Back bead appearance (mild steel) needs serious improvement

[Macfun]

Hi all !

Practicing and practicing butt weld on 1.5 mm plate, I sometimes reach "acceptable" looking bead on front side.
But the back bead usually looks ugly (at least).
I know 1.5 mm might be uneasy to start but I have tons of free plates ...

Here are my settings :
1.6 mm blue or gold or grey tungsten (none are my favourite yet, I use what I have in the box), Nr 7 shroud, 2 mm rod, no gas lens, 55 to 80 Amp trials.
7l/min argon (at torch), 5 mm stick out, 30° sharpened "the right way".
Actually a water-cooled Rohrman R420W connected to a Castotig 2002 ACDC. I rebuilt this machine and wanted to try pro and con.
I have the original air-cooled G220, too.

Here are the results.
Where should I improve (please don't tell me "go gardening instead welding" ...yet ... ) ?

I made other trials starting at 55A up to 85A (well I forgot to reduce Amps after tacking ...), pictures later.

60A front and back



70A front and back



70A front and back with more filler (so speed decreased a little)

 

[AndersK]

Looks a bit hot to me.
If you have some, go down to 1,2 mm filler.
Current should be about 45-50A but go down to 30-35 and work upwards in 5A increment.

And, it's a looong way from being told to garden instead

 

[Brad93]

You’re cooking it. Faster travel speed with more filler addition to the puddle required.

before you do joints just try doing some flat beads on the material. Once you get the beads sorted then move onto butts.
1.5mm is not the best material to learn on because it becomes heat soaked and warps.
If you’ve got some 2mm or 3mm youll get on a lot better.

 

[Macfun]

This thread is opened to every beginner with same questions, of course.

OK, I restarted from the beginning, with the air-cooled torch, I got a little better back beads as far as I remembered.
I set to 58A and tried to control the puddle to a narrower one, with more frequent filler and smaller drops (well, at least it's what I tried to).
I don't have 1.2mm or 1.6mm rods, anyway 1.6 is on my list to buy.
2mm rods and 1.5mm plates being free ... I didn't resist.

Why 55-60A ?
I started from there based on the 40A/mm from tutorials.
I'll try lower Amps but I'm a little afraid that it will slow the weld and spread more heat in the sheet.
Good opportunity to measure and compare heated widths with different Amps.

I made these beads before reading your above hints, it has better appearance to me (worse being a hole ... -> garden !).
Still butt welding, but I believe it's on the good way, less liquid metal floods.
Bead restart is part of my training, too.


Bead 1



Bead 2

 

[AndersK]

Getting better already

Results are all a combination of current, filler rod diameter and travel speed. With smaller rod you can lower current and move faster, and easier to dab less material.

With the 2mm rod you can't lower the current to the levels I said. Then it will take longer to heat so you must go slower, hence increased heat input.

You can cut mig wire and twist together while waiting for tig rods. 3x0,8 equals roughly 1,4 mm.

I go by the rule 30-35 A /mm thickness for a butt weld. Reason for saying start lower is that every machine is unique and will deliver different current regardless of what display says. I am assuming you don't have a calibrated industrial rig.

 

[Macfun]

Good tip tu temporarily use twisted MIG wires, I gonna steal some from my Cebora unit.
Even if 3x0,8 probably melt faster than a single equivalent.

For real current measurement, I can use the (calibrated) Fluke ACDC clamp unit from work.
Maybe using "MAX readout" could be a way ?
No matter if clamped on ground cable or torch cable, I believe.
The Castotig 2002 being a rebranded Fronius MW2000, I guess it is a good old school (25Y old) unit.

If someone could post a picture of a good back bead on similar thickness and weld, I could figure out does it look like in the real world.

A good weld in not only a beautiful one, it's like an iceberg and its visible part.
10 seconds of poetry ...