I've done in-depth research studying hydrogen movement in welds - "hydrogen distribution and redistribution in the weld zone of construction (structural) steel welds". That took me a long time because doing applied research, I had overcome whatever obstacles came along, whereas with a more conventional academic research you can shift the objectives around so you can run down familiar paths, then pretend the outcome was the place you intended to go in the first place.
I did learn some underlying welding skills, and tried to get as many as I could. But I kept hearing references to "cellulosics" and kept reading of them in relation to pipewelding, where they are used with "some special downhill welding technique". Clearly something special. Then there were the strange references like "we made a special power source for cellulosics - you could bend the electrode before the arc went out". Or "they only gave up when they bent the electrode like a banana". Ehh???
Their existence tugged at the edge of my research work, because they
give an unbelievably high hydrogen level compared to low-hydrogen
electrodes which would generally be favoured - something like
The mystery remained for
Now, finally, I know. And using celluloscis seems to have been a skill which came to me easily, contrary to the experience of the majority. Cellulosics use a clear appliance of scientific principle which to my way of doing things makes it easy to know how to use them correctly. I find the opposite situation, "it'll come with practice" a frustrating circumstance often where others are happy and getting on well. So I know I am good at doing things conversely.
There is something incredibly definite about the way you use cellulosics, particularly for root-running, which is their majority, specialist, use. No other electrode is used in anything approximating to the same way. I tend to think of them by the nick-name "psycho-trodes" quite often. Many seem completely fazed by their fierce characteristic, and back away on the edge of success. The thing is, in their characteristic use in root-running, you straight away blow a hole through the weld root then control this hole, "the keyhole", and ride it down the weld. When you "get it" as a technique, it gives you enormous control and you can ride it through quite a range of changing conditions of joint fit-up, temperature, etc., enabling consistent welds in rough real-world conditions.
Jumping to the end of the story, as root-running V-prep (preparation) butt joints in plate steel using cellulosics with the keyholing technique came so easily, (my first full sample was good and passed City & Guilds tests), I never tried another technique. So in the final session I got the instructor to show me root-running with a rutile rod, which is now the majority method. I was left with only one question: "why bother at all?". It seemed highly sensitive and unstable, with little control possible, either melting through or showing lack-of-penetration defects, needing incredibly precise accurate and consistent fit-up to get a "good" weld. The instructor suggested, if you are comfortable with cellulosics and their use is allowable regarding hydrogen grounds, you would never chose to do different.
Back to cellulosic root-running of butt joints. That might be joining two steel plates together to make one larger expanse of plate, or it might be joining a section of pipeline onto the pipeline laid so far. Blowing a keyhole is one astonishing feature compared to the soft smooth arc of, for instance, a rutile rod. The cellulosic sounds like it should be generating 100pounds of jet thrust, just to intimidate the squeamish. The other unfamiliar thing is that you actual drag the electrode down the joint, making definite firm contact with the base metal. With other rods (basics, rutiles) you draw an arc, hold an arc column, of about 3mm (1/8th inch) between the weld pool and the present end of the electrode. So here again, there is an unfamiliar fierce technique associated with the cellulosic rod. Then finally...
This was like finding the pot of gold at the end of the rainbow. I now know what this business is about bending the electrode. By leaning on / pressing on the electrode, you can force the keyhole to stay open against adverse conditions. Not entirely sure how it works, even though I am practiced at doing it now. But if say the fit-up is going against you, with a thicker weld root face and less root separation than would be desired, you can respond to it by leaning on the electrode. And if conditions get worse, you lean on it harder and harder. Until finally the elctrode bends / buckles. That is when a cellulosic welder is honourably defeated. Show the site organiser an electrode bent through something like a right-angle, and the welder is absolved. They have done all they can... But then there is the welding machine in all this. If it can keep the arc going, refusing to let the arc be stubbed out by this hard physical pressure of the rod against the weldment, still not having given up when the rod finally bends / collapses under the pressure, then the welding power source is a good one for the job.
It took a long time, those
Now, reality stuff here. Largely, cellulosic welding is like from the era of the steam locomotive. You can still use one, and it's very effective if that's what you have to do the job, but you wouldn't chose it, on economic and other grounds, compared to more modern alternatives. Just about all "stick" (SMA) welding is uneconomic these days, compared the the high productivity of solid-wire and flux-cored-wire MIG welding.
But - someone can lie on their back in a muddy trench in the pouring rain and reliably produce a specimen perfect penetration bead on a pipe weld using cellulosics (pipeline - you have no access to the inside - so the penetration bead must reliably be perfect for engineering stress distribution reasons and smooth fluid-flow reasons). So it's not to be disrespected.
Why I found this all so interesting. I know I would be looked at as a
bit mad by someone who has done the "damn'" things day-in day-out for
It's the ferocity of the things compared to other "stick" / SMA welding electrodes which appeals to my wayward nature. It's the way that the fiery spitting arc, blasting out iron-oxide smoke, produces conversly the most smooth controlled agile welds (remember the name "Fleetweld"). By the way, while the crucial underbead is excellent, the top-bead is rough, just to let you know. And it's the way the scientific issues can be seen to work. The cellulose in the coating produces a way high hydrogen level which shields very well and send the arc voltage way up, nearly double, packing a huge punch for the amperage. Low amps means less rod heating, so you can pack that punch without burning-out the rod before its time. Then the hydrogen-rich arc is stiff, like a little hard rod which can poke and lance its way though gaps, giving the controllable keyholing technique. Then with most of the flux coating going as gas, there is little slag to over-run the weld, plus with little mineral slag cover the weld is fast-freezing, allowing fast weld pool control and making fast downhill welding techniques possible.
Finally, there is another trick with cellulosics which really does make people wonder about you. Cellulosics do need to have some moisture. That's why they come in tins. It's to keep the moisture in. If they dry out too much, they don't work properly. You can see it. You get a limp wondering broad unfocussed arc, a "flat" fizz/woosh replacing the fierce roaring and crackling arc sound, and it is prone to chronic "arc-blow" (some sort of magnetic effect deflecting the arc way over to one side, looking for all the world as if there is a fast wind blowing it away). The answer is to dampen your electrodes. No-one can tell you to do this, as recommending having some water next to an electric welding site cannot be done. What about hydrogen level from moisture, when for the low-hydrogen welding rods much effort goes into keeping them baked dry in an oven? Well, with cellulosics, "in for a penny, in for a pound". You are going to have a sky-high hydrogen level, anyway. What some do is to have a container of water next to them, into which you dip the electrodes or leave them for a moment. Not too long - the cellulose will absorb so much water and swell so that the coating will flake off. But put the next one in as you take out the rod you are about to use works well. It adds a cutting edge to the weld penetration.
A Richard observation about moisture and current. If you suddenly break the arc and flip up your visor to look at the electrode, it seems a good sign that there is a little jet of flame shooting out of the end of the electrode for about a second or so. There will also be a flame like a match flame rising from the tip for a few seconds. So far so good. A major electrode manufacturer had no problem with this observation. What you do not want to find is no flame and a charred blackened end to the rod, for perhaps the first 3mm or more from the arc end. That means the cellulose burned away before it got inserted into the arc. See the charred end and the water option would tend to come into view. I made a little "tube-vase" exactly the length of a welding rod, so that there is a convenient small amount of water being used and I can put in and pick up the electrode without gettimg my gloves wet (steam would scald you if you touched anything hot). Some cellulosic rods seem to like being dipped, others seem to be fine as they are and not like more water (they immediately swell, and don't give the impression of needing it anyway).
Other use of cellulosics - they will blast through rust, mill-scale, grease and oil far better than any other welding option. So they are still used for on-site maintenance welds, where it is simply impossible to make things shiny-silver clean. They are used with a drawn arc, not dissimilar to other welding electrodes, in this case.
So, even if cellulosics go the way of the steam locomotive, it would be a pity if you couldn't sometimes give them an outing... It's a skill that's good to have.
Richard Smith, 26 July 2004