[Adam35C]

I am trying to figure out the cleaning zone around an aluminum weld and how to make it tighter to the weld. I thought that the AC balance would do it but it didn't. I am using an Everlast Powertig 210ext and I've found 30% works well. Went down to 15 and up to 45 to see the effects but I dont see a difference at all, not enough to notice at least. Tried smaller cup, #5, and still no difference. Is it a torch height/angle thing?

[BugHunter]

I'd say a buffer is about the only way to get rid of it.

arc length will affect it some though. Tighter arc = less hf zone.

[cj737]

Frequency will effect it more than balance. However, outside corners are difficult in addition. Try bumping your frequency up to 150 and try a sample. Gotta always keep a tight arc no matter the balance or frequency.

[Oscar]

I see un-cleaned aluminum. Correct me if I'm wrong.

[v5cvbb]

Does gas lens help any on aluminum cleaning?

[Oscar]

Does gas lens help any on aluminum cleaning?

I'd say clean aluminum helps the most. The etching is the break-up of aluminum oxides. If the part is cleaned really really well, then there won't be much oxides to remove and there should be less etching in conjunction with less cleaning, about 75-80%. From what I gather a small cup can minimize the etching zone, but only if you both hold a tight arc and minimize the stickout. Supposedly that helps restrict the arc cone, and thus the cleaning action as well. So yes, torch height and angle do play a large role, I'd say.

[TraditionalToolworks]

Does gas lens help any on aluminum cleaning?

I will give you a slightly different answer than Oscar. Please take what I say with a large grain of salt...

The gas lens effects how the gas is dispersed over and around the metal, which in turn has to do with contamination from the air, it keeps the weld clean.

The cleansing comes from the aluminum and has to do with the balance of negative and positive to the metal.

I see these as being not dis-related but 2 different elements of welding aluminum.

Cleaning only cleans the surface of the aluminum, AFAIK. Cleansing comes from the aluminum itself. Someone please correct me if I'm wrong, I will certainly stand corrected.

OP, 30% should be good on AC balance, 45% will near destroy your tungsten.

[DougW]

Now for my 2 cents. For me, when I weld, all things being equal. If I have the cleaning setting, balance, where it's 'generally' recommended, 65-75 % EP, 25-35% EN, the greatest influence on the cleaning width is torch standoff. The further I move the torch from the piece the greater the affected area becomes. Angling the torch in excess creates similar results as moving the torch away from the work piece; which in reality is exactly what's taking place.

Cleaning/cleansing is kind of a misnomer in so much as what's really happening is the removal of the oxide barrier inherent on all aluminum. Soap/chemicals(acetone n' such) will not remove oxidation - a wire brush will but it starts coming back as soon as you stop moving the brush on the surface. When Oscar mentions 'dirty' aluminum I take that to mean he can plainly see it's hasn't been wire brushed to removed heavy oxide. I don't think wire brushing has any impact on the width of the cleaning action which is basically determined by: AC/DC balance, torch stand-off, torch angle

[Oscar]

Does gas lens help any on aluminum cleaning?

I will give you a slightly different answer than Oscar. Please take what I say with a large grain of salt...

The gas lens effects how the gas is dispersed over and around the metal (agree), which in turn has to do with contamination from the air, it keeps the weld clean.(agree)

The cleansing comes from the aluminum (not sure what you mean here---comes from the aluminum how?)and has to do with the balance of negative and positive to the metal.(agree)

I see these as being not dis-related but 2 different elements of welding aluminum.

Cleaning only cleans the surface of the aluminum, AFAIK(agree, for there is no aluminum oxides other than the surface of aluminum, save for horribly cast parts). Cleansing comes from the aluminum itself (again, comes from the aluminum how?). Someone please correct me if I'm wrong, I will certainly stand corrected.

I think you have a generally good idea, but some of the things you said are a bit vague/ambiguous (see my comments in red above.

Interesting things to note...

• is that the formation of cathodic etching only occurs within the envelope of ionized argon shielding gas, whereby one can clearly define an anode and cathode
  • which is non-coincidentally why Jody and many others prefer the #5 cup for aluminum welding (IOW, if you restrict the envelope of argon shielding gas, there is less of a ionized volume whereby cathodic etching can occur (but there is a catch that has to do with travel speed, as you will see below....)
  ,
• BUT just as important to note is that the rate of growth of the diameter of the cathodically etched zone has peculiar properties.....
  • The diameter of the initial etching circle grows non-linearly. The vast majority of the growth occurs within the first 1000-1200ms where the growth rate is very high, after which there is still growth, but the growth rate is far less
  • More DECP % gives better cleaning as well all know, but this cleaning is obviously based on time (which is what balance does, shifts more time for the DCEP cycle). Unfortunately the more time is permitted on DCEP, the more time there is for the cathodically etched zone to spread out.
    • The diameter of the initial etching circle during the first 1200ms at 20% DCEP is about 1.5x compared to using 10% EP.
    • Similarly, the diameter of the initial etching circle during the first 1200ms at 30% DCEP is about 1.5x compared to 20% DCEP
    • If you compare 30% DCEP to 10% DCEP, the diameter of the initial etching circle during the first 1200ms ends up being roughly 2x as large.
  • If you add up the bullet points above, it should be easy to see that lingering too long in one area with too much DCEP % will allow the shielding gas to spread out somewhat, thus allowing the ionization volume to be larger, which then allows more cathodic etching to occur
    • and as a corollary, you can see how too slow of a travel speed would also create a larger etching zone by allowing the shielding gas to spread more somewhat
• Frequency above 60Hz, has little change to the growth rate of the etching zone, but when the AC frequency is taken way down to 30Hz, the growth rate, and thus size, of the etching zone during those first critical 1200ms diminishes dramatically by a factor of about ¼

Source: Welding Journal No 89, January 2010 -Cathodic Cleaning of Oxides from Aluminum Surface by Variable-Polarity Arc

[Oscar]

I don't think wire brushing has any impact on the width of the cleaning action which is basically determined by: AC/DC balance, torch stand-off, torch angle

It does if it means that you can use less DCEP. The cleaner it is of heavy oxides, the less oxides there are to clean using the arc. One follows from the other.

BTW, it's not AC/DC balance, its DCEN/DCEP balance.

[TraditionalToolworks]

The cleansing comes from the aluminum (not sure what you mean here---comes from the aluminum how?)and has to do with the balance of negative and positive to the metal.(agree)

Wasn't trying to be vague, as the surface layer does have some effect on the cleansing action, but we can't take that layer away by using solvents to clean the aluminum. We could remove them by grinding/sanding/wire-brush, but it would form again over time in reaction to the air, at least my understanding. With aluminum we need to blast through that surface layer to penetrate and create a weld pool, so we can move it, and in that weld pool itself is where the cleansing is taking place for the most part, but maybe I'm looking at it the wrong way.

which is non-coincidentally why Jody and many others prefer the #5 cup for aluminum welding

Seems that Jody often prefers a #8, but many folks do prefer a #5, Roy as an example. I know the frequency has an effect on the width and size of the weld pool and/or bead in general, but didn't think the size of the cup had that drastic of an effect on the cleansing action other than it is pretty much based on the weld pool. You could be right that the weld area needs to be clean from contaminates to perform properly and the cup effects it.

Do you think stickout and/or torch distance from the aluminum has to do with that at all? Because the small cup allows for less stickout and in theory the diameter of the tungsten will determine the distance one should use to get the ideal weld pool.

Frequency above 60Hz, has little change to the growth rate of the etching zone

That's not my experience, and I find that when I turn the frequency up to say 200hz the weld pool and bead will be narrower, which does have an effect on the cleansing zone. That could be due to the weld pool being smaller in general.

All that said, I don't have a heapin' lot of experience welding aluminum, which is why I tossed in the disclaimers to begin with. I don't want to mislead anyone. In regard to the wire brush I do believe it can have an effect on the weld pool and/or cleansing in general as the arc will be able to penetrate more and the weld pool will have less of the top layer oxidation on it, AFAIK. That seems it would have an effect on the cleansing action overall.

[Spartan]

Seems that Jody often prefers a #8, but many folks do prefer a #5, Roy as an example.

I definitely prefer a 6-8 cup for AL. Usually 7-8, actually. I tried it with a 5 after everyone and their mother started praising it not too long ago, but I just didn't have great results with it. May be because most of the AL I run is on the thicker end of the spectrum, i.e. 1/8" minimum. I imagine that 5 cup may be good for 1/8" thickness and below, perhaps, due to the smaller puddles.

[Oscar]

Frequency above 60Hz, has little change to the growth rate of the etching zone

That's not my experience, and I find that when I turn the frequency up to say 200hz the weld pool and bead will be narrower, which does have an effect on the cleansing zone. That could be due to the weld pool being smaller in general.

You're correct. 200Hz will produce a narrower bead and sometimes etching zone. What I was referring to was the growth-rate of the etching zone as a radial distance per unit time, not the sheer size of it.

and in that weld pool itself is where the cleansing is taking place for the most part, but maybe I'm looking at it the wrong way.

Once you actually see the weld pool, oxides have already been blasted away (broken up) and have floated away to the aforementioned cathodic etching zone, and the weld pool is free of contamination/oxides. I mean of course it starts where the weld pool initiated from because that is the hottest part of the region is. I don't know if that is how you were looking at it, but it's the general scenario.

[v5cvbb]

Ok guys. There is some very good stuff here that I need to read again after getting some sleep. I'm learning stuff that I didn't know I needed to know. I never thought it was possible to have too much gas coverage. I see more aluminum practice in the near future.

Thanks.