DCEN, DCEP ..

I have always always always only ever stick welded using DCEP. It works just like I expect it to. I recently learned that in the modern parlance this is called "reverse polarity". I have also heard that if you want less penetration, you can go to DCEN, confusingly (to me) called "straight polarity". I have two questions. First, is everything I wrote above technically correct? DCEP means more penetration?

My second question is more to do with the terminology. Why is DCEP which is what I believe is mostly used everywhere called reverse? When I hook it up, it's "red on positive black on negative" which is consistent with a whole lot of things, what is backwards or reversed about it?

I've been wondering this for some time now but have hesitated to ask for fear of looking dumb. Oh, well, there's a difference between stupidity and ignorance, the latter is curable with a little perspicacity (hard work).

GWE

Reply to
Grant Erwin
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IMO, what you have said is correct for stick but there may be some rod/workpiece combination where it isn't.

I have wondered about the straight/reverse polarity designation. Perhaps it is because the current in an electric circuit is electrons and they flow from negative to postive which would be rod to workpiece. If you make the electrode positive then the electrons are flowing from the workpiece into the rod which is "reverse". Just my guess! Billh

Reply to
billh

If I recall correctly, one of the primary differences between DCEN and DCEP is the point in the circuit where the majority of the heat is generated. One of them produces 70% of the heat in the workpiece and

30% in the rod, the other was the reverse.

Which is which, I do not recall...nor am I completely confident in my memory of the distinction. How's THAT for useful information? ;-)

Dan

Reply to
Dan B.

DCEN gives greater penetration, DCEP is shallower.. Think of the electron velocity and flow from the electrode to the work in either case...

Reply to
Rick

Don't think most would agree with this latter point...

Reply to
Richard Smith

parlance

polarity".

correct?

either

Please elaborate-I may learn something...

Reply to
Rick

Hi all

I was here at this point in November 2003

Here is the thread as it can be seen at Google

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Thread title was "cellulosic -- DC-ve (DCEN) or DC+ve (DCEP)"

Furhtermore, it is reputed that MIG is massively more penetrative on DCEP than on DCEN... See

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things are not so straight-forward...

You run "straight polarity", DCEN, with TIG. Other elecrical devices are "straight-polarity", DCEN - X-ray tubes and thermionic "valves". TIG DCEN, you do get more heat at workpiece than at the electrode. And it all works as you would expect. But I was stood corrected that with a consumable electrode and a complex welding system with metal in the arc, fluxes, and/or whatever makes the difference, DCEP is more penetrative.

Am thinking - really do want to "scientifically" try welds DCEP and DCEN and measure bead size, time to run the rod at current (depostion rate), and the penetration. Would be good to show this for real...

Richard Smith

Reply to
Richard Smith

parlance

polarity".

correct?

either

I suppose I should have typed "to and from". One of those cases where I know what I mean, but others may not, lol...

Reply to
Rick

Rick - posted separately in response to other mesg. in thread. Hopefully you will find the info. and links you want there. Despite being a scientist, I don't know a convincing explanation why things are the way they are. Regards Richard Smith

Reply to
Richard Smith

/239670e7a9bab0b1

devices

(depostion

Interesting. The three welding books I have indicate otherwise, but I stand corrected...

Reply to
Rick

I think that this would make for a perfect sci.engr.joining.welding experiment. Someone could run a butt weld bead with DCEN and DCEP and then do some cutting and comparison of penetration. That someone could even be me, but I'll have little welding time for the next few days.

i
Reply to
Ignoramus1729

I am not familiar with MIG, so I looked it up in one of my reference books. You are correct, it is the opposite of the TIG process with respect to polarity/penetration..

Reply to
Rick

Rick

I suppose in TIG it is the "pure" situation where things work as you expect - the electrons pull off the -ve pole tungsten, accelerate across the gap (well there is Argon there, as a plasma, but nothing else), and "slam" into the +ve pole workpiece, releasing a lot of heat into the workpiece, and yes, it is penetrative in welding terms.

But beyond the "simple" situation of TIG, things simply don't work that way.

RS.

Reply to
Richard Smith

Despite

reference

I just did a quick run of 1/16" 6013 on both polarities, and DCEP did "seem" to go deeper. Indeed, the chart I have for covered electrodes shows the two deepest penetrating electrodes to be used with reverse polarity also.

I suppose in simplistic way we could imagine more electrons being emitted by the work surface, leaving a bigger hole for the molten electrode metal to fall into, lol..

Nice to have learned a little something today- it will be interesting to see what the more experienced people have to say.

Reply to
Rick

Why not? Straight polarity (DC -) provides the highest electrode current capacity, and the deepest penetration potential. Reverse polarity (DC+) provides a shallow wide weld pool.

The electron flow to the weld ensures that the most of the arc heat is on the positive side of the arc. In the case of DC- the positive side of the arc is the work piece. This means the work piece receives the most energy, thus deeper penetration. Remember electron flow is from the negative to the positive. Approximately 2/3d's of the weld heat is on the positive side of the arc.

And that's the truth, and I am sticking with it.

Reply to
Diamond Jim

I, too, had the hardest time learning these things about polarity. Finally, I learned that if it had a + positive designation, that it had more (+ means more) penetration, and if it had a - minus designation, it meant less penetration. Then, came straight and reverse polarity. I remembered it this way, USN, or U S Navy, and it was Straight Stinger Negative. Straight polarity was stinger negative.

Then, I welded with 6011 for years as repairs for wrought iron field welding, before I discovered HERE that it was only a DCEP rod!. Well, it works fine as a electrode negative rod when you use the 3/32" rods, and maybe only because it is it is for the smaller rods. The larger rods might not burn at all.

But, I share your confusion about plus and minus and straight and reverse, until I just calm down and look at the plus or minus and the straight and reverse.

It is getting easier, but I still have to stop and think. I have no clue why they didn't come up with something simpler.

Steve

Reply to
SteveB

"Rick" wrote

Whaaa? 7018 is a shallow penetration rod? I guess that is why it sits up there so even and pretty.

I don't have a clue what you mean about electron velocity.

Is that Vulcanese or Klingon?

Steve

Reply to
SteveB

"Richard Smith" wrote

Boy, I am glad I don't understand it, just know how to do it.

Steve

Reply to
SteveB

So, I guess it amounts to: do you want your filler metal to be cold or hot. One way the rod is the hottest, the other way, the work is the hottest.

But wait, what if the work is 4 times the thickness of the rod? Or eight times? Doesn't that absorb and diffuse more heat because of the mass when it is the positive side of the equation?

Now I'm really getting confused.

Steve

Reply to
SteveB

Straight and reverse is old terminology that hopefully be abandoned one day. I remember straight by picturing in my little mind small minus signs leaving the electrode holder. ( straight lines ) I suspect that the ionisation of different materials between the electrode and surface has an effect. We are dealing with inert gas, carbon dioxide, nitrogen, oxygen and ionised metal particles. I would think that there would be a multitude of variables here. Randy

I, too, had the hardest time learning these things about polarity. Finally, I learned that if it had a + positive designation, that it had more (+ means more) penetration, and if it had a - minus designation, it meant less penetration. Then, came straight and reverse polarity. I remembered it this way, USN, or U S Navy, and it was Straight Stinger Negative. Straight polarity was stinger negative.

Then, I welded with 6011 for years as repairs for wrought iron field welding, before I discovered HERE that it was only a DCEP rod!. Well, it works fine as a electrode negative rod when you use the 3/32" rods, and maybe only because it is it is for the smaller rods. The larger rods might not burn at all.

But, I share your confusion about plus and minus and straight and reverse, until I just calm down and look at the plus or minus and the straight and reverse.

It is getting easier, but I still have to stop and think. I have no clue why they didn't come up with something simpler.

Steve

Reply to
R. Zimmerman

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