My Aluminum Welds are so wide - why?

[XTWalt]

Another Noob question.

When I started trying to learn to Tig Aluminum with my new square wave 175, my weld beads always came out about 1/2 wide. 1/8" plate, 3/32 Pure Tungsten electrode, 3/32 filler wire & 15 cfh Argon.

I've made some progress going to a 1/16 lanth electrode, better cleaning and lower current - now its only about 3/8 wide. AC mode seems so violent compared to DC-, much less focus on the arc. Any suggestions?

I assue I'm getting it too hot, so how do I keep the heat more local? Sharpen the electrode point? Get the electrode closer? More Argon flow?

Thanks,
Walt

[pulser]

Originally Posted by XTWalt

Another Noob question.
.... how do I keep the heat more local? Sharpen the electrode point? Get the electrode closer? More Argon flow?

Good thinking, if the heat is not concentrated, it is very inefficient in melting a puddle, you have hold stationary too long to establish a puddle, then you have to travel slowly to keep the puddle, because most of the arc heat is being conducted away throughout the part.

There are some things which should help give a more concentrated energy density and increased arc efficiency.

First, as you mentioned, get the electrode closer. The arc diameter increases very rapidly as the arc length (tip to work distance) is increased, and you want a very small constricted arc, so it is critical to keep the arc length as short as practical. Around 0.060" is good for manual welding.

Second, you mentioned sharpening the electrode point. Well, many welders would probably suggest a fairly sharp point to get the most concentrated arc, but they would sadly be wrong. For a given current, the arc needs a certain amount surface area on the tungsten tip. If the tip is very sharp, the arc climbs up the taper to satisfy this surface area, however, as the angle becomes more blunt, the arc stays further down toward the tip. The arc initially tends to come off of the tungsten at 90 degrees to the surface of the tapered point, and then it bends to the workpiece forming a gaussian (bell curve) energy distribution. So for the very sharp thin taper the arc is wider and less concentrated than for the blunt taper. Here is a previous thread with a picture of different electrode angles and the resultant arcs and welds. http://weldingweb.com/showthread.php?t=6875

Third, you asked about gas flow. No, just need enough flow for good shielding. However, if you can afford helium, it's thermal conductivity is around 9 times that of argon, so for a given current, you transfer much more heat to the puddle.

Basically, with aluminum you need a lot of amperage, you need to hit it hard with full power to get a puddle fast, and then move along as fast as practical. Low amperage and traveling slow just spreads the heat to the base metal and promotes wider welds.

[DesertRider33]

If you have a balance control, set it for more penetration and less cleaning. 30% cleaning is about average.

[Rojodiablo]

Pulser has a great point; I use primarily 3/32 tungsten with a blunted sharpened tip. And that keeps the arc smaller. Also, keeping tungsten clean really helps!!! Finally, if you can adjust the frequency, then take it up a little higher; that will make for a smaller puddle.
Good luck.

[XTWalt]

Thanks for all the great advise - all makes sense.

So, next time I'll go back to my 3/32 Tungsten and a more blunt point or a balled tip. This opposite to what I was doing, going smaller and sharper. (nice explanation on the link) Also, I'll try to go stay closer, use more heat and move faster.

Unfortuately, my Lincoln Square Wave 175 has no adjustment for balance or pulsing. I assume that the problem here is my technique, and not the welder. It doesn't have the latest bells and whistles, but I'm hoping its capable once I get more proficient.

Thanks,
Walt

[papabear]

Originally Posted by XTWalt

Thanks for all the great advise - all makes sense.

So, next time I'll go back to my 3/32 Tungsten and a more blunt point or a balled tip. This opposite to what I was doing, going smaller and sharper. (nice explanation on the link) Also, I'll try to go stay closer, use more heat and move faster.

Unfortuately, my Lincoln Square Wave 175 has no adjustment for balance or pulsing. I assume that the problem here is my technique, and not the welder. It doesn't have the latest bells and whistles, but I'm hoping its capable once I get more proficient.

Thanks,
Walt

If your machine has HF, you can adjust the point gap. Most Lincoln's come with them set at .015", try closing it a bit, ~.008 should help tighten up any arc wander.

[XTWalt]

Thanks papabear. The gap is still factory set (From 12 years ago) at .015". resetting to .008" wont hurt anything will it?

Thanks.

[papabear]

No; it won't hurt anything. Also take into consideration every thing that pulser said. I don't know if he also included the fact that you should NOT be using pure tungsten with square wave or inverter machines. I personally like lanthinated for alum., it seems to hold the sharper tip better. Keep working at it, you will find the results you're looking for.