Help to TIG of aluminium 6061-t4 with 0 porosity

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Hi all,I have a project of welding aluminium 6061- T4 and the requirements is 0% porosity. The machine that I am using is a Miller Syncrowave 250, 4043 filler material and 100% argon gas.Currently, I'm still unable to archieve the target and wondering if there are any useful tips from experienced aluminium welders. Any suggestion regarding the cleaning method, preheat treatment or new gas composition will be greatly appreciated !Cheers
Reply:I'm no expert in aluminium welding but 5356 filler works fairly good for me when welding 60xx alu.Also tungsten composition,cup size,tungsten stick-out and size, weld speed and many other variables come to mind when talking about alu welding...--------------------------------------------------------------www.becmotors.nlyup, I quit welding.. joined welder anonymous
Reply:what about material thickness? Maybe you need some Helium in there?Lincoln Power Mig 210MP MIGLincoln Power Mig 350MP - MIG and Push-PullLincoln TIG 300-300Lincoln Hobby-Weld 110v  Thanks JLAMESCK TIG TORCH, gas diffuser, pyrex cupThermal Dynamics Cutmaster 101My brain
Reply:the aluminium thicknes is aprrox 1.5 inch (3cm) thickness@Donoharm why do you recommend 5356 filler? @Joker11 approximately how much percentage of helium should be mixed into the argon gas.Thanks for the suggestions. I am able to trial weld before proceeding with the project.
Reply:I doubt that you'll have much sucess on something that thick with that small of a machine.
Reply:Originally Posted by majal_katathe aluminium thicknes is aprrox 1.5 inch (3cm) thickness@Donoharm why do you recommend 5356 filler? .
Reply:You are  not using an aluminum oxide wheel are you?  If you look up 6061, the recommended filler is 4043.   How much gas flow?    Gas lens?   CLEAN CLEAN CLEANLast edited by David R; 02-22-2012 at 10:35 AM.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Think you're whistling in the wind trying to AC weld 1.5" material with a Sync 250.  Maybe the breeze is blowing your covering gas away.Not sure of the configuration, but sounds like DC and straight helium is your only hope.  Doesn't sound like you've got the experience for the task at hand.Also, I disagree with the recommendation about using 4043 filler vs 5356.  If the part will not be subjected to constant temps greater than 150 deg F, 5356 is a better choice.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 welds4dI doubt that you'll have much sucess on something that thick with that small of a machine.
Reply:Originally Posted by SR20steveA sync 250 does 310 amps, it's got plenty of balls. Preheat it if you have to.
Reply:Steve,The Syncrowave 250 is so powerful that even Miller (you know the guys who build the machine) even rate it for 3/8" Aluminum.Don't get me wrong.  I'm a big fan of Sync 250's (owned one since '77--3 different machines), but 1.5" aluminum (don't care how much preheat you use) is not in it's range if the part has any mass at all.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:As for why its called a 250 and not a 310.  I believe if you look at the 40% duty cycle number it's at 250.  Miller typically rates 'industrial grade' at 60%.  So that would make the Sync 250 a '200'.  Note Miller does in fact make machines that are rated at 100% duty cycle - for hanging off a robot.For the OP's original question - pictures would help a lot.Full settings - tungsten type, tungsten point, diameter, amps, balance, cup, gas flow rate etc.I cannot comment on how far pre-heat + helium will get you, the real question is can you form  a puddle or not.   Since the OP says he's already tried this on a 1.5" block of aluminium, the obvious answer is yes... unless he's welding it cold (no fusions of base metal).  Shape of the metal and joint configuration play a role.  If there is not enough metal for the heat to escape to, it will melt the metal. But the original question is simply, what to do about porosity.  The OP didn't mention how he determine he had porosity (sectioned the weld, or visible, or x-ray or?).  Generally porosity is entrapped gases or dirt.So:1) Not enough gas coverage.  Aluminium can take 50% more than the equivalent steel.  II have no idea what the parameters would be for 1.5" thick single pass.2) Moving to fast - both outrunning the gas and allowing the metal to cool too quickly.  I've never out run the gas on TIG (I'm not that fast), but with MIG I have.3) Dirty base metal.  Aluminum seems to respond best to wire brush cleaning (dedicated for aluminum only, stainless steel brush) followed by a wire down with a solvent (acetone works well - always let the solvent evaporate before you weld - goes for any solvent).4) one last one - just because the metal is so thick, if you aren't letting the puddle form before you dip the rod, you could be essentially stacking cold welds on top of cold welds - and more or less form air-pockets.  Make sure your fill is going into the puddle, and make sure the next puddle is properly fused into the previous one.As for using DC + Helium.  I think you can use 75% Helium and 25% argon with DC (from books, no personal experience), but you have far less cleaning action.  The base metal has to be that much cleaner.Last thought, 1.5" thick aluminum is not really the ideal process for manual TIG.  Gotta wonder what some of the bigger boat builders are using (aren't some Navy destroyers aluminum hull?) (I think Bradley fighting vehicle is also aluminum armor).  I would generally recommend aluminum MIG, but there is no way even my 350P has enough.Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:DCEN with helium. Set your machine at about 175 and use the pedal. Sharpen the tungsten to a point then grind a small flat on the end. 3/32 2% thoriated is fine. Welds like mild steel. Cake.Two turn tables and a microphone.
Reply:Use a helium mix gas, turn your frequency up, balance toward the weld end of the spectrum, make sure the metal is very very clean (stainless wire brush and acetone wipe with a rag that wont leave lint) do not clean with a power brush or abbrasive of any kind, stainless steel hand brush only. Make sure your bevel is right and preheat the part to something around 300*.
Reply:Originally Posted by ironmangqUse a helium mix gas, turn your frequency up, balance toward the weld end of the spectrum, make sure the metal is very very clean (stainless wire brush and acetone wipe with a rag that wont leave lint) do not clean with a power brush or abbrasive of any kind, stainless steel hand brush only. Make sure your bevel is right and preheat the part to something around 300*.
Reply:ironman,You want to explain to me how he's supposed to TURN THE FREQUENCY UP on a transformer machine.I understand setting the balance (on a Sync 250) to 8.5 or even 9, but i've only had Syncrowave 250's since 1977 and I still haven't figured out how to turn the frequency up.  It's pretty easy to "turn the frequency up" on my Dynasty though.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 PangeaDCEN with helium. Set your machine at about 175 and use the pedal. Sharpen the tungsten to a point then grind a small flat on the end. 3/32 2% thoriated is fine. Welds like mild steel. Cake.
Reply:Originally Posted by SundownIIIironman,You want to explain to me how he's supposed to TURN THE FREQUENCY UP on a transformer machine.I understand setting the balance (on a Sync 250) to 8.5 or even 9, but i've only had Syncrowave 250's since 1977 and I still haven't figured out how to turn the frequency up.  It's pretty easy to "turn the frequency up" on my Dynasty though.
Reply:HI all thanks for the prompt replies!I have made a mistake about the dimensions.The outer diameter is 1.625 " while the thickness is 0.058"Other information is the argon flow rate is 15 cubic feet per hour and using a AC high frequency 50-80 A.Some suggested preheating to 300 degree, but why do you choose 300 degree and how long do you preheat the aluminium.As for the helium to argon mixture, roughly whats the percentage of the mixture.ill get back to you guys on the tungsten setting.Regards
Reply:Well now, that changes the whole debate!
Reply:I read up and there were information of adding NO additive into the gas mixture to improve the welding. However, it is from a research paper and I am quite skeptical. Anyone have experience in using NO additive and how is the outcome?
Reply:Ummm.....Why would you get porosity on .058 aluminum with pure Argon?   "high frequency" I believe refers to the starting mechanism for the arc which will keep the arc going as the AC wave goes through 0.  The frequency of your AC wave is set at 60 Hz, which I actually like alot.  Set your machine to AC, 80 amps, AC balance of 10 (which was 68% DCEN on my S250 IIRC), and use the pedal to control the bead.  1/16 or 3/32 filler.  Am I missing something?TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:Originally Posted by con_fuse9Are you saying that 1.5" aluminum can be easily welded with 175 Amps + Helium?I'm asking because I don't know, not trying to be a smart ***.