Reckon 6010 would be best. But 6010 very rare here in UK (please trust me on this, N.Am. folk).
Between 6013 and 7018, which would be best?
Have close fit-up between 2mm thk galv'd and 8mm thick pre-primered. So can run high amps and short arc to blast galv & primer. Which means 7018 doable??? - short constant arc length and stringer bead.
Any suggestion for technique?
Concern for me - location is outdoor in windy area - fume blown clear.
6013 is usually a poor choice on cruddy materials like galvanized or primed. It is a fast fill rod with relatively low 'force'. Cranking the amps up doesn't help that much. But if the galvanzing is thin, can be cleaned off with sander, wire brush, or acid, it should be ok. Just ok.
IMHO, 6013 is properly referred to as a 'fast follow' rod, I would never consider it as 'fast fill', that designation is usually reserved for rods containing iron powder in the coating such as xx14, xx24, xx18, xx27-8.
Fast follow ability is particularly useful when welding thin or other material which requires a high travel speed, as the puddle will follow the arc without skipping. The puddle of a good fast follow rod (with proper heat setting, rod angle and high travel speed) will be an elongated shape. Often the heat can be adjusted quite high and the fast follow ability will allow high travel speeds to keep the arc ahead of the heat buildup and help to prevent burn through, welding downhill often helps. A long stroke whipping techique can also be used/tried but requires a fine touch and good timing and vision.
with relatively low 'force'. Cranking the
6013 is a 'low penetraton' rod which can be both its strength and its weakness. IMHO it is seldom my first choice as a general purpose rod but does have some special properties which I have found useful enough to always keep some (mainly smaller sizes) on my rig.
But if the galvanzing is thin, can be
For most work, I would definetely agree. Most 6013 (and 7014) is used with machines that lack the power to run 7018, particularly small AC buzzboxes.
IMHO, 7018 is by far the best general purpose rod, provided you have the power to run it.
I would need more information regarding joint type and orientation, but suspect that both galv and primer will require increased heat which will cause burn through problems on the thin sheet. Rod angle and travel speed will be important factors. I suspect you will need to direct most of the arc force (and heat) towards the thicker material and just let the arc and puddle wash into the thinner sheet, beware cold laps.
First priority is always to keep your head out of the smoke.
a "strut" used for the electricians, plumbers, heating and ventilation and I.T. network folk for securing their variable tubes and cables - which is about 40mm square section with on side open, that open side having both edges folded inward into "lips" which standard fittings can grip. The "corners" are rounded at about 3mm radius.
the 8mm thick angle-iron frame in the shaft.
The strut is heavily galv'd, the angle-iron is pre-primered.
The economics of the job don't allow for grinding, linishing or acid-dissolving the zinc galv.
I read the "fast-follow" explanation with interest. Here in UK we don't tend to use these classifications like "fast fill", "fast freeze" and "fast follow" which seem to be common knowledge in North America.
If a 6013 is "fast follow" as you explain, that might be to my advantage. That means you are running fast and the arc is searing straight onto the bare metal + galv + primer just ahead of the fast-following weld-pool.
Another thing to my advantage is that they are using a "branded" Rutile-Cellulose rod. It's AWS6013 but ISO its E 48 0 RC 11, the RC signifying Rutile-Cellulose. The arc has a fair bit of bite.
You are completely right that you have to focus most heat onto the 8mm pre-primered angle-iron and see the pool "wash" along the 2mm thick galv'd "strut". However, the run is fast and the metal is getting a bare blast of the arc, rather than arc'ing onto the pool. So it flows well.
My "welder's instruction" is to ensure that the struts fit totally tight up against the angle-iron with no gap at all. Bevel the ends, chop the length or whatever to make fit-up tight side-to-side. So that you can turn up the heat and run fast stringer.
Plus - don't worry about the start-up - set-off fast and you'll have a fully formed bead within 10mm, with well more than 50mm remaining to make the strength. That's so you don't get the far worse "6013 curse" of slag building up ahead of the weld-pool causing a "tunnel" of slag under the weld which sustains along the full weld. Galv and primer trash the first few mm, but you know you've burning bare metal with the arc for the rest of the run, with a deep penno'd weld bead. Plus can start the run at the "outboard" end of the joint.
Does this make sense?
And I'll make sure my head is out of the smoke! It's a good "open" location standing freely on both feet with unrestricted view - and the wind is always blowing upwards in this shaft.
I have welded lots of these electrical 'struts' (the proper name escapes me, conduit clamp tracks?) It is a major task for 'elecrician weldors on union jobs' and is considered a soft job as you spend most of your time waiting and dragging weldleads with lots of time for bsing with other trades. A full shift will seldom use more than a handful of rods and the electrical pay rates and benifits are usually the best on the job.
My first choice for this job would be 6010 then 6011 because of the instant start and deep penetration through the primer layer, but 6013 is almost as good on DCRP if you crank up the heat, and it can be whipped if things start getting a little too hot. All of these rods have good tolerance for welding with higher heat settings provided that you are moving fast and using care not to burn through, but I doubt that you will get any complaints if you do. Just say that it is proof of complete penetration, most of thse jobs are pretty crude and QC will not much care about appearance as long as the 'struts (tracks)' are firmly attached.
Welding with increased heat settings will result in increased heat buildup in the rod stubs and you should use caution or you will burn your (nice new, very soft, outside seams, and very expensive but not heat treated electrician's 'Rough Rigger' ) gloves when changing rods. These are by far my favorite work gloves but are often hard to get as the foremen hoard them, and obtaining them usually requires some 'negotiation'. They come in several sizes (9,10,11)
There has been a lot of studies done on the effect of welding on galvanized parts such as this and the conclusion has been that the weld will penetrate under the galvanized layer and that the finished weld will have increased corrosion resistance provided that the heat has not been excessive enough to cause the galv to be burned back from the weld. Most of these jobs do not require max strength welds and have a low consequence of failure.
I suspect that it is another geographic specific trait, but here in NA many welders (and farm boys) chew unshelled sunflower seeds often called spitz. A small handful can be placed in the cheek and deshelled on at a time, raising the facemask after a weld is accompanied by a shower of empty shells. This habit is at least as satisfying as chewing gum or snuff and is organic and an interesting exercise in multi-tasking akin to 'walking and chewing gum'. The litter of old shells is common evidence. I have found that chewing spitz REALLY helps to remove the metallic taste of welding galvanized material, which seems to occur no mater how careful we are with fume avoidance.