[welddoctor]

I'm new to TIG welding. I've watched and seen a lot of videos. I'm having a hard time with aluminum lap joint. I can get and maintain a puddle when working on a flat surface, however when I try to fuse the lap joint I get either the top or the bottom to start a puddle and can't get the other side to have a puddle at the same time. One side gets melted and the other side gets black with a white line.
I'm using an Arccaptain TIG on 220V with 3/32" Lanthanated tungsten. I've tried a sharp point, but the tungsten ends up rounded after a few attempts. I have a gas lens and have tried various size cups. The TIG welder has square wave and triangle wave. I seem to be able to do a little better with the triangle wave. I have tried various Hz settings and various amps. I've tried cranking up the Argon to well more than I need.
Another issue is the filler rod melts before I can introduce it into the puddle.
Any info would be helpful...Thanks

[tweake]

welcome

what size material are you welding and what is your machine settings?
if you can post some pics, it makes it easier to see whats going on.

[welddoctor]

I'm trying to weld some 1/2" sold square stock to a 1/2" x 3" sold stock. I was just looking at a tungsten chart and it showed that my tungsten at 3/32" is too small. I've ordered a larger size. I will post some pictures with the new tungsten size...thanks

[ekbmuts]

For what it's worth, if you're welding 1/2" aluminum, you're going to need some amps. When I was starting out, I tried to weld 1/2" aluminum with a 175 amp machine. Didn't even come close to any sort of decent penetration. What is your machine set at, amps-wise? Never mind voltage. Secondly, your tungsten is supposed to ball on the end on AC. You want that to happen and it will happen. Just a couple of suggestions when your post reminded me of my early days on aluminum...

[tweake]

I'm trying to weld some 1/2" sold square stock to a 1/2" x 3" sold stock. I was just looking at a tungsten chart and it showed that my tungsten at 3/32" is too small. I've ordered a larger size. I will post some pictures with the new tungsten size...thanks

going by my miller welding chart here, 1/2" aluminum lap joint requires 400 amps (and 3 passes). for a 200 amp machine your going to need a boat load of preheat.

provided its fairly clean material, i would drop the cleaning action down to 20%, use a 5 or 6 cup, NO gas lens, 1/8" tungsten. preheat and multi pas weld. you might get it with 200 amps.

[tweake]

Another issue is the filler rod melts before I can introduce it into the puddle.

arc length, as jody says run a tight arc. also torch angle and feed angle. rule of thumb is feed at 90 degrees to the torch. if you have excessive torch angle the arc will throw forwards a lot and into your filler. feed into the front of the puddle, not the center or the edge.
also pull the filler out of the torch gas flow. let it cool down a bit in the air. aluminum is kind of opposite of what you want for stainless/steel.

[cj737]

In addition to changing the AC balance, also crank up the Freq to as high as your machine will go. Prior to a preheat, use a clean stainless brush and brush the edges of the stock and the surface where the lap joint will lay. The stainless helps cut through the oxide layer so the TIG arc gets into the base material to weld it.

If your filler is melting before you get it to the puddle, likely your arc length is too long. Move the tungsten closer to the work, maximum 1/8” away. The tighter the arc, the better the penetration of the arc. Once you get your puddle, the filler gets introduced quickly in the front edge of the puddle and move away. Takes some practice and 1/2” aluminum is NOT “new TIG welder material” to cut your teeth on.

[tweake]

also crank up the Freq to as high as your machine will go.

as low as you can go.
higher the freq the less heat (due to more off time). i've just come in from welding some stainless and i use high freq pulse to increase my amp settings as my cheap machine doesn't do low amps very well.

also on cleaning/brushing oxide, your just cleaning off thick oxide. as soon as air hits the base metal it forms thin oxide. the thinner the oxide is, the easier it is for the cleaning action to deal to it.

[tweake]

i should add, you really want to be learning on thin material, ie less than 1/8", where things are a bit more forgiving.

[cj737]

also crank up the Freq to as high as your machine will go.

as low as you can go.
higher the freq the less heat (due to more off time). i've just come in from welding some stainless and i use high freq pulse to increase my amp settings as my cheap machine doesn't do low amps very well.

also on cleaning/brushing oxide, your just cleaning off thick oxide. as soon as air hits the base metal it forms thin oxide. the thinner the oxide is, the easier it is for the cleaning action to deal to it.

Tweake we feel differently about the freq. I run most of my aluminum at 250Hz. The rapid cycle changes actually put more heat into the material and helps the keep the puddle stable. I know this flies in the face of historical wisdom, but modern inverters actually perform better this way than the older transformers where lower freq was needed.

It’s true about the oxide layer and the instanteous regrowth. But cracking the thicker layer does help.

[BillE.Dee]

Welding 1/2 inch solid aluminum will take some horsepower. You can help with pre heat and adding helium if you can find/afford it. you want the tungsten stick out a bit, and keep the tip of the tungsten as close to the material as you can and straight as you can and still be able to see where you're working. Focus into the joint, watch for the puddle and add some filler to make a spot to start working from. It will take several passes with your machine. I'm not familiar with the machine so unable to help with settings.

[tweake]

also crank up the Freq to as high as your machine will go.

as low as you can go.
higher the freq the less heat (due to more off time). i've just come in from welding some stainless and i use high freq pulse to increase my amp settings as my cheap machine doesn't do low amps very well.

also on cleaning/brushing oxide, your just cleaning off thick oxide. as soon as air hits the base metal it forms thin oxide. the thinner the oxide is, the easier it is for the cleaning action to deal to it.

Tweake we feel differently about the freq. I run most of my aluminum at 250Hz. The rapid cycle changes actually put more heat into the material and helps the keep the puddle stable. I know this flies in the face of historical wisdom, but modern inverters actually perform better this way than the older transformers where lower freq was needed.

It’s true about the oxide layer and the instanteous regrowth. But cracking the thicker layer does help.

jody has a video on this (and a few other people as well). higher the freq the lower the penetration is. however i do see the arc is more focused with higher freq.

https://youtu.be/XzsfBV6_vNY?t=221

[cj737]

Tweake - see if you can watch this: https://www.facebook.com/watch/?v=1091139382314841

Don’t know if you have access to Facebook videos, but Chris has some absolutely novel insights on aluminum welding. He does often revert to Helium mixtures, but his evidence for higher frequency has some legit decades of experience behind it. And he welds very thick aluminum with very small torches…

[tweake]

Tweake - see if you can watch this: https://www.facebook.com/watch/?v=1091139382314841

Don’t know if you have access to Facebook videos, but Chris has some absolutely novel insights on aluminum welding. He does often revert to Helium mixtures, but his evidence for higher frequency has some legit decades of experience behind it. And he welds very thick aluminum with very small torches…

just had a quick look at that vid.
hes using 250 amps and doing quite small welds that you could do with much lower amps. thats also why his tungsten not melting off. which is my point here, higher freq = lower heat. his quite right in that the freq gives him a lot more precision which is excellent for that use.

[cj737]

Tweake - see if you can watch this: https://www.facebook.com/watch/?v=1091139382314841

Don’t know if you have access to Facebook videos, but Chris has some absolutely novel insights on aluminum welding. He does often revert to Helium mixtures, but his evidence for higher frequency has some legit decades of experience behind it. And he welds very thick aluminum with very small torches…

just had a quick look at that vid.
hes using 250 amps and doing quite small welds that you could do with much lower amps. thats also why his tungsten not melting off. which is my point here, higher freq = lower heat. his quite right in that the freq gives him a lot more precision which is excellent for that use.

For the most part, he runs at 400 amps and 400Hz. He welds up engine cases (which are very thick aluminum castings with those settings. He does use a pedal so at times he may only be using 250 amps, but his point is that the freq setting allows him better input. Since the “lap joint” described in this posting won’t be a full penetration weld, I’d crank the freq up and give it a whirl.