devo, If you are useing a foot pedal I don't see any harm in controling your heat by decreaseing your heat input. I do not allow the puddle to completely freeze though because you just have to heat it up more so you can add more rod kind of defeats the purpous. also you say you are grinding your tungsten for aluminum welding you should be useing a boulbous tip it makes the heat spread faster cleans a larger area and allows you to add rod quicker when you do get the puddle established. Also in regards to cleaning try to watch the tinning action as the material heats up you will have a hard time adding rod if you do not allow this to happen before you dip the rod . Do not forget to wire brush your material before starting. Don't loose hope aluminum welding can be very trying at times and even the best can have problems with it, but once you figure it out it is quit easy if the material is clean and there is a lot of satisfaction in doing a nice tig weld on it ,not a lot of guys have the patence for it . It is not something that you can hurry through. Hope that helps.
That bubblely surface may be caused by to high a gas floe ???
I have done a lot of aluminum GTAW over the last 20 years, and there are always 3 constants: use only pure (green) tungsten, clean argon gas, and a clean stainless steel wire brush before every pass. I like to burn each pass in hot and fast, especially if I'm purging the backside. If you're purging, make sure you keep the pressure in the required range on your wps. Because pure tungsten is so brittle, if you dip it, you probably have left an inclusion, and it needs to be ground out. I have learned to always start with a clean electrode...for your .065" wall thickness, I might use 3/32" and grind a slight crown onto the end, then "run it in" on a piece of clean, wire-brushed scrap. This makes a very clean, rounded end on the electrode for excellent control. The "stubbly" appearance of your bead surface may be due to poor gas quality, not enough gas, too much gas, or the wrong kind of gas. Pure, oil-free argon works best, in my opinion. If you are having trouble keeping your arc steady, try increasing the amperage and learn to feather the footpedal to maintain it. You don't want to allow the puddle to solidify, as this can cause cracking and lack of fusion at the toes. As for not getting burned on the job, try using an old glove or a scrap of leather or glass cloth, wrap it completely around the tubing and secure it with a few strips of heat tape all the way around it, just tight enough that you can rotate the entire thing around the OD of the tube. That way you can hold the thing like a bike handlebar and pull your wrist without changing your angle. Once you have that down, you can easily master walking the cup over 180 degrees or more of the tube in one pass.
Thanks for the feedback everyone. Now a few clarifications...
Re:Makeithot I use an inverter machine, so the bulbous tip you describe is not what is recommended. I grind my tungsten to an included angle of 30-45 degrees with a flat about one-third of the diameter. This preparation gives a nice shiny round tip once I begin to weld. I am cleaning everything(rod, tungsten, base metal) with a SS brush and acetone before welding. My gas flow is 12 cfh. The stubbly appearance I described is intermittent. It only happens with the 4043 rod, not the 5356. I suspect it is either contaminated rod, as it is stored in a big open box in the supply store, or I am holding a long arc.
Re:DaveBoyer. I used to grind the gunk off my tungsten and just keep on welding, but now I just switch tungstens until the box is empty, then have a grinding party. I notch the tungsten just below the dirty tip with a cut off wheel and break it off with pliers. I'll so this for all of my electrodes then prepare the tip on all of them, so I have a nice fresh batch of tungstens to dip into the puddle, I mean to produce gorgeous code quality welds with.
Re:Bozaktwo1 Pure tungsten is not for me(see above). I am not purging, as this is just practice and I have never even seen a WPS. The argon I use comes from the welding supply house I use. They produce medical grade oxygen in addition to their welding gas, so I assume it is clean. I have seen several posts on this site that refer to "clean" argon. Is there any other kind? Do you have to slip the girl at the welding store a fifty and say "gimme the good sh#t"? Are there inline filters to use? The advice on wrapping the tube with an old glove is right on the money. You ended your post with a comment about "walking the cup over 180 degrees or more in one pass". I am familiar with the technique, but if I am walking the cup, wouldn't my hand be free to move the torch back and forth and not holding the tube? If you could clarify what you meant, you would be doing this rookie a huge service.
It's all personal preference, as far as how you manipulate. When I weld pipe, I try to hang the ball of my palm on the pipe and manipulate the torch a lot like you might use chopsticks. I can't explain that any better without showing you! As far as everything else goes, like I said, "in my opinion," and the most important part of laying good weld is being comfortable with the way your doing it. That includes type of electrode, filler wire diameter, amperage, etc. I use 3/32" for almost everything I do; saves on collets and gas lenses! With aluminum, I have used both heavier and lighter electrodes, pure, thoriated 1%, cerated, and some other exotics I can't even remember...I don't remember them because none worked as well as pure for me, even on T6 applications. 3/32" works well for hot and fast, until you get to 3/16" base t and over. It sounds like you're doing all the right things, just find your comfort zone and go to town, man.
Use 1/16" (0.0625") or 0.040" diameter ceriated tungsten ground to a 1 1/2-2X taper (forget about balling) and radiusing the taper by welding the tungsten end shut. If, the tungsten forms a ball increase tungsten diameter. You will need only 40 to 70 welding amps. Use 0.035, 0.040 or 0.045 filler (GMAW/MIG) wire diameter. Use a material like "Scotch Brite" to clean the oxide off all sides of (root face, back and face sides) material and filler wire (if it has oxidized). Wipe clean with acetone. If the machine has an AC balance control, set it to provide 60% time at negative or greater.
Max has given you the best advice.
To help keep your pinkies cool you might get a small section of steel pipe of a slightly larger diameter and use it as a sleeve around your aluminum. This way you can rest your hand on something with a much lower rate of thermal conductivity and still be able to rotate your project within it. You could also just invert a piece of 2 inch angle iron and lay it on top of half of your work as a hand rest.
Thanks for the advice. I am doing everything you said, except I am using .065 filler. It's all I've got right now. One point I'd like you to clarify, after preparing the tip of the electrode, you say to "radius the taper by welding the tungsten end shut." What do you mean by this?
After the tungsten is ground to a taper, weld with the tungsten with a bit more amperage than is needed for welding. This is done to melt the end of the taper and form a radius, but not a ball. This melting/forming a radius fuses the cerium, thorium or lanthana to prevent splitting or nodule separations.
This radius forming is why balling of thorium tungsten was done in the first place. Thorium tungsten was first used to weld with more current than pure tungsten could carry. Try welding with a new piece, out of the box, of 1/8" thorium tungsten on 50/50 (balanced) AC. Notice even with a ball it is not smooth without imperfections.
Get some GMAW/MIG wire - 0.035, 0.040 and 0.045", it will be a lot easier than 0.0625.
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