v-up 7018 fillet - stringer more productive than weave?

Advice on stringer-bead vs weaved-bead, if you could...
Often gaps - sometimes on temporary works big enough to slide your
little finger in - so about 10mm (3/8th-inch) (the crew I was with could give the impression of being "ree-tards")
Stringer-ing (straight run, no weave or even any oscillation) I found I could hold 150A with 4mm (5/32nd-inch) electrodes vertical-up and other positional.
Try any weaving to gap-fill or increase bead-size, and you seem to always seem to end-up at 110A with a 3.2mm (1/8th-inch) electrode.
Throw-out "7018"-specific restriction to keep short-arc tightly covering the weld pool and I've seen up to 130A doing large rapid weaves with 3.2mm rods demonstrated to gap-fill.
Gap-filling with the 150A 4mm rod condition - as soon as the stringer-run can't bridge the gap (small!), switch the deposition to be a series of stringer-beads making a pad-weld ("buttering") the thicker / larger part, until the remaining gap can be bridged and the fillet-size built-up. So you are "striping" a lot of stringer-beads - but they are very smooth so slag flakes off with a wipe of the chipping-hammer, and you are on the 150A deposition rate - so very productive ??? And smooth, with very little effort...
Does this describe what is familiar to you?
Curious after my last job ended 3 weeks ago, I played with the transient-state heat-flow equations available (there are few(?)) - and found they do anticipate that if you stringer-bead you will be able to hold a higher Amps than if you weave. That you can hold 150A stringer and "only" 110A weaving.
I found it with the "semi-infinite body solution" - which plots "T/T_0" against "x/(2*square-root(Dt))" giving a single graph line for all situations which fit the "semi-infinite body" model. Basically, that heat is propagating out from a hot place and never reaches any boundary. Which is OK for this situation - in the seconds which matter, the heat is still racing out into "new" plate still at ambient temperature. The "t" (time) and "x" (distance) - I worked "per second", finding with 150A 4mm rod you'd be running at about 2.3mm/s making a 6mm fillet. So that's t=1 and x=2.3*10^-3m (0.0023m) - staying in SI units to avoid slip-ups. That makes "x/(2*square-root(Dt))" = 0.26, so looking-up on the graph, "T/T_0" is about 0.75. ie. about 1175C under the rod is explained by previous weld heat keeping up with you, with the arc in control of the remaining temperature from 1175C to the melting-point of steel at just over 1500C. Controlling at 150A?!
Gap-fill by weaving and given weld-bead area is a square of bead size and you can easily reduce travel-speed to a quarter or less, reducing "x/(2*square-root(Dt))" by the same amount (as "t" stays at 1s). So "T/T_0" increases much closer to 1 (unity). Which means most temperature under your rod is explained by accumulated heat, so only a small arc power can be used and keep control.
150A vs 110A ?
Anyone able to comment on this? Those calculations were a pleasant evening on the sofa for me, by the way.
Rich
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On 4/1/2020 1:03 PM, Richard Smith wrote:

Probably not what you're asking for but interesting info about strength of Stringer vs Weave.

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Hiya.
That's a super-brilliant video. I didn't know of it before. The welder and the lab-guy getting together in that cooperation - stands-out brightly.
Appreciated, and I'd recommend it to anyone else. Speaking as someone who is a trained metallurgist, has worked in a steelworks test-house (same equipment), has done weld tests and research on welds and welding.
I was thinking about that too - the properties. Stringer'ing, everything was exactly as it should be. Should get the properties in the manufacturer's data-sheet. Short-arc and no weave, so weld-pool should always be propertly shielded - chemistry correct and no atmosphere pick-up of anything like nitrogen which would knock-down impact toughness.
Regarding properties of stringer and weave, "Basic" / lime / CaCO3 flux SMAW, typically 7018, should have about the same proportionality as stringer and weave E71T-1 (Rutile FCAW).
Anyway, I should have those properties - and I know what it looks and feels like stringering at 150A with a 4mm (5/32") 7018 rod. I only did it for a day, not realising I was "on the money".
So my main question is - when I get the chance, what should I be developing and what might it be useful for me to know about the practice of welding? eg. what can be a problem and what to do about it, etc.
Regards,
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On 4/5/2020 3:14 AM, Richard Smith wrote:

I'm glad you liked the video. I'm not a welder. I bought a tombstone welder for $50 used. I use it to stick two pieces of metal together with metal. A grinder is very useful for me. :-) Mikek
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"Tombstone" as in it is massive? Some of these have a really good arc - very sweet characteristic. Need a really good inverter to beat. Probably some "Darwinian selection" on the "tombstone" welding machines left - the best endured the decades and were kept during clearouts, etc.
Is it AC? DC?
One of the best ever for me was in a boatyard where, for outdoor welding, the two SMAW machines were both AC only. One air-colled, one oil-cooled. I found a rectifier in the store. Never seen a stand-alone rectifier before or since. Well, both welding machines put through the rectifier had a fantastic characteristic with 6010's. Could push a 2.5mm (3/32nd-inch) 6010 straight through a 12mm (1/2-inch) plate and have only something like half burned-away when the rod slid onwards. The one where you present an offcut with what looks like a rod shot through it to the rod's midpoint like an insane case of archery.
Enabled me to weld barge / boat superstructures in one pass, seam'ing the 5mm plates. Disconnect the rectified and send AC through to the stinger, raise the current to 200A and "wash" downwards with a big 6013 to get a flat slightly-raised finish which flushed-off with a quick "wipe" with a 9-inch angle-grinder.
I sketched - is at bottom of this page http://www.weldsmith.co.uk/dropbox/my/work_boatyard_0801/work_boatyard.html
Occasionally day-dream about how I could make a stand-alone rectifier. Practical advice appreciated. Less and less need now with inverters getting better and better. But no inverter I have yet met will run a 6010 "keyholing".
Rich Smith
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"Richard Smith" wrote in message
Occasionally day-dream about how I could make a stand-alone rectifier. Practical advice appreciated. Less and less need now with inverters getting better and better. But no inverter I have yet met will run a 6010 "keyholing".
Rich Smith
======================================================https://www.electronics-notes.com/articles/analogue_circuits/diode-rectifiers/full-wave-bridge-rectifier.php
Start with the welder's maximum current, lets say 300A. https://www.digikey.com/product-detail/en/vishay-semiconductor-diodes-division/VS-300U60A/300U60A-ND/80681 The 300UR is reverse polarity. You need two electrically isolated heatsinks, the positive one for the two diodes whose threaded studs are cathodes and the negative one for the two that are anodes. Insulating the four diodes from a single grounded heatsink is possible but liable to hidden short circuits and the diodes will run hotter.
https://www.dummies.com/programming/electronics/components/electronics-components-diodes/
Large finned aluminium heatsinks are common cheap electrical scrap, if you know where to look. You may have to experiment to find how large a fan it needs.
The hardest part may be finding and fabricating heat-resistant electrical insulation that will withstand rough handling. I'd try unperforated FR4 unclad circuit board material rather than the temping PVC pipe. The high current terminals can be brass bolts through the insulation. I've found threaded copper starting motor terminals at a Diesel electrical shop and lathe-turned them into the high current studs I needed for a current measuring shunt.
The housing for it can be a welded cube of angle iron with flat sides, if you don't have equipment to bend sheetmetal. Be sure that at least one side can be closed without access to the interior, i.e. tapped instead of clearance holes for the screws.
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On 10/04/2020 07:56, Richard Smith wrote:

My 1st stick set was a cheap 180A buzz box and I was so happy when I bought a 180A Pickhill oil cooled welder as it's virtually silent and 50V and 80V OCV ranges and probably continuous duty cycle. Not long after buying that I came across an old Max Arc HF unit so that gave me AC TIG capability. I then found a Max Arc rectifier unit at another local welding supplier so then had AC/DC capability. Both the HF and rectifier units had Dinse connectors so with a suitable set of leads it was quick and easy to swap settings. The rectifier unit apart from having a full wave bridge rectifier assembly, had a large inductor on the output for smoothing. Having now upgraded to a modern inverter TIG set the HF and rectifier units are on long term loan to a mate in West Sussex, the Pickhill I still have for the odd bit of AC stick welding.
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"David Billington" wrote in message writes:

My 1st stick set was a cheap 180A buzz box and I was so happy when I bought a 180A Pickhill oil cooled welder as it's virtually silent and 50V and 80V OCV ranges and probably continuous duty cycle. Not long after buying that I came across an old Max Arc HF unit so that gave me AC TIG capability. I then found a Max Arc rectifier unit at another local welding supplier so then had AC/DC capability. Both the HF and rectifier units had Dinse connectors so with a suitable set of leads it was quick and easy to swap settings. The rectifier unit apart from having a full wave bridge rectifier assembly, had a large inductor on the output for smoothing. Having now upgraded to a modern inverter TIG set the HF and rectifier units are on long term loan to a mate in West Sussex, the Pickhill I still have for the odd bit of AC stick welding.
=============================================The no longer needed 50A buzz box welding transformer I turned into a variable DC power supply has enough inherent self inductance that the rectified output ripple, with 78000uF of capacitance, is only about one volt peak to peak at 20A load current. The self inductance limits the short circuit current when the electrode sticks. A clamp-on ammeter with sufficient range can measure it.
The transformer's 20% duty cycle at 50A translates to about 25A continuous for a transformer winding temperature rise of 50C in 1/2 hour. I made it to fast charge my 24V solar batteries from a generator, and to test power components such as breakers and rectifiers.
The unregulated supply is a good match to this very nice and versatile unit, though it will fast charge a battery without the regulator if watched for overvoltage. (Amazon.com product link shortened)86527749&sr=8-2 The reviewer doesn't understand how to use it.
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Yes, having bayonet connectors. You can leave the transformer at some remote / fixed location, and run the AC leads to near where you are working. Have the rectifier near you. Then you have 3 options for tuning your welding conditions, without having to return to the transformer: * DCEP * DCEN * AC (disconnect the rectifier entirely) With cellululosic rods, you can penno "like mad" on DCEP, gap-fill on DCEN, and "wash" the welding-side surface with a 6013 running AC. Useful if you are working on floating hulls - don't have to go back to the quay very often to adjust the transformer :-)
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