Stump the professor II

Date 12-08-2012 09:28 Edited 12-08-2012 10:59

Dear Madam,

how privileged Lawrence, your welding educator, must feel having students around such as yourself.
And how privileged this whole forum must feel, that you, the 18 year old "farm girl", are addressing your queries here.
Truly wonderful your questions are - to me, purest, since only driven by the willingness to understand.

You know then.
Millions of words have already been written and surely billions of thoughts have already been thought by innumerous and impassioned individuals in history, aiming at answering "your" questions.
Hard for me to say this, but my personal problem is that since the world wide web exists, the amount of available technical information has increased exponentially, e.g. WIKIPEDIA etc.
Only look at the overwhelming number of articles and web-links regularly provided by "ssbn727".
Hence, I suppose it will be hard for everybody to answer your questions without knowing what you already have researched by yourself and/or have already learned through the discussions with your welding educator.
As being the best example, look at myself. I was thinking that I'd kept it simple as I was posting my comments to the 'rectification' subject.
I have to learn - I failed. Therefore, please accept my apologies.

However, on the other hand.
Just even yesterday I had a long chat with a very good friend of mine, thoroughly working in welding arc research.
Each time we discuss, and this is taking place quite often at the very least, we say good bye, being aware, that each other is having more questions in his head to consider vs. the point in time the discussion started.
I'm telling you this, because I would like you to know that the questions you - fortunately - ask are "simple" as long as you are treating their answers from a "longer distance". Say 10 meters, figuratively spoken.
But, if you're stepwise approaching them, reducing the distance to them, say meter by meter, and then centimeter by centimeter and so forth, it is similar to the use of a microscope. Things do become visible, apparently invisible before. And the closer you get to the subject of interest, the more difficult become even those things, that have seemed so unbelievably obvious and "simple" formerly.

I suppose that exactly was the root cause for Lawrence once to say: "Do you think you will answer it with a quick two words "current density" and skip off on your merry way?"
I must admit. I did very much like this statement, as it describes the subject quite precisely. "Quick two words" may suffice for a distance of say "9.8 meters" and therefore they may suffice to comprehensively answer your question, but they even fail as you may be asking: "What is current?".

And at the end of the day. You have to end up with physics, because all questions you ask are based on physical phenomena.
And, hence, finally you'll end up with mathematics, since this is - finally - the only language suitable to approximately describe what seems to occur in a welding arc.
To me, in person, this is joy and definitely always makes my day. I praise the Lord for filling me with this joy.

To keep the long short.
It might take a time to respond to your questions listed.
And, it might take some effort to provide you with the "comprehension" you desire to obtain, simultaneously however, excluding mathematics from the explanation(s).

For the beginning it would help to know if you may imagine an atom or it's theoretical structure, since being the fundamental brick in the "wall of knowledge".
I'm sure, or better, I hope that I haven't erred as yet, here are some exceptional persons around, explicitly including Lawrence, your welding educator, capable of providing you with answers.

Thank you Madam, for asking questions and thank you for taking your precious time to read these lines.

EDIT:
I had to return to this post since something came back to my mind again - suddenly.
At least in my understanding. The "burritos" may be considered a rather secondarily important particle species in the plasma.

By Northweldor (***)

Date 12-08-2012 13:42 Edited 12-08-2012 13:57

Diesel:

This is a fairly brief and clear answer to your first and second question about plasma,

http://education.jlab.org/qa/plasma_01.html

and, all welding arcs have plasma (energy applied to a gas, turning it into plasma), and ions are positively charged atomic particles, while electrons are negatively charged atomic particles, making up a plasma of a particular gas.

By electrode (***)

Date 12-11-2012 21:22

Either "deisel" or "diesel",

I hope both all is good with "ssbn 727" and that he may be able soon to post and further discuss.

I would like to begin suggesting my interpretation of the original posters questions, being:

1. "Why does SMAW have greater penetration with EP vs GTAW having greater penetration with EN?"

2. “Why the difference in penetration between the processes as it relates to polarity?"

First of all, it may prove reasonable from my personal viewpoint to split both processes from each other to – hopefully – later connecting them again for finally "comparing" them – whether or not this shall make physical sense.

GTAW - EN:

Presuming GTAW - EN then, as given by the OP, we may – or may not – state a "deeper" (whatever this is) penetration vs. GTAW - EP. This finally could end up in some sort of academic discussion.

However, for even allowing this interesting thread to continue we should presume deeper penetration with electrode negative polarity.

For what we (seem) to know is that the electrode (= cathode; in this case) is emitting electrons, suggested to carry the "greatest" (whatever this is) amount of electric current and “heat” (whatever this is) to the workpiece (= anode; in this case).

Here it becomes difficult already because actually it would require some formulae (most likely) or numbers at least, to more thoroughly explain this. But, as we said, that should be tried, to avoid and hence we use words.

It was found that electron emission from the cathode comes along with some specific amount of cathode "cooling". Here, discussable though, I’d like to compare this to water which requires energy to be evaporated from a bare skin surface. I guess this ordinary "cooling" effect is very well-known due to this causes some inconvenient shivering.

According to the common accepted theoretical models the electrons are carrying the greatest amount of current through the arc plasma. The greatest amount of heat produced at the anode, or workpiece, is then found arising from "electron condensation", as the electrons are considered dissipating their relatively high kinetic energy, gained along their way crossing some very particular and spatial extraordinarily limited zones of the arc, into thermal energy i.e. – heat.

Now the electrons arrive and condensate at the metallic workpiece, having, according to chemical composition etc. specific physical properties governing the interaction with the "heat" transferred by the electrons. This is often referred to as "thermodynamic" properties and usually hard to explain without extensively making mathematical assumptions. Hence, we won’t be digging deeper here in to this.

Now the weld pool is produced by the interrelationship between arc and workpiece and, weld pool size, -depth, or -geometry in general seems to prove a very complex function of a high number of variables which themselves again are complex depending on another high number of variables.

However, what should be of particular interest to us is, that, if choosing and adjusting the boundary conditions properly, some quasi stationary condition is taking place here resulting in some specific average weld pool shape, or, more specific, -depth. That is. We should be able to produce some similar average weld pool geometry-, fusion depth etc. as we are moving our arc, the heat source, across the workpiece.

And this average value shall serve us now as, let’s say, our very own "reference penetration depth" in a sense as the OP has been formulated.

Let us say.

Our reference average penetration depth at constant boundary conditions simply equals: 1.

GTAW - EP:

The OP points out that the electrode negative version of GTAW has higher penetration vs. EP.

That is. Our achievable depth of penetration using EP hence must be < 1.

And, presumed the chosen boundary conditions allow for noticeably achieving this magnitude < 1, we should, by adequate consideration, be able to infer the cause for this difference in penetration depth.

Therefore we should consider first – again – that our reference value '1' can only be one as long as the electrons, emitted, or let’s simply say, evaporated at the cathode, have two inverse effects. The first, as described, cools the cathode, and the second heats the anode.

Now, after already having discussed all this above, we are certainly able to understand that, without dealing here (although actually needed) with some intricate details and further variables, the heat flow to the anode seems being a function of, or more simple, depends on, the electric current height; simply because the height of current is just another expression for a particular number of electrons transferred through an electrical conductor (e.g. an electric welding arc). I hope you may agree so far.

But, why should the penetration depth with GTAW - EN be deeper then vs. GTAW - EP?

Most simplified, because the weld pool is our cathode now, and this cathode is cooled by "evaporating" (emitting) electrons, which btw is a matter of fact since the theory has been investigated and proven quite often through experiment.

And these electrons emitted, are passing the arc to finally condensate at the anode, being our (EP) tungsten electrode. Exactly this has repeatedly been properly described and explained, if I could read this correctly at least, by a number of fellow forum members along this thread.

That is, the tungsten anode is, literally, faced with an increased amount of heat caused by condensing electrons which were cooling the cathode before however, by being emitted.

So far, this should - from a "9.0 meter distance" - roughly make understandable the difference in penetration depth between GTAW - EN and GTAW - EP.

At least so far I do very much hope, Madam, that this may prove comprehendible to you - although I guess a higher number of fellows may say now that this could have been explained better either this or that way.

As noticeable this is only the first fraction of the answer(s) to be created for – hopefully – entirely covering the OP’s questions, I will be trying to continue writing soon for having a closer look at the SMAW (EN / EP) conditions. I'm afraid however that this, although underlying the same physics, may prove somewhat more complex.

By electrode (***)

Date 12-12-2012 10:57 Edited 12-12-2012 12:17

"deisel" or "diesel",

Resume.

SMAW.

As you may have learned certainly from Lawrence, your designated welding educator, one of the most significant differences between GTAW and SMAW is that the latter is a consumable electrode welding process. That is. As the tungsten electrode with GTAW only carries the arc but remains (almost) stable in shape and geometry, additional filler for producing the weld bead is required fed either manually or mechanised. With SMAW the electrode proves both carrying the arc – or heat source – and simultaneously supplying additional metal to produce your bead.

Apart from this you may have learned as well, that – in most or regular cases – stick electrodes used in SMAW have a coating which may vary in its composition. Without digging deeper in to the different cover types (sure that has been perfectly done by your weld educator) I nonetheless would like to point out some important characteristics of the cover constituents.

Why is this needed (at least from my point of view)?

Because we are dealing with a topic that explicitly includes the polarity under which a covered electrode is being processed and; I am sure, you may have already learned that, e.g. a basic covered type proves different welding behaviour depending on the polarity chosen to apply the consumable.

Hence, yes. The polarity plays an important part in using covered electrodes just as it does when using GTAW, as we have heard already.

So, one question could be. How does this connect to the elementary things we have discussed already for GTAW?

Electrode covers are - regularly - made of some fundamental ingredients, and for simplification reasons, I will be avoiding to more detailed discuss their chemical character here. The basis however, for these constituents or compounds, may be found being respectively metals and/or their oxides, or non-metals (and/or their oxides). As long as these substances are "solid"; i.e. part of your electrode cover, it may be hard for you to visually figure out their differences.

However, as soon as they have been transformed into the 4th state of matter (plasma) they strive for showing their "true" character.

Let us briefly return to the electron emission subject. Of course there’s no difference in SMAW vs. GTAW in respect of "who" is emitting the electrons and "who" is gaining their energy as soon as they passed the arc gap or plasma column. It remains the cathode or negative pole that emits the electrons and it remains the anode or positive pole which is heated by them.

The major difference however vs. GTAW is, that the electrode cover substances in SMAW may considerably change the ability of emitting (EN) or receiving (EP) electrons from the arc plasma.

To most likely make this a little more understandable to you, we should focus on a "basic" slag - or 'low-hydrogen' - character electrode type, e.g. AWS 5.1. E7018.

Why does this type prove so remarkably difficult to weld when choosing electrode negative (EN) vs. electrode positive (EP)?

And further. Why is this rather not the case when e.g. choosing an E6013 type instead?

Simply spoken this arises from some very specific characteristics of electrode cover compounds. And without going in to detail here, as I think Lawrence can provide you with thorough advice on this, it’s actually one particular substance that makes it so difficult to obtain stable welding conditions when using EN for an E7018.

This substance is referred to as fluorspar, or more correctly, calcium-fluoride, applied for improving the slag's wetting behaviour.

I unfortunately cannot protect you from stating its chemical denotation: CaF2.

It shows that 2 atoms of Fluorine (a very reactive chemical element) are connected to 1 calcium atom to end up with 1 neutral ion.

Not too dramatic. However, what happens to this substance when the arc is ignited and the plasma needs to be maintained by consistently "pumping" electrons from the cathode toward the anode?

Please accept my apologies for stating one expression hereafter, as it improves the understanding I suppose.

The CaF2 compound is split in the high temperature arc atmosphere, or, more correctly, 'dissociated' according to this scheme:

CaF2 --> Ca+ + 2 F-

This shows that each Fluorine (F) atom, when separated from the ionic compound, removes one electron from the CaF2 ion, thereby becoming negatively charged. Btw, here we have one of our 'anions' (F-) already mentioned previously in another post.

The calcium atom as denoted by the (+) remains being positively charged. And now the difficulties begin. As soon as these single elements enter the arc plasma they interact with other particles, e.g. free and accelerated electrons, that have sufficient high energy for stripping electrons from their nuclei ionising these thereby (please recall one of the previous posts).

Forgive me using further numbers to improve the understanding for what happens now. The specific energy required to strip one electron from the orbit is referred to as 'ionisation energy'. One special unit (not further dealt with herein) to scale this is the so-called 'electron-volt' (eV), expressing nothing else however, than 'energy'.

Now, here’s the numbers. As the calcium shows (first) ionisation at ~ 6.11 eV, Fluorine whereas is losing its first electron at ~ 17.4 eV.

A significant difference, as I suppose, you may notice. Hence, high energy levels are needed to ionise the Fluorine 'anions'.

To be continued?

If yes. I'll return soon.

EDIT:
I had to return sooner than expected, but just as I have forgotten something fundamental.
That is. I had forgotten to reference the values eV for Ca and F.
These can be found at:
http://www.webelements.com/calcium/atoms.html
http://www.webelements.com/fluorine/atoms.html
Conversion factors for eV to kJmol^-1 can be found at:
http://physics.nist.gov/cuu/Constants/index.html

By welderbrent (*****)

Date 12-12-2012 14:54

Well, I hope you continue even if our student doesn't post a response yet.

May be a little deeper than what she or Lawrence expected, but I think I see the connection thus far.

I did find the reference I was looking for as far as some good information goes on simply explaining the plasma column. It is in the Welding Handbook, Volume 1, Welding Science and Technology, Chapter 2-Physics, about page 67 for some specifics but you really need to read the whole chapter to put it together.

I would encourage Lawrence to add it to his school library if possible and not already there.

Add that to electrode's posts going into a deeper explanation and it is already answering the 'WHY' that started this whole thing. And yes, I agree electrode, several here have contributed to the why it just hasn't been quite but together in a completed picture combining ALL the different factors that contribute to the picture.

Much has been focused on coparing the two processes instead of taking each on it's own and then answering 'why does one penetrate more on EN and the other on EP?' .

Have a Great Day, Brent

By electrode (***)

Date 12-12-2012 17:26

"deisel" or "diesel".

Unsure, because a young lady you are, whether I may call you Kara.

First of all, my thanks to "welderbrent" for his - again - very friendly comments. Encouraging they are to me.

Resume.

We have heard that Fluorine is hardly losing electrons since requiring relatively high amounts of energy to remove them from its orbits around the "core".
We also know that the fluorine actually has its origin in the electrode coating, chemically bound to the element calcium, forming CaF2 (calcium-fluoride).

Therefore we may suggest for SMAW-EN e.g. using an AWS 5.1 E7018 basic type electrode as follows.

CaF2 is supplied from the coating to the cathode (your electrode). Here it is split or dissociated. The resulting calcium ion enters the arc plasma and, likely to be further ionised, may provide negative charge carriers (electrons) to the plasma for being accelerated toward the anode (workpiece).

O.k., but, what does happen now with the fluorine, produced at the cathode itself (being your electrode)?

Well, this may cause some problems.

Why?

Being negatively charged the fluorine ions aim at reaching the anode (recall previous posts), being your workpiece, simultaneously quasi, in common with their negatively charged "partners" i.e. the electrons, emitted at the cathode (your electrode). But there is one most significant difference between the Fluorine ions and the electrons which are also striving for reaching the anode.

And this is – their mass.

For a better understanding it seems valuable to know that 1 electron carries only (another impressive number) 1836.152 672 45(75) (see: http://physics.nist.gov/cgi-bin/cuu/Value?mpsme|search_for=proton), or ~ 1/2000 the mass of 1 single proton (recall the previous post dealing with the atomic "core").

And now, I suppose, it's understandable that, because Fluorine has an atomic core, or correctly termed, nucleus, containing 9 protons; the mass of 1 single Fluorine ion proves 16525.3740521175 (or ~ 16525) times heavier than 1 electron.

This, amongst others, is one of the major reasons for that the "greatest" (whatever this is) amount of current (or heat) within an arc is carried by electrons. They are simply much smaller and much faster because they're simply much easier accelerated within the plasma. And this btw is also one of the reasons for that the anode is that "much" heated through electron condensation. Much simplified, because these tiny particles gain some impressive amount of kinetic energy along their way through the plasma (or very particular zones of it*), released as, or transformed to, thermal energy while interacting with the anode/workpiece.

I can catch myself extravagating, forgive me.

The Fluorine ions. Now we seem to understand that these particles have a considerable greater mass and volume vs. our electrons. These, as we've heard, are accelerated for finally reaching the workpiece (anode). Now happens this. The Fluorine ions are massive, but negatively charged. Produced very close to the cathode (your electrode coating) of course they try as well to get to the anode. But, the anode itself is simultaneously producing and providing positive ions (to maintain the electric circuit and thus the plasma). These positive charge 'cations' try reaching the cathode (your electrode).

Now imagine, that permanently Fluorine ions (particles) are produced through splitting or dissociating fluorspar (CaF2). Simultaneously to this continuous "pumping" of negative ions into the plasma, their transmission toward the opposite pole (your workpiece = anode) is impeded. Most simplified, because, having a relatively high mass and volume, they collide with those heavy particles (cations) on their way from your workpiece toward the cathode (your electrode). Seeking a common term maybe for adequately describing this condition one could say: "A bottleneck is created."

Hence, what we can see, is that electrically negative charged Fluorine particles (ions) accumulate before the cathode (your electrode) which additionally emits, and permanently provides however, electrons to your arc.

Now one could raise the question: " 'electrode' (exceptionally that’s me this time), is this what you say provable anyhow?" And I myself would reply: "Yes, it is."

Since the increased amount of negatively charge particles in front of the cathode (your electrode) can be measured causing a higher arc voltage vs. SMAW-EP**.

To be continued?

If so, a pleasure it would be then for me to return soon.

Notes.
*) I intentionally avoid expanding the discussion on this extremely complex arc region here (yet one of the last unrevealed secrets in arc physics).
**) For those disagreeing to the way I'm trying to simplify all this. I seem to understand that one of the huge benefits of mathematics is a considerable decrease in the number of "words" when treating physical phenomena. I seem to understand however, that effort should be devoted along this thread, to keep it "simple" but not wrong. Hence, and of course, I'm always open for discussion, critical comments and arguments.

By deisel

Date 12-13-2012 15:14 Edited 12-13-2012 15:48

You can call me diesel or Kara I'm used to either one, and I know deisel is incorrect but diesel was taken. What is fluorine? From what you're saying its part of the flux, right?

I'm sorry I'm having a hard time following your post, but I think I'm starting to understand. You are comparing dc negative and dc positve with the smaw process, and your saying dc negative have more negatively charged particles, right? And since negative charged particles, the electrons I mean, are what carry the current that's why the one polarity has more penatration?

By welderbrent (*****)

Date 12-13-2012 15:26

I knew there had to be a purpose behind the misspelling. You could have just used some numbers behind 'diesel' to make it different, but, don't worry about it now.

And you knew you couldn't shake her off with all the deeper explanation Electrode. She is just too persistent and curious (a good thing).

Kara, have Lawrence show you an MTR on steel. Just as when needing to do a Carbon Equivalency check on steel one needs the percentages of even the most miniscule component of the steel all ingredients are evaluated in the process of examining the Plasma Column and how it functions in each particular circumstance. And YES, it is present in the compounds making up the flux, even if only as a byproduct when the chemical transformation takes place when ignited.

But, I will let Electrode carry on. He is doing quite well as long as he doesn't try to get himself in too deep before giving us his evaluation of 'WHY' they work opposite oneanother.

Forgot who, but someone else posted up a pretty good explanation yesterday as well. (thought I would edit this and give 'Northweldor' his credit, good read).

I'm hoping his absence doesn't mean Henry has slipped again. His health has not been well. (nothing against Electrodes work here, Henry just usually comes through with lots of references and support material to help you check things out for yourself. But I am enjoying Electrode's participation. Don't understand all of it, but the train of thought is coming together).

Have a Great Day, Brent

By electrode (***)

Date 12-13-2012 21:45

Then I'll call you - Kara,

many thanks, and thanks also to "welderbrent".

Definitely I intend to finish, what I was starting here.

Hopefully I'll not be going to disappoint you and "welderbrent" too much when coming to my summary in very due time.

I'm thinking about whether I must ask you to accept my apologies again, for the "hard times" you have. But I decided not to apologise, because I mean it's good, learning it "this" way. That makes the brain cells valuably working for forming new synapses and; everything too quickly understood, does not last that long in mind, at least that is the case with me.

And finally, it makes me glad to see you saying: "…but I think I'm starting to understand."

I can also see, you're asking questions. That is good. That is very good.

You ask: "What is fluorine? From what you're saying it’s part of the flux, right?"

I reply: Fluorine is one of a high number of elements, structured in the periodic table of the elements. Please ask Lawrence and I'm sure he will be happy to explain this in greater detail to you. Please use also this link: http://www.webelements.com/fluorine/atoms.html, for deeper explanation of 'Fluorine'. Briefly, Fluorine is the chemically most reactive of all existing elements. That means, it is heavily aiming at producing compounds with other elements, e.g. Calcium. The new "substance" created from this is even calcium-fluoride (denoted CaF2). It is used in basic electrode coatings because it's helpful in lowering the viscosity of the slag formed upon your weld bead, originally arising from your electrode coating.

You ask: "You are comparing dc negative and dc positve with the smaw process, and your saying dc negative have more negatively charged particles, right?"

I reply: I have just even begun to deal with some very details of the SAMW process as when it comes to what's going on at both electrical terminals; i.e. your stick electrode and your workpiece/weld pool.

You ask: "And since negative charged particles, the electrons I mean, are what carry the current that's why the one polarity has more penetration?"

I reply: Yes! You have understood.

You may probably ask. Is all this really needed just to answer such simple questions? And I honestly consider all this (and actually even much, much more) necessary due to having in mind Lawrence' statement, saying: "With the 6013 EP is definitely better for penetration."

Hence, if we would not treat an electrode type different to E6013, how should we try to estimate the reasons and causes then for some particular amount of "penetration"? I thus stick to dealing with the AWS 5.1 E7018, simply because to me it's the most adequate piece of filler metal to describe what is going on in a close distance to the electrode tip.

Resume, thus.

So, last we heard that a higher arc voltage is measurable using basic covered electrodes at straight polarity. This leads to some "sharp" acting arc, perturbed weld behaviour and unstable droplet detachment, joined by an increase in spatter.

However, how about SMAW-EP using AWS 5.1 E7018?

Choosing this polarity now the workpiece emits electrons moving toward and hitting the anode (electrode). This, highly heated up thereby, again produces Fluorine ions by dissociation of CaF2 (recall the electrode coating). The Ca+ ions are attracted by the cathode (workpiece) this is agreed, but how about the Fluorine ions? Well, these are attracted by the electrode itself of course, due to being positively charged. They are found almost instantaneously absorbed again as they're no further required to cross the whole arc gap (plasma column) to reach the opposite positive. That causes both an increase in arc stability (uniform arc attachment, termed anode spot, at the molten droplet) and an additional heating effect at the droplet surface. This additional heat is transferred to the workpiece/weld pool again by the molten droplet, whose heat content may be suggested higher vs. DC-EN. Finally, however, (E7018) SMAW-EP is running visually more stable vs. SMAW-EN.

Strange! Haven't we heard actually that – in non-consumable electrode GTAW – the cathode emits electrons and the anode may be supposed "hotter" thus, due to being permanently hit by these electrons?

Shouldn't we further consider these laws of physics to govern also our E7018 DC-EN application?

What about our penetration depth, then? Shouldn't it be "greater" thus using EN7018 at electrode negative?

We actually should be able already to deduce the answer from what's been discussed as yet. But wait. We need to consider one important detail. In a basic electrode arc the electron density (the number of electrons across the whole arc plasma volume) is reduced. Why this? Simply speaking, this is also due to the accumulation of negative charge carriers in front of the molten electrode tip, even where dissociation of CaF2 into Ca+ and 2 F- occurs.

For a better understanding, one further detail becomes important, thus it needs appropriate mention.

The area that accumulates the negative charge carriers (negative Fluorine ions and electrons) is joined by one interesting phenomenon, quite having the power to "shift" all those boundary conditions in charge of a smooth electron emission towards the anode. It is termed 'space charge'. Unnecessarily complicating the whole subject I'll pass up treating this here further. However, this space charge, a result from the surplus of negative charge carriers in front of the molten electrode, significantly impedes electron transition to the arc column allowing them thereby to be transmitted to the anode.

It importantly changes also the height of the anode's attractive force, regularly acting upon each single negative charge carrier to finally "capture" it. Hence, the amount of electron condensation at the workpiece is reduced due to the:

- decreased number of electrons in the arc column, caused by
- changed conditions in front of the electrode, which causes a
- change in the space charge conditions, that
- impedes the electron emission to the plasma column.

Here we come full circle.

Because due to the reduced electron condensation at the anode, often treated as a representative for "heat" transfer to the anode, we may suggest the cathode (electrode) to be "hotter", and thus assumingly weld fusion depth may be found decreased at the workpiece applying direct current electrode negative.

I did never investigate this by myself as yet, but, actually, and according to what I was allowed to learn (a number of years ago much greater than your own age, Kara) that should prove, at least to me, a somewhat logical consequence from all of this. By the way, this is what makes this thread so interesting, because the questions are so fascinatingly interesting.

Thus, I suppose if not even a "deeper", but at least a significantly changed penetration profile to occur – always presuming "regular" (whatever this is) boundary conditions given – with DC-EP.

However and by all means, I’ll be back soon, for what it’s worth. Because slowly, I suppose, we have to draw some conclusions, don't we?

By electrode (***)

Date 12-15-2012 14:01

Kara,

final thoughts.

Recall the OP statement: "With the 6013 EP is definitely better for penetration.".

We should try to analyse the main constituents used for an AWS 5.1 E6013 covered stick electrode.

To keep it concise; there is a great amount of a metallic compound used for the electrode coating. This is referred to as Titanium-Dioxide (short TiO2), also known as rutile.

Significant differences may be found between rutile and, see previous posts, CaF2 (fluorspar), used for basic electrode coatings (e.g. E7018). Fluorspar is known constricting and perturbing the arc while at direct current electrode negative; rutile, however, does not.

On the contrary, it rather is some quite valuable constituent when it comes to improve arc stability, or, as discussed sometimes along this thread, improving electron emission into the arc column.

An interesting question could be raised from this: "Why?"

As usual, a more detailed answer may be also somewhat more complicated. We should focus on the fundamentals by considering the separation (dissociation) of TiO2 (recall previous post, this says: 1 titanium atom bound to 2 oxygen atoms) in the arc atmosphere. One of the final results from these reactions is oxygen, which is referred to as "surface-active" sometimes, due to decreasing your liquid weld pool’s surface tension causing additional effects. All this however, should not be further dealt with herein.

For approaching an evaluation of penetration depth using rutile coated stick electrodes (e.g. E6013) in relation to the electrical polarity either DC EN or DC EP, we should be concerned rather with the fundamental balance between electrons and ions in the arc plasma. As we heard, for the basic coated type E7018 this "healthy" balance could be found slightly disturbed during DC EN. Here, the cathode – that actually should be the "colder" of both electrical poles in the welding circuit, appeared "hotter". Hence, we were suggesting the heat at the workpiece (anode) lower. From this we were supposing some difference occurring in either the fusion profile or – maybe – the fusion depth; of course, always depending on the boundary conditions chosen. As we could discuss one of the major facts with the E7018 DC EP application was the greater uniformity of arc attachment at the anode area, actually, at the molten droplet surface. Leading to greater arc stability, reduced spatter (consider this as increased heat to the weld pool, since the pool doesn't lose matter) and smoother droplet detachment this may result in "deeper" penetration.

How about the E6013 type? Does electrode tip, droplet shape and -surface, arc attachment and -behaviour, respectively, prove similar to the E7018 type depending on being connected as either DC EN or DC EP?

Does it even make sense to ask these questions? Not really sure, but, if there is a measurable difference in the E7018 behaviour when connected to either to the positive or negative, then; I suspect, a difference should be noticeable with the E6013 either.

Again - if the E7018 proves hotter at EP and one indication for this is due to the arc is smoothly covering and uniformly attaching at the droplet molten droplet surface, then, I suggest, the questions make sense.

Actually because one could relatively "easy" distinguish between the "hotter" and the "colder" electrical pole, and from this, maybe, infer some distinction in the electrode's penetration behaviour.

And now it comes. This very specific distinction in the arc attachment – or 'anode spot'-behaviour could (to the best of my knowledge) not be found with (thick coated) rutile coated electrode types.

On the contrary; the molten droplet, forming at the tip of your welding electrode, could be found uniformly covered whereas by the arc, thus supposed to uniformly heating the droplet volume in either polarity – EN and EP.

Hence, the appearance of the arc attachment at the electrode tip or molten droplet respectively, seems no reliable indication for deriving some assessment on penetration depth.

Short. Based only on this detail one cannot say whether a greater or lesser penetration depth is possible with E6013 DC EP.

What however, about the OP's statement: "With the 6013 EP is definitely better for penetration"?

To be honest, at this point I have no idea.

But wait.

If we consider the anode to receive more heat from the arc, that should be agreeable with the E6013, then it should also melt one unit of the given electrode length faster vs. DC EN, wouldn't it? I seem to remember that this has also been said by some others along this thread. An increase in the weld deposition rate should occur thus when using E6103 EP vs. EN. And some other had also mentioned already that the heat at the anode (electrode tip) will be returned to the weld pool by the molten droplet itself, containing this heat. This maybe could finally be our indicator then for a greater penetration at E6013 EP. Investigations have shown; yes, the electrode is really consumed measurable faster when connected to the positive pole.

I should not forget to mention that, in average, also a basic electrode is consumed faster, when at electrode positive (DC EP). And as we had already discussed previously, we should logically suggest the penetration profile (if not even the depth increased) when choosing e.g. E7018 at DC EP.

So, finally this could lead us to the assumption that, when applying an E6013 at DC EP, the penetration may prove greater vs. DC EN, and thus, that might prove the statement coming from the OP, saying: "With the 6013 EP is definitely better for penetration" reflecting a true and valuable observation.

But this doesn’t answer the very first and crucial question asked in the original post:

"Why does SMAW have greater penetration with EP vs. GTAW having greater penetration with EN?"

Well, I guess after all the different comments and suggestions along this interesting thread, this might be answered quite easily. And honestly I was thinking you, Kara, would have already stated it in a recent post, as you were saying:

"If tig welders used consumable tungsten which deposited filler instead of using filler rod we would use dcep in that process like in stick welding, correct?" [sic!]

I tend to say. This is extraordinarily well said. Why?

This, amongst others, should be found under paragraph xii, in some (simplified) "conclusions" below.

I guess it is high time that we finally should draw these now, before tensioning this thread to death.

From all being said and written we may conclude as follows:

i. The arc plasma may be considered an electrical conductive gas consisting of different particles (e.g. electrons) capable of carrying the current from electrical negative (cathode) to electrical positive (anode).

ii. The free electrons in the plasma, although having a much lower mass vs. the remainder atoms, may be suggested carrying the highest fraction of the total amount of current and heat.

iii. Depending on the experimental boundary conditions in GTAW electrode negative (EN) mode; i.e. the electrode emits electrons, we may be able to derive some specific "reference" penetration depth. This representatively may be numerically stated, equal to 1.

iv. In GTAW electrode positive (EP) the penetration depth was stated by the OP, "lower" or < 1, vs. GTAW EN.

v. In SMAW using a basic coated electrode (e.g. AWS 5.1. E7018) the physical mechanisms governed by specific coating constituents (e.g. CaF2) may account for respectively, the penetration profile changed, if not even its -depth increased, at DC EP vs. DC EN.

vi. Applying an AWS 5.1. E7018 electrode at SMAW DC EP, the arc "covers" the molten droplet present at the electrode tip more uniformly vs. DC EN. This however, may not be suggested being a reliable indicator for the penetration depth change or -increase, respectively.

vii. Paragraph vi. may account for the fact, that the arc attachment to the molten droplet using a rutile coated electrode (e.g. AWS 5.1. E6013) is similarly uniform; independent however, on either DC EN or DC EP.

viii. Hence, another cause may be assumed in charge of the, if any, changed penetration behaviour at SMAW DC EP.

ix. This cause may be suggested found in the increased heat content of the molten droplet(s) formed at the electrode tip heated by the electrons condensing at the droplet surface. This additionally causes an increased melting rate.

x. It may also cause an increased heat transfer to the molten pool, hereby maybe changing and, as claimed by the OP, increasing the penetration depth at given boundary conditions.

xi. Despite the doubts whether it may prove physically reasonable to compare both welding processes to each other. The reason for the difference in penetration depth between GTAW DC EN and SMAW DC EP may be suggested due to the simple fact, that, the increased heat arising from DC EP in GTAW is not transferred into, and adding heat thereby to some sort of "droplet(s)" but is accumulated in the tungsten electrode. Here, it is carried away in part and amongst others by radiation and interaction with welding torch parts (copper collet etc.).

xii. It is thus finally suggested that, if using GTAW DC EN, we would state our reference value being 1 to become "greater", applying DC EP by (theoretically) and assuring the tungsten metal, containing the additional heat from electron condensation, transferred to the liquid weld pool. It must be explicitly emphasised however, that this is purely theoretical and dealt with entirely disregarding the most different material properties between tungsten and iron (steel). It is thus suggested that the penetration depth may be increased when hypothetically using GTAW DC EP with "melting" tungsten electrodes.

As you may notice, this is nothing else than a brief summary of all the 99 previous comments and suggestions stated so impassionedly as yet by the forum fellow member, along this thread.

However, I would find myself glad if this could make some sense to you.

I rest my case.

By welderbrent (*****)

Date 12-15-2012 14:39

Are you sure?? I'm not sure that the last chapter has yet been written :confused:

.

No, really, very well done from this non-physics major point of view. You took a lot of time to do all that Electrode. Thanks. Again, while having had High School Chemistry and Physics much of this is out of my league. But, while trying to follow you and compare with chapters from the afore mentioned 'Welding Science and Technology' and of course with the thoughts and input from several other members, I find some interesting conclusions following some very interesting process descriptions.

I too hope Kara was able to in some degree piece this together to get her 'WHY' question answered. In some ways, it may have boiled down to not only a 'WHY' but more importantly 'Does it really?' Or, 'Can it be proved mathematically or scientifically?' We know that under all the proper circumstances it could be proven by testing. But, I have not seen evidence that would cross the line of stating 'why' one penetrates deeper with EN while the other penetrates deeper with EP.

Now, I do have one question: Am I following you correctly in your final conclusion statement that it may be the opposite with GTAW such that Both Processes may actually have deeper penetration with EP, at least under some circumstances?

If I am correct in my interpretation, does this apply when all other factors between GTAW EN and GTAW EP are equal? Or are we changing some other perameters to arrive at this condition?

Have a Great Day, Brent

By electrode (***)

Date 12-15-2012 17:10

"welderbrent",

I do thank you for both comments and questions.

First of all, please allow to quote yourself, saying:

"We know that under all the proper circumstances it could be proven by testing."

I do fully agree. This is well said and would definitely help to cleanse the boundary conditions frequently marked unknown as yet.

Further to your questions:

"Am I following you correctly in your final conclusion statement that it may be the opposite with GTAW such that Both Processes may actually have deeper penetration with EP, at least under some circumstances?"

Yes. This is my suggestion. Simply, because the physics behind, governing all this, remains constant.

In brief, and in accordance with this thread, penetration may be found with:

SAW DC EP: >1 vs. DC EN.
SMAW DC EP: Penetration, according to the OP applying E6013 (boundary conditions unknown, however): >1 vs. DC EN.
GMAW DC EP: >1 (regularly) vs. DC EN.
GTAW DC EN: 1 = Our pratically observed reference value.
GTAW DC EP: <1 But actually? "Unprovable" and "incomparable"due to tungsten shows the highest melting point among all known metals.

So, the question is.

Should the governing mechanisms, driving the penetration depth to increase at DC EP with the common fusion welding processes (as listed), suddenly switch to act inversely? Just because the "consumable" welding electrode's being replaced by a "non-consumable"? Would that prove reasonable in a physics sense? I do really not know.

Further.

"If I am correct in my interpretation, does this apply when all other factors between GTAW EN and GTAW EP are equal? Or are we changing some other perameters to arrive at this condition?"

Well, at least in my understanding this can be briefly responded. But, again, always under "regular" boundary conditions (whatever this means). And these can, dramatically differ - sometimes; leading to some marvellous shiftings from the so well-known and convenient "Regularity".

GTAW DC EN assures electron emission at the W-electrode. Their kinetic energy gained along their way through the column, released as thermal energy at the (steel) anode or workpiece proves sufficient for liquefying the anode.

The inverse condition.

GTAW DC EP assures electron emission at the steel anode. The energy however released by the electrons at the (tungsten) anode proves insufficient due to the thermophysical properties of tungsten. Amongst others, its high melting temperature.

In short, and despite the weld pool is losing energy by evaporating electrons. We would either need to increase the electron energy coupled into the tungsten anode hereby to increase the thermal impact to the material, or, we would need to change the thermophysical properties of the anode material, being the highest melting metal at all.

However, the first may prove difficult since there are some physical limits drawn by the laws of conservation and the second might prove difficult since one would most likely need to continuously approach the cathode melting temperature to "really" equalise the conditons for a final approval of our suggestions and assumptions.

Nonetheless. As long as we haven't observed GTAW DC EP supplying the liquid weld pool with molten anode material (tungsten), that long I'm afraid, I for one would be very careful claiming:

"GTAW DC EN shows "deeper" penetration vs. GTAW DC EP."

As you may see. The whole matter is subjected to a high number of variables. This, amongst others, makes welding my life.

Hoping that this makes some sense, I now rest my case.

By Lawrence (*****)

Date 12-15-2012 18:25

Rest your case in peace !

Kara is fortunate you all (especially you Electrode and Brent) have taken such a generous interest in her.

My my... over 100 helpful and polite postings on a single thread.

Professionally executed

Diesel is now back on the farm for Christmas break..

What will she come up with in January I wonder?

Electrode... Prepare yourself to fill her desire to comprehand the minimum 32 CC/CV vairables in a synergic GMAWP operation.. :)

By electrode (***)

Date 12-15-2012 18:59

Lawrence,

fortune is definitely with me, reading your kind message.
Hopefully the young lady will enjoy the few days off from all this confusing stuff, before returning and firing her marvellous questions again.

Like once I said. I bow my head before you, as all the others active in education.
Twice even, as you make them becoming valuable members of both the human society and the welding community.

And how fortunate I can estimate myself for having been allowed to be one humble part of this enjoyable discussion.
Now, however, I have to switch on the brain for stand-by mode already, to be well-prepared for the 32 CC/CV variables.

One's for sure. Having individuals such as yourself, "welderbrent" and all the innumerous others around, short; remarkable fellows and welding experts - nothing can go wrong!

By welderbrent (*****)

Date 12-15-2012 18:59

Lawrence,

It has been a pleasure for me (I'm sure for Electrode as well). To be able in any way to help our young people get their questions answered without just saying 'because the book says so' is really a blessing to all of us.

Digging into the books, listening to one another, and then following the information provided by Electrode has been very enlightening. I would hope all who read this will glean something from it. After all, our profession is so much more than being able to strike an arc. So much more than just laying a 'pretty' weld pass.

As I stated in an earlier post, you can't ask too many questions. You can't get too much information. You can't know everything about this great process we call our profession.

And we certainly can't share too much of it but we must share as much as we can in order to train up the next generation and preserve the knowledge that has been thus far accumulated.

Wishing one and all, Kara especially, very wonderful holidays (meaning: MERRY CHRISTMAS AND A HAPPY NEW YEAR!!).

Now, I have to try and get home. I am 100 miles north, in Flagstaff, and it is snowing heavily. Probably should not have even come up here this morning but they were working my job and I must be here when work is being done. It is already about 16" deep. Started yesterday but it was only about 4" in the morning and 6" going home last night. With all the traffic on I- 40 and I-17 they have many accidents and are talking about shutting them down until it stops and the plows can get ahead of it.

Have a Great Day, Brent

By deisel

Date 12-15-2012 21:39

Thank you for the posts, however I have a lot of work to do over break so it might have to wait till next semester before I get to a computer again. I've been dating a master electricians son for the past few years and the master electrician needs help installing a few hundred lights for a few different companies. I'll be asking him questions about polarities for the next week or so. Electrical work seems to use electricity in a very different way compared to welding from what I've already asked him about. I also have to exercise my horse and my dad is going to help me learn how to tig weld pipe.

Thank you very much for answering my questions, I'm really glad Larry posted these questions on here. I never thought I'd get to learn physics through welding. I hope you all have a merry christmas and a happy new year, and I'll be thinking over everything you've been teaching me on process.

Thanks again,

Kara

By DaveBoyer (*****)

Date 12-16-2012 06:17

Would it be possible for You and Your students to actually do a 6013 EP & EN test with as many variables held constant as possible and measure penetration? And then test GTAW similarly, of course using amperage low enough for the tungsten to hold up on EP ?

It would be interesting to see HOW MUCH difference polarity makes.

Someone somewhwere along this thread mentioned the polarity difference between self shilded and gas shielded wire feed welding, but that would be a whole other ball of wax with fewer similarities to make a comparison with.

By welderbrent (*****)

Date 12-08-2012 22:25

Kara,

There is no such thing as too many questions! That's how we all learn. And I agree with electrode. It is refreshing to see someone curious about more than just how to manipulate the electrode in order to pass a qualification exam so you can get a job and make money.

But, sounds like you may need some science courses. Chemistry, Physics, and other Applied Sciences to really get to the bottom of your questions. But, we will try to help. I need to look something up but maybe while I'm looking someone like Henry (SSBN727) or electrode will carry on.

Have a Great Day, Brent

By Superflux (****)

Date 12-09-2012 00:37

Deisel,
Welcome to the forum.
WOW! You have an insatiable curiosity. AND ask some very interesting and challenging questions.
From what I've read here, sounds like you should go all the way and get an engineering degree.
As for part of your latest question, NO... and yes, sorta. There is a minute amount of plasma created at the electrode gap on a spark plug that detonates the rest of the fuel/air mixture in the cylinder, hence the term "internal combustion engine". None in a diesel.
As matter goes from solid to liquid to gas to plasma it becomes more energetic. The transformation to plasma requires exponentially more energy than the others.

FWIW, I taught my daughter to weld, and she got an engineering degree so she wouldn't ever have to... but she's always hitting me up to make a welded thingy for around her house.
Best wishes to you on your career.

By electrode (***)

Date 12-09-2012 07:09

welderbrent,

"I need to look something up but maybe while I'm looking someone like Henry (SSBN727) or electrode will carry on."

If that I was meant. Thank you.

I'm yet seeking for words.

By electrode (***)

Date 12-09-2012 11:00 Edited 12-09-2012 21:38

Madam,

you say: "I think, that the arc is not necessarily plasma but it has plasma in it."
I dare to say: An electric welding arc, and this is what is discussed here, literally is a plasma.

You say: "And Plasma is nothing more than energized gas."
I dare to say: It is and it must be more than this, because "energised" gas can also be found in the pressurised oxygen bottle you're opening the valve at before using it to most likely bevel your welding samples.

This is due to the "energy" that has been supplied to the gas to decrease 10,000 metric litres of oxygen into a bottle having a volume of only 50 metric litres.
However, the "outcome" is the 200 bar = 20 MPa ~ 2,9 ksi pressure inside the bottle.

To keep it short. The major criterion of a plasma, to me and as being discussed in our context, should be considered as:

It is electrically conductive.

This again is not the regular case for any gas, being the third stage of matter, as already mentioned by others.

How can this happen?

Returning to the atom, that I was mentioning already in a previous post to be a fundamental brick or, better, constituent, or even better, species in all plasma considerations.

Basically a gas is consisting of atoms, at least according to the physical model regularly applied.
Now, what is the difference between the compressed "energised" gas in your oxygen bottle and the "gas" in a plasma?
The former is still consisting of electrical neutral atoms, similar to the surrounding atmosphere actually a gas mixture of oxygen molecules (O2), nitrogen molecules (N2) and some noble gases. Btw the latter prove to be single atoms, whereas the former (molecules) exist as "couples" of two atoms. And the main difference is that, due to its electrical neutrality the gas regularly hardly can conduct an electric current. I know, some of the other forum fellow members will be screaming up now, but nonetheless I would like to use the comparison between a metal (whatever this may be) and wood. If you’d be using a "wooden stick electrode" clamped into your electrode holder and would try to weld - of course I hope you now shout out - that must fail. Simply, since it doesn’t carry the electric current existing within your welding circuit, just waiting for being conducted through your arc (plasma).
But using a metallic electrode whereas, allows you to ignite an arc, or, very simplified, induce a plasma.

A gas in its "neutral" state is (regularly) physically similar to the wood described, which is considered an electric insulator. However, while wood remains an insulator this is different for any gas. Therefore we need to recall that each gas atom in electrical neutrality is consisting of a "core" comprising electrical "positive" charge carriers (protons) and (remember equal electric charges repel-, as oppositely charged attract themselves) "neutral" particles (neutrons), some sort of "glue" so to speak, even allowing the core to be packed by throughout positively charged protons.

Further. To assure however, electric neutrality of the gas atom, otherwise it would show a positive charge (wouldn’t it?) some "balancing" particles are needed. And these are the "negative" charge carriers or short, electrons. For each proton in the core one can regularly find one electron which, and this is crucial, orbits the core at discrete distances. It would certainly go too far to dig deeper into this, as I guess this can be found on the 'www' a thousand times. Nonetheless, to make the "neutral" gas achieving a state of electrical conductivity that is, carrying electrons (and non-neutral charge carriers) from one electric pole to the other, one must take care for "pumping" sufficient energy into the gas.

Resume.

We should stick for the beginning to the gas that you are, most likely according to the instructions of Lawrence, using for GTAW; i.e. argon.

To make this "monatomic" gas electrical conductive you have to strip at least one electron (this is what has been found to carry to the greatest amount the electric current in a welding arc) from its orbit around the core. What you obtain from this then is – at least – 1 free electron and the core, having now however 1 proton more than electrons to balance the core charge. This "positively" charged core now is regularly referred to as "ion". Nothing else thus than a electrical non-neutral argon atom.

Resume.

As your welding educator did certainly teach you. The electric welding circuit comprises two different electric poles, that is, the positive (termed anode) and the negative (termed cathode) pole. Mr John Wright did embed a wonderful link in one former post explaining this in much greater detail and surely much better than I ever could.

Each electric charge either negative (electron) or positive (ion) is attracted to the opposite, as we did already say. That is. The negatively charged electron is striving for reaching the anode as the positively charged ion tries to get to the cathode.

And to very simplifying it; i.e. "10 meter distance". Each particle has a mass and thus a volume and on their either ways toward the electric poles they collide to each other what causes some sort of "avalanche" of negatively charged electrons, positively charged ions and, depending on the boundary conditions, many further species (e.g. excited atoms, negatively charged ions etc.). And this, in brief and observed from "10 meter distance", is referred to as plasma.

That is, a former electrical neutral gas (e.g. argon), now containing sufficient energy to strip electrons from their orbits to be carried across the distance between your tungsten- or welding electrode and your workpiece.

I must not forget. I’m sure this could have been explained much more detailed or in a much better way. But like I already said, it’s hard for me to interpret how much you, Madam, do already know. And I have really struggled finding the right words for expressing this very first "insight", if even.

Also, sure I am that much more explanation is needed before returning to your welding educator’s original post. Although it’s hard for me withstanding to post something, that could already fire up the whole "penetration depth" debate.

Please ask, if there is any question. Sure it is.

EDIT:
Thanks to "Northweldors" comment I was rereading all this once again and have replaced a comma - not "in the brackets", however.

By Northweldor (***)

Date 12-09-2012 19:05

"...negatively charged electrons, positively charged ions and, depending on the boundary conditions, many further species (e.g. excited atoms, negatively charged ions etc.). ..."

You have a small error in your brackets above.

By 46.00

Date 12-09-2012 20:23

By electrode (***)

Date 12-09-2012 20:30

Northweldor,

I seem to understand that at least one person, namely you, did read what I have written.
Thank you for this.
Nonetheless I must admit that I cannot see the mentioned error in the brackets.
Is there anything wrongly spelled?
Do I overlook something here?

I kindly beg your pardon.

By Northweldor (***)

Date 12-10-2012 11:54 Edited 12-10-2012 12:17

There are no "negatively charged ions", to my knowlege , since, as in the first part of the quoted sentence, ions are "positively charged". Please correct me if I am wrong.

EDIT: Sorry, I have since learned about cations and anions, and I am wrong!

By electrode (***)

Date 12-10-2012 12:39

Northweldor,
thank you.
Now I seem to understand what you've meant.
One tiny detail only in the complexity of a plasma but; as I stated, depending on the boundary conditions, also negatively charged ions (anions) may be produced.
Hence, depending on the boundary conditions, both cations (positive charge) and anions (negative charge) can exist.
At least, to the best of my knowledge.

By welderbrent (*****)

Date 12-09-2012 22:10

Okay, electrode has provided a very good description of the process of 'plasma'. I was looking for a book that I believe I left at the job site in Flagstaff, Welding Handbook Volume 1, 'Welding Science and Technology' (it may be Volume 2, 'Welding Processes'). If I remember correctly, it has a simple explanation and definition of the process establishing a plasma stream and what it's function is as pertaining to the welding processes. And believe me, SIMPLE is good for me. I don't have the scientific and/or engineering background of Electrode.

I will see if I can contribute anything further that would expand this conversation when I can review the book. Of course, it will only be to make it more simple in understanding, which may be necessary to help build a foundation upon which to build the more complete and deep explanations.

Have a Great Day, Brent

By electrode (***)

Date 12-10-2012 08:48

welderbrent,

thank you. I, actually being the most secondary important person in this whole subject, feel nonetheless privileged reading your kind comment.

Further: "...which may be necessary to help build a foundation upon which to build the more complete and deep explanations.".

This is very well said, very well.

I hope the questions will come, from the young and eager for knowledge lady.

By welderbrent (*****)

Date 12-10-2012 17:21

She definitely is an 'information sponge' attempting to soak up all the information and knowledge she can from Lawrence and all participating here.

My book has yet to give me the information in the format I was expecting. It must be somewhere else. Hopefully, maybe with Lawrence's fine help, she can dig into your answer and see how the plasma stream works and then apply it to her two different welding processes.

Maybe this will help some: "Arc plasma. A gas that has been heated by an arc to at least partially ionized condition, enabling it to conduct an electric current." AWS A 3.0

"Ionization: production of ions: a process in which an atom or molecule loses or gains electrons, acquiring an electric charge or changing an existing charge"
Microsoft® Encarta® Reference Library 2004. © 1993-2003 Microsoft Corporation. All rights reserved.

So, what starts the process? The electric arc which when initiated heats the gas from whatever source to where the ionization process begins. With the continued arc a plasma stream is created which carries (conducts) the electric current. When this is done with SMAW our plasma stream is from the electrode to the work (not necessarily in direction, just in reference to the two points involved). This heat also melts the electrode and creates the gas shield from the flux and protects the plasma stream as well as the weld pool from atmosphere. The plasma stream not only conducts the electric current across the gap but carries the metal particles in a gaseous state from the electrode to the weld pool.

Now, maybe, from my limited perspective, a speculation as to our all elusive 'WHY' when it comes to why one penetrates more on EN while the other penetrates on EP.

Our plasma streams are produced from different gases, one from the gases supplied for shielding being GTAW/Argon, the other from gases from the flux of the electrode being SMAW. Besides the fact that the GTAW is going to have a finer concentration of arc in the first place (which doesn't really matter since we are comparing it to itself and not to SMAW) we need to find out how the gas supplied that contributes to the plasma stream affects the width of the plasma stream and thus the arc width. The narrower the width the deeper the penetration, while a wider stream will spread the heat out over a larger surface area and give us less penetration.

To keep this short, I would then conclude that it is probable that the streams are different because of the variations in gas supplied which will amount to many variables in electrons, atoms, ions, inoization and so on. Thus, one is creating a narrow plasma stream while being used on EN while the other creates our narrow stream while being used on EP.

And while I still believe there are other considerations, I hope this sparks more conversation as to my thoughts and how our discussion of plasma, with all of it's technical terms that Kara wanted to know more about, relates to the 'why' originally asked by Lawrence.

Am I headed the right direction? Let's get some more educated people involved here (more educated than me, not than all other posters). Does my reasoning make any sense? And maybe someone else already headed this way and I just missed it. I know too that I have left much out and am grasping at a conclusion without presenting all the support data. But hopefully the wiser amongst you can let me know if I am on track.

Have a Great Day, Brent

By electrode (***)

Date 12-10-2012 21:23

welderbrent,

another considerable post from you.
I nonetheless must admit something.
After trying to review all what's been written and suggested here I can find myself somewhat dizzy.

I also seem finding this thread attended by a very few remaining individuals in the meantime - the atomic nucleus so to speak.
Perhaps due to the fact that it's content may really have become confusing rather than enligthening.

Perhaps it's really high time now to finally focus on answering the original questions raised by Lawrence, viz.:

- "Why does SMAW have greater penetration with EP vs GTAW having greater penetration with EN?"
- "The main thrust is why the difference in penetration between the processes as it relates to polarity?"

I dare to suggest that the answer is the essence of all comments and assumptions stated as yet.
However, on the other hand we should wait for "ssbn 727", as he was mentioning to post soon.

I will keep quiet now, waiting for Henry's comments and then I'll make my own personal estimation - if this makes even any sense.

By Lawrence (*****)

Date 12-11-2012 12:47

Just so you know Diesel does more than ask questions...

Below is a little grinder rack she built for me last week.

We have been having troubles with students removing guards or putting improper/unrated wheels on grinders.

The solution is to hang them in the open with *pictures* of how they should look... I don't think I can be any more clear.

But she did some nice crafty work on this one... I showed her a picture of something I saw that I liked and she fabricated exactly what I needed..

By electrode (***)

Date 12-11-2012 12:59

Lawrence,

seeing your awesome post makes me breaking the silence.
Hence, no other comment from me than citing "RonG" who was saying:

"...Hands on people are some of the best Engineers."

Nothing to add on this.

By Lawrence (*****)

Date 12-11-2012 14:28

Oh I'm with Ron G

Just gotta fill her with confidence...

We have one recent Ferris state grad from my program and another accepted just now.

Both females!

By electrode (***)

Date 12-11-2012 14:40

And so am I - that is for sure.
I was already supposing you to do your job very well - and I can learn; obviously I was right in my assumption.
The male students seem required to gain momentum vs. the female in order to somewhat balance the relation again.