Hope you don't mind going around a fairly familiar topic again. I am likely to drop out of the newgroup activity but may demonstrate welding every now and again. So want to get my facts straight.
Cellulosic electrodes (SMA/"stick" welding) and the effects of soaking them in water prior to use.
I believe that you get these effects from soaking your cellulosic "stick" electrodes in water prior to use:
(i) the electrode can take a higher current without charring the end portion of the rod -- for a 2.5mm (~0.100inch) rod, can go from 70A (rec'dd) to 80A
(ii) the arc becomes even more penetrative than the standard penetrative cellulosic arc -- due to high hydrogen-in-arc levels?
(iii) arc-blow is lessened -- not understood, but often the main reason weldors dip their cellulosic rods in water before welding with them
What you can achieve through dipping your cellulosic rods in water:
- deeper weld penetration. (ii) alone makes for an ability to make or demonstrate "keyholing" through thicnesses of weld-root exceding the wire diameter of the welding rod. (ii) and (iii) combined (say 80A DC with a 2.5mm rod) allows you to get full corner fusion / penetration on fillet welds even when the plates are scaled rather than ground silvery clean (for lap joints, can get corner-fusion on mill-scaled bulged-edge rolled flats)
- the arc-blow thing - keep harshly-crackling directional arc focussed to the intended position of the weld pool right to the end of weld, where otherwise arc-blow can be causing a soft undirected arc towards the end of the run.
Looking to the "on the other hand" aspect, there are no deleterious effects from having pre-soaked the rods in water prior to welding? Is this true? Are mechanical or any other properties affected? As a metallurgist, I would have thought that the water, dissociated in the arc, would deliver itself as oxygen to the weld pool and would chew into more of the deoxidisers and maybe reduce the weld carbon level, giving a slightly soften structure - but then, the shield of hydrogen is going to be even greater and all in all, you expect a sound welds averaging at some insignificantly slightly softer yield strength compared to "out of the can" rods???
For sure there will be more hydrogen in the weld, but it's a case of "in for a penny, in for a pound" with cellulosics -- if the steel is higher-strength and hydrogen-susceptible (to hydrogen cracking) you are going to need precautions like preheat whether or not you dipped your welding rods in water???
How I do it (soaking the cellulosics prior to use):
I have a "tube vase" of about 40mm dia (1~1/2inch) tube standing upright from a flat sheet base onto which it is brazed. The tube is cut to a height which just the exposes the metal top of the rod, which goes in the clamp, sticks out of the top. The tube is filled with water. I put a new rod in as I take one rod out, leaving one rod in the water for the duration of the run of one rod. The exact height allows me to keep my welding gauntlets dry (avoid getting them wet), as only have to touch the dry top of the rod. Only some cellulosic rods seem to be happy with this (Fleetwelds don't seem to like this, for instance).
Main cellulosics I have used are 6011's (because pipe-welders also use AC oil-cooled welding machines here) - "Arcos Nu5's" - which seem to be well-liked in these parts (UK).
Particular reason for asking:
I particularly want to check my facts for if I am ever demonstrating welding with cellulosics. If there is something wrong with doing these "techniques", I want to know now...
That I can get corner fusion in filler easily is one reason why one would show the "soaked cellulosic" trick. The inherent extra penetration plus the ability to use an extra 10A and still have a clean-running rod right to the stub allows a visible gouged-in corner penetration. I judge the extra 10A to be acceptable in this way -- one deduces no charring if on suddenly breaking the arc, whipping up ones visor and looking at the rod end, there is a little jet of flame (few mm) out of of rod for a second or more, plus a yellow flame like match flame rising vertically from the end of the rod for a few seconds (charring and the cellulose would already have been burned away so no flames and blackened burned end of rod is seen).
The other reason is that one would be tempted to show just how much root-face you can keyhole through with a cellulosic rod. It is some demonstration!
What I like to demonstate:
I really like the "keyholing-the-root full-thickness weld penetration" with cellulosics on a V-prep joint because it demonstrates spectacularly
- effect of hydrogen on the arc characteristics
- very clear use of liquid metal surface tension effects to control a weld
One would contrast these characteristics to the very limited penetrating power of other rods such as rutiles, though show their smooth top-beads.
The "welding" demonstrations are a more controlled and applied version of the demonstration where you soak a cellulosic in water and slowly push the rod through a 12mm / 1/2inch steel plate, keeping the rod burning unmoving in the same place, until the rod goes right through the plate, you slide it onwards until the arc goes out, release the clamp from the electrode then tell everyone they can lift their visors and have a look. The sight of a 1/2inch plate with a thin rod stuck right through it looking like some super-arrow is usually considered an "awesome" demonstration by class. Particular thoughts on this demonstration?
So any thoughts / knowledge / experience on this matter ?
Many thanks in advance.