Tig - Aluminum Penetration

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I tried a couple butt joints last night on 1/8 aluminum in class.  Settings were 1/16 tungsten (red), 3/32 4043 AL filler rod, 115 amps...  Cleaned with SS brush first.   I'm not sure what is right on penetration?  Should I have some melt through on the backside, or none?  I asked the instructor and he said it didn't really matter because aluminum is not really load bearing and more for dressing stuff up... He's a nice guy, but 20+year stick/mig - no tig..  Just trying to understand what the back should look like?  Anybody got examples of what a good front and back AL weld is on similar material? Attached Images
Reply:Was there any weld prep on those pieces?In a perfect world, you should see a slight sag on the backside which indicates complete penetration - like in your second photo.  And - despite what your instructor says, there are countless applications for structural aluminum.  It's not only for aesthetics.You need a little prouder weld profile in your first photo to be a pretty darned good weld (from the internet, photo based evaluation).  The bead profile in the second photo shows promise but lacks the penetration of your first photo.  You might need to bump the amps up as you add more filler.  I run 1/8" butt welds at around 180A to start and back off to about 140A for the run.  By the end of a 4" long run, you might be at around 120-130A.A smooth, continuous weld is considered more desirable from a structural standpoint.  I will leave it at that for now.I think it looks good, just work on your consistency and you are good to go.ScottLast edited by MXtras; 02-20-2008 at 01:55 PM.Haul a bike without straps - visit  www.mxtras.com  to see how!
Reply:I agree with all that MXtras said mate.I much prefer your second weld, first one looks too hot.Ally has a bad habit of closing up as you weld , have a look at the under side you will notice its closed up on you.More tacks needed, it will help a lot.Learning to properly tack up a job will speed the rate of improvement of your welds and the quality of the weldment.If the welds getting too hot and you haven't quite mastered your foot control , stop , let it cool down, start again.On 1/8 material I prefer 3/16 electrodes (thats 2.4mm right?)A good guess is better than a bad measurement
Reply:3/16" = 4.76MM which is a ~2.4MM radius.....  I use the same (3/16") but I am running a transformer machine (Synchrowave).  The inverter guys claim they have a different set of rules.  I still prefer pure (green) tungstens but I use Red (2% Thiorated) for the smaller work and smaller diameter tungstens.ScottHaul a bike without straps - visit  www.mxtras.com  to see how!
Reply:Ah thats right..I meant 3/32 electrode in preference to a 1/16 (Bloody Yanks and their funny way of measuring things!)A good guess is better than a bad measurement
Reply:as said, your instructor is talking nonsense regarding aluminium applications. It is used for structural purposes and a semi penetrated butt weld results in a giant stress riser for cracks to grow fromi tried to explain and showed how to do it here... http://www.weldingweb.com/vbb/showthread.php?t=18625there's few other threads on the same subject too (all posted around the same time in the 'projects and pictures' forum)i would step up to a 2.4mm (3/32) tungsten above 70amps AC
Reply:Thanks for the info!  I will try a 3/32 tungsten also.. One of the biggest problems I have is even at 115 amps I don't get the nice raised bead with penetration.. I cleaned it, and get things going but it spreads out and seems to cave in which means too much heat to me.. I can do as suggested and start higher amps, but I'm afraid it will just make a much wider bead..  I'm fairly new to tig, but can run a pretty good SS and mild steel bead with good penetration.. Aluminum just seems to spread wide, and not get the root penetration...  I'll try again and upload future results..
Reply:Originally Posted by deere2210Thanks for the info!  I will try a 3/32 tungsten also.. One of the biggest problems I have is even at 115 amps I don't get the nice raised bead with penetration.. I cleaned it, and get things going but it spreads out and seems to cave in which means too much heat to me.. I can do as suggested and start higher amps, but I'm afraid it will just make a much wider bead..  I'm fairly new to tig, but can run a pretty good SS and mild steel bead with good penetration.. Aluminum just seems to spread wide, and not get the root penetration...  I'll try again and upload future results..
Reply:I like the description given by Brett.  I have always called it the "Eye" but it has more of a tear drop or keyhole shape.  This denotes your penetration.  Closely monitoring and constantly adjusting speed, amperage or both to maintain the same sized eye or keyhole during the entire weld is the biggest challenge but determines the consistency of the weld and it separates the good weldors from the average.  What I use to instruct new AL Tiggers is this: Wet the bed (create the keyhole or eye), fill it up, move forward, repeat with uniform consistency.  With practice, this sequence can be done continuously without any hiccups or hesitations.  The weld profile is created by the addition of the filler - the more filler, the prouder the bead.As Brett mentioned - stuff the filler in there.  Don't be afraid to back the torch off the work to create a little more room - most folks tend to run too close and end up contaminating their tungsten and their work by either dipping the tungsten on the back of the weld pool when they add filler or they hit the tungsten with the filler.  Give yourself the room you need.  Too far is bad for gas coverage and control so there is a limit, of course.  I run the tungsten probably about 3/8" (9.5MM) above the work at a forward tilt of around 15-20 degrees from perpendicular.  This angle changes to perpendicular at an outside corner, by the way - otherwise the arc will want to shoot over to your filler.Generally speaking, the use of a larger tungsten than necessary is less detrimental than too small of a tungsten.  There are exceptions, but when in doubt use a larger tungsten.ScottHaul a bike without straps - visit  www.mxtras.com  to see how!
Reply:You mentioned brushing w/SS brush, but after that , you should clean it by wiping with a cloth saturated with acetone , or maybe M E K . Then move the acetone, etc. far away from the weld site.[SIZE="5"Yardbird"
Reply:Originally Posted by MXtras ... I run the tungsten probably about 3/8" (9.5MM) above the work at a forward tilt of around 15-20 degrees from perpendicular.Scott
Reply:Originally Posted by Roy HodgesYou mentioned brushing w/SS brush, but after that , you should clean it by wiping with a cloth saturated with acetone , or maybe M E K . Then move the acetone, etc. far away from the weld site.
Reply:Originally Posted by hotrodderthat's a typo right? you don't have an arc length of 3/8"?
Reply:Originally Posted by zapsterI'm between 1/4" and 3/8" at times away from the piece with no problems...Horsepower!...zap!
Reply:Originally Posted by BurnitMe too, thought that was normal (?)Is it?
Reply:Originally Posted by zapsterI'm between 1/4" and 3/8" at times away from the piece with no problems...Horsepower!...zap!
Reply:Power! I am only using like 130 amps most of the time but the machine is set at 200+. More Pedal! Kill It!Like those inside corners when something just doesnt wanna wet, bbvvvvpppppedal!!
Reply:Originally Posted by hotrodderthat's a typo right? you don't have an arc length of 3/8"?
Reply:A butt joint on 1/8 plate SHOULD be welded on both sides, so penetration would only need to be about 60% into the joint on each side.The biggest thing you are doing wrong is selection of the tungsten diameter is too small making you take too long and therefore the plate is getting too hot.With TIG the magic rule is this HOT, CLOSE , FAST. Always have that in your head.With a 3/32 tungsten you would get the penetration AND you would keep your speed up which would keep a tighter narrower bead.That 1/16 tungsten is where you got started on the wrong foot.Just change that an you will have all the problems solved.
Reply:Originally Posted by MXtras3/16" = 4.76MM which is a ~2.4MM radius.....  I use the same (3/16") but I am running a transformer machine (Synchrowave).  The inverter guys claim they have a different set of rules.  I still prefer pure (green) tungstens but I use Red (2% Thiorated) for the smaller work and smaller diameter tungstens.Scott
Reply:Red is good enough for the girls I go out with.Miller 250DXTD Cutmaster 100Duct TapeBFH
Reply:can't believe what i've just read
Reply:Originally Posted by Donald BranscomA butt joint on 1/8 plate SHOULD be welded on both sides, so penetration would only need to be about 60% into the joint on each side.The biggest thing you are doing wrong is selection of the tungsten diameter is too small making you take too long and therefore the plate is getting too hot.With TIG the magic rule is this HOT, CLOSE , FAST. Always have that in your head.