Confused about polarity

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I am wondering why EP welding would penetrate better than EN. If the positive side of the arc produces the most heat it would seem to me that having the work piece positive would provide the most penetration.  There must be something else going on that I don't understand. How do most people determine what to use? I would think AC would work well in most situations. The more I play with my new welder...the more questions I have.
Reply:The negative is the stronger side. Don't hold me to this but I seem to remember about 70% is through the -. AC has it's strong uses as does DC.  Iron powder rods run nice AC, but thats about the only time I use it apart from ali.I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:The reason I am confused is that information on TIG welding says that the best penetration occurs when the electrode is negative,  opposite of information on stick welding.  When I use two carbon rods to generate an arc, the positive carbon rod is much hotter.
Reply:Originally Posted by TazThe reason I am confused is that information on TIG welding says that the best penetration occurs when the electrode is negative,  opposite of information on stick welding.  When I use two carbon rods to generate an arc, the positive carbon rod is much hotter.
Reply:Hi Taz, you have a good question.  The reason why DC- has more penetration is because most of the heat is on the plate or pipe instead of the Torch or Rod.  Tungsten has a melting point of around 6000 degrees and this is why the tungsten doesn't melt.  But if you flip polarity you will quickly see the tungsten burn up.  Because now the heat is on tungsten instead of the project.  But the reason why you switch to DC+ when stick because you want to be sure the heat is on the electrode to insure the flux melts into the puddle.  You can weld on DC- with stick but it is not recommend on most projects because it is easier to have porosity or other discontinuitys. If you go DC- with 6010 it can be a crude way of cutting metal.  Wirehunt is correct when he said that the heat ratio is about 70% to 30% depending which way the current is flowing. When it is on DC- 70% of the heat is on the plate, and 30% on your torch.  DC+ 70% is on the electrode and 30% is on the plate.  This is to insure proper flux breakdown.  AC on the other hand is a 50 50 heat ratio.  Someone else is going to have to explain why you do this on Aluminum I know it is for a cleaning action but I have little experience with Tig welding on AluminumHope this helps
Reply:Here is an old thread which goes into this subject pretty thoroughly:http://weldingweb.com/vbb/showthread.php?t=22308Regarding the cleaning action of reverse polarity on Aluminum,  the books say that the electrons leaving the surface disrupt any thin oxide coating which has formed. I've never seen a technically detailed explanation, but perhaps it's similar to an electrolytic cleaning action in which the oxide molecules are actually reduced to metal and free oxygen, and the oxygen blown away before it recombines nearby.Can anybody here either confirm or deny this as the proper mechanism?? Or, is the hard oxide surface literally just broken up and 'blown away"? Do the small bits become easily charged and get attracted towards the positive electrode, or repulsed by the negatively charged plate??  Maybe Alfred wants to go to a good library and research this???Last edited by Oldiron2; 12-17-2008 at 09:35 PM.
Reply:I thought the cleaning on AC tig was from the ionized gas molecules getting bombarded into the workpiece.  The gas molecules have an electron (or several?) ripped off when they get ionized. This make them positively charged.  When the AC cycle is in the electrode positive portion these molecules get accelerated towards the workpiece.  If you see an arc then you have (or had) ionized gas.  The light gets emitted when the electron snaps back into place.The degree in physics has an application after all!Dynasty200DX w/coolmate1MM210MM VintageESAB miniarc161ltsLincoln AC225Victor O/A, Smith AW1ACutmaster 81IR 2475N7.5FPRage3Jancy USA1019" SBAEAD-200LE
Reply:so electrons flow from neg to pos??
Reply:For Aluminum:According to The procedure to Arc welding book DC- provides no cleaning action.  Which is why it is really only recommended for machine welding.  Also that the plate has to  be extremely cleaned.  DC+ has the best cleaning action but also has a wide and shallow penetration.  It also says commonly used for root pass in pipe.  And AC is a happy medium which is usual preferred by both automatic and manual welding.@Loose07AC                                               50% 50%DC-70% work / 30% electrode electrode- / work+electron flows towards work DC+30% work / 70% electrodeelectrode+ / work-electron flows towards tungstenLast edited by Ryer; 12-17-2008 at 11:04 PM.
Reply:Taz:Don't try to re-invent the wheel or try to over-analize the process. Science has already figured those parameters out, use them. TIG on mild steel is DCEN. TIG on alum is AC for the most part, MIG solid core is one, flux core is the other. Read the box for what the stick rod wants to be fed (most likely DC+). O/A wants a neutral flame, unless you're brazing. CC is for TIG and stick, CV is for wire feed. Welding is very complicated without questioning the basics. Once upon a time I pondered everything, now I go by the science.9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:Originally Posted by Ryer  When it is on DC- 70% of the heat is on the plate, and 30% on your torch.  DC+ 70% is on the electrode and 30% is on the plate.  This is to insure proper flux breakdown.  Hope this helps
Reply:Opps ya im under the influence right now.  My mind says one thing and my fingers are saying another.  Thanks for the correction.
Reply:I am a little troubled by the vagueness of the inital question... Might have got clearer answers if you asked something process-specific.General Rule of Thumb: Whatever is "Positive" is getting the majority of the heat... Simple and easy to remember.For GTAW:I disagree that AC is 50/50 split.  That was the old technology - plagued with arc rectification and overheating.  Now, we have software to control almost every aspect of the wave form - Ramp up, Peak Amperage, Downslope, Background Amperage etc etc.  This software is also what allows for Pulsed GTAW.  As far as the balance positive/negative while using AC Hi Freq, that is up to the operator to adjust to his application or preference, and to the amount of cleaning required.Anything close to 50% on the positive cycle will overheat and melt the Tungsten.Last edited by Black Wolf; 12-18-2008 at 12:01 AM.Later,Jason
Reply:I guess i always thought electrons were supposed to go to - not the pos why  it diff from everything else dc? Or have i been missinformed this whole time about juice going from pos to neg?
Reply:Originally Posted by wirehuntOther way round Ryer. DC- is 70% on the rod.  Or maybe a better way to put is DC electrode - 70% blah blah.  And it's a great way to put a root in with the 6010, don't know about extra porosity etc because of it.  In fact I find that hard to believe.
Reply:Well I'm not here to argue, I'm learning most of this stuff and welcome all advise and tips.  I have very little experience using tig with ac.  I'm just dc- on mild steel.  But I thought that when using Ac with tig you run a larger tungsten to avoid it melting.Last edited by Ryer; 12-18-2008 at 12:39 AM.
Reply:Follow this link:http://www.millerwelds.com/resources...calculator.phpDC Electrode Positive is basically not recommended because you need a HUGE Tungsten to run any amount of amperage without melting.It's pretty straight forward.Plug in the numbers, and see for yourself.Later,Jason
Reply:Black Wolf, you are correct about needing a huge tungsten for dc+.  This book says you will need a 1/4 tungsten to run at 125 amps while only needing 1/16 at 125 amps for dc-.
Reply:Originally Posted by RyerBlack Wolf, you are correct about needing a huge tungsten for dc+.  This book says you will need a 1/4 tungsten to run at 125 amps while only needing 1/16 at 125 amps for dc-.
Reply:A thick maroon book right.  Ya best 36 bucks I ever spent.  Anytime I forget something there I pull this amazing door stop from the floor and it keeps my facts straight.  I would like to get into writing procedures one day.  But for now a job would be amazing.
Reply:Originally Posted by OMSLets get this straightened out.DCEN (DC-) STRAIGHT POLARITY, ELECTRODE NEGATIVE will provide approx 70% more heat to the work and approx 30% to the electrode. DCEP (DC+) REVERSE POLARITY, ELECTRODE POSITIVE  will provide approx. 70% to the electrode and approx. 30% heat to the work.Sorce: The Procedure Handbook of Arc Welding. The Lioncoln Electric Company.
Reply:Better add: I think I hope I'm right   the memoryI'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:Originally Posted by Loose07I guess i always thought electrons were supposed to go to - not the pos why  it diff from everything else dc? Or have i been missinformed this whole time about juice going from pos to neg?
Reply:You cannot explain how a picture tube works without accepting the fact that electrons travel toward the positive. Anyway I think that everything makes sense to me now after reading all this. Now we just have to find the  guy that first said the wrong way to  weld is "straight" and the right way to weld is reversed.
Reply:Originally Posted by Loose07I guess i always thought electrons were supposed to go to - not the pos why  it diff from everything else dc? Or have i been missinformed this whole time about juice going from pos to neg?Originally Posted by SupeFlow of electrons and the accepted flow of electricity (current) are two separate things.  Its best to keep them separate without going into the semantics of why they do it that way (I've seen some electrical engineers get into some pretty heated arguments about the whole thing).
Reply:Originally Posted by RyerA thick maroon book right.  Ya best 36 bucks I ever spent.  Anytime I forget something there I pull this amazing door stop from the floor and it keeps my facts straight.  I would like to get into writing procedures one day.  But for now a job would be amazing.
Reply:Let me first say that a lot of people get ripped off purchasing Lincoln Foundation publications.  the list price online is 25 dollars!!!!!https://ssl.lincolnelectric.com/foun...p?PID=16&cat=8
Reply:Well I dont feel ripped off, and I would pay 36 bucks for it again.
Reply:Short history lesson re: straight vs. reverse polarityThe names came about way back when electric welding was done with a bare wire electrode and nothing else. This was generally done DC electrode negative (straight polarity)....Greater deposition, better control, and higher quality running DC electrode negative. Electrode positive isn't real practical for most situations. Flux changes things a lot.Short physics/chemistry lesson (quite oversimplified): Electrons are negative. In an electric field (such as set up between the electrode and the workpiece in welding) the electrons are 'attracted' to the more positive side, as are any negative ions formed in the arc plasma. Positive ions are 'attracted' to the negative side. In the TIG arc, where the plasma consists almost solely of electrons and positive ions of the shielding gas (argon and/or helium, in general), the electrons transfer more energy then the positive ions, in major part due to the small size and mass. They can accelerate to greater speed, and they are the charge carrier in the metal, so they hit hard, regain energy easily when they lose it in collisions in the plasma, are less likely to lose energy in the plasma (than the larger, heavier, slower ions of the inert gas), and don't take energy from the metal surface to act as a current carrier (since they enter the metal to carry current and the ions need to get an electron from the metal, which takes energy)The positive ions are heavier. The cleaning action in TIG is mostly (but not entirely... See the AWS welding handbook) due to the mechanical impact of the heavy positive ions on the surface of the material (mostly relevant when welding aluminum, with its tough, nearly inert oxide).In stick welding, the shielding gas comes from the flux coating, and most fluxes provide a mix of positive and negative ions and a variety of deoxidizing compounds to clean the surface, and the balance of heat can be such that more heat from the arc goes to the positive side or to the negative side. The tip of the electrode sputters small drops of metal into the pool, and these drops carry a lot of heat to the work, so the heat balance of the arc is less important here. If more heat goes to the electrode, more metal sputters to the work, bringing the heat along. The flux can be used to add heat, as well.In both cases, a fair bit of the energy is carried as light radiation, some from photons released by recombination in the arc, and a good part due to black body radiation, since the plasma is very, very hot.
Reply:enlpck,  Thanks for that, I've just never thought (or cared) about how the finer details work.  But it was good to read this.I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.