Cleanliness

[metallurgy]

I'm going to take some aluminum welding classes soon, but I have some (more like "a lot") of welding to do before then. I do not have a problem with appeance, penetration, and cleanliness in general, but...

I have two problems every time I start the arc. One, the HF goes up inside the nozzle for a short period of time, usu under a second until the amperage goes up a little. It drives me nuts, I haven't used different machines so I don't know if it's "the norm".

The other problem is oxidation right at the weld start (happens simultaneously with the hf climbing up the tungsten). Everytime I light an arc it'll leave a lil bit of ugly (oxidation) that I have to clean up before I take another shot at it. It also makes tack welding difficult, since even slightly dirty aluminum acts like an angry marshmallow. I'm using an old sine wave machine, no preflow so I'm assuming that's the problem. Pure 3/32 tungsten, ball slightly larger than 3/32, 1/8" rod...

Yes, the aluminum is spik-n-span.

Are these traits the norm, and can I avoid them? Is it just due to the lack of argon for the first fraction of a second?

Thnaks for the help.

[yorkiepap]

Hey metallurgy,
You need to post more information.

What machine/model are you using?
What are your settings? Amp?/gas flow cfh?/Tung. stickout?/clean width%?
How thick is material & grade of alum.?
Joint configuration?
What are you cleaning the aluminum with?

Get rid of the pure tungsten & get some 1.5% Lanthanated or Ceriated. Aluminum has to be virtually germ-free & your best results would be with a good SS toothbrush & acetone. No pre-flow may cause an issue but may not, although you should not be getting results like that unless the alum. is still dirty. Cleanliness is next to godliness with aluminum.

Give us more info...

Denny

[mcostello]

Polarity correct?

[metallurgy]

Sorry, here you go:

Machine: OLD SCHOOL airco "orange thing". I can't find it on the internet. I think it goes up to (edit) 310 amp AC/dc. Continuous hf, plain ol ac sine wave (no bal.) aircooled torch, #4 nozzle, long back cap....

Amps: 130+ (according to dial on machine) I doubt it's a very efficient machine so that number is probably on the high end (comparatively). Gas flow upwards of 13 cfh (100% argon), up to around 25 with the hot stuff (like 3/16 fillet weld). Lowest settings I use for 1/8" butt weld, the torch has a hard time handling anything above 3/16 fillet. Roasty toasty

Tungsten stickout: 1/8" - 3/16" for flat, increasing if access is restricted (like fillet). Arc length maybe 3/16". Using pure because it's recommended for old school transformer machines- I understand ceriated is for inverters and lan. is the next best option for sinewave transformer machines. Pure was a huge step up from th. tungsten, with the added bonus of no radiation. It forms a nice sphere but it jiggles with more power.

Alum: I think it's mostly 6061, in this case 1/8 fillet. 1/8 rod (a tad big, I know), I think 4043 rod.

I clean it with a SS brush I hide and store in a plastic bag so no one uses it and it doesn't ever touch ferrous metals. It's new. And I clean the aluminum well. I'm not using scotchbrite on the rod although if you think that would help I would be glad to try.

Acetone may be over the top, i'm not sure I want to deal with solvents yet. The machine is at least 30 some years old, it's not going to be doing anything for nasa. If it'll help me though maybe i'll give it a shot.

Ac, so both polarities unless your eyes can go back and forth really really really fast. 120 hz for hf, correct?

[metallurgy]

...Keep in mind I weld trouble free as soon as that first puddle is formed and I start moving along. The welds come out pretty clean. You want pics I get pics.

[59halfstep]

... You want pics i get pics.

yup ;)

Charlie

[Rocky D]

... One, the HF goes up inside the nozzle for a short period of time, usu under a second until the amperage goes up a little. It drives me nuts, I haven't used different machines so I don't know if it's "the norm"....

Thanks for the help.
This is due largely to how the tungsten is ground, most folks just ignore it. Grind your tungsten with the striations going in line with the tungsten, and what you use to grind them with should not have been used in any other material. I use 2% thoriated, with argon. All that said, it is fairly normal. On some machines you can adjust the HF start current, which helps a lot.

[ArgonWelding]

Here here on that striations orientation thing there Rocky. Although I would not use something caked up with gunk to grind my tungsten, I do us a belt sander, and it gets used for steel often. I will also note that if you are doing your tip wrong, it will show with it's appearance after some welding. It should be more ball shaped than before and turning a nice shade of purple. I am of the school that your tip should barely stick out past your cup if any. Maybe you are using one of those big "gaslens" type torches.

I have an old machine that has a knob labeled "Intensity". It does the job of ramping up the power for you so you can just step on the pedal. That's not how I do things, so I just have the knob turned all the way up and control with my foot. This knob may be the one Rocky refers to.

[metallurgy]

I am using a wheel that I dedicated to tungsten. Other people might use it when I'm not around, I have no idea. I grind it properly (although the wheel is pretty coarse) but I don't think it matters with aluminum since no matter what it forms a sphere or half-sphere. Pure tungsten especially.

What kind of arc length do you's use?

[ArgonWelding]

My arc length varies from case to case. Whatever gets the job invoiced.

[metallurgy]

Hah.

I got some pics of welds I did a couple weeks ago. I think it was 1/8". The second one was a weave thing over the first.

[Pangea]

You weld left handed?

Add less wire more often and don't move so fast. Those sharp edged "stack-o-dimes" welds have lots-o-stress risers. Back out of your termination a little slower and back step some too. that will get rid of the huge crater you have at your weld termination.

I'm not seeing the oxidization that you described.

[metallurgy]

Backhand- Torch in right hand. I can go the other way but I can't see the back of the puddle. What am I doing wrong?

I was using 1/8 filler so i'll see if I can find something thinner. I'll give it a shot, thanks!

[Rocky D]

Backhand- Torch in right hand. I can go the other way but I can't see the back of the puddle. What am I doing wrong?

I was using 1/8 filler so i'll see if I can find something thinner. I'll give it a shot, thanks!
Not wrong, just different...backhand technique is used to weld Titanium, and I use it on aluminum, sometimes. To weld right to left, position the weld joint so that you can see, and pull the tungsten out and hold a longer arc...doing all of that will let you see what you are doing.

[Pangea]

What do you need to see the back of the puddle for? :confused: Weld from right to left with the torch quill leaning to the right. Learn what the front of the puddle needs to look like so that you get the desired bead. It's easier to track the joint if you do it this way.

I never welded titanium backhanded. It never entered my mind to try. Why would you do that Rocky? Maybe to keep some shield gas on the cooling weld and not use a trailer cup? Please share. This interests me.

[Rocky D]

What do you need to see the back of the puddle for? :confused: Weld from right to left with the torch quill leaning to the right. Learn what the front of the puddle needs to look like so that you get the desired bead. It's easier to track the joint if you do it this way.

I never welded titanium backhanded. It never entered my mind to try. Why would you do that Rocky? Maybe to keep some shield gas on the cooling weld and not use a trailer cup? Please share. This interests me.
We used trailing cups, too, but they couldn't be used in some of the jigs we had, so with butt joint secured in a jig, with copper clamps, welding backhand keeps the gas coverage enough to make it come out like chrome. We couldn't take the chance of having the weld come out yellow or blue. This was in a clean room...white coats, and cotton gloves, etc.

[Pangea]

Thanks for the info Rocky.

[4sfed]

The other problem is oxidation right at the weld start (happens simultaneously with the hf climbing up the tungsten). Everytime I light an arc it'll leave a lil bit of ugly (oxidation) that I have to clean up before I take another shot at it. It also makes tack welding difficult, since even slightly dirty aluminum acts like an angry marshmallow. I'm using an old sine wave machine, no preflow so I'm assuming that's the problem. Pure 3/32 tungsten, ball slightly larger than 3/32, 1/8" rod...

Is it just due to the lack of argon for the first fraction of a second?

Thanks for the help.

I vote for the lack of pre-flow causing the oxidation at the start of the weld. Even with a short pre-flow, my first weld of the day will do the same thing becaused room air has diffused far enough into the hose that the pre-flow will not purge it all.

Before starting your weld, pull the torch away from the work and step on the pedal for a second to start the gas flowing. Then start your weld during the post-flow.

Jim

[walker]

Ditto 4rsfed, only to add that you might try stepping on the peddlw more aggresively when starting, getting all your starting current flowing right away makes it want to jump the gap quicker. In other words, stomp on the peddle quicker when you start.