Tig Advice

admin

Few problems I ran into today.Doing some .065 wall stainless and ive lost all control over my arc, the puddle gets way to hot to fast without getting full penetration which is important for my work. Because of this it either blows through the tube in some spots or the puddle just wanders off for a second leaving a big ugly erratic spot. Im fusing the tube together at butt joints, some straight cuts some miter cuts.Ive tried less heat, slower travel speed, the tungsten is sharpened correctly (%2 red 3/32), pulser has been on and off (around 6pps when it was on) and nothing changed.  Ive had it from 85-105 amps which is what I normally run.Ive been doing this (welding the tubes with no problems) daily for a few months now and I have no idea whats wrong, and my boss is getting mad...This is an example of my work, but not one of the models I did today.  Second thing, Ive never been able to get uniform butt welds on flat pieces.  I put a slight bevel on the pieces (today it was 1.5"x1/4" stainless angle) and the puddle gets bigger than the bevel and just floats around.  I needed to be hot cause it had to be strong, but was I to hot?  Dial was at 150, pedal was maybe 3/4 to all of that?Have we all gone mad?
Reply:Are you grinding your tungsten with the grindmarks running parallels to the length of the tungsten.Arguing with a Welding Engineer is like wrestling with a pig... after a while you realize the pig likes it
Reply:yup, just like I always do.  Thats why this is bothering me so much, everything is the same as it used to be as far as I know.Have we all gone mad?
Reply:Ive had it from 85-105 amps which is what I normally run.
Reply:80 amps is cool for what I normally run, usually its at 90-100.  97 seems to be the sweet spot, I can move fast and still get the penetration I need.  But now, thats not the case.  I usually keep it around 80-85 when im welding those fittings you see to the tubes.I always tack the tubes at at least 4 places. Sometimes more if the fit is poor.Why would I have to start at tack 4?Have we all gone mad?
Reply:Originally Posted by sn0border8880 amps is cool for what I normally run, usually its at 90-100.  97 seems to be the sweet spot, I can move fast and still get the penetration I need.  But now, thats not the case.  I usually keep it around 80-85 when im welding those fittings you see to the tubes.I always tack the tubes at at least 4 places. Sometimes more if the fit is poor.Why would I have to start at tack 4?
Reply:Zap, I don't understand starting at tack #4.  I don't see why you can't start at tack 1, 2, or 3.
Reply:the problem is, I dont just tack pieces and weld them, as you can see the tubes I make are made of several pieces, the whole thing is tacked first and fit in a jig before any welds are made.I also do a number of each model at a time, so I tack a few pieces into larger pieces, then tack the larges parts into 1 entire assembly, then once all are done I grab the closest one and start welding.I understand why you think its the logical place to start, but in my case its not.Have we all gone mad?
Reply:Originally Posted by WelderBoyZap, I don't understand starting at tack #4.  I don't see why you can't start at tack 1, 2, or 3.
Reply:Originally Posted by WelderBoyZap, I don't understand starting at tack #4.  I don't see why you can't start at tack 1, 2, or 3.
Reply:Originally Posted by WelderBoyZap, I don't understand starting at tack #4.  I don't see why you can't start at tack 1, 2, or 3.
Reply:You guys are good.. ...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:soo... about post #1.... Have we all gone mad?
Reply:Originally Posted by sn0border88soo... about post #1....
Reply:Isn0border88,do some reading on Marangoni Flow, also called Thermocapillarity.  This may be your problem, you were successfully welding tubing with a relatively high sulfur content (60 ppm or greater) and deep penetration characteristics, and now you got a new batch of tubing that has a very low sulfur content (30 ppm or less) with low penetration characteristics.See if you can get a copy of the chemical analysis for the tubing from your supplier.  The elements in the steel are reported in weight percent.  A sulfur content reported as 0.003 wt% translates to 30 ppm. Here is a link to a previous post on the subject.http://www.weldingweb.com/vbb/showthread.php?t=5417If this is your problem, there is not much you can do the welding process to fix it.  It will help to weld with the tightest arc length possible, and you can try 95% Argon- 5% Hydrogen gas mix, both act to concentrate the energy distrubution of the arc, and Hydrogen greatly increases heat transfer from the arc to the weld.Another process tweek that may help, try a super radical high current pulse.Try something like this, it sound radical, but figure out the average current, it only about 50 to 60 amps because the peak pulse is very short duration.pulse frequency = 1 to 2 pulses per second,peak current = 250 to 300 ampsbackground current = 5 ampspeak time = 15 to 20%The best fix is to only buy "high penetration" (high sulfur) tubing, but this may be difficult to find, and since several other elements also affect thermocapillarity, a higher sulfur content does not always translate to high penetration.Last edited by pulser; 08-28-2007 at 10:45 AM.
Reply:Another reference on the subject.http://www.arcmachines.com/appPages/sulfur01.html
Reply:Im working on closeups of the welds, I currently am camera-less.That acually makes alot of sense, we just switched from expensive american made rath-gibson tube to some cheap taiwan junk.  Its less than half the cost of the other stuff, and since we go through hundreds of feet per week it really adds up.  We didnt think it would make a difference, but maybe it is.Ill look into the comp of the tube.Have we all gone mad?
Reply:Now it's time to readjust your whole set up...Start at 50 amps... ...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:ya, ill crank it back down and see what works, but if the case is as above it doesnt seem like there is much i can do, maybe try a weave to keep the puddle cooler while still getting plenty of heat into the joint.I cant keep it real low because I have to move on these, 1 tube takes 30min to an 1hr depending on the model, and we usually sell at least 5 a day.  Plus all my other jobs, its hard to keep up.Have we all gone mad?
Reply:Originally Posted by sn0border88That acually makes alot of sense, we just switched from expensive american made rath-gibson tube to some cheap taiwan junk.  Its less than half the cost of the other stuff, and since we go through hundreds of feet per week it really adds up.  We didnt think it would make a difference, but maybe it is.Ill look into the comp of the tube.
Reply:Originally Posted by pulserIt would help confirm the Marangoni theory if you can compare the material chemistry for the old and new tube.  You would think that expensive American tube would be very "pure", with very low sulfur content, and hence be the low penetration material.  And likewise you would guess that the cheap taiwan junk tube would be "dirty", with high sulfur content, and hence have deep penetration characteristics.  But, if your difficultly is a Marangoni issue, then the American stuff is high sulfur, and the Taiwan stuff is low sulfur.Just to reiterate the problem with low sulfur SS, the fluid flow in the weld pool is outward from the center, and most everything you do to get more penetration, like increasing the current or slowing down travel speed, just drives the outward flow stronger, making the weld wider and wider, without much increase in depth.
Reply:Originally Posted by sn0border88As for the first paragraph, it would seem to me american steel would be made with high penetration in mind, so maybe the high sulfur is on purpose, and costs more to get it at the right levels.As for the second one, thats exactly whats happening, nothing I can do will keep the puddle centered and it randomly lops around.
Reply:The pulsing did it, 140-150 amps on the dial, 30% peak, 40a background and 5-6pps.  It welds nicer than ever, the welds stay small and dont undercut.Any advice on doing buttwelds, thats my other issue.  They never turn out very nice.Have we all gone mad?
Reply:OK, so to calculate the "equivalent" constant current weld amps, we do this:Ipk=150A x 30% = 45AIbk=40A x 70% = 28AIavg= 45+28 = 93AThis is a good moderate pulse.A radical pulse would be something like 350 amps @ 20% and 15 amps @ 80% = 82 average amps.  Just a wild hair guess, may not work worth beans, and also needs to be balanced with the pulse frequency and travel speed.Generally, a pulse weld such as this will require lower average amps than a constant current weld, because it is primarily the Ipk pulse at 150 amps that is doing the melting.  So for this particular material and joint, it will take more than 93 amps, probably 110 or more to make an "equivalent" weld.5-6 pulses per second (pps), sounds ok, the pulse frequency is balanced with the travel speed to produce a good overlap of the pulses.  If the frequency is too slow for the travel, the "spot welds" are too far apart and there are ripples in the penetration depth.  Generally, you want at least 70% pulse overlap.I though you were doing butt welds?  0.065" SS tubing, butted together?Plus, did you consider the 95% Argon/5% Hydrogen gas mix? It may give the added kick you need.  Not only does it increase heat to the weld at a given amperage, but it "reduces" surface oxide, meaning that the hydrogen combines with surface oxides and removes them.Last edited by pulser; 08-30-2007 at 09:47 PM.
Reply:^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^We need pulser as the site scientist... You have my vote.. ...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.Zap,thanx for the vote, very generous!I'll knew I'd never make it to arc-duke, so maybe I've found a different nitch.There is only one Zap, that's a given!By the way, if you ever run into the high and low penetration/Marangoni thing I was talking about, it will blow your mind!  My welds were beautiful, now they suck, what happened?
Reply:Well you have the metalurgest thing down!!!And I know you do not "google" your answers... I give you the Weldingweb scientist badge.. When it comes to the "Lets break this down" approach..Nobody else comes close with answers that one can actually understand...Give him the scientist title!!...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 problem is pretty much solved, a combination of new techniques and pulsing and everyhting is welding good.  Thats for all the info, maybe it'll come in handy later.Have we all gone mad?