Thread: GP rod help!!

Hi Sam, without knowing what amps your running its a bit of a guess.

Knowing the characteristics of this sort of rod, ,I would say its down to the sloppy flux pool that the rod creates.

I would be using it, with the amp settings towards the top of the recommended amp range for this rod.

In addition keep your arc length extremely short.This stops the flux rolling under the molten arc and slag inclusions.Pictures if possible, will help a lot.

Grahame

Lincoln 6013 3.2mm rods from Gasweld $15 for 5kg, work alright for me at 140A DCEP on an inverter.

Attachment 139068

samham00,
I missed the comment on running them on electrode pos

Those GP electrodes are not suitable for running on electrode positive,

Swap the polarity around and you get a much better result.

Grahame

Thanks mate, those tips surely helped, I was running at the lower end of the range, and i think a shorter arc did help with the slag. And thanks for the polarity tip, just what i was after, cheers

Can someone clarify the electrode pos vs neg thing? It sounds like most of the time electrode neg is the go, but some specific rods prefer EP. But I've also heard you might also choose EP to change the level of penetration or heat in the work?

DCEP carries 2/3 of the heat at the electrode so melts the electrode before the job. GMAW and MMAW are usually DCEP.

DCEN carries 1/3 of the heat at the electrode so melts the job before the electrode. GTAW is usually DCEN.

That said there is always cases put forward in different circumstances to reverse polarity for reasons relating to penetration, control etc.

After reading Grahame's post on DCEN I gave the 6013's a go on DCEN and the slag pool was definitely a lot more controlled than on DCEP which meant you had a better opportunity to see the weld pool and manipulate it as required.

Originally Posted by RustyArc

Can someone clarify the electrode pos vs neg thing? It sounds like most of the time electrode neg is the go, but some specific rods prefer EP. But I've also heard you might also choose EP to change the level of penetration or heat in the work?

Mild steel electrodes -6012s,13s, and iron powder rods require EN,whereas low hydrogen groups plus stainless steel and nickel based electrodes run on best on EP.

It's all to do with the flux make up and the electrode application where in say, the LH electrodes the heat is a no,no and excess heat could alter the properties of the parent metal.

Its been a generally accepted notion that 2/3 of total heat build up occurred in the electrode and 1/3 in the work on EP. On electrode negative its the other way around.

Most of the electrodes will perform adequately on AC.
Amperage coupled with a shorter arc length has a greater effect on penetration.

A shorter arc length gives deeper penetration whereas a longer one will spread the arc wider and decrease penetration.The longer arc length increases heat input as it increases the arc voltage.

Inverter type welder machines run electrodes much better as they have better control of the arc voltage which forms and control the arc effect effects.Some machines have controls that allow adjustment of the voltage. DC output generator machines have had a voltage control adjustment for decades.
Does this help?
Grahame

Thanks Ben and Grahame - for all my Googling, I've been unable to find a simple, straightforward answer like that. Even last Friday when picking up a new welder, I asked the bloke at the counter, who was adamant that you *always* use EP.

One more question - might you change to EP when welding particularly thin material to reduce the heat in the work and avoid blow-through?

You could do that .

Remember with 2/3 heat in the electrode that you will be using small electrodes ( on very thin sheet) and the electrodes are going to get real hot, real quick.

There is a practical limit to how thin you can go down to.
I surmise you might have to get a bit creative and try backing your extra thin sheet with some copper sheet to avoid burn through.

What you are dealing with is 6000C of arc temperature which is has to be dissipated - cooled down very quickly.

On thicker material, the heat is absorbed into the surrounding volume and it operates like a heat sink. On thin stuff the heat can't be drawn away quickly enough and poof!!! you have a hole.

Grahame

Informative posts.
With GMAW (mig) welding we use electrode positive and with FCAW (fluxcore) electrode negative whats the theory behind this? Why? What happens if reversed etc..
While were on a roll, I thought it would be nice to know, now that i know the stick theory, cheers, Sam.

I've pondered this having just bought my first MIG welder that also does stick.

At the moment I'm using flux core wire, which means I can very easily swap between MIG and stick without changing any connections, but once I get hold of some gas, I'll need to change the connections around.

My half-arsed theory is that the flow of shielding gas with EP GMAW serves to cool the wire a bit?

As for my EP stick for thin material idea, I guess the best way to determine its viability would be to try it, but I'm guessing the rod will be burning up at a fierce rate

Originally Posted by samham00

Informative posts.
With GMAW (mig) welding we use electrode positive and with FCAW (fluxcore) electrode negative whats the theory behind this? Why? What happens if reversed etc..
While were on a roll, I thought it would be nice to know, now that i know the stick theory, cheers, Sam.

Just to throw a spanner in it....

Don't always use DCEN for FCAW, depends again on what the manufacturer recommends.

Originally Posted by samham00

Informative posts.
With GMAW (mig) welding we use electrode positive and with FCAW (fluxcore) electrode negative whats the theory behind this? Why? What happens if reversed etc..
While were on a roll, I thought it would be nice to know, now that i know the stick theory, cheers, Sam.

As far as I can work it out (coming from a bit of a physics background, more recently from a sparkie background and most recently a background of about 5 hours of trying to work out was going on with the crappy, narrow roapy beads when I forgot to change the polarity round after doing flux cored welding and changing back to gas ) it's all to do with electron flow.

When you have an arc struck you get a flow of electrons from the negative to the positive. When you are welding with gas and you are set up with the workpiece negative (DCEP), it has a larger surface area to emit electrons from (than the wire in the gun) and hence more electrons flow. More electrons on the move = more heat on the workpiece. Make the electrode negative and you have a very small surface area you are trying to emit electrons from hence the crappy cold welds that I had dramas with.

I'm guessing that the DCEN configuration for flux cored has to do with the fact that you need more heat in the wire to vaporize the flux to make the shielding gas and you don't want the negatively charged oxygen in the air oxidizing the positively charged tip of the wire while you are welding. Better to have the oxygen attracted to the positively charged weld pool that is being protected by the flux. That's a bit of a guess though...

Originally Posted by dalejw

When you have an arc struck you get a flow of electrons from the negative to the positive. When you are welding with gas and you are set up with the workpiece negative (DCEP), it has a larger surface area to emit electrons from (than the wire in the gun) and hence more electrons flow. More electrons on the move = more heat on the workpiece. Make the electrode negative and you have a very small surface area you are trying to emit electrons from hence the crappy cold welds that I had dramas with.

I don't think this is right. Current = electrons. If you have 70 amps you have a certain number of electrons per second regardless of direction or cathode surface area.

My understanding is that in an arc 2/3 of the heat is generated at the anode and 1/3 at the cathode. This is because the electrons fly off the cathode into the wild blue yonder and most of the heat comes from the electrons crashing onto the anode. But in stick welding (MIG too I guess) the heat distribution is then changed because the anode melts and the molten metal flies off towards the cathode taking the heat with it. When the metal hits the workpiece it generates more heat. So, DCEP melts the stick faster and therefore the workpiece less. DCEN avoids this and the extra heat on the workpiece promotes greater penetration.

Unfortunately this explanation disagrees with your results so maybe I've got it completely wrong. I generally use type 12 sticks and some like DCEP and others like DCEN so maybe the flux is the determining factor here.

Cheers,