Aluminum Beads and Keyholing

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How does one avoid the keyhole at the onset of a TIG bead?  Do you start in the middle of the piece and go the other way to the other end to finish the bead?The bead pics are with the following settings:.060 Aluminum coupons60 amps(one is pulsed at 90 A peak, 30 A background, 50% pulse time, 120 Hz)80% EN100 Hz AC Freq1/16 Ceriated with Gas lens at 12 CFH Ar3/32 4043 filler rodI still have a ton to learn, so Im trying to get as much hood time as possible.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:the pulsed one:TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:I try to make the cold start at the edge.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:That's what I'm doing.  I step on the pedal at the beginning and back off the pedal as I go when the metal starts to heat up and the bead starts to widen.  I'm also finding that I need to move faster and dip rod faster as I go.   Would you start 1/4" in from the edge, then fill backwards to the edge when beginning the bead, then start moving forward?  I always get that stupid notch at the start no matter how cold I try to start it.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:You should be able to start so cold that it doesn't even melt the metal. Then bring the heat up really slow until it starts to get shiny and ad filler and your off.  If you can't do this, then your heat range is to high or your machine is not working properly Mac
Reply:I assume you are talking about where you melted back the edge at the start.  You can backstep the weld starting a short distance from the edge and then backing up, or you can start on the filler. you should however be able to start on the edge as the others have suggested.If you want some really good info on alum tig, take a look at Kevin Morin's posts in these two threads. i think he's got another one somewhere but I couldn't find it right now where he clearly shows the keyhole melted in his post ( if anyone remembers it, please link it for me so I can make a note of it.)http://weldingweb.com/vbb/showthread.php?t=43012Post #17 by Kevin.http://weldingweb.com/vbb/showthread.php?t=47001&page=2Post # 40 by KevinTo me all those welds you show all look cold. Flip the pieces over and lets see the back. I'm betting you really don't have good penetration even with material that thin, at least from what I see up top. Alum that thin is a real PITA. It's so thin it melts too fast for most new tig welders. You have to punch up the amps fast to get the puddle going and then run to stay ahead of it. Try to keep the amps down to keep from blowing thru, and you get a pile of alum just sitting on top. Looks ok if you have no clue, but you really didn't get into the base metal at all. You really need to have heat and puddle control down pretty good to be successful with alum this thin. At the tech school we use 1/8" alum. It's thick enough the students have a bit of room to adjust their heat and speed, and thin enough they don't need 300 amps to weld it. Alum looks like it would be easy, but it's not. It's a great heat sink and wants to pull heat away from the puddle. If you go low with the amps or take your time, it will pull it away faster than you put it in. Meanwhile the whole piece is heating up. All of a sudden you get close to the welding point and the whole piece wants to melt at the same time instead of just the edge at the bead. The solution is tons of heat dumped in faster than the alum can suck it away. You punch the throttle and bang you get an almost instant puddle, back down a bit and then out run the heat as the plate heats up. It takes a good bit of skill, coordination and control to do this with thin metal that heats up much faster than say metal 2x as thick. Add to this that the surface oxide layer melts at a higher temp than the bare alum does. If you've got poor prep and are tring to melt thru the oxide layer, as soon as you do the interior is already molten. This is especially true if you take your time, or if your material is thin.But joints are also one of the hardest to do. You need to punch thru the plates and not blow thru completely. Not the easiest thing to do. A gap or bevel would help.IIRC you are new to tig in general. I'd strongly suggest you start at the beginning with steel. If you can make decent tig welds in 1/16" steel in all positions, you might be ready to start in on 1/8" alum. I don't see the control needed here yet to do alum this thin. Steel is much easier to see whats going on and much more forgiving in terms of heat and speed. Start with lap joints where you have more thickness at the weld seam. Then T joints followed by open outside corners where the inside corners just meet. The very last joint students do is usually a beveled but joint and it's usually the hardest for them to get thru. They seldom get good penetration until they've worked at it quite a bit. After they master all these joints in flat, they'll go on the horizontal, followed by vertical and overhead, doing the same joints in order each time until they get them right. After that they can move on to thinner materials and repeat the process from step one.There's no shortcut.  Trying to jump to chapter 5, will not get you ahead faster. You need the basics. With the basics down you actually move faster even though it seems to take longer to get there. The burn back at the edge is all about heat control. If you understood whats needed to control the heat, you wouldn't need to ask the question. Yes it's boring and tedious... but that repetition will train you to make minute adjustments in heat and speed that will allow you to do this at a later point with ease, probably with out even needing to think about it..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Kevins posts are amazing... does he teach or something?!JoeMiller 140 Autoset (2010)Miller Syncrowave 250 (1996)
Reply:You need to do what I call a "Back Dip"...Start the weld about 1/8" from the end and after you get the first dip made instead of going away from the end back up without stopping the arc and ad a dip to the edge and maybe another one THEN proceed to weld as usual..You also need to stop making the craters at the end of the weld by going in small circles at the end with the torch and add a dip and another dip to build a "tit" while at the same time backing off the pedal so there is not so much heat..It's easier to show someone this in person rather to try to explane it by typing...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:First thing I'd recommend is turn the dang pulser OFF.No need for it on most aluminum welds.Aluminum is a tremendous heat sink in it's own right.  Aluminum likes to be welded hot and fast.  Purpose for pulsing is to reduce the "average" heat put into the weldment.Start hot and use the pedal to back off the amps as heat builds in the material.  This is why a remote control (foot/fingertip/etc) is important for aluminum tig.The backstepping mentioned is the best way to prevent blowing out the edge when starting.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by SundownIIIFirst thing I'd recommend is turn the dang pulser OFF.  SNIP
Reply:Bead BackTA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:Backside looks good.   "Buttcheeks" in the aluminum.  Penetration was plenty.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:I stand corrected. You did get decent penetration. Tops still looked cold..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:That was the pulsed one.  The others had similar penetration.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:When you're first initiating the puddle, move the arc backwards and forwards across the joint, so that the shiny puddle starts a fraction away from the joint on each side (not right inside the joint), that'll help to avoid the gap growing.you could try thinner filler rod... which means you need a smaller puddle before you start adding filler, which means less keyholing at the start. Another thing is to place your coupons on a metal (ideally copper) backing plate, so if it keyholes you can just back up and fill it up. Mick
Reply:TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:Thanks again for all the help.  Kevin Morris' illustrations and explanations helped alot.  I didn't realize you actually wanted it to keyhole before adding filler rod.  It makes sense now, the key holing happens when you have full penetration (never a bad thing).  I'm starting to get it now.  There is no slow-go with aluminum.  Got to get it hot fast and move, otherwise I get cold beads with little fusion or melted metal.  The above bead was using 70 amps and Zap's backup method and "tit" on the end.  I stopped a little short and was a little cold at the start.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:try a smaller diam. Filler. The .060 sheet edges are melting away before your filler puddles.Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:You got it!Now fix this guys chair in my sig.  I sent him away.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:I go about it a different way. I use a finger switch and i just start at the start (no back tracking) i just fire up on at and add filler the very moment it arcs, not giving it time to keyhole. I rarely use a foot pedal, but when i do i slam the pedal to the metal on starts like that. there is a delay in ignition on my machine that you have to master (unlike the the on/off where your adding filler and pressing the button at almost the exact same time) Anytime i have ever used any upslope in amps i would rarely be quick enough to prevent it from keyhole.www.performancealuminumfabrication.com