[drizzit1aa]

I can weld stainless and it still be silver when it has to be, I can laydown a 1/16th fillet weld on 1" solid rod to 1/4" aluminum plate with zero problems. Why can I not fusion weld an outside corner to corner (slight overlap) mild steel box without it looking like swiss cheese with TIG?
I have used a 220 multimatic and a Dynasty 400, PPS 0 to 5000, 3/32" and 1/16" lanth. 2%, 80 to 120 amps, 100% argon, 15-25 CFH, cup 8 to 1 1/8", 14 gauge material. Admittedly no backing, I have nothing to use but some 2" by 6" copper I use to fill in holes and 1" by 12" aluminum I use for stainless I can't afford to cut down.
I don't normally weld steel but this company keeps giving it to me, hard to say no to money but this is really "steaming my biscuits" to put it politely.

[BugHunter]

Without filler, I can't get it to stay cool enough either. Nice pic btw. Looks plenty clean enough and the fit looks great. I'd probably drop the amps and use 1/16" filler. Maybe file the edges some before starting to get them super clean (even more than they are now). Smooth surface also helps vs having marks from cutting or shearing. Smooth just flows better, as looking close at that it appears there's some areas without full coverage.

Try a small amount of filler to help it flow in better and see if that doesn't fix it.

[cj737]

If you are attempting to weld that outside corner with pulse, for 14ga I use: 90 amps peak, 50% on time, 20% background, and 1.2 PPS. I use no larger than a #8, often a #6, and 10cfh for a 6, 15 cfh for an 8. 3/32 tungsten, super tight arc.

The Dynasty will let you set those adjustments, the MM220 will not. It can be done with different settings, but that’s what I use without issue.

[drizzit1aa]

Thanks for the reply, guys. I downhill MIGed it, the supervisor gave me 16 and told me their guys get them done in a day (30 min. a box) which the MIG let me get it done that fast. Well 25 min. but ya. The owner won't care I MIGed it, the super. wont like it. If they give me more in the future, I'll give those settings a try. Thanks again

[cj737]

The thing to understand when TIG welding an outside corner is the gas cone is “split” across that seam. Therefore, a larger cup actually produces less coverage than a smaller cup. If that were ally, I’d weld it with a #5. The #6 does a better job with steel because I still run a gas lens, but lower the CFH (10). You simply can’t keep the gas coverage together which is why your welds look dodgy.

You might even try (for experience’s sake) to use a collet body with a #4 and have a go. Everyone welds differently and there’s no “right” or “wrong”, only “what works for you”.

[Louie1961]

looks to me like you are struggling with too long of an arc length.

[drizzit1aa]

So ya'all don't think I am a total dip the last 2 pics are a new job I got in, 1st is an older job all mild steel. Just those outside corners kicked by keester. Thinking it might be cup size, if I get more in, I'll try it. I don't have anything under #8 given I have never needed it with aluminum or stainless ... yet.

[Coldman]

Low carbon steel really needs the deoxidisers that filler wire provides to achieve a good weld and finish, unlike staino and aly.
For your thin gauge joints try twisting two mig wires together ( one end in a vice the other in a battery drill).
Pulsing will also improve finish .

[cj737]

Low carbon steel really needs the deoxidisers that filler wire provides to achieve a good weld and finish, unlike staino and aly.

Not always. This is an autogenous weld on hot rolled tubing, pulsed and it came out fine. Not an outside corner joint, but works just fine.

[Coldman]

If you saw lab test results on that weld you'd change your mind. If it hasn't been de-oxydised it's a bad weld doesn't matter how nice it looks.
Every weld will fail given enough time. Every good practice we employ as welders is designed to extend that time to failure as much as possible. Neglect any of these good practices and the life of the weld is compromised.