[tekmachinewerx]

Can i still weld as u are saying with a footpedal that is just on and off. Not adjustable. I not to weld aluminum and im saving for a acdc tig. But right now i have jobs that require aluminum welding. It just welding in holes on thick aluminum. So can i use 200amp dc tig with 98% hel 2% argon was it 25-35psi
so run down on questions
can i still do this with off, on foot switch
do i round or point tungsten
green or red
and thank you for ur time

plz guys dont post anything about im stupid or whatever that crap i ask question because i need to know.
sorry some forums i get called names because i dont know simple things

[Superiorwelding]

tekmachinewerx,
Welcome to the forum! You will NOT be out down for your level of knowledge here. We all started on the bottom. Those are great questions and I want to try an prod a few members that have a little more experience at DC tig than me to answer.

When you find time go introduce yourself in the Member Introduction section!
-Jonathan

[Braehill]

Tek,
You say that you need to fill holes in thick Aluminum and this can be done on DC but will require you to use a very heavy electrode. 200 amps is not a lot of amps while welding Aluminum. If you said that you were trying to fill holes in thin plates, I would say that you'd have a better chance at a positive result.

How big are the holes? Can you get down in there and put more than 1 pass? A picture of what you're trying to do would help. More info will get you more help. This may be something that you're not able to do but we can't tell yet with the information provided.

As Jonathan has said, you'll not be put down for any question here or that person will be gone post haste.

Len

[Bill Beauregard]

I've only experimented with aluminum DC-. I was welding two 1/4" plates together. It was prepped well, 2 35Degree bevels, 1/8" land, 1/16" apart, copper backer. 1/8" thoriated tungsten 15 cfh argon. I needed a large puddle that was beneath a skin of dull grey crud. I could push filler through the skin to fill. It was in flat position, wasn't pretty on the surface, but cleaned up reasonably well with Norton Blaze on a 4-1/2" grinder. I'm concerned that if your holes are not the right ratio the "Skin" won't float up as you fill. if they are too big and you have to werd in concentric rings to fill, they certainly won't clean enough to bond. I think this is a project to farm out if you aren't equipped. Better to say to a customer I'm not equipped, than screw it up.

[DeweyO]

Tek -
How thick is thick? 1/4"? 1/2"? A full inch? You could easily use 200A on 1/4" Al. but the diameter of the hole is a big factor too. An inch hole in 1/4" plate would take less amps initially. This is where the progressive foot pedal shows its worth. If you're just looking for on & off, you might just as well be scratch starting, a technique used for decades before foot pedals. (Like when it was called heliarc).

[RocketSurgeon]

I've gotten into this debate many times with younger welders right out of school all the way up to welders twice my age and experience. The debate about TIG welding Aluminum on DC. They all say you Can't do it! One thing I've learned in my 15 years in welding is there no such thing as Can't in this industry, you just don't know how. So, figured I'd post something about it and see what all you welders around the world have to say.

Here is the recipe I like to use...

Set machine for welding Steel no more than 190-210 amps regardless of thickness, need a foot pedal for this
Standard or gas lens set up (Gas lens is a bit cleaner but not needed)
2% tungsten works fine 3/32-1/8 sharpened
4043 rod 3/32 (depending on thickness of course)
25-30 psi of Helium (use the helium to bump up the heat not the amps)
5 psi Argon (helps clean up the weld a bit but also not always needed)

A few Pros and Cons

Pros...

-Don't have AC and need to weld aluminum!
-No Preheat for thick parts
-Makes for a great small root pass (preheats for the cap) or one large pass
-Burns much hotter so you can get in and out with minimum warpage but still getting good penetration

Cons...

-Dirty looking weld (until you figure out the right angles). If the material is dirty it really shows in the top and bottom of the weld (as in the photo) but comes right off with a wire brush. This was just handles for a base plate so didn't need to clean up nice.
-Wire will ball up very easy if not added properly. It's not forgiving so add it in the right spot
-Uses a lot of Helium which isn't cheap but if you're welding of a machined billet plate that can't warp too much...


Anyone else ever try this? If not give it a try.

Our recipe:
DC- (reverse polarity)
115-135~ amps, depending on thickness
Pure, dry He @20cfm
2% Thoriated electrode
#7 cup
2sec lead in
5sec lead out

[MinnesotaDave]

RocketSurgeon - you've got a typo:

DC-, DCEN, straight

DC+, DCEP, reverse

[RocketSurgeon]

RocketSurgeon - you've got a typo:

DC-, DCEN, straight

DC+, DCEP, reverse

Whoops. You are correct, sir.

DCEP is the polarity we use.

[MinnesotaDave]

RocketSurgeon - you've got a typo:

DC-, DCEN, straight

DC+, DCEP, reverse

Whoops. You are correct, sir.

DCEP is the polarity we use.

That's awfully hard on the tungsten - and pure argon works well on DCEP, why spend the money on helium?

Normally people use 100% helium on DCEN for deep penetration.

[RocketSurgeon]

It's what we use at work because of the alloy. 2219 and 2195. 2% Thoriated keeps a nice focused arc and the He keeps the parent material hotter without cranking up the Amps.

Add the rest of the recipe and we can keep the weld clean without AC or a wandering arc. We have to for the customer.

[MinnesotaDave]

What thickness are you welding with 135 amps DC+ (DCEP) and pure helium?
What size tungsten?

[RocketSurgeon]

What thickness are you welding with 135 amps DC+ (DCEP) and pure helium?
What size tungsten?

.625" 2219 parent with 2195 plug. 3/32" tungsten. 2319 filler.

[MinnesotaDave]

What thickness are you welding with 135 amps DC+ (DCEP) and pure helium?
What size tungsten?

.625" 2219 parent with 2195 plug. 3/32" tungsten. 2319 filler.

Then respectfully, I think you are confused about polarity.

Over 1/2" thick material, and only 135 amps, 100% helium, no wandering arc - this says DC-, DCEN, straight polarity to me.

[RocketSurgeon]

Ground clamp on the negative leg, torch on the positive (our symbol for this is DC-). We work to WPS that has been used for a couple of decades and approved by our customer: NASA.
These are high grade parent materials that must have 0 porosity and 0 inclusions and 0 contamination.

We've been doing this technique for a while. We don't follow AWS or ASME standards and specs. We follow MilSpec and NASASpec.

[MinnesotaDave]

Ground clamp on the negative leg, torch on the positive (our symbol for this is DC-). We work to WPS that has been used for a couple of decades and approved by our customer: NASA.
These are high grade parent materials that must have 0 porosity and 0 inclusions and 0 contamination.

We've been doing this technique for a while. We don't follow AWS or ASME standards and specs. We follow MilSpec and NASASpec.

Again, respectfully, there is some confusion somewhere, DC-, DCEN, DC electrode negative, straight polarity.

Are you saying that NASA and the military labels these backwards from welding industry standards?

I guess I would not be surprised

My torch and work clamp do not get switched around either - I use the selector on the machine to set DC-, DC+, or AC.

When I select DC- my torch is negative, therefore I am welding DCEN, straight polarity.
When I select DC+ my torch is positive, I am welding DCEP, reverse polarity.

Do you suggest that I am incorrect?

[RocketSurgeon]

Mil and NASA specs can be niche techniques that only apply to one or a few applications. The R&D can take years (or sometimes by chance). I've seen overkill work that would be completely unnecessary in the public world, but makes total sense to NASA.

We build man-rated space flight vehicles. Their argument that overkill is necessary is rarely debated, let alone argued.

I completely understand your questioning about the nomenclature used here and the techniques. It isn't the typical AWS or ASME when it comes to the vehicles. It's their own. When all you see is their symbolism and terminology every day, you can not only confuse others, but yourself as well.

[MinnesotaDave]

Mil and NASA specs can be niche techniques that only apply to one or a few applications. The R&D can take years (or sometimes by chance). I've seen overkill work that would be completely unnecessary in the public world, but makes total sense to NASA.

We build man-rated space flight vehicles. Their argument that overkill is necessary is rarely debated, let alone argued.

I completely understand your questioning about the nomenclature used here and the techniques. It isn't the typical AWS or ASME when it comes to the vehicles. It's their own. When all you see is their symbolism and terminology every day, you can not only confuse others, but yourself as well.

You didn't answer the question actually - does NASA and the military label their stuff backwards from the welding industry?

When I select DC- my torch is negative, therefore I am welding DCEN, straight polarity.
When I select DC+ my torch is positive, I am welding DCEP, reverse polarity.

DC+ will melt a 3/32" tungsten super fast.
DC- works great with a 3/32" tungsten.

I am not confused by what I have said.

[RocketSurgeon]

I know for sure that NASA does. They consider the ground clamp as a constant. Everything is based off the ground.

[wheresmejumper]

Ground clamp on the negative leg, torch on the positive (our symbol for this is DC-). We work to WPS that has been used for a couple of decades and approved by our customer: NASA.
These are high grade parent materials that must have 0 porosity and 0 inclusions and 0 contamination.

We've been doing this technique for a while. We don't follow AWS or ASME standards and specs. We follow MilSpec and NASASpec.

I didnt know that different laws of physics apply to NASA and the military?!
0 porosity 0 inclusions etc is a pretty common requirement,even down here on the earth.and away from the front line too.

[DeweyO]

From the limited experience I've had using DC on Al. I would have to support Minnesota Dave. I've personally experimented on Al. castings and found DCEN works surprisingly well. The weld although dirty does clean up easily and full penetration is attained. In my case I used Argon only as that's all I had, and after all, I was experimenting. Basically, I treated the whole job as if it were steel.

[rick9345]

I know for sure that NASA does. They consider the ground clamp as a constant. Everything is based off the ground.

NASA
Government supported
government specs
ya sure-you betcha

budget $'s hidden from public in obfuscation

[Otto Nobedder]

Let's keep the politics out of this, please.

RocketSurgeon works for a contractor, not Uncle Sam himself.

Steve S

[rick9345]

The comment was to help explain the procedures RocketSurgeon needs to follow

Not meant as political statement
If offended someone my apologies

[Otto Nobedder]

We all saw "Men In Black"... and know about those $30,000 toilet seats...

[skepsis]

I signed up for this.. Not intended to put anyone 'out there', but now I'm lost, completely (regarding terminology).
I'm very open/loving to 'controversial'/'gotcha' facts, however, fact being imperative!

To save everyone (including myself) the need to scroll over a number of pages in this thread, please let me start by quoting the posts (as far as relevant) that make me confused/curious/interested..

...
Our recipe:
DC- (reverse polarity)
115-135~ amps, depending on thickness
Pure, dry He @20cfm
2% Thoriated electrode
#7 cup
2sec lead in
5sec lead out

RocketSurgeon - you've got a typo:

DC-, DCEN, straight

DC+, DCEP, reverse

Whoops. You are correct, sir.

DCEP is the polarity we use.

It's what we use at work because of the alloy. 2219 and 2195. 2% Thoriated keeps a nice focused arc and the He keeps the parent material hotter without cranking up the Amps.

Ground clamp on the negative leg, torch on the positive (our symbol for this is DC-). We work to WPS that has been used for a couple of decades and approved by our customer: NASA.
...
We follow MilSpec and NASASpec.

Mil and NASA specs can be niche techniques that only apply to one or a few applications. The R&D can take years (or sometimes by chance). I've seen overkill work that would be completely unnecessary in the public world, but makes total sense to NASA.

We build man-rated space flight vehicles. Their argument that overkill is necessary is rarely debated, let alone argued.

I completely understand your questioning about the nomenclature used here and the techniques. It isn't the typical AWS or ASME when it comes to the vehicles. It's their own. When all you see is their symbolism and terminology every day, you can not only confuse others, but yourself as well.

You didn't answer the question actually - does NASA and the military label their stuff backwards from the welding industry?

When I select DC- my torch is negative, therefore I am welding DCEN, straight polarity.
When I select DC+ my torch is positive, I am welding DCEP, reverse polarity.
...

I know for sure that NASA does. They consider the ground clamp as a constant. Everything is based off the ground.

Now.. I'm really sure I read this a number of times and I'm not mis-interpreting/representing these quotes (neither have I missed anything relevant to it).

So you (RocketSurgeon) state: "Ground clamp on the negative leg, torch on the positive (our symbol for this is DC-)." (emphasis mine) and agree it's DCEP, but call it "reverse polarity" and label it "DC-",

• am I understanding this correctly
• Who exactly is "our"

You continue: "When all you see is their symbolism and terminology every day, you can not only confuse others, but yourself as well."

If you see and set this on a daily basis, I assume that ("DC-") is what the labels on your welding-power-supply say (when you set it to DCEP)?

• Might I ask, which brand and model (you might refer to) uses such a counter-standard labeling (for NASA/MIL spec. environments)? Maybe even post a picture (as this seems to be so rare)

You (RocketSurgeon) also clearly state that (at least) NASA (which you are "certain" of, but you are hinting at military as well) has their DC labeling and terminology ("nomenclature" as you say) REVERSED from the rest of the standardized welding-industry (and electro-technical industry/engineering in general for that matter).

• Can you please provide any authoritative reference(s) to that, preferably where we can all see/verify them online

It's not that I don't (want to) believe this, it's just that I really can't find any reference to such practices at all (in fact I can find plenty of NASA sources that state exactly the opposite of your claim).


Electricians and usually physicists agree that what they call "conventional current" flows in the same direction as potential/voltage/('tension' as the re-discoverers in recent history called it): so from +/positive to -/negative.
However, as we all know (I assume), electrons move from -/negative to +/positive.
For the vast majority of physics and pretty much all circuits, this doesn't matter, the location/distribution of current is the same, just change the sign.
But in some cases, like welding, it does matter: every welder knows there are distinct clearly observable differences in 'polarity' (explaining them seems to enter a sort of electro-chemical world where the direction of electrons actually is important, at least for the explanation/theory, which in turn can lead to improvements based on understanding (almost the seemingly uninteresting difference between: hot air rises vs (the truth:) cold air pushes hot air upwards) ) .
Luckily, regardless of "conventional current" and potential (having the same polarity-designations; that what your standard multimeter tells you) and the theoretical "real current", we have 2 other words to describe this, that in no way suffer from ambiguity:

• Anode (conventional positive)
and
• Cathode (conventional negative).

Let's see what lessons NASA has to offer on http://llis.nasa.gov/lesson/663:

In Gas Tungsten Arc Welding for 2219 aluminum, heat required to join the aluminum is generated through an electrical arc applied at the joint. An inert atmosphere of helium surrounds the arc to prevent oxidation during the welding process. The type of GTAW covered in this practice is direct current, straight polarity (DCSP) in which the torch serves as the negative electrode (cathode) and the work piece as the positive electrode (anode).

...

Among the important practices that will aid in ensuring high reliability welds are welding in the proper position, use of high purity shield and plasma gasses, proper cleaning of the joint prior to welding, operator certification, and computer control of the welding process. The use of 2-percent thoriated tungsten electrodes for GTAW and VPPAW provides arc stability and increases electrode service life over that of standard tungsten electrodes.

...

1. Gas Tungsten Arc Welding (GTAW) (DCSP) for 2219 Aluminum

As shown in Table 1, the flat (downhand) position is preferred for the best weld uniformity and penetration. Welding in the direct current, straight polarity (DCSP) mode while using high purity helium shield gas provides deep penetration without oxidation or contamination. (Welding in the alternating current mode is particularly suitable for welding thin aluminum as it produces less heat and provides good cathodic cleaning.) Pulsing of the weld current can be used to provide better control for some out-of-position welds. Minimizing the number of weld passes will decrease the tendency for distortion. A pointed tip electrode is used in GTAW. A positive torch "lead angle" is desirable for GTAW (DCSP) to provide preheating and more uniform melting.

Lower energy inputs generally increase weld strength. GTAW (DCSP) is a preferred process for tack welding of aluminum. GTAW (DCSP) also can be used for welding steels (including stainless steel), titanium, magnesium (with care), and refractory metals. The 2219 aluminum is an excellent alloy for maximum strength in cryogenic applications with good weldability.

NOTE: there is also a picture on there that clearly labels "anode"="+" !!!


Here is another source (of many): http://ntrs.nasa.gov/archive/nasa/casi. ... 139717.pdf from 2004:

Polarity and Why It Matters

The energy to pull an electron out of a metal is expressed as a voltage drop called the "work function."

At the anode or positive electrode the heat that must be supplied to maintain equilibrium is approximately (neglecting thermal radiation effects) the heat conducted "away" by the electrode metal. Besides heat generated by the higher resistance of a locally cooled plasma, heat is brought to the surface by the amount of the energy gained when an electron enters the electrode metal (work function) and by the greater plasma temperature of the entering electrons.

Because the electrons extract heat from the cathode and deliver heat to the anode, the welding process is considered to be more efficient when operated in "straight polarity", when the torch electrode is negative, the workpiece positive, and electrons flow to the workpiece. Unless there’s a reason not to, welding torches are operated in the straight polarity mode.

But there is a reason to weld in "reverse polarity", where the electrons flow away from the workpiece: the cathodic cleaning effect. A high speed movie of the vicinity of a GTA weld pool in the reverse polarity mode will reveal a display of sparkling points of light, miniature explosions continually occurring all over the surface. This is thought to be caused by electrostatic breakdown of a thin surface oxide layer. The positive ions in the arc accumulate on the surface of the oxide layer and induce a balancing negative charge. If the oxide layer is thin, it doesn’t take a lot of charge to produce an electric field (volts per distance) big enough to cause the oxide layer to break down in a mini-explosion. Cleaned surface is distinct and visible around the crown of a weld made in reverse polarity.

But to get the cleaning necessary to weld aluminum alloys one takes a hit in power available for welding, and the effective capability of the machine is reduced.

yes, the rest of the text mainly talks about PAW, but as you might know, the basic properties overlap with GTA

Hmm, let's see, am I comparing apples and pears?
Material: 2219 aluminum (check, that's what you and this NASA text talk about)
Tip: 2-percent thoriated tungsten electrodes (check)
GTAW.. (check).
Nope, I'm comparing apples with apples..

Is it authoritative.. well.. I'm not sure, but, it does say NASA.gov ...

'Clearly', in these texts, "they" (nasa.gov) UN-ambigously say:

• direct current, straight polarity (DCSP) in which the torch serves as the negative electrode (cathode) and the work piece as the positive electrode (anode) and electrons flow to the workpiece
  (Which we also call "DCEN" and label "DC-")
• "reverse polarity", where the electrons flow away from the workpiece: the cathodic cleaning effect
  (("DCRP") Which we also call "DCEP" and label "DC+")

Clearly, the terminology "they" use in these texts (spanning >10 years) is not reversed ("straight"="DSCP"/"+"(/DCEN) and "reverse" is the opposite of "straight" (and if "+" is for straight, then logically "-" must be for reverse)).

Using the same terminology as the rest of the world (and labeling on general welding appliances) really would make sense, especially to NASA who re-confirmed (using millions of tax-payer-hard-earned cash) on September 23 1999 that it's rather important to get your units (and terminology) "straight" (pun intended)..


Here is where I get lost even further. You say (seemingly with the intention of explaining the reasoning): "They consider the ground clamp as a constant. Everything is based off the ground."

By all means, that would depend on the welding-power-supply (I intentionally use this word as it doesn't implicate the working, neither a earth-reference)..
An old trafo AC-out 'buzzbox' would have it's 'ground' referenced to 'earth' because the neutral wire is connected to earth in your home/shop's power-entry-point (because that saves the electricity-distribution-company 25% wire), which is why the 'ground' is 'safe' as there is a minimal potential between trafo-'ground>you>earth. In electronics we also call it neutral or cold or (misleading "-" as general accepted symbol). The other wire "hot"/"live"/"+" (were you connect your electrode-clamp) swings above and below this "neutral"/"cold"/"ground"/"-"..
Now, judging from the published specs and waveforms of most of the manufacturers I've seen, inverter-based ac-TIGgers do the same (swing a hot around a ground).
DC-Out buzzboxes are often 'not floating', so again, they have a reasonably safe end and a "hot end" (with respect to the earth). Reversing polarity by reversing the clamp and torch-leads therefore just shifts the 'danger'-part from torch to workpiece and vice-versa. At the very least, cheaper models do the same by flicking a switch.

However, since we get AC (revolving around earth-potential) from the wall-outlet to start with (unless you use dc car-battaries), setups (that one could compare with an audio-power-amp) could keep one lead referenced to earth regardless of polarity (a 'simple' matter of choosing which half (positive or negative referenced to earth)) of the power-supply is to be used. Naturally there are other methods and tricks..

Now, assuming that most welding-power-supply have one 'lead'/'output' referenced to 'ground' ('earth' Is what I assume you really mean), or even just any potential-difference referenced to another potential,

• why should (for example) +70 volt (so 70 above reference) be labeled with "-" (or be called "reverse") as you say

One could answer that by stating that (based on theory) the current will be minus something (as resistance will also come into play, making it pretty awkward to talk/reason about, etc. etc. and a lot of proverbial horses beaten after death..).

So please, RocketSurgeon (who planted the seed of reversal-doubt') or anyone else, help clear this up:
What machine(s) and What NASA (or anything else in current use) specifications have this terminology and/or labeling reversed , and please point to an acceptable reference!

Thank you very much!!