I'm practicing GTAW with some 1" Al tubing, approx . .063 (bought it as scrap but it is weldable). I notch one piece of tube and fit it as a T to another piece. The fit up is good. I am using a dedicated stainless steel brush on a flex shaft to clean the metal of oxides. My machine is a Miller Syncrowave 180, argon gas flowing at about 12 and amps set variously at 90 to 100, AC, pure tungston, balled (1/16) and 4043 or 5356 filler (1/16). The weld is not cracking, does not seem to suffer from porosity and I usually avoid burn through.
My question is how do you control the size of the bead with this joint? I have trouble with how much filler goes into the weld, with it ending up much too great in my opinion. If I am running a bead on a sheet of Al I seem to control the bead reasonable well. Also, what is the rule, if any, about when and when not to use filler metal.
Thanks
Ken Dougherty
It sounds like you have everything set up. Welding aluminum to me is like a skill of its own within welding. Since your electrode is balled up or blunted and using AC current, you are natually going to get a wider, fatter bead. Now when your talking about controling the "size" of your bead, do you mean width or hight? If its width, try not to weave the electrode just move it in a straight progression along the joint. If you are talking about hight, try "pushing the puddle", adding a little bit of filler metal to the front of the puddle as you progress along the joint. Keep an eye on the puddle and what it is doing. Do not keep dumping off filler metal, get a good bead going first and add just enough to fill the crater as you are moving forward. As far as a rule of when and when not to add filler metal, I would guess that depends on the design and code of what you are welding.
I remember a while back someone posted a message or passage about a welding machine that could weld aluminum on DC with a sharp tip. Helping to shrink the size of the bead. Perhaps someone can give you some imput on that.
And your argon pressure, I could have swarn that in class we were taught to use between 15-18cfh. Can't remember on that one, maybe someone can help me out on that issue :)
David
Ken,
Rule of thumb, GTA fillet welds with aluminum tend to have a larger leg size than do steel fillets. Similarly the reinforcement (melt thru) on groove welds tends in most cases to be greater. Is the length of the largest leg (distance from the root to the toe of the weld) greater than twice the thickness of the thicker material?
Still there are things you can do to reduce the size of your weld. I'll list a few
Aluminum likes to be welded fast, this takes practice. How many starts and stops are you making? Is your tube fillet rotated on a table or fixture?
Technique; Getting in tight in a fillet is important for bead size and more importantly for obtaining fusion at the root! The further away your electrode is from the work the more your arc and filler metal will want to make a "Bridge" on each leg of the work, this increases the risk of leaving a void the length of the weld at the point the two pieces intersect (root). You can experiment with different sized cups, going a bit smaller is often times possible with fillets as they tend to hold the gas shielding a bit more efficiently than a groove or build up weld.
A pointed tungsten can help keep your arc a bit more directional; it is nearly impossible to keep a sharp tip on a pure (green) tungsten. However, Zirconium (Brown) and Ceriated (Orange) tungstens have a higher current carrying capacity and will keep a point quite well when working with 1/16th inch electrodes on 0.063 aluminum fillets. My advice is to discard pure tungsten electrodes after trials with Zirconium and Ceriated to decide which works better for your job.
A water-cooled torch and a full length of electrode with a long cap (if accessible) will also allow you to put more energy into the work before the electrode begins to distort.
For good practice; cut your base pieces into 2.5 inch lengths and weld the tube on, then cut the thing in half and check for fusion at the root.
With most aluminum manual GTA welding filler is a must. Especially with 6061. Filler starved aluminum welds tend to crack immediately.
Balence control toward max penetration will also help in narrow the profile of your bead. Begin at a balenced position and increase the dwell time on EN until you get what you want. Remember you can take this too far, porosity or scum on top of the puddle is a sure indication. The further the balence control is set to max penetration the more important perfect surface prep becomes.
A great exercise to practice the avoidance of "bridging" and a good example to actually see the difference between sharp and balled electrodes is butting the bottoms of pop cans together and welding them out.
Ken, you are getting excellent advice, I would suggest simply extending your tungsten out a little more and increase your gas flow some before doing anything elaborate. Aluminum doesn't like to be welded autogenously. And as stated, 6061 has to have filler. There are exceptions to every rule (someone will point them out!!) but generally speaking all of the aluminum welding I do requires filler metal. Be careful turning the balance too far, old aluminum requires a certain amount of the cleaning action from the electrode positive side of the sine wave. Good luck and keep us posted on your progress.
Respectfully,
Mike Sherman
Shermans Welding
Thanks to all for the replies. I took a systematic approach about changing the variables and had good luck. First of all, I measured the material and discovered that it is .047 so I was more careful with heat, not going beyond 90 amps.
First trial, I took Mike's suggestion of extending the tungston out a bit further - to 3/16 in a # 4 nozzle and I increased the gas flow to 15 cfh. I also ground somewhat of a taper to the tungston, leaving a 1/4d flat which resulted in a smaller ball and used 4043 filler. The results were improved with a smaller, neater bead but without nice ripples and with some possible porosity. The ball on the tungston moved off center slightly.
Next, I changed to a 7" tungston and kept the other variables the same. I had been using 2" tungston with a stubby cap. That seemed to run the tungston cooler and the ball seemed more stable. (I don't have a water cooled torch nor can I adjust balance.) The results were consistent with the first trial.
For the third trial, I used a 2% ceriated tungston, 7", ground to a point with approx 1/4d flat on the end and I switched to 5356 filler. I kept the other variables the same. That resulted in an improved bead with some ripples and the bead was of the appropriate size. The porosity seem to be less also.
Basically, by combining everyone's tips, I ended up with much improved results. Thanks everyone.
Now, another question. If the tungston is dipped in the puddle but it stays shiney, it is ok to still use it or has it still been contaminated? Sometimes on a practice piece, I keep welding and notice no visual change in the weld after a second or two. And, should the weld at the point of tungston dipping be ground out or treated in some way?
Thanks
Ken
Also, something occured to me. Using the notched tube fitted as a T joint the joint actually phases from a T to a lap then back to a T. There is an awful lot going on with this type of weld!
Hi Ken, I am glad to see your welds are improving. As to dipping the tungsten in the puddle, it depends on what end results you are looking for. If you are doing code quality work you should stop, regrind your tungsten and grind the contaminated area. If you are doing say a handrail where your priority is strength and aesthetics, than if the weld still looks good I would keep going. I hope this helps.
Respectfully,
Mike Sherman
Shermans Welding
Mike said this perfectly, but the point he makes is so important it should be said at least twice.
When the electrode touches the work, both the work and the electrode are in fact contaminated. Its like the peanut butter cups commercial in the 70s, "You got aluminum on my Tungsten" well "You got Tungsten all over my Aluminum! However unlike the candy, they do not go great together :)
With aluminum on your electrode you will loose some benefits of balence control. I can't even Imagine what a machine like yours that controls balence automatically does with a fouled tungsten. As it seems that appearence is important you will also find it less easy to make a narrow bead profile with a fouled electrode.
One last thought came to mind as far as the "rippled appearence" you seek. You might try going up one size in filler wire diameter, this will help with heat control and ease of dipping a consistant amount of filler. This is often a cure for situations where the welder finds he is overheating the work and he has tried all other options to cool the puddle.
Enjoy
Lawrence Bower
Welding Instructor
United Airlines
Like that analogy. An excellent reply Mr. Bower.
Thank you Mike and Lawrence. These are the kind of tips and explanations that are hard to come by. With respect to a fouled tip and balance, is the issue rectification? One other question (probably not), is a gas lens something that only has a specific purpose or can/should they be used routinely? Would there be a savings on gas consumption since efficiency of the stream is improved?
Thanks
Ken
Hmm, Never given much thought as to why a fouled tungsten is foul. Experience says arc voltage will change (not a major factor in most hand Tig.), also all the junk the tungsten picked up will be heated to about 5000 degrees as it rides upon the electrode and then hotter still as it is burned off the tungsten <vaporized> and traverses the arc only to splash down in your weld puddle. What changes that aluminum you picked up on your tungsten has gone thru before it returns to the puddle is out of my leauge. The cleaning action (etch) will be distorted also. You may or may not experience rectification, depending on how badly you have soiled your tip. Your Miller has the Auto-balence thing and I don't know what triggers its adjustments, no doubt some sort of adaptive feedback system. Maybe based on arc voltage? Miller techs feel free to chime in here!
Gas lenses often solve coverage problems, on the other hand they may hinder visibility at times where a smaller standard cup allows better access. I like them and use them where practical, taking special care to inspect the fine mesh inside before every use as chattery AC operations can cause them to get messy and that can hamper gas coverage. It is possible sometimes to pull off little balls of melted mesh or even a layer of screen from a gas lens which has been rendered unusable.
The welds and joint geometry you describe are common enough and you may see them on fancy mountain bikes, take a look at one <make sure its an aluminum frame> and take note of the size of the welds in the different style joints. Both Aluminum and titanium production componants can sometimes demonstrate rather large weld bead profiles. Its good to be able to make a small bead but not always best.
Lawrence, Thanks for the discussion. I know my question was rather esoteric but fun to puzzle through. I'll start paying attention to various bike frames. By the way, as you suggested, I picked up some 3/32 4043 to experiment with today but have not had a chance to use it.
Ken
#8 cup, at least 3/32 tungsten, plenty of argon flow, probly 4043 1/16 wire
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