I was shocked (welding)

I had always heard that welding with the electrode positive gives the best penetration because the heavier ions bombarding the workpiece impart more kinetic energy than the lighter electrons do when welding with the electrode negative.

Dan

(lots of other source of information snipped)

FWIW, I took a welding class this summer; most of the material was from Hobart tapes. According to them (and the instructor, who has several decades of experience) DCEP is hotter and gives deeper penetration; DCEN gives less penetration. Also, you use the right polarity for the rod: we were using E6010, which is specified for DCEP.

That source is describing GTAW (TIG), not SMAW. Go back a couple of pages in the article to

I've got no experience with TIG so I'm in no position to say whether it works the same as SMAW or not.

Basically when the work is positive the work becomes the hottest part of the circuit and penetration of the base material is highest. When the electrode is negative the electrode becomes the hottest part of the circuit and metal transfer is highest.

At least that is the way the welding companies seem to describe it.

While I admit it is a very personal observation I believe that anything the Wiki says should be taken with a very large grain of salt.

Bruce in Bangkok (brucepaigeATgmailDOTcom)

What you are confusing is the difference between TIG and SMAW. In TIG you are ONLY dealing with the current flow. In TIG, DCEN has HIGHER penetration than DCEP because in DCEN more of the heat is flowing in the direction of electron flow.

Electrons are negatively charged and flow from Negative to Positive.

In SMAW you are dealing with a FLUX coating which changes the arc entirely. With DCEP more of the electrons are flowing back at the electrode tip, from the base metal, but this means the flux burns hotter, making it more active and aggressive.

With DCEN on SMAW the flux is less active so the arc is not as hot.

Sounds like the courses I took at Los Medanos Community College. Instructor was Andres Ochoa who was 71 at the time and had been welding since he was 15. His brother Jesse taught there too. That guy was GOOD. I guess he should be after welding for over 50 years.

Wayne

Bruce, what you are describing here is the same thing in both instances. In one instance you have the work positive (which makes the electrode negative) and in the other instance you have the electrode negative(which makes the work positive). I'm sure you didn't mean it this way.

Jim

"Jim Chandler" wrote: Bruce, what you are describing here is the same thing in both instances. (clip) ^^^^^^^^^^^^^^^^ As in, "Heads I Win--tails you lose."

With EP (electrode positive, or reverse polarity) it provides deep penetration on the workpiece. (Which concurs with the Miller reference and the Wiki article.)

How can that be, one might ask, if the electron flow is towards & impinging on the electrode?

What you need to understand is a basic principle of electricity, and that is current flow is opposite electron flow. So if the electrons and flowing towards the electrode, the current (AMPS) flow is towards the workpiece, resulting in more heat at the workpiece.

Most folks understand the concept of electron flow, but get stumped on current flow.

Tony

The physics of electricity doesn't care about the flux or welding process. Flux won't make the arc hotter or cooler. It only shields the weld puddle.

Right. In TIG you are only dealing with current flow. The tungsten does not melt. In SMAW you are dealing with current flow and the melted metal from the electrode. So in SMAW all that heat that went into melting the electrode gets transferred to the base metal. Plus the ions are heavier than the electrons and they are flowing the opposite direction from the electrons.

Dan

Not exactly. The flux also helps the arc. Most obviously in AC rods where the flux contributes a bunch of ions that keep the arc from extinguishing as the current goes thru zero. So the flux promotes more ions and that makes the arc different.

Most of the time when we think of electricity, we only need to consider electron flow. In metal wire electrons are easily stripped off from the metal atoms and move in response to the field. However in a semiconductors we need to consider hole flow, which is in the opposite direction of electron flow. And in plasma ( ionized gas ) and in electrolytes current is by both electron flow and ion flow.

I used to have this argument when I was in the Navy, where they tried to convince me that current flowed from negative to positive.

Dan

well the Navy had it right. You don't necessarily have to understand why it works that way, just accept it and get your welding job done :^)

I don't know the actual reason DCEP gives deeper penetration, but I'm confident that's not it: the only reason the conventional direction for current flow is opposite the direction of electron flow is that the mechanism of current flow wasn't known when the flow was discovered. They had a 50% chance of getting it right, and got unlucky -- and by the time electrons were discovered, the convention was too firmly established to change. The only thing that "really" flows is electrons.

Hmmm.... here's a possible mechanism: the arc is a plasma. With DCEP, the voltage differential across the arc will tend to draw the positive ions from the rod toward the work, so they'll hit with some inertia. With DCEN, you don't have that; if anything, the ions are repelled by the workpiece.

Ummm...WRONG. The flux generates a shielding gas. The type of flux determines the content of that gas shield. Cellulosic rods inject CO2 and Hydrogen into the arc, boosting the arc temperature way up.

How long have you been welding?

In comparison I have about 25 years of welding and 15 years of teaching welding.

If you think the flux doesn't affect the arc, try stick welding with no flux.

Ernie,

we are suitable impressed with your resume, but I'm not going into my backround to avoid a battle of the nerds.

All rods containing a 0 or 1 as the last digit of the designation i.e. 6010 contain cellulose. And you will notice, the specification for these rods is DC+. It's the DC+ current that is doing the work and providing deep penetration. If you think some kind of exothermic reaction is occuring to heat up the weld, as if the flux even contained nitrocellulose, the added effect would be minimal compared to the current crossing the gap.

Flux does affect the arc, but it provides shielding, stabilizes the arc by providing an electrical pathway, & protects the weld puddle from contamination. Various gases, whether supplied as inert gas (argon/co2/He) or products from flux decomposition in SMAW, have different electronegativity values and valance electrons, and can affect the heat of the arc to some degree. But still the EP/EN thats directing the direction of the current.

Lets all use AC and call it even :^)

Tony

I had my ah-ha moment when I was working on electronic circuits such as pnp or npn transistors, and the concept of how current flow was opposite electron flow became apparent, and how the same concept was related to welding.

Tony

I wrestled with this for a long time learning to weld. Then, I realized that + and - were the keys. Stinger + is MORE (plus) penetration. Stinger - is LESS (minus) penetration. And still, referrals to straight and reverse confuse me.

SSN, or social security number = Straight Stinger Negative, and from there, it takes me about thirty seconds to get it straight in my convoluted mind.

Steve

Then in your universe 6010, 6011, and 6012 all burn the same because they all run DCEP. You are categorically wrong.

6012 is mild, 6011 is aggressive and 6010 is incredibly hot. The only difference is the flux coating.

BTW you can run any rod DCEP, just some work better than others.

7014 and 6013 run fine in DCEP and they are very low penetration rods.

Same polarity, same amperage, and a lot lower arc heat.

Your belief that the flux has little affect on the arc is just wrong.

Theory is a lovely thing, but I think you are making some HUGE assumptions.