Polarity Question

[diogenesNY]

Hey Y'all:

Noting that this question is solely restricted to stick:

DCEP seems to be the polarity of choice for most arc welding I have encountered. I have read the reasons and textbook explainations, and this seems to make sense as a default. When first learning to stick weld I played around with the AC setting on the Dynasty 200DX i was learning on (school welding lab).... didnt seem to work quite as well, but operator error most likely overwhelmed any real observational data.

Real question is this: in 'real world' terms, when would you _prefer_ to use AC or DCEN for welding? What kind of specific situations? examples?

Thx in advance
diogenesNY

[Sberry]

DCEP is the most widely used, some EN with sheet metal by some I never switch. For most new operators set it to EP and bust the knob off, relieves the temptation to keep fooling with it.

[thingy]

Well you left out dcep,which,is the only way to stick weld,,can't think of a reason to use ac or dcen instead of dcep,to stick weld with,[sure somebody will],but I can't,,maybe somekinda strange rod or something??thingy

[TEK]

Like Sberry said, some circumstances it will help. Like 6010 on thin stuff. Most times you wont ever need it.

[Blacksmith]

AC - nasty noisy welding, but gets it done.
DCEP - nice arc, use it 90% of the time.
DCEN - I don't have a MIG and sometimes need to weld thin/sheet metal.

[Hotfoot]

...and, for all those boys and girls in the Peanut Gallery who get confused by those tags...straight from the glossary on this site...

" Direct Current Electrode Negative (DCEN)-The specific direction of current flow through a welding circuit when the electrode lead is connected to the negative terminal and the work lead is connected to the positive terminal of a DC welding machine. Also called direct current, straight polarity (DCSP).

Direct Current Electrode Positive (DCEP)- The specific direction of current flow through a welding circuit when the electrode lead is connected to a positive terminal and the work lead is connected to a negative terminal to a DC welding machine. Also called direct current, reverse polarity (DCRP)."

[jerryo]

DCEP gives the best welding arc. It also gives the most penetration and the highest electrode melting rate. AC is nasty! Lots of spatter and noise. the arc actually goes out every cycle as the polarity goes from - to +. You need to learn to read the code on the welding rod to determine the correct polarity. The last # in the code in say E7018; 8 means that the rod should be used on DCEP or AC. Always use dc where possible for the best arc. Google -welding rod polarity- and you will find info on what polarity the last number in the code means. DCEP, used with the rods that are designed for it gives less penetration. The chemical composition of the flux coating determines at which polarities that the rod can be used.

[TRG-42]

Here is a cut and past from a previous post (http://hobartwelders.com/weldtalk/showthread.php?t=25630 )

First off you need to be careful to say which polarity has more penetration because polarity alone only tells part of the story. Electrode type is also a significant factor

However, you can make a general statement that states for stick electrode welding (not true for TIG and some self shielded flux cored BTW)

DC - has the lowest penetration
DC +has the most penetration
AC splits the difference

Where it gets complicated is different classes of electrodes can run only on certain polarities and different electrodes penetrate more than others

The common E6011, E6013s E7024s run very well on AC, DC+ , DC- so the rule above applies

If you are welding sheet metal the cats meow is E6013 (penetrates less than a E6011) on AC or DC –


Here is where it gets really complicated !

Most E7018s should be run on DC+ (but never –ve) or AC (generally not the best on AC)
E7018 “AC” rods should be run on AC and can be run on DC+ or DC – .

E6010 and E7010 etc should be run on DC+ and can run DC – for sheet metal work but never AC

Electrode Class Makes a Difference in Penetration

Try using a E6010 on DC+ on sheetmetal vs a E6013 or E6011

This difference if more radical than any polarity change could make



Where does the common misconception that DC is "cooler" come from

This stems from the fact that electrode that can run in AC and DC , the recommended setting on the welder is slightly higher amps for AC

Example ( copied from a Lincoln handbook ) : a 3/32 E6013

75 - 105 on AC
70 - 95 on DC +
70 - 95 on DC -

So, to the casual observer you would think since AC needs more amps, the penetration is more . This does not take into consideration the nature of a welding arc (that says with SMAW the heat is generated by the +'ve ions striking the cathode ( -ve )

[thinkharderchri]

DC+ or reverse polarity, is the most common process used as has been stated before. 100% of the structural welds I do I use DCEP because I get a more constant weld bead out of it. With any rod you can tell as soon as you strike an arc if the polarity is not on the right setting.

The only rod we use DC- with is 6022 witch we use to weld down decking, it blows right thru and as long as you do not have to build up the weld it is great.

[hankj]

DiogeneseNY,

One instance where you may need to revert to AC is if you encounter "arc blow", the common solutions (relocate the work lead, etc.) don't clear up the problem, and you have to get a bead in there.

Other than that, it's silly to use AC for steel.

Hank

[Brianstick]

Alot of those ol'timers out there are spoiled.All they ever want to weld with is DC.It's true that DC is a smoother arc, but it's still a good idea to know how to weld well with AC.

[thingy]

Seems like alot o young timers speak without knowing what they are talking about too,[yeah,I was young once too],,,,listen,if you can stick weld,,and yes,pass a test in all postions to become a "real welder",like us old timers,, using say dcep,you can stick weld using ac,,,you youngsters might not know this,but believe me its true,,,,but who would want to? thingy

[Brianstick]

Thingy, what i mean is if you go to your buddies house to help him with something and you need to weld something, and all he has is a lincoln ac225 welder,are you going to weld it with that or are you going to go all the way home to get your dc welder? For alot of people the lincoln ac225 is all they have.

[thingy]

Well of course thats what you'd use. You can do a fine job with an ac welder. And many just have an ac stick welder,and it does all they need,no argument there.

Its just this,many people who have never welded want to get them a little buzz box to patch things up with,,they know nothing about the equipement,they sell these ac welders everywhere,so a welder is a welder to them and that ones the cheapest,so they get it. What I'm trying to explain to those who don't know is for a little bit more money they can get an ac/dc one,which will run smoother and allow you to use every rod out there. When you are first learning you need all the advantages you can get,,using dcep instead of ac will maybe make your learning experience a little more enjoyable. thingy

[Brianstick]

Thingy, to get yourself into a ac/dc stick machine your looking at another $150.00 at least. And even then they usually only give you 125 amps of dc to use. For the occasional user a $150.00 more is not a "little more money".

[Sberry]

125A is plenty for most small jobs, I never really need more in almost all cases in a small shop. I think the 150$ is "only a little more" especially compared to so much consumer junk most people don't have a problem paying for, its a bargain.

[hankj]

I don't think there would be any argument with the statement that the welding machine found most in garages and barns around the country would be a red tombstone.

And, nobody said you can't weld with AC!

Still, if you have the ability to run DC reverse, what is the logic to run AC instead?

Hank

[Brianstick]

Yeah, i prefer dc too. But sometimes it's just not available.

[thingy]

Brian,yeah I know,money is tight,I've been broke more times than I've had money,I know,,but,,,my point is that many who buy a welder for first time don't know this [ac/dc thing],,and have the extra 150 or whatever it is,they just didn't know,so thats my point here,I'm not cutting anybody down who now has an ac only welder,you can weld most anything around the farm or home with ac just like with dc,,its just its easier to learn on the right equipment,,so,for you newbies out there who are planning on buying you a little stick welder,get you one that has dc as well,,maybe 50-60 percent duty cycle at 120-130 amps,[at least],,than you will be set,,northern tool has one in their catalogue,a hobart,for 419 dollars,free shipping it says,,,now a good drill /driver will cost you at least a couple hundred,so,,,,thingy

[Rocky D]

Well I guess the old Elder Weldor will have to enlighten some of you folks about straight polarity usage, since I just read all the post and nobody mentioned it....carbon brazing, is done with a sharpened carbon, (I like 3/16" arcair), for it...you use this process for galvanized sheet metal with silicon bronze wire. You start by sharpening the carbon in a pencil sharpener, slap it in your stinger, and away you go! I doesn't need much current, as I recall, to melt the SB wire.
Also for years I welded TIG on the old Hobart generator machines, left over from WWII. That was all DCEN. Straight polarity.

[6010]

one instance where AC works better is for welding on metal that is slightly magnetized. Where there is a lot of rubbing action involved, it think I read somewhere an example would be a grain elevator. This causes a lot of Arc blow. I have had to weld several times near a magnet and you can really tell the difference between AC and Dc. AC is changing polarity 120 times per second. Trying to weld something that is magnetized with DC is like trying to put two magnets together with like poles.

[txfireguy2003]

One benefit to getting the AC only machine aside from price, IMHO, is that once you learn on an AC only machine, you actually appreciate the DC machine. Plus, it's harder to learn with AC, so you learn a lot more control, thereby making you a better...."non-real" weldor.