Richard.
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Me tooI got the last bit at least
- Thread starter Farside
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Farside
Badly Welded Man
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I don't have a Fizzicist's Hat, but I've got a manky old set of Igorveralls...
When the electrons are flowing (that's like the start of a song)
from workpiece to rod or vice versa, there is a huge release of energy, almost akin to downing five cans of Red Bull and farting a rivet.
This engerly is leaping up and down, and every time it sleeps down it releases LICHT und NACHT STOFF which warns the cockles of the workplieces heart and cause it to meltiphore, at the same time making the dog blink and giving Mrs Jones from next door an all-over tan. Phowarr...
The
When the electrons are flowing (that's like the start of a song)
from workpiece to rod or vice versa, there is a huge release of energy, almost akin to downing five cans of Red Bull and farting a rivet.
This engerly is leaping up and down, and every time it sleeps down it releases LICHT und NACHT STOFF which warns the cockles of the workplieces heart and cause it to meltiphore, at the same time making the dog blink and giving Mrs Jones from next door an all-over tan. Phowarr...
The
DCEN has been discussed before on here a couple of times. I think only in the context of 6013s.
Some people seem to prefer it as it's easier.
I found it was better with thin stuff with 2mm rods. I never used it much with thicker rods.
Why not use a more appropriate process or thinner rods? I only had arc and 1.6mm rods are hard to get and nasty to use.
Worth remembering and experimenting with if you have a DC arc set.
Some people seem to prefer it as it's easier.
I found it was better with thin stuff with 2mm rods. I never used it much with thicker rods.
Why not use a more appropriate process or thinner rods? I only had arc and 1.6mm rods are hard to get and nasty to use.
Worth remembering and experimenting with if you have a DC arc set.
Hello chaps, and I must apologise to Farside for taking the thread off on a tangent, I do generally use DCEP as that seems to be the convention, as I said the book I have by A C Davies says the opposite and you would think in the 10th edition it would have been corrected by now.
I am still trying to figure out an explanation that I can follow, that is a bit Physic'y. If the answer is in the TWI site I can not access it as I can not get passed the FAQ's so if there is a technical paper I would love if someone could send me a copy of the text.
I did find the following on the Lincoln website
Polarity: the type of welding polarity used affects penetration level. With most arc welding processes, DC+ (direct current electrode positive) polarity produces more weld penetration, because more arc energy is focused into the base plate. Conversely, DC- (direct current electrode negative) polarity produces less weld penetration, because more arc energy is focused into the electrode and not into the base plate. This is the case with the Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW), Flux Cored Arc Welding (FCAW) and SAW processes (see figure 3). The exception is the Gas Tungsten Arc Welding (GTAW) process, in which the effect of polarity on penetration is opposite. With GTAW, DC- polarity results in more weld penetration (with DC+ polarity generally not used).
It does not tell me what this arc energy is and what I have found more confusing it has said there is most heat in the workplace on DCEP and threads on here for example Al saying there is more heat in the electrode to give more pen, so it is because of these differing descriptions, I am finding it confusing, it still does not stop me sticking bits together with metal glue'y stuff.
In fact that is where I have been tonight at college. During the day was ever so enthralling Safety Passport renewal.
What I will do if I ever find something myself that can explain why, and I instantly think OK yes understood, will post it in a thread on it's own.
Adrian
I am still trying to figure out an explanation that I can follow, that is a bit Physic'y. If the answer is in the TWI site I can not access it as I can not get passed the FAQ's so if there is a technical paper I would love if someone could send me a copy of the text.
I did find the following on the Lincoln website
Polarity: the type of welding polarity used affects penetration level. With most arc welding processes, DC+ (direct current electrode positive) polarity produces more weld penetration, because more arc energy is focused into the base plate. Conversely, DC- (direct current electrode negative) polarity produces less weld penetration, because more arc energy is focused into the electrode and not into the base plate. This is the case with the Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW), Flux Cored Arc Welding (FCAW) and SAW processes (see figure 3). The exception is the Gas Tungsten Arc Welding (GTAW) process, in which the effect of polarity on penetration is opposite. With GTAW, DC- polarity results in more weld penetration (with DC+ polarity generally not used).
It does not tell me what this arc energy is and what I have found more confusing it has said there is most heat in the workplace on DCEP and threads on here for example Al saying there is more heat in the electrode to give more pen, so it is because of these differing descriptions, I am finding it confusing, it still does not stop me sticking bits together with metal glue'y stuff.
In fact that is where I have been tonight at college. During the day was ever so enthralling Safety Passport renewal.
What I will do if I ever find something myself that can explain why, and I instantly think OK yes understood, will post it in a thread on it's own.
Adrian
I used to work for LincolnBut, bu , b. ....b,,, Now come on Al stop confusing me.
Adrian
and it says pretty much the same as I posted earlier (I think)
These to seem to be contradicting, to me at least, in one DCEP to get the heat in the electrode, in the other DCEN to get more heat into the electrode.
Adrian
They are years apart.........I obviously changed my mind......
I might NOT have written the Lincoln stuff........I cant remember. I did write a lot of stuff but Ive been left 6 years or so.
Ive just read up on it (AWS book) and my recent comments concur with that publication
I might NOT have written the Lincoln stuff........I cant remember. I did write a lot of stuff but Ive been left 6 years or so.
Ive just read up on it (AWS book) and my recent comments concur with that publication
Richard.
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obviously changed my mind......
Lol. Bloody metallurgist's do that a lot.
The other part that confuses me is where I see various articles talk about conventional current flow going from Positive to Negative, as in how we are taught at school, where as electrons go from Neg to Positive and the holes or nothings go from Pos to Neg, and I have got the impression some texts interchange these at will.
As I said not an issue, I just have this picture in my mind that in both cases the workpiece will soak heat away from the arc the same. But in DCEN, 2/3 heat goes into the workpiece to heat the metal and create a larger/deaper crator, that being the penetration, but the downside is you get less filler metal on top. Where as DCEP puts 2/3 heat into the electrode which burns off rods quicker giving more fill that sits atop the smaller workpiece weld pool. There being mixing in the creater/weldpool in either case.
It may be that the heat is transferred with the metal leaving the tip going into the weldpool this is putting more heat into the workpiece, but there is be the same total heat input Amps and Volts in both scenarios, so where is the extra heat to be more. As @Farside showed in the first post, there is very little difference in the pictures between his DCEN and DCEP in both height and penetration that I can see.
Still welding and still using the convention of DCEP and if I wanted to get deep root pen then 6010/6011 would give higher pen but because of the coatings. Would just need a machine that would run them.
Adrian
As I said not an issue, I just have this picture in my mind that in both cases the workpiece will soak heat away from the arc the same. But in DCEN, 2/3 heat goes into the workpiece to heat the metal and create a larger/deaper crator, that being the penetration, but the downside is you get less filler metal on top. Where as DCEP puts 2/3 heat into the electrode which burns off rods quicker giving more fill that sits atop the smaller workpiece weld pool. There being mixing in the creater/weldpool in either case.
It may be that the heat is transferred with the metal leaving the tip going into the weldpool this is putting more heat into the workpiece, but there is be the same total heat input Amps and Volts in both scenarios, so where is the extra heat to be more. As @Farside showed in the first post, there is very little difference in the pictures between his DCEN and DCEP in both height and penetration that I can see.
Still welding and still using the convention of DCEP and if I wanted to get deep root pen then 6010/6011 would give higher pen but because of the coatings. Would just need a machine that would run them.
Adrian
wheresmejumper
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I think the article I read had something along the lines of,more power/heat in the rod tip on ep,which burns with more force,and propels the molten particles towards the work due to the path of least resistance plus the magnetic properties of the arc and workpiece.
its the years of training
Liquid Metal
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I was always under the impression it had nothing to do with electron flow through the arc. I thought it was more to do with the gases invloved being ionised (turned into plasma) and traveling in the opposite direction and this giving the heat involved??
Maybe wrong tho, was years ago done the theoretical side of it lol
Maybe wrong tho, was years ago done the theoretical side of it lol
Liquid Metal
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^^^^^
Ionised with a positive charge that is, opposed to the negative charge of the electrons
Ionised with a positive charge that is, opposed to the negative charge of the electrons
Dimitri De Spiegeleer
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7018, welded twice with the same amps and travel speed, once DCEP, once DCEN.
So looking at that Dimitri, I assume the left with the plus sign is saying the rod was DCEP and - is therefore DCEN.
So slightly different profiles above and below the surface, the DCEN with a slightly deeper looking penetration, would be better for things like fillets. What I am surprised at is the higher build-up of deposit above the surface, that bit I do not understand?
What other variables are there with Amps and travel speed the same? How much one stuffs the rod in?
Adrian
So slightly different profiles above and below the surface, the DCEN with a slightly deeper looking penetration, would be better for things like fillets. What I am surprised at is the higher build-up of deposit above the surface, that bit I do not understand?
What other variables are there with Amps and travel speed the same? How much one stuffs the rod in?
Adrian
Sarto
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I think the coating does a lot, about the behaviour of the electrical arc.
As an aside, all the 7018s I tried so far (3 different brand, not a ton) on
dc+ weld well and smooth. On dc- instead they seem to stutter, weld with big
droplets.
As an aside, all the 7018s I tried so far (3 different brand, not a ton
) ondc+ weld well and smooth. On dc- instead they seem to stutter, weld with big
droplets.
Richard.
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Id expect to see increased cap height on DCEN as its more of a reinforcing polarity in the respect it lays material on rather than Penetrating deep, which brings in the confusion with that sample. The dcen also shows increased pen depth. I would say those haven't been done at the same speed or current or both because there should be similar amounts of weld metal deposit just displaced differently on the top plate line.
Please correct me if I'm wrong but they look like there was more variables going on.
Please correct me if I'm wrong but they look like there was more variables going on.
