going to have to try some different cups to test now.So basically, Tung. size and cup affect the puddle size?  I would assume the larger the Tung. the bigger the arc, therefore more puddle also.Lots to learn with TIG.  I though GMAW and FCAW were hard to learn in the beginning, TIG has a lot more variables to work with.  I guess that's what makes TIG superior to other welding types.Thanks for all your help!  Back to the welding table...Build a Barstool Racer at BarFlyRacers.com!
Reply:Each pass should be no wider than 2 1/2 times the diameter of the filler you're using.  This is the rule I was tought, and has always worked for me.  Has less to do with tungsten size and the like, and more to do with deposition rate, prevention of undercut, etc.
Reply:malich,I think you are asking, can you judge the depth of penetration by looking at the puddle diameter?  The depth and width of the weld puddle are obviously related, hotter weld = wider weld = deeper weld.  But the ratio of depth to width is not a constant, it is controlled by a zillion factors, one of the major factors being the effect of material chemistry on the fluid flow patterns with in the pool.See the attached weld cross section photos.  Both welds made under precisely controlled identical conditions, 200A, 9.5V, 100%Ar, 6 ipm.  The extream difference in weld shape (morphology) is due to a chemistry dependant, temperature gradiant and surface tension driven fluid flow within the weld pool, called Marangoni flow or thermocapilarity.  Photo (a) is low sulfur  150 ppm.  See http://www.weldingweb.com/vbb/showthread...ight=marangoniOh, by the way, Phd's have been trying to develop computational models to predict weld morphology based on welding parameters and material chemistry for the past 30 years or more.  The AWS welding journal has published many papers on the subject.  You can find related papers by searching the WJ for "modeling" and "Marangoni".  The super simplistic starting point for the earliest models was the Rosenthal equation, which as I recall, pretty much predicts that point heat source will create a "half round" weld shape, where the depth is 1/2 the width. Attached ImagesMarangoni.pdf (36.0 KB, 106 views)Last edited by pulser; 09-05-2007 at 02:33 PM.
Reply:Hi Pulser,Thanks for the reply!I not looking to get too technical on the question.  I am able to make a nice puddle which gets me 100% penetration to the back side when adding filler.  I was mainly curious of other opinions.When I form the puddle it is almost like you can tell it is ready to go and you start moving.  When done the penetration was perfect and no burn through.  When I learned GMAW and FCAW I was burning through a lot, I have never burned through with TIG.And thank you Supe for your reply.  I think my puddle is about about the size you mentioned.  I will just keep working at it and eventually I will be good at it.  I can still remember my first FCAW welds..  scary.. and today people compliment them.Thanks again to everyone that has posted replies!Build a Barstool Racer at BarFlyRacers.com!