[Welder]

Hi all, I finally decide to take the 3g Course for SMAW, since eventually I end up stick welding some serious stuff from time to time (I work mostly automated processes, SAW, GTAW, FCAW etc. etc., and less manual).
My experience is almost 5 years. I have stick welded various stuff of various material type, shape and thickness over the years, mostly repair welding, that has nothing to do with sheet metal welding. Still, most of the time I used standard welding techniques. and I do believe this experience did help me a bit...

Today was my 1st 3G day, I welded for almost 7 hours without stopping, but I am a bit frustrated by some things, and I need your advice.

I will try to explain everything as accurately as possible, since in my country we use metric will do the conversion for you.

1)Electrode Type: Lincoln Electric 7018 3.25mm, Length: 450mm. (Imperial: diameter 1/8" , Length: 17"

2)Plate Type: Mild Steel, thickness 8 mm, 5/16"

3) plate preparation: Done(not by me, plasma cut) at around 15-20 degrees bevel. Root Face height: unclear, around 1~1.5 mm
Quality of cut: satisfactory, I removed the mill-scale on the rear side (the root side) using the chipping hammer before welding. Makes significant difference in root quality.

4)Joint preparation: I tack weld the 2 plates, the distance between them is the diameter of the rod (I use a spare rod)
Afterwards I bash the plates against the cast-iron welding-table, in order to 'open" them up a bit.(since root bevel angle is not big enough)

5)Power Source: DC transformer "mother" station, that supplies multiple welding stations, each one fitted with a ballast rheostat to adjust the amperage using levers and switches at predefined Amps. 3 Switches each giving 80A when on, 1 switch giving 40A, 1x20A, 1x10A and 1x5A.

My impressions, thoughts, problems:

1)I think this plate thickness is just not enough for 3.25 1/8" electrode. Or these plates should be welded with the smaller electrode size, 2.5 mm)
2)The bevel angle is absolutely not enough for this rod diameter.
3)I cannot get the rod inside of the joint "enough". (read above)
4) The Current is always too high. I set it to 75 amps, and it is still too hot. I don't understand if it's something wrong with the power source or the ballast rheostat. Cable from PS to BR seems thin (around 25-35 mm^2). cable from BR to electrode holder is the same, so the current should actually be lower than expected? total cable length less than 8 meters (25 ft)
5)I have to use welding technique similar to cellulose 6010 rods, by avancing the rod too much forward, and then bringing it back in order to fill the keyhole.
6)The keyhole gets HUGE, around 5-6mm in diameter,
7)I have to advance the rod forward too much (around 15 mm or even more) every time, or I will simply overheat the extremely huge keyhole and make it further impossible to fill.
8)The Lincoln Electric electrodes I used are amazing. Haven't used 7018s with better restart capabilities (probably only Bohler 7018-1 could compare). I expected much worse restart capabilities given the archaic power-source we used.
9)The Volt-Amp characteristic of the power source/ballast rheostat seems too "flat" (aka "hard", MIG/SAW/FCAW/GMAW) like. Meaning: even shortening the arc length won't reduce the amperage significantly. This gives me almost no control over the heat input and deposition rate.

I managed to make only 2 decent root welds with decent looking penetration, by following the teacher's/instructor's welding technique. He is really experienced welder, can make amazing welds without even looking.
The welding technique aka electrode movement he used was like the L letter. He would establish a keyhole (still pretty big keyhole, because of the thin plate, and high current), then fill it a bit, then immediately move the electrode up (along the bevel of one of the plates(I do it on the right plate, since I am right handed and this allows me to see better),going up 10-15 mm, then comes back down to the now cooled-of a bit puddle, fill it a bit, re-form-re-heat-re-establish a keyhole, then go up again as described above and repeat the process.

Using this technique, the root of the weld on the backside becomes perfect.

Down Sides: its extremely difficult, and a single mistake/slowing down/overheating can ruin your weld, cause the keyhole to grow, or overfill the root side, causing both slag and weld to drip like a snot.

I was afraid that advancing that much above the keyhole/puddle and the backing down again, no matter how quickly may be the cause for slag inclusions. instructor said that basic electrodes tend to chase the slag away unlike rutile.

Additional information:
I weld "free hand", I do not hold the electrode holder with 2 hands.
I may hold the hanging cable with my left hand sometimes, but avoid doing so since this makes my stance too "rigid" and slows me down.
My hands do "shake" a bit, causing the electrode tip (especially on the Lincoln 17" rods) to wander a but to the sides, but as the rod melts down, this slowly goes away. Doesn't seem to be the cause of undercuts, if I fill the area where I 'gouged' long enough with proper technique.
I do usually rest the front/mid section of the electrode when welding out of position using thinner 2.5mm (3/34") rods
ATM, I am alone (no other welders/students coming, so no one to share opinion with). But I did take a look at already welded plates and most of them were absolutely terrible.

I would like to thank anyone for their suggestions in advance.

Things I will do tomorrow:
I will play around more with the powersource/regulator to see if I can lower the Amps more. The current current is just too much.
I will change plates more often, so that they can cool a bit.

BTW, this is how the ballast rheostat looks like:
https://ua.all.biz/img/ua/catalog/13486559.jpeg

[Welder]

Ok, a follow-up:

I have been weldin a lot, vertical and overhead too, once I got used to the machine everything started to work out.

The instructor showed me very interesting techniques, I tried at least 10 and decided which ones worked best for myself.

I chose a welding technique and electrode motion that is giving me ability to push the slag away, fill in any possible undercuts appearing, and also get a nice and smooth appearance.

I am now using thinner electrodes (2.5 mm) for the root and cap pass.

Today I welded a test plate, that was thicker (12 mm) and that was machined(beveled) on a mill.
This is not the exam plate, just a test one so I can get the feeling)

The results were excellent.

So the way you set up the sheet metal DOES matter a lot.

On the overhead position, it's quite hard to push the metal up, I do get the root melted but after removing the slag on the top (root) side, it is concave. According to the instructor it's fine, since the root showed up on the other side.

On the exam day I will be given the opportunity to weld either vertical or overhad. Will absolutely go for vertical.

Another thing I found out the hard way: it is always better to set up the current a bit on the hot side, and if I see that the keyhole grows too big, I just stop for a few moments, then re-strike and continue welding. The electrode tip and the puddle are is still red hot, so I am not worried about inclusions. (on vertical the slag does run down so it helps).

One thing I am worried I may not be allowed to use a grinder on the exam, meaning I will have to weave a bit more to make sure the root melts and fills the sides better, so that no low spots and slag pieces/trapped slag is left between the bevels and the root itself.

Cap and fill pass: I now have 3 different techniques that I use depending on rod diameter and thickness. I am getting good results, the welds are smooth and quite even. No undercuts at all.
Learned a nice "circling-weaving" motion that gives amazing results with one hand, without resting/helping with my left.
This motion proves especially useful when I wanna lay down "compact" beads (not too wide).

As for overhead, my cap passes look quite better following the last week, but there is still room for improvement. Sometimes I leave undercuts, and sometimes I run too fast and get low spots.

Hope this information helps those who are going for 3G.

Also don't forget that different machines will weld differently. Also different arc length on different machines will give different amperage, heat input and rod melt rate.
Best machines are those with large copper chokes inside, the arc is soft and will current will not change even if you make a mistake/fast motion/shorten the arc abruptly.
If you are welding with modern inverter based machine, make sure it's possible to adjust the HotStart time and most importantly the ArcForce characteristic (DIG).

The ArcForce/DIG is the lower-right part of the Volt-Amperage characteristic of the power source, meaning the way the machine drops Voltage/Amperage when you are welding with short arc.