[nova_70_383]

need to clear up some confusion. can some one explain electrode positive, electrode negative. wich one is reversed and staight. also wich way current flows for each. thank you in advance.

[Greg From K/W]

Electrode Negative is when the whip or the electrode is charged with a negative polarity. The ground from the machine carries the power to the work piece in that instance. Essentially the power would go from the work to the electrode.

Electrode Positive is when the whip or Electrode would have the positive charge from the machine. The ground from the machine carries the Negative side to the work piece. So the power goes from the electrode to the work. I think that is the easiest way to explain it and I know that someone else may have more or better info but that is my stab at it.

[GWD]

Electron flow is always from negative to positive.

Here is an explanation from Miller. It is mainly about TIG but applies to SMAW as well.

Direct Current Electrode Negative (DCEN) is also sometimes
called straight polarity. DCEN is used while welding steel, stainless
steel, copper, titanium, gold, and pretty much any other
material that can be welded with the exceptions of aluminum
and magnesium, which are welded using AC.
The torch is connected to the negative terminal of the power
source and the work lead is connected to the positive terminal.
Power sources with polarity switches have the output
terminals marked electrode and work.
When the arc is established while welding in DCEN, electrons
flow from the negative electrode to the positive work piece. In a DCEN arc, approximately 70 percent of the heat generated
by the arc occurs in the work piece — thus you can use a
smaller electrode, as well as a smaller gas cup and reduced
gas flow. The more concentrated arc allows for faster travel
speeds. This concentrated arc also accounts for the deep penetration
when using DCEN for TIG welding.

Direct Current Electrode Positive (DCEP) is also known as
reverse polarity. Welding is not typically done with DCEP.
When using this polarity, the electron flow is still from negative
to positive; however, the electrode is now the positive
side of the arc and the work is the negative side. About 70 percent
of the heat of the arc is focused on the positive side of
the welding arc. On DCEP, 70 percent of the heat is focused
directly on the tungsten, which creates a large ball on the
tungsten. For welding with DCEP, a very large tungsten is typically
needed. Between the large tungsten and the nature of a
DCEP arc, the arc can be very erratic and quick to wander —
which is the main reason that this polarity is typically undesirable
for TIG welding.

[nova_70_383]

so if all this is true, why do they recomend dcep on the rod box? wouldnt dcen keep the heat in the work instead of the welding rod? dcen is reverse polarity correct?

[GWD]

Yes, DCEN is reverse polarity.

You want the heat in the work normally. Some people even pre-heat certain carbon steels (and other metals) first to make sure there is adequate penetration.

Read the Miller discussion again and it will be clear why DCEN is the preferred polarity choice. There is much more information from Lincoln and Miller if you do a Google search.

[Ultralow787]

Yes, DCEN is reverse polarity.

You want the heat in the work normally. Some people even pre-heat certain carbon steels (and other metals) first to make sure there is adequate penetration.

Read the Miller discussion again and it will be clear why DCEN is the preferred polarity choice. There is much more information from Lincoln and Miller if you do a Google search.

GWD, You just contradicted what you posted from Miller above. It is easy to do! This terminology of "Straight" and "Reverse" is something the welding world created. You never hear these terms anywhere else.
I would personally prefer that the terms DCEP and DCEN were the only ones used, but that is not likely in our lifetime!

The explanation regarding where the heat is concentrated makes good sense and is easier to comprehend. DCEP is used quite often (depending on the rod and application) when SMAW welding to provide a deeper penetration of the weld into the work, but not very often with GTAW.

[GWD]

Right you are. Dam(n). That stuff drives me nuts.

[lazerbeam]

DCEP-reverse polarity-used for almost all DC SMAW (stick welding) because the electrode is consumed.

DCEN- straight polarity-used for almost all DC GTAW (tig) because the electrode is not consumed.

Straight and reverse are confusing terms that are finally being left out of a lot of welding literature. After all electricity flows in a circle. Always going from negative to positive.

[harleyotto]

why do they recomend dcep on the rod box? wouldnt dcen keep the heat in the work instead of the welding rod?

[Ultralow787]

I've actually been doing quite a bit of research into this subject lately. I have read everything I can find on the subject and the consensus from the experts at Lincoln Electric is that:
1) When it comes to SMAW (Stick), DCEP (Reverse Polarity) gives you the deepest penetration. DCEN is only recommended for welding on thin materials. With DCEP, heat is concentrated at the work piece. It is a forceful digging arc.
2) When it comes to GTAW (TIG), DCEN (Straight Polarity) gives you the deepest penetration. 70% of the heat is at the work piece, and 30% at the tungsten electrode. Because of this, you can carry a lot higher amperages at the electrode (1/8" tungsten can carry 400 amps).

I have not found a "simple" explanation for this. There is a section of the Lincoln Electric textbook that is called "nature of the arc" that tries to describe this phenomenon, but is difficult to follow. From what I can gather, it has something to do with the way Ions and electrons are exchanged between the material and the electrode. With GTAW, there is no metal transfer through the arc between the electrode and the work piece. There definitely is metal transfer through the arc when using SMAW.

If anyone can explain this better, I would love to hear it!

[weldprof]

The AWS tried, for the most part, years ago to eliminate the terminology "Reverse" and "Straight" Polarity. Welders (operators) have not let go of the terminology. There is much correct information on the responses to the question. The important fact that I either missed or was not discussed was the "CONTROL" factor. Because 70 percent of the heat is located at the point where the negative electrons bombard (the positive) electrode in the case of DCEP. This in turn allows the welder (operator) to have more control for 'out-of-position welding. IF the work is positive and 70% of the heat generated at the work, control would be much less. The metal of the filler rod and the parent metal would be at the highest temperature and the welder (operator) would have a difficult time controlling the puddle. Gravity would pull the weld pool down and making a quality weld would be non-existent. By moving the arc closer or further from the puddle the welder (operator) can control the heat input to some degree (in SMAW, DCEP). In GTAW welding the electrode is a non-consumable electrode, therefore the operation must be done in DCEN to preserve the electrode. Alternating current can also be used for non-ferrous materials. Books have been written on this subject and what I have written above is nothing more then an abbreviated version.

Weldprof

[mArc]

Hi, I'm new to the forum, and have been thinking about this exact topic.

Ultralow787 wrote:

I've actually been doing quite a bit of research into this subject lately. I have read everything I can find on the subject and the consensus from the experts at Lincoln Electric is that:
1) When it comes to SMAW (Stick), DCEP (Reverse Polarity) gives you the deepest penetration. DCEN is only recommended for welding on thin materials. With DCEP, heat is concentrated at the work piece. It is a forceful digging arc.
2) When it comes to GTAW (TIG), DCEN (Straight Polarity) gives you the deepest penetration. 70% of the heat is at the work piece, and 30% at the tungsten electrode. Because of this, you can carry a lot higher amperages at the electrode (1/8" tungsten can carry 400 amps).

I have not found a "simple" explanation for this. There is a section of the Lincoln Electric textbook that is called "nature of the arc" that tries to describe this phenomenon, but is difficult to follow. From what I can gather, it has something to do with the way Ions and electrons are exchanged between the material and the electrode. With GTAW, there is no metal transfer through the arc between the electrode and the work piece. There definitely is metal transfer through the arc when using SMAW.

If anyone can explain this better, I would love to hear it!

I haven't read the Lincoln Electric textbook, but I reached a similar conclusion.

SMAW relies on metal transfer through the arc.

With DCEN, the workpiece is positive, i.e. the power supply withdraws electrons from it. The electrode is negative, i.e. the power supply supplies electrons to it. I'm not sure what exactly happens in the arc in order to transfer electrode metal to the workpiece.

But with DCEP, I think I have a better picture of what happens in the arc. The power supply withdraws electrons from the electrode rod and supplies them to the workpiece. The electron withdrawal at the electrode ionizes the metal. The positively charged ions are then attracted electrostatically to the negatively charged workpiece, i.e. they are accelerated in the arc, towards the workpiece, and collide forcefully with it. Hence the good penetration.

My two cents...

By the way, the leads on my newly bought inverter stick welder are color coded for DCEN: positive and the workpiece clamp are red, while negative and the electrode holder are black. This is what confused me and lead me to this forum. If stick welding uses DCEP, why are stick welders color-coded for DCEN?

[Ultralow787]

mArc,
One of the confusing things about electricity and electronics is that in automotive work, we have been conditioned to see RED as Positive, and BLACK as negative.
When it comes to electronics, RED is often the negative, and BLACK is used for Positive. I have no idea why this is, but it makes things confusing for sure!

In my RV, WHITE is used for Positive and ORANGE is Negative on all the 12 volt DC wiring! In AC, white is always neutral!

I don't know whether this was the thinking behind colour coding on the welding machine or not.

[mArc]

Yes, I realize that color coding is not constant from one system to another. Here in South Africa, even single phase AC has two different color codes: one is for "behind the wall" (live=red, neutral=black, earth=bare or green-yellow), the other for appliances and extension cords (live=brown, neutral=blue, earth=green-yellow).

However, my point is this: my inverter welder has a black socket (negative) and a red socket (positive). The workpiece lead has a red plug, while the electrode lead has a black plug. Instinctively, I would plug black-into-black and red-into-red. But this gives me a DCEN setup. In order to achieve DCEP, which seems to be pretty much the norm for stick welding, I have to switch the plugs to the "wrong" socket. I suppose it's a remnant from the days when DCEN was seen as "straight" and DCEP as "reverse" polarity. The operator's manual makes provision for both, but doesn't explain them.

[weldin mike 27]

Hi there,

Don't forget the possibility the person who made it messed up. It happens. Sometimes if you think about things to hard you make a mountain out of a mole hill..

Mick

[martinr]

Interesting topic. Coincidentally, I've been doing some experiments on the very same topic today. As for the 70%/30% heat distribution and electron flow, I gave up on that a little time ago because the explanations seemed inconsistent and somewhat contradictory, and in the end I decided I didn't give a toss for the theory, half-baked or not, I would simply accept what happens in practice: TIG is electrode negative (except aluminium, which is AC), and SMAW/stick is either DCEN or DC+ve depending on manufacturer's recommendations based on flux coating (AC is used arc blow is a problem). (And you can watch the tungsten glow almost white if you flip and set the electrode +ve.)

Lincoln's book New Lessons in Arc Welding states (for stick electrodes) "The covering on the electrode designates which polarity is best and all manufacturers specify on the electrode container which polarity is recommended." A couple of pages later it states that currents around 250-300 amps are sufficient to cause arc blow on most jobs. So in the table of electrode type versus preferred type of current, for electrodes 7/32" and above are run on AC except for the EXX10 and the EXX15, which are both run on DC+ve.

For smaller electrodes they generally specify:

EXX10 DC+
EXX11 AC
EXX12 DC-
EXX13 DC-
EXX14 AC
EXX15 DC+
EXX16 DC+
EXX18 DC+
EXX24 AC


That said, where a rod will give a stable arc on both DC + and DC -, it's generally accepted that you will get greater penetration if the electrode is DC + over that with DC -. To test this, I did some tests today using Oerlikon Overcord Z which are a rutile-cellulosic rod classed as an E6013. Despite the box specifying AC or DC -, I found no problems with DC+. Welding vertically up, I struggled to find any obvious difference between DC - and DC+ using the same current (85A), so I ran 3 beads in the flat position at 120A (with arc force switched off): DC-, AC (squarewave) and DC+. I cooled the plate between welds and tried to keep speed and technique the same. I sectioned and etched the plate afterwards. There was indeed more penetration using DC+ over AC or DC-, but it really was nothing to get worked up about - I'd say marginal. The bead was a little flatter on DC+ than on AC or DC-. Finally, the crater at the end of the bead was concave with DC+, but slightly convex with AC and sligthly more convex with DC-. So, yes, there's more heat going into the job if the electrode is +ve, but to me it looks fairly marginal.

Martin

[Otto Nobedder]

Now, that is interesting!

I've used 7024 a bit, and always DCEN with excellent results. I've seen a newbie run it DCEP with dismal results. I'd never considered it as an AC-capable rod, as I've never seen it run that way.

I've only used it, and seen it, as a 1G only rod, and on DCEN, the slag always pops off on it's own, usually in long sections.

Thanks,

Steve

[martinr]

Hi Steve,
Some extracts from Lincoln's New Lessons in Arc Welding (note this is all about MMA only - NOT TIG), relevant both to the topic and your kind reply:

"With few exceptions, electrode-positive (reversed polarity) results in deeper penetration. Electrode-positive (straight polarity) results in faster melt-off of the elctrode and, therefore, faster deposition rates. The effect of different chemicals in the covering may change this condition. The high-cellulose covered mild-steel rod such as Fleetweld 5 is recommended for use in positive polarity for general welding. Some types of shielded electrodes function on either polarity, though some operate on only one polarity."

"Though AC itself has no polarity, when AC electrodes are used on DC they usually operate best on one specific polarity. The covering on the elctrode designates whcih polarity is best and all manufacturers specify on the electrode container what polarity is recommended."

"For proper penetration, uniform bead appearance, and good welding results, the correct polarity must be used when welding with any given metallic electrode. Incorrect polarity will cause poor penetration, irregular bead shape, excessive spatter, difficulty in controlling the arc, overheating and rapid burning of the electrode." (Page 1-38)

"The decision to use either AC or DC is based on which one will permit the operator to produce the best welds in the least time. Genreally speaking, AC is best when using iron-powder electrodes or when arc blow is a problem. DC is best for low-current or any application where arc blow is not likely to be a problem." (Pge 1-42)

"... It follows then that any AC electrode will work on DC, but that not all DC electrodes will work on AC" (Page 1-17)


I'd be tempted to re-write this last sentence as: It follows that any AC electrode will work on either DC straight or reversed polarity, and, in some cases, even both.

Regards

Martin

[Otto Nobedder]

Martin,

Nice summary. It reminds me just how much of this information my brain has lost over the years, through doing things by example and from long habit & practice.

I might have to find a copy of that book.

Steve

[martinr]

Hi Steve,

Well, if I had to choose between theoretical knowledge and practical skills, I'm sure I don't need to tell you which one I'd go for.

The Lincoln Foundation believes in getting the knowledge out and operates not-for-profit, so the book costs only $10. I'm in the UK and their books are so cheap that I was happy to pay the considerable shipping charges to get them. The other book I'd especially recommend is "Metals and How to Weld Them" - again only $10 for a hard-backed book packed with valuable info. You might remember, Jody recommended that book in one of his videos. (I also have the Lincoln Procedure Handbook of Arc Welding and their GTAW handbook. The Procedure Handbook is only $25; if anyone else were publishing it, I'd expect it to cost hundreds of dollars.)

http://www.jflfoundation.com/SearchResu ... w=5&page=1

By thw way, I found out today that the Lincoln Foundation in the UK does sell some of the Lincoln books, so for any UK person inteested, it'd be worth calling them first. (0114287 2401/1910)

Regards

Martin

[WerkSpace]

The Lincoln Foundation believes in getting the knowledge out and operates not-for-profit, so the book costs only $10.
http://www.jflfoundation.com/SearchResu ... w=5&page=1

The downside of these low cost books from the Lincoln Foundation is that they use UPS for international shipping.
I've had so many bad dealings with UPS that it makes me sick to think about it. I refuse to do any further business with them.
I find it astounding that most of shipping companies can get the job done at affordable rates but UPS still remains in business.
( For example; the book that was quoted above for $10 will cost me $56.80 US dollars to get into my hands via UPS.)
Now, how can a company like Amazon.com ship to me a similar book for $6.35 shipping fees and taxes?

[martinr]

I expressed similar frustrations about the cost of shipping by UPS to one of the sales team at The Lincoln Foundation, pointing out that the cost was a major disincentive to my buying the books, but it fell on deaf ears. I then realised that even shipping within the US was similarly exorbitant. I think James F Lincoln would not be too happy to know that you pay more for the shipping than the books. In the end, I bit the bullet; even factoring in the shipping charges, I was still getting the books for a fair price.

Martin

[martinr]

To reinforce some of the things said above, here's one other piece taken from the Lincoln book New Lessons in Arc Welding, Lesson 1.45, butt weld in pipe, horizontal axis, welding down, using Fleetweld 5P (E6010) DC+ , or a Fleetweld 35 (E6011) AC:

"DC (+) is normally recommended; however DC (-) (negative polarity) can be used for the stringer pass to minimize burn through and to reduce internal undercut. This polarity change is especially appropriate for thin wall pipe. Hot pass and subsequent passes should be run DC (+) (positive polarity). Running DC (-) on the stringer pass will not be harmful to either mechanical or matalurgical properties."


Martin
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