Actually, I mean to ask "do 7018 rods from different makers feel different when welding?"
I've only welded with Lincoln 7018 (mostly 1/8") and recently at work I switched from Lincoln to Radnor (Airgas house brand) and I can't weld for shit - they keep sticking and I can't maintain the arc. At first I thought someone screwed up the welder but then I brought in some Lincoln 7018 1/8" from home in and I could weld again! :-)
So...was something wrong with the rod or was it me? Or is it just one of those personal preference things?
If someone blindfolded you and had you use 3 or 4 different makes of
7018 rod, would you be able to tell the difference?
Doesn't the % of metal powder in the coating on 7018s vary with manufacturer? I have certainly seen a lot of 7018 rod, and they do look slightly different depending on the mfr.
These differences have been a topic of conversation between welders in lunchrooms around the world for untold years. Everyone has their favourite brands. I have not heard as much complaint about varieties of hard wire but as for flux core it continues unabated. For some reason the difficult wires and rods always seem to be chosen by management because they are cheaper. Hmmm! It couldn't possibly be that the consumable has to be cheaper in order to move it off the shelves eh? I have uneasy feelings when I crack open a package of 7018 Esab but have found some of the nicest Esab flux core wire. Randy
I've only welded with Lincoln 7018 (mostly 1/8") and recently at work I switched from Lincoln to Radnor (Airgas house brand) and I can't weld for shit - they keep sticking and I can't maintain the arc. At first I thought someone screwed up the welder but then I brought in some Lincoln 7018 1/8" from home in and I could weld again! :-)
So...was something wrong with the rod or was it me? Or is it just one of those personal preference things?
If someone blindfolded you and had you use 3 or 4 different makes of
7018 rod, would you be able to tell the difference?
I find that AC E 7018 rods are prone to porosity just at the start. One has to be careful with arc height at start. Until I got used to AC rod every tack would have that porosity start. I was using them on a DC machine. Randy
I wonder if the difference could have to do, not just or so much with the amps, but with the voltage? I know I may be revealing my newbie ignorance here, but the symptoms described in the original post sound just like my experience trying to use some Forney 7018 AC rod on a
110v buzz box -- no matter how high I turned up the amps. That little buzz box had a very low OCV (around 50), and low voltage under load as well. My current machine (a 50-year old monster that I love dearly) has a much higher OCV (90), and a much higher voltage under load (I think around 36). This machine seems to run the 7018 and any other rod just fine, even in my relatively inexperienced hands. I think that most new machines have a somewhat lower OCV, and perhaps also voltage under load, than my old monster; I wonder if the difference between a rod running smoothly or not at all might be, say, the difference between OCV of 75 and OCV of 80, or something like that?
Okay ... but still the question remains whether the problem in question might have to do with voltage on a given machine. Since some rods are marketed as formulated especially for low OCV machines (including, IIRC, some special versions of 7018 rods), clearly there is some factor at work that has to do with voltage. Could the reason that one person is having trouble with one brand of rod versus another, while another person says they all run fine, be due to the first person having a machine that perhaps puts out just a bit less voltage (OC or under load, take your pick)?
The answer is a bit involved. Let's first address a basic transformer stick welder without hot-start and arc-force controls and move on from there. The ability to strike an arc is based to a large extent on the OCV of the machine (as long as the set amperage is within the proper range for a given size). Once the arc is established, the voltage between the electrode tip and weldment is the arc voltage and it is considerably less than the OCV. Now if the electrode gets stuck, and has a short-circuit, it becomes a function of how quickly the machine can clear the short, or possibly not at all and then you are left with yanking the rod from the work.I think machine slope comes into play at this point. If your machine were an ideal CC machine, then there would be no difference in current at an arc voltage of 0 or 20volts. Machines are not ideal though, and generally there is a current increase as the arc voltage decreases.This to a certain extent helps to clear the short. In order to further assist arc stability for the low OCV transformer machines, the electrode manufacturers add different compounds. I don't know what they are off the top of my head, but as you have noticed, most electrodes labeled as low OCV really do work better on a low OCV machine, then a regular (non- low OCV) electrode. Now if you have a new fangled inverter, you will note they have a hot-start feature and in most cases a 'dig' or arc-force control. Because the OCV of the machine is set in the design stage, and cheaper inverters can be made with a lower OCV, the concern became how to create a quality stick arc even if the OCV is low. Enter the hot-start. There are automatic versions (miller) and manual versions (thermal-arc). Basically because the OCV is already set, the way they achieve this is by increasing the amperage for a brief period of time (few to maybe 100msec). The manual controls allow you to set the amount of increased amperage as well as the time duration. So, that should get your arc started adequately. But what if you are a beginner, and continue to drag the rod, when you should be maintaining a seperation? Ah, well that is where the arc force or dig control comes into play. In miller's version, and I assume others to be similar, the amperage increases linearly as the arc voltage decreases below 19volts.The amount of dig is set as a percentage of the base amperage. Well this kind of sounds like the machine slope that I described earlier, right? Well if you look at any of the characteristic voltage/amperage curves for the inverter machines, you will see that the 'stick function' curve looks very much like a constant current machine. That is, there really isn't any change in amperage whether the arc is 30volts, or 0 volts. So to help the newbie welder with arc stability when he's dragging the rod (and shouldn't be), the dig function increase the amperage and clears the short. Now an experienced welder can take advantage of this. By whipping the electrode up, the arc voltage increases, the amperage goes down, and the weld pool cools. By swinging the electrode back in place, the arc voltage decreases, the amperage goes up, and you've got a hot weld pool again. Most people increase the dig function a lot for e6010s and to a smaller extent for e7018s. I hope this helps to explain your concern.
I didn't read this the first time around, sorry. I think a higher OCV helps to start the arc, but maintaining the arc is a function of both arc voltage and amperage. We all know that if the amperage is too low, regardless of the arc voltage, the rod will stick and not be stable. Likewise, a low arc voltage and a marginally low amperage may not be very stable either. So if your 'beast' had a sufficiently higher arc voltage for the same given amperage as the little transformer box, then it stands to reason the arc would be more stable. I'm trying to figure out how, though, the arc voltage would be higher for your beast. Could it be that if your machine is designed with a higher OCV, that your arc voltage for a given arc length will be greater as well? Did you measure the arc voltage at 36V, or is that a spec from your manual?
OCV mainly affects starts and to lesser degree weave. Common start is tap rod aginst work, hold arc a little long heating up rod and work to lesser degree then shorten arc starting to weld. With lower OCV have to adapt start without holding long arc. Have to tighten up way you weave with low OCV using no long arcs. Easy adaption depending on how you weld.
After reviewing most of the miller stick machines, it appears that they all support similar arc voltages for a given amperage. 27,28V for
200amps, 32V for 300amps, and 36V for 400amps. This would indicate that the arc voltage is based on the ionization potential of the shielding gas envelope, fluxing compounds of the electrode, and the nominal arc length. So the 'beast' in question probably has a specified arc voltage of 36V for a 400amp output. So for a straight transformer machine without hot-start and dig, I would say that OCV is a large contributor to the quality of the arc start.
I have the pleasure of several machines to choose from and two different wires on site. Quick summary: (flat, 3/32" wire, wire direct from oven at about 220F, padding, two beads before swapping wire, A36 plate, about 5 or 6"long beads- a full stick to the end of the flux)
Lincoln motor-generator (bullet) machine: Esab 7018 runs much better than Lincoln 7018MR. The machine has a nice soft arc characteristic and is very forgiving. Runs (faily) clean. The Esab wire lays a bead that self cleans- the flux peels itself off like 7024. The Lincoln lays a nice, smooth bead, shiney with hard ripples, but the slag is a bitch to get off, even with a wire brush on a 4 1/2" grinder. very adherant. No undercut with either.
Miller Synchrowave 350: Both rods are squirly. Stiffer arc, even with the machine in the softest position. Doesn't dig, but not forgiving. Unsurprising, given that his machine is optimized for TIG. The Rods run differently, but the Lincoln isn't that much tougher to clean on this one. Neither had particularly a better arc or easier control. Both left hard to clean areas aroung th HAZ. No major undercut, but a little with both. (I don't use this machine for stick usually-- don't have a good feel for it)
Hobart Megaflex 650 (I think it's a 650) in stick mode, arc force set at about 2, current at 85=ish amps (on the meter). The Esab wnd the Lincoln acted like on the bullet welder- Esab a little easier and self cleaning, the Lincoln with adherent slag and very smooth between the ripples. Arcs different, but neither particularly better- just different. Lincoln maybe flowed better, Esab maybe softer arc and easier fill on undercut?
Overall, a tough call. The rods are different, but not majorly. The primary difference being the slag cleanup and ripple. I wouldn't pick one over the other except for the cleaning. Again- note that the Lincoln was MR and the Esab wasn't. If both were or both weren't, the result might have been closer. There was a noporosity visible with the Esab, and a little near the start on the Lincoln on all of teh samples. I didn't section the welds, so there may have been no difference below the surface, and the difference may have only been due to the shinier surface on the lincon making this more visible. In the last several weeks I have run clean bends with both wires in several positions.
e (wondering if y'all can tell I have too much time on my hands, and thankful for the variety of equipment available to me. Total time to run all of these: about 1/2 an hour :)
Hey e, What was your voltage (or fine current) control set at on the bullet (lincwelder?)? I'm expecting that because you mentioned it had a soft arc--or very little variation in current if you were to change arc length---that it was set on the high side.
low 50's. Typical for what the machine is usually used for: out of position, 1/4" and up plate and structural shapes, with a dash of old boiler thrown in. These machines essentially have current feedback to stabilize them. The field current is varied by the output current. The current varies enough to give some control over dig and cleaning without resetting the machine, which is real nice on old metal.
I do not have a manual for the "beast," but the face plate specifies the following:
Primary volts: 220 Primary amps: 42.2 Secondary amps: 200 Secondary volts: 36 Time rating: one-half hour (I'm assuming this means 50% duty cycle???) Open circuit secondary volts: 90-50
Actually, the unit has taps for up to 275 amps, and the OCV is 90 for all the taps up to 200 amps, and then ramps down to 50 volts at the
275 amp tap.
It also has a chart for recommended electrode size; on that chart, it seems to suggest that the arc voltage is 15 at 20-55 amps, ranging up to 28 volts at 200-275 amps. I'm not sure how to correlate this chart with the ratings on the face plate.
In any case, this beast seems quite happy to run any AC rod I've thrown at it.
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